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Why does drinking milk lead to increased fractures?

Why does drinking milk lead to increased fractures?


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Milk has always been associated with strong bones due to the high amount of protein and calcium in it. Yet reading it up on wikipedia,

A study published in The BMJ that followed more than 45,000 men and 61,000 women in Sweden age 39 and older had similar results. Milk consumption in adults was associated with no protection for men, and an increased risk of fractures in women. The risk of any bone fracture increased 16 percent in women who drank three or more glasses daily, and the risk of a broken hip increased 60 percent. It was also associated with an increased risk of death in both sexes.

My question is:

Why did this happen? Can someone explain the biological reason of this observation?

Even though milk really does provide large amount of calcium and proteins yet isn't is contradictory that the fracture rates increase?

This is the aforementioned study.

Michaëlsson, K.; et al. (2014). "Milk intake and risk of mortality and fractures in women and men: cohort studies". The BMJ. 349: g6015. doi:10.1136/bmj.g6015.


The authors suggest a reason in their abstract:

Given the observational study designs with the inherent possibility of residual confounding and reverse causation phenomena, a cautious interpretation of the results is recommended.

There are variables they haven't measured that lead to the observed patterns. A simple one is that the respondees to the initial survey are self-selected (they return the survey). What if milk-drinkers are more likely to respond? Even if the base rate of fractures remains the same, then there will be an apparent association of fracture with milk consumption.

They also discuss physiological reasons, which is the subject of a different answer.


Lactose-Intolerant People Should Drink More Milk, Expert Says

WEST LAFAYETTE, Ind. -- Many people who claim to be lactose intolerant really aren't, says Dennis Savaiano, dean of Purdue University's School of Consumer and Family Sciences.

The problem, Savaiano says, is that dairy foods can be difficult to digest, and people who don't eat these foods often enough haven't acclimated themselves to the foods.

According to the National Institutes of Health, as many as 50 million Americans are lactose intolerant. Although lactose intolerance itself isn't harmful -- it may result in gas, bloating or nausea -- it does affect a person's health in the long-term because avoiding dairy foods reduces calcium intake. According to Savaiano, three-fourths of all calcium in diets in the United States come from dairy foods.

Too little calcium in a diet can reduce bone growth, which can lead to osteoporosis later in life. Osteoporosis, which affects 35 million Americans, can result in weakened bones, causing fractures and injuries. Patients in the United States spend $13 billion a year on osteoporosis treatments.

A big problem with both calcium intake and lactose tolerance, nutritionists say, is that most people, especially teen-age girls, don't consume enough dairy products.

"If you only consume dairy products once in awhile, you are more likely to have symptoms from them," Savaiano says. "Also, if you consume them by themselves, as opposed to as part of a meal, they tend to be transported throughout the intestine more rapidly and are more likely to cause symptoms."

Savaiano has four tips to improve digestion of milk and dairy products. "These approaches can improve lactose tolerance to the point that people can consume diets that are quite rich in calcium and in milk and experience no difference in their symptoms from eating a diet without the milk," he says. His tips:

  • Don't overeat dairy foods, and eat them only in moderation.
  • Eat dairy foods as part of a meal, such as a cup of milk over cereal with fruit.
  • If necessary, use over-the-counter digestive aids.
  • Eat yogurts. "Yogurts are very well tolerated because they contain a lactase that helps digest lactose in the intestine."

Lactose is a form of sugar, or carbohydrate, found in milk and dairy products. This sugar is too large to be absorbed by the intestine, and is broken down by an enzyme, lactase, produced by the body. Most adults don't produce enough lactase to completely break down the lactose. In fact, up to three-fourths of the world's population doesn't produce enough lactase.

However, Savaiano says it is possible to train one's own digestive system to break down the lactose.

"Our studies have shown a really amazing adaptation of the large intestine of humans," Savaiano says. "The large intestines contain bacteria that help digest lactose. By altering the diet over time, bacteria more effectively digest lactose, making milk better tolerated.

"The bacteria are very fastidious and very adaptable. An individual who may produce excessive gas may feel uncomfortable after eating milk products. But if they adapt to small amounts of milk for a couple of weeks, at the end of that period, they are producing far less gas than they were two weeks ago from the same amount of milk, and they tolerate dairy products extremely well."

Research studies on calcium metabolism have shown the effectiveness of this form of treatment, Savaiano says.

"We've found that if you do controlled clinical blind trials, where people don't know what they are consuming, and you take out that placebo effect, you can give subjects a glass of milk with breakfast and another with dinner and they exhibit almost no symptoms.

"Further, we just completed a study at Purdue last summer with a group of African-American adolescent girls who were part of a calcium diet study. On the first day of the study many complained about having to drink the milk -- they said they didn't like the milk and that they were intolerant. When we tested them they had only a very modest level of symptoms, though -- almost incidental. Two weeks later, after they had been consuming a dairy-based, high-calcium diet, we tested them again. Every one of these girls had absolutely no symptoms."

According to Savaiano, although many people think that some babies are lactose intolerant, actually this isn't the case. "Milk allergy is often confused with lactose intolerance, but they are physiologically different," Savaiano says. "Babies do not develop lactose intolerance until they are 3 to 5 years old. The intestinal lactase remains high in all infants, except the very rare situation where there is a genetic lack of the enzyme from birth."

Savaiano says milk allergies appears in 5 percent of newborns, but that almost all infants outgrow this allergy by their first birthday. "The best way to deal with this is to continue breast feeding," he says.


It can cause acne

Dairy is known to be inflammatory as nutritionist and dietitian Vanessa Rissetto explained, thanks to D-galactose, "a breakdown product of lactose that has been shown to be pro- inflammatory " and which milk boasts as opposed to milk products such as cheese or yogurt. This means that if you're suddenly breaking out after necking three glasses of the stuff, there's probably a connection there. Michelle Beckner, a certified nutrition coach, further warns, "Drinking milk every day, this source of inflammation can lead to acne that seems to never clear up."

It may seem like a small setback, but considering that what we put into our bodies tends to show up on our skin (as anybody who's scoffed an entire tub of ice-cream in one sitting can attest) if there's anything that can help clear up your skin, especially something as simple as cutting down on daily dairy intake, then surely it's an easy choice to make.

If you're really craving a milk fix but don't want to take the risk, Dr. Joelle Cafaro suggests "opting for more nutritious (and less processed) dairy options like plain yogurt and kefir" as an alternative to drinking cow's milk, as these products are still yummy but are less likely to make you break out.


White Lies? Five Milk Myths Debunked

Last month, a study was called into question for suggesting that chocolate milk could be beneficial for teens recovering from concussions.

Not surprisingly, the study was funded by the dairy industry. For decades, milk marketers have been spreading misleading information about the supposed health benefits of dairy products.

Thanks to these marketing campaigns, milk myths abound in our culture. But science doesn’t support them. Let’s take a look at five common claims about dairy products:

Myth 1: Milk builds strong bones.

The dairy and bone health link is one of the most pervasive milk myths. One large-scale Harvard study followed 72,000 women for two decades and found no evidence that drinking milk can prevent bone fractures or osteoporosis. Another study of more than 96,000 people found that the more milk men consumed as teenagers, the more bone fractures they experience as adults. Similarly, another study found that adolescent girls who consumed the most calcium, mostly in the form of dairy products, were at greater risk for stress fractures than those consuming less calcium.

Myth 2: Drinking milk can help you lose weight.

While advertisers would like you to believe that drinking milk can slim you down, studies consistently show that dairy products offer zero benefits for weight control. One major study even found that dairy products might lead to weight gain. In 2005, the Physicians Committee petitioned the FTC to put an immediate end to the dairy industry’s misleading campaigns about milk and weight control. In response, the government no longer allows advertising campaigns to claim that dairy products lead to weight loss.

Myth 3: Milk is “nature’s perfect food.”

Cow’s milk might be ideal for growing baby cows, but it’s far from a perfect food for humans. More than 60 percent of people are lactose intolerant, which can lead to uncomfortable symptoms like cramping, diarrhea, and bloating. Regular consumption of dairy products has also been linked to prostate cancer, lung cancer, breast cancer, and ovarian cancer.

Myth 4: Kids need milk to be healthy.

After babies are weaned from breast milk or formula, they do not need any type of milk to be healthy. Milk consumption during childhood has even been linked to colic and type 1 diabetes. Another study found no evidence that low-fat milk plays any role in preventing childhood obesity.

Myth 5: Milk is heart-healthy.

Milk and other dairy products are the top sources of artery-clogging saturated fat in the American diet. Milk products also contain dietary cholesterol. Diets high in fat, saturated fat, and cholesterol increase the risk of heart disease, which remains America’s top killer.


Is Milk Good for Our Bones?

The galactose in milk may explain why milk consumption is associated with significantly higher risk of hip fractures, cancer, and premature death.

Transcript

Milk is touted to build strong bones, but a compilation of all the best studies found no association between milk consumption and hip fracture risk, so drinking milk as an adult might not help bones. But what about in adolescence? Harvard researchers decided to put it to the test.

Studies have shown that greater milk consumption during childhood and adolescence contributes to peak bone mass, and is therefore expected to help avoid osteoporosis and bone fractures in later life. But that’s not what they found. Milk consumption during teenage years was not associated with a lower risk of hip fracture, and, if anything, milk consumption was associated with a borderline increase in fracture risk in men.

It appears that the extra boost in total body bone mineral density you get from getting extra calcium is lost within a few years, even if you keep the calcium supplementation up. This suggests a partial explanation for the long-standing enigma that hip fracture rates are highest in populations with the greatest milk consumption. Maybe an explanation why they’re not lower, but why would they be higher?

This enigma irked a Swedish research team, puzzled because studies again and again had shown a tendency of a higher risk of fracture with a higher intake of milk. Well, there is a rare birth defect called galactosemia, where babies are born without the enzymes needed to detoxify the galactose found in milk, so they end up with elevated levels of galactose in their blood, which can cause bone loss even as kids. So maybe, the Swedish researchers figured, even in normal people who can detoxify the stuff, it might not be good for the bones to be drinking it every day. And galactose doesn’t just hurt the bones. That’s what scientists use to cause premature aging in lab animals They slip them a little galactose and you can shorten their lifespan, cause oxidative stress, inflammation, brain degeneration, just with the equivalent of one to two glasses of milk’s worth of galactose a day. We’re not rats, though—but given the high amount of galactose in milk, recommendations to increase milk intake for prevention of fractures could be a conceivable contradiction. So they decided to put it to the test, looking at milk intake and mortality, as well as fracture risk, to test their theory.

A hundred thousand men and women followed for up to 20 years what did they find? Milk-drinking women had higher rates of death, more heart disease, and significantly more cancer for each glass of milk. Three glasses a day was associated with nearly twice the risk of death. And they had significantly more bone and hip fractures too.

Men in a separate study also had a higher rate of death with higher milk consumption, but at least they didn’t have higher fracture rates. So a dose-dependent higher rate of both mortality and fracture in women, and a higher rate of mortality in men with milk intake, but the opposite for other dairy products like soured milk and yogurt, which would go along with the galactose theory, since bacteria can ferment away some of the lactose. To prove it though, we need a randomized controlled trial to examine the effect of milk intake on mortality and fractures. As the accompanying editorial pointed out, we better figure this out soon, as milk consumption is on the rise around the world.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.

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Milk is touted to build strong bones, but a compilation of all the best studies found no association between milk consumption and hip fracture risk, so drinking milk as an adult might not help bones. But what about in adolescence? Harvard researchers decided to put it to the test.

Studies have shown that greater milk consumption during childhood and adolescence contributes to peak bone mass, and is therefore expected to help avoid osteoporosis and bone fractures in later life. But that’s not what they found. Milk consumption during teenage years was not associated with a lower risk of hip fracture, and, if anything, milk consumption was associated with a borderline increase in fracture risk in men.

It appears that the extra boost in total body bone mineral density you get from getting extra calcium is lost within a few years, even if you keep the calcium supplementation up. This suggests a partial explanation for the long-standing enigma that hip fracture rates are highest in populations with the greatest milk consumption. Maybe an explanation why they’re not lower, but why would they be higher?

This enigma irked a Swedish research team, puzzled because studies again and again had shown a tendency of a higher risk of fracture with a higher intake of milk. Well, there is a rare birth defect called galactosemia, where babies are born without the enzymes needed to detoxify the galactose found in milk, so they end up with elevated levels of galactose in their blood, which can cause bone loss even as kids. So maybe, the Swedish researchers figured, even in normal people who can detoxify the stuff, it might not be good for the bones to be drinking it every day. And galactose doesn’t just hurt the bones. That’s what scientists use to cause premature aging in lab animals They slip them a little galactose and you can shorten their lifespan, cause oxidative stress, inflammation, brain degeneration, just with the equivalent of one to two glasses of milk’s worth of galactose a day. We’re not rats, though—but given the high amount of galactose in milk, recommendations to increase milk intake for prevention of fractures could be a conceivable contradiction. So they decided to put it to the test, looking at milk intake and mortality, as well as fracture risk, to test their theory.

A hundred thousand men and women followed for up to 20 years what did they find? Milk-drinking women had higher rates of death, more heart disease, and significantly more cancer for each glass of milk. Three glasses a day was associated with nearly twice the risk of death. And they had significantly more bone and hip fractures too.

Men in a separate study also had a higher rate of death with higher milk consumption, but at least they didn’t have higher fracture rates. So a dose-dependent higher rate of both mortality and fracture in women, and a higher rate of mortality in men with milk intake, but the opposite for other dairy products like soured milk and yogurt, which would go along with the galactose theory, since bacteria can ferment away some of the lactose. To prove it though, we need a randomized controlled trial to examine the effect of milk intake on mortality and fractures. As the accompanying editorial pointed out, we better figure this out soon, as milk consumption is on the rise around the world.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by Katie Schloer.


The Relationship Between Soda and Bone Health

I’ve had many clients who were avid cola drinkers, even using their Coke or Pepsi as a breakfast coffee substitute. I also have seen plenty of people who readily recognized that they were addicted to sodas — using several of these drinks a day to stay alert and functioning. Somewhere deep down, I believe all of us know sodas are not nourishing but not all of us are fully aware of the detailed relationship between soda and bone health.

Even so, because so many of us continue to drink soda, I don’t believe we truly understand the detrimental effects on our health. Especially when you consider the average American consumes nearly 45 gallons of soda a year. We drink more soda than any other beverage, including bottled water (28.3 gallons), beer (20.8 gallons), and milk (20.4 gallons), according to 2010 figures from the Beverage Marketing Corporation.

Excessive soda use paves the way for many degenerative diseases including diabetes, obesity, metabolic syndrome, heart disease, tooth decay, and osteoporosis.

For example, researchers studied soda and bone health and found the effect of drinking three cola-type sodas or more a day. They found that women who drank cola — whether regular, diet, or noncaffeinated — had nearly 4% lower bone mineral density in the hip. (Non-cola sodas were not found to have the same effect nor did the men in the study show lower hip bone density.) For young girls the data is even stronger documenting increased fracture risk with soda use. In fact, studies show a 3 to 5 fold increase in fractures among teenage girls who regularly consume acidic soft drink beverages.

Bone experts have several ideas as to why soda and bone health are related:

• Many colas contain phosphoric acid. As the body tries to neutralize the acid, it is forced to draw substantial amounts of alkalizing calcium compounds from our bones.

• Many sodas contain caffeine. Caffeine may increase your body’s excretion of calcium, contributing to lower bone density.

• The “replacement” theory. This is the idea that the more soda you drink, the less likely you are to choose water and other more healthful beverages.

The damaging effects of each ingredient on your bones are cumulative and additive. And, in addition to the caffeine, phosphoric acid, and other chemical additives, a regular 12-ounce soda contains 9–10 teaspoons of sugar — usually in the guise of high-fructose corn syrup.

So what are some healthy, summer-refreshing alternatives? If you are looking for the caffeine boost, iced green tea is an excellent choice. Alkalizing fruit spritzers made with soda, spring, or mineral water give a healthful lift. Fresh squeezed lemon or lime with a bit of raw cane sugar alkalizes while it refreshes. Iced fruit smoothies are delicious and chuck full of antioxidants, much less fresh-from-the garden carrot and vegetable juices.

Right now I’m going to start my day with a “green drink” — juicing greens and celery from my garden along with a few carrots and an apple. I bet you also have creative ideas for alternatives to soda for you and your family. I’d love to hear about your favorites. Be conscious of the relationship between soda and bone health. Be well and enjoy every minute of the summer!

Wyshak, G and Frisch, RE., 1994 Wyshak, G,2000. “Teenaged girls, carbonated beverage consumption and bone fractures”. Arch Pediatr Adolesc Med. June, 2000, Vol 154, No. 6. pages 610-613.

Greer, B. Food Works. University of Tennessee Extension Document # SP468.


Does Milk Actually Build Strong Bones? Sugar Content May Lead To Greater Fracture Risks

A recent report from Sweden has not only added proof to the growing consensus that drinking milk doesn’t help our bone strength at all but also suggested that it may be compromising our lives. The study even found a correlation between high milk consumption, bone fracture occurrences, and increased mortality risk. Although at this point cause and effect cannot yet be proven, the findings may still be enough to get you to decrease your daily milk consumption.

Mankind’s relationship with milk post-infancy is still relatively new. In fact, two-thirds of the human population still lack the enzyme needed to break down the lactose in milk and will most surely end up with the monster of all stomach aches if they drink too much. Still, for those of us who are able to drink milk without too much of a discomfort, we've drank with the idea that we were somewhat improving our bone health.

However, many scholars have noticed that when it comes to osteoporosis and milk consumption, the numbers just don’t add up. The countries with the highest rates of osteoporosis, such as the United States and countries in the European Union, are some of the biggest global milk consumers, Slate reported. Could it be that milk actually doesn’t do all that much for bone health after all?

In order to answer this question, which could potentially lead to a revision of medical books throughout the world, a team of Swedish researchers followed 61,433 women and 45,339 men for between 11 and 20 years, tracking their diet and bone health. Results showed that for women, higher milk consumption was not associated with a reduction in fracture risk. On top of this, women who drank more than three glasses of milk a day were found to have a higher risk of death than women who drank less than one glass. The men showed similar results with an even more pronounced association between high milk consumption and higher risk of death.

“Our results may question the validity of recommendations to consume high amounts of milk to prevent fragility fractures," wrote the study’s authors in a press release. "The results should, however, be interpreted cautiously given the observational design of our study. The findings merit independent replication before they can be used for dietary recommendations."

There is a bit of hope for dairy lovers, though. Although higher consumption of milk was found to be associated with negative health consequences, a high intake of fermented milk products with low lactose content, such as cheese and yogurt, was found to lower the risk of bone fracture and death. This observation was especially prominent for women.

The study was only able to point out a pattern between milk consumption and increased health consequences but emphasizes that more research is needed.

“As milk consumption may rise globally with economic development and increasing consumption of animal source foods, the role of milk and mortality needs to be established definitively now," said lead researcher Karl Michaëlsson.

Source: Michaëlsson K, Wolk Alicja, Langenskiöld S, et al. Milk intake and risk of mortality and fractures in women and men: cohort studies. BMJ. 2014.


Too much milk may be bad for your health

Drinking lots of milk could be bad for your health, a new study reports.

Previous research has shown that the calcium in milk can help strengthen bones and prevent osteoporosis. These benefits to bone health have led U.S. health officials to recommend milk as part of a healthy diet.

But this new study found that drinking large amounts of milk did not protect men or women from bone fractures, and was linked to an overall higher risk of death during the study period.

However, the researchers said the results should be viewed with caution.

Women who drank three glasses of milk or more every day had a nearly doubled risk of death and cardiovascular disease, and a 44 percent increased risk of cancer compared to women who drank less than one glass per day, the researchers found.

Men's overall risk of death increased about 10 percent when they drank three or more glasses of milk daily, said the study, published online Oct. 28 in BMJ.

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"The study findings have, for myself, been strong enough to cut down on my milk consumption," said lead author Karl Michaelsson, a professor in the department of surgical sciences at Uppsala University in Sweden.

Still, the findings only suggest an association and not a direct link, said Mary Schooling, a professor at the City University of New York School of Public Health, who wrote an editorial accompanying the study.

People should not change their diet based on these findings, Schooling said.

"We can't draw conclusions at this point," she said. "We need a study involving people who genetically can and can't digest milk easily, and compare whether those who can digest milk have a difference in cardiovascular disease, death and fractures from those who can't."

The study involved more than 61,000 women and 45,000 men in Sweden who previously filled out dietary questionnaires for other research projects, the women in the late 1980s and the men in 1997. All were over 39 years of age.

Researchers compared their reported milk-drinking habits to health data kept by Swedish officials, to see whether milk consumption could be linked to risk of death or health problems.

The investigators found that a large amount of milk in a daily diet did appear to be linked to an increased risk of death in both men and women during the study period.

In addition, excessive milk drinking appeared to actually increase a woman's risk of broken bones, compared with women who drank little milk.

The risk of any bone fracture increased 16 percent in women who drank three or more glasses daily, and the risk of a broken hip increased 60 percent, the findings indicated.

Lots of milk did not appear to either protect against or promote broken bones in men.

Michaelsson and his colleagues said the increased risk of death they observed could be explained by the high levels of sugars contained in milk, specifically lactose and galactose.

Galactose has been shown to prematurely age mice in the laboratory, Michaelsson said, noting that the milk sugar promotes inflammation.

By contrast, a high intake of fermented milk products with low lactose content -- such as yogurt and cheese -- was associated with reduced rates of death and fracture, particularly in women, the researchers reported.

While interesting, these findings are too preliminary to warrant a change in nutritional guidelines, said Isabel Maples, a registered dietitian in Haymarket, Va., and spokesperson for the Academy of Nutrition and Dietetics.

About 55 percent of older adults -- 44 million Americans -- either have osteoporosis or are at high risk for brittle bones, Maples said. She added that the U.S. Dietary Guidelines recommend three servings of dairy per day, not just for bone health, but also to reduce the risk of heart disease, type 2 diabetes and high blood pressure.

"They don't base the guidelines on fads. They don't base it on trends. They don't base it on what has been the traditional advice. They look at the scientific evidence," she said.

First published on October 29, 2014 / 11:59 AM

© 2014 HealthDay. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.


Study: Milk may not be very good for bones or the body

Milk is often touted as one of nature's most perfect foods -- and for good reason. It contains many essential nutrients and in particular, the high calcium content has been touted as crucial for good bone health when fortified with vitamin D, as it is in the United States.

But a new study from researchers in Uppsala University in Sweden suggests that consuming more milk could actually be associated with higher mortality and bone fractures in women and higher mortality in men.

“I've looked at fractures during the last 25 years. I've been puzzled by the question because there has again and again been a tendency of a higher risk of fracture with a higher intake of milk,” said the study's lead author Karl Michaelsson, a professor at Uppsala University.

The study, published in the British Medical Journal, utilized data from two large, long-term Swedish studies of adult men and women, which asked about their dietary habits -- how much and what types of milk and dairy products they consumed.

Women who consumed three or more glasses of milk a day had a higher risk of fracture and a higher risk of death. Men who drank three or more glasses of milk a day had a slightly higher risk of death -- mostly associated with cardiovascular death -- compared to those who drank less than one glass a day. And there was no reduced risk of fracture as milk consumption increased.

Michaelsson's team also analyzed data from the two studies about the levels of a biological marker of stress in some of the participants.

In both men and women, the amount of milk they consumed was also associated with higher levels of a biological stress marker -- oxidative stress -- which has been associated with aging, cancer and cardiovascular disease.

Other studies have observed a similar -- and seemingly paradoxical -- relationship between the consumption of calcium-rich milk and bone fractures.

Meta-analysis studies in 2007 and 2011 found that there was no association between hip fractures risk and milk consumption.

But why milk consumption might be associated with mortality is a much more difficult question to answer.

Notably, the association between fractures or mortality and dairy consumption was not seen with derivatives of milk, such as cheese, yogurt, sour milk, and other fermented products. In fact, in Michaelsson's analysis, each serving of cheese or fermented milk products reduced rates of mortality and hip fractures by 10-15 percent.


Why does drinking milk lead to increased fractures? - Biology

H. Wayne Sampson, Ph.D., is a professor of human anatomy and medical neurobiology and nutrition at Texas A&M University System Health Science Center, College of Medicine, College Station, Texas.

By about age 35, people reach their peak bone mass. Women lose bone mass slowly after that point until a few years after menopause, when bone mass is lost very rapidly. For middle–aged and older women, healthy bones depend on the development, during younger years, of a strong bone structure and an adequate peak bone mass. There is tenuous evidence that moderate alcohol consumption may protect bone. But human and animal studies clearly indicate that chronic heavy drinking, particularly during adolescence and the young adult years, can dramatically compromise bone quality and may increase osteoporosis risk. Further, research indicates that the effects of heavy alcohol use on bone cannot be reversed, even if alcohol consumption is terminated. Research suggests that in addition to alcohol, other lifestyle factors—such as tobacco use, nutrition, weight–bearing exercise, increased body weight, and hormone replacement therapy—affect bone development and osteoporosis risk in women. However, there has been little examination of how alcohol interacts with these factors to influence bone health. Key words: osteoporosis bone mass density risk factors female AODE (alcohol and other drug effects) alcoholic beverage tobacco in any form lifestyle physical exercise obesity nutrition estrogens hormone therapy literature review

Osteoporosis is a skeletal disorder characterized by low bone mass, increased bone fragility, and susceptibility to fracture (see figure 1). 1 ( 1 Osteoporosis is classified as either primary or secondary depending on its underlying causes. Primary osteoporosis is subdivided into two types: Postmenopausal [Type I] osteoporosis occurs 15 to 20 years after menopause in females, following a decline in estrogen levels. Age–associated, or senile [Type II] osteoporosis occurs after approximately age 70 in both genders. In contrast to these two types of primary osteoporosis, secondary osteoporosis is the result of specific conditions such as disease, surgery, and drugs [Riggs and Melton 1988].) Approximately one in two women and one in eight men over age 50 will have an osteoporosis–related fracture in their lifetime, and these fractures account for approximately $14 billion in direct medical costs (National Institutes of Health 1999).

Figure 1 Normal bone (top) and bone from an alcohol–treated rat (bottom). Note that lighter–colored specules of bone are missing in the bottom image.

At approximately age 35, people reach their “peak bone mass”—the point at which their bones are as dense, or strong, as they will become (Edelson and Kleerekoper 1995). After age 35, women lose 0.5 percent to 1 percent of their bone mass each year. At menopause, when the ovaries stop producing estrogen, the rate of bone loss increases, in the absence of estrogen replacement therapy, from 3 percent to 7 percent per year, building to 15 percent to 35 percent loss in bone mass in the first 5 years after menopause (Bonnick 1994).

For middle–aged and older adults to have healthy bones, they need to have developed a strong bone structure and an adequate peak bone mass during their younger years. Bone structure and peak bone mass are greatly affected by lifestyle factors, including alcohol use, especially during the adolescent and young adult years (see figure 2). This article reviews research on how alcohol use and other factors affect bone health and osteoporosis risk in women.

Figure 2 Peak bone mass is affected not only by genetic and other biological factors but also by lifestyle variables such as nutrition, exercise, tobacco use, and drinking. In this figure, factors along the steeper line contribute to higher peak bone mass.
SOURCE: Amanda Arnold.

MODERATE DRINKING

The effect of moderate* alcohol use on bone health and osteoporosis risk is unclear. (*Editor’s Note: Definitions of moderate drinking vary. Federal guidelines consider moderate drinking to be no more than one drink per day for women and no more than two drinks per day for men [U.S. Department of Agriculture and the U.S. Department of Health and Human Services 1995].) A few epidemiological studies in humans have indicated that moderate alcohol consumption may be associated with decreased fracture risk in postmenopausal women (Hansen et al. 1991 Felson et al. 1995). One large study (Diaz et al. 1997) found that women age 65 and over who consumed alcohol on more than 5 days per week had a significantly reduced risk of vertebral deformity 2 compared with those who consumed alcohol less than once per week. ( 2 Crush fractures of the anterior vertebral body cause most women’s bone–related visits to the doctor.)

This apparent beneficial effect of moderate drinking on bone health has not been found in animal studies, which can control for the amount of alcohol consumed as well as for other lifestyle factors (see figure 2). For example, Sampson and Shipley (1997) gave ovariectomized and sham animals (animals in which abdominal surgery was performed but the ovaries were not removed) 0.38 g/kg of alcohol a day for 6 weeks (the equivalent of two glasses of wine per day, containing 12 g of alcohol per glass, for an average 63–kg woman). Removal of the ovaries led to decreased bone density and bone volume compared with control animals, but comparisons with animals that were not fed alcohol showed that these changes were not significantly altered by alcohol consumption. In contrast, in a study of rats administered alcohol for 4 months, Turner and colleagues (2001) reported a decrease in the replacement of old bone with new bone tissue (i.e., bone turnover) following moderate alcohol consumption. These studies found no beneficial effect of moderate alcohol use on bone quality.

CHRONIC HEAVY DRINKING

Effects of Alcohol on Growing Bone

Almost all epidemiological studies of alcohol use and human bone health indicate that chronic heavy alcohol consumption, particularly during adolescence and young adulthood, can dramatically affect bone health and may increase the risk of developing osteoporosis later. Although alcohol appears to have an effect on bone–forming cells (i.e., osteoblasts), slowing bone turnover, the specific mechanisms by which alcohol affects bone are poorly understood.

Studies in female animals have also demonstrated unequivocally that early chronic alcohol consumption compromises bone health, including decrements in bone length, dry weight (weight of the bone with the water removed), and mineral content. Research has shown that young, actively growing rats chronically consuming alcohol had reduced femur lengths when compared with pair–fed control rats until they were approximately 9 months of age (see figure 3 for a comparison of rat and human ages). Eventually, the femurs of alcohol–fed animals caught up with the growth in length of animals in the control group (Sampson et al. 1997 Hogan et al. 1997).

Figure 3 Comparison of rat and human ages.

This ability of the femur to make up for lost time, however, did not extend to all measures of bone health: Relative to control animals, alcohol–fed animals’ bone density was significantly reduced and remained so throughout the animals’ lives (Hogan et al. 1997).

In further examinations of these same animals, computer analyses of microscope slides of the upper tibia revealed greatly reduced bone volume in alcohol–fed rats compared with control rats (Sampson et al. 1997). In particular, the analyses showed a reduction in the number of thin plates (trabeculae) that form the soft, inner part of the bone. Further, after the animals had stopped growing, the overall thickness of the inner (cancellous) bone was also reduced in alcohol–fed rats compared with rats in a control group.

Additional evidence that alcohol causes bone–growth deficiencies in actively growing animals is provided by studies of the developing tissue, known as growth plates, near the ends of long bones (Sampson et al. 1997). These studies revealed that alcohol severely slowed the proliferation of cartilage cells, important precursors to bone development, and arrested longitudinal bone growth.

Studies of rats fed alcohol from 1 month of age throughout their lives indicate that alcohol–induced bone deficiencies may stem from a lag in growth, rather than from a loss of bone content (Sampson 1998). That is, the animals may not be losing bone per se, but they may not be growing and maturing as they should. This conclusion is supported by measurements of blood levels of a hormone, known as insulin–like growth factor 1 (IGF𔂿), that helps maintain bone density. In both groups of rats, IGF𔂿 values were greatest in younger animals and diminished until the animals stopped growing at 9 months old. Alcohol greatly reduced initial IGF𔂿 values however, the magnitude of this reduction decreased with age, so that at 9 months, alcohol–fed rats’ IGF𔂿 values were similar to those of control animals. These findings lend support to the idea that during the younger years alcohol’s effect may be on growth more than on bone itself.

Finally, in these young animals, chronic alcohol exposure also compromised the bones’ mechanical properties, including their elasticity, stiffness, load–carrying capacity, and toughness (i.e., amount of deformation before breaking) (Hogan et al. 1997). It appears that bone’s cortical area (i.e., the tubular, mid–shaft part of the bone) and its shape in cross–section were unaffected by alcohol exposure. Over the long term, alcohol–fed animals seemed to adapt, at least partially, to these reductions in tissue quality and strength by producing generally larger bones with thinner cortical walls (Sampson 1998).

Nevertheless, the effects of alcohol consumption on bone could not be reversed, regardless of whether alcohol consumption continued or was terminated (Sampson et al. 1997 Hogan et al. 1997). The mechanical integrity of the alcohol–fed animals’ bones—the source of their strength—did not “catch up” with control animals.

Effects of Alcohol on Adult Bone

Although alcohol’s damaging effects on bone are most striking in young people, research has shown that women between the ages of 67 and 90 who consumed an average of more than 3 ounces of alcohol per day (the equivalent of six drinks) had greater bone loss than women who had minimal alcohol intake (Hannan et al. 2000). (For information on how light–to–moderate drinking affects bone health in older women, see the article in this issue by Register and colleagues.) In addition to such research in human adults, studies of animals that began consuming alcohol as elderly animals also revealed deficiencies in bone volume and density (Hogan et al. 2001). These studies in adult animals agreed with cell–culture studies, suggesting that in these adult animals, alcohol consumption has greater deleterious effects on bone formation than on the breakdown (i.e., resorption) of old bone.

OTHER RISK FACTORS FOR OSTEOPOROSIS

In addition to alcohol use, lifestyle factors such as tobacco use, exercise and body weight, nutrition, and hormone replacement appear to play a role in bone health and osteoporosis risk, although the magnitude of these roles is not well understood. Brief summaries of research on such osteoporosis risk factors are provided below, followed by a discussion of how alcohol might interact with each factor. However, as these discussions underscore, in most instances, there has been very little research addressing their association with alcohol’s effects.

Many—although not all—studies have shown a link between tobacco use and decreased bone health. Heavy smoking has long been associated with greater risk for osteoporosis (Daniell 1972) a higher incidence of bone fractures, lower bone density, and fewer teeth (Johnston 1994) a dramatic decrease in the mineralization of bones in the hip, hand, forearm, and heel decreased bone healing (Hollinger et al. 1999) and a decrease in new bone formation (Yuhara et al. 1999 Fang et al. 1991). Studies have demonstrated a causal link between heavy smoking and decreased bone mass (McCulloch et al. 1991 Friedl et al. 1992), whereas moderate or light smoking appears not to cause such harm (Daniel et al. 1992). Research with premenopausal female twins revealed that smokers had markedly lower bone densities than did their nonsmoking twins. Finally, some researchers have reported that among postmenopausal women, smokers lose cortical bone (i.e., tubular, mid–shaft bone) about 50 percent faster than do nonsmokers however, the causes of this increased rate of bone loss are unclear.

Some recent research, however, has been more equivocal. Hannan and colleagues (2000) found that although older men who were current smokers lost more bone mineral density than did men who never smoked, there was no such difference between female smokers and nonsmokers. Likewise, recent research in animals (Syversen et al. 1999 Iwaniec et al. 2000) has failed to confirm the results of earlier studies that had reported a decrease in bone mineral density following smoking (Hollo et al. 1979) or nicotine exposure (Broulik and Jaráb 1993).

Despite uncertainty over the role of tobacco use in bone health, researchers have suggested several mechanisms by which smoking may affect osteoporosis risk. In postmenopausal women, smoking may speed the breakdown (metabolism) of estrogen, resulting in lower estrogen levels and increased bone loss and risk of fracture (Kiel et al. 1992). Other suggestions for the mechanism of smoking’s effect on bone include smokers’ lower body weight, decreased physical activity, decreased absorption of calcium, increased alcohol intake (see the next section) and other nutritional deficiencies, resistance to the hormone calcitonin (which suppresses bone resorption), and direct effects of tobacco on bone cells.

Alcohol and Tobacco Use. People who drink alcohol are 75 percent more likely to smoke than are nondrinkers, and smokers are 86 percent more likely to drink than are nonsmokers (Shiffman and Balabanis 1995). One activity attenuates the impact of the other—for example, smoking appears to slow the release of alcohol from the stomach, causing more alcohol to be broken down in the stomach and less to be absorbed into the circulation (Chen et al. 2001). By lowering blood alcohol concentrations in this way, smoking allows one to drink more before getting drunk. Although there has been little research addressing this issue, it seems reasonable that anything that increases alcohol consumption (as smoking does) might be detrimental to bone physiology. The only investigation of the combined effects of alcohol and tobacco on bone health, an epidemiological study by Deng and colleagues (2000), found no effect on bone mineral density as a result of drinking or smoking, but did find a significant effect in participants who both smoked and drank. However, as this research is in its infancy, these findings should be considered preliminary.

Because the major determinant of whether or not a woman develops osteoporosis is her peak bone mass and her rate of bone loss, it is of interest to know whether exercise can influence either of these two factors (Stevenson et al. 1990). Although the mechanisms are not fully understood, mechanical stress—such as that imposed by muscle contraction and weight–bearing exercise—increases bone density (Marcus and Kiratli 1998 Snow et al. 1996). Bone that is immobilized and has no weight–bearing function, as occurs in space flight, spinal cord injury, or prolonged bed rest, tends to lose mass rapidly (Turner 2000).

Only a few studies have focused on the effect of exercise and bone mass in osteoporotic patients. This research found that patients who exercised showed an improvement in bone mineral density by 1 percent over time and by 2 to 3 percent above nonexercising control subjects (although the greatest benefit of exercise was to increase participants’ functional capacity and decrease the incidence of falls) (Marcus and Kiratli 1998 Millard 1996).

In addition, carrying extra body weight amounts to weight–bearing exercise, and thus, like weight–bearing exercise, obesity is also associated with both reduced risk and lessened severity of osteoporosis. In fact, there has been some suggestion that the association between smoking and osteoporosis may derive, at least in part, from the fact that smokers tend to be less obese than nonsmokers (Broulik and Kapitola 1993). Research shows that obese women lose relatively little bone at menopause, whereas thin women tend to have a greater risk for osteoporotic fractures (Broulik and Kapitola 1993). And in one study of older women, those in the lower weight quartiles and those who lost 5 percent or more of their weight during the study had significantly more bone loss than did those who were heavier or who did not lose significant weight during the study (Hannan et al. 2000).

The reasons for the link between obesity and lower osteoporosis risk are not fully understood. Some experts postulate that estrogen produced or stored in fat tissue might attenuate bone loss. In addition, having extra body weight means that most movement is “weight bearing,” and thus obesity is a powerful determinant of bone mass (Heany 1995).

Exercise, Obesity, and Alcohol. There has been little research on how alcohol consumption and exercise or weight might together influence osteoporosis risk. Preliminary studies of exercising, alcohol–fed animals have demonstrated that exercise did not mitigate any of the negative effects of alcohol (Reed et al. 2002).

Bone requires many nutrients to develop and remain healthy, including calcium phosphorus zinc manganese copper vitamins D, K, C, and A and protein. During growth, it is especially important for people to take in enough calcium to build as high a peak bone mass as is genetically possible for them—a window of opportunity that remains at least partially open until women are in their thirties (Heaney 1995). Especially for pregnant and lactating mothers, it is necessary to replace the calcium lost daily through the kidneys, the intestine, and through sweat. When sufficient calcium is not brought in through the diet, it is removed from bone.

Vitamin D is also crucial to bone health, as it plays a major role in calcium absorption. Many people do not produce sufficient vitamin D through exposure to sunlight (because of variations in sun exposure, skin pigmentation, and aging–related decreases in the ability of skin to make the vitamin). For this reason, it is important for such people to eat foods that are rich in vitamin D, such as milk and other fortified foods and fish oils. Nutrition is also important to bone health in that it contributes to body weight as discussed above, carrying increased body weight, by acting as weight–bearing exercise, helps build bone mass (Heaney 1995).

Nutrition and Alcohol. As is the case for other lifestyle factors that affect osteoporosis risk, little research has addressed how alcohol might interact with other aspects of nutrition to influence bone health. It is known, however, that severe alcoholics are usually malnourished, a condition that exacerbates alcohol–induced vitamin D deficiencies, and thus impairs bone health by impairing calcium absorption.

Estrogen and Hormone Replacement

Undoubtedly the greatest risk factor for the development of osteoporosis in women is menopause, when estrogen levels drop precipitously. Normally, the breakdown of old, worn bone is balanced by formation of new bone. It is not known how estrogen normally regulates this balance of bone remodeling. What is clear is that when estrogen declines dramatically, as it does during menopause, the cells that are responsible for breaking down old bone (osteoclasts) live longer. Osteoclasts’ longer life span gives them increased capacity to break down bone, disrupting the balance between bone resorption and new bone formation and resulting in bone loss.

Recent research has shown that postmenopausal hormone replacement therapy greatly protects against loss in bone density (Hannan et al. 2000) and reduces the risk of hip, spine, and other osteoporosis–related fractures.

Estrogen and Alcohol. There has been speculation that alcohol’s effect on bone is mediated by estrogen, but the evidence to support this idea is unclear. Some studies in humans have demonstrated what may have been an estrogen effect. In contrast to these findings, most studies in animals have seen no changes in estrogen, testosterone, or conversion of androgens to estrogen (a process known as aromatization) as a result of alcohol consumption. Some researchers believe that the effect seen in humans was a red wine antioxidant effect rather than an effect of alcohol itself (Purohit 1998).

Human and animal studies clearly demonstrate that chronic, heavy alcohol consumption compromises bone health and increases the risk of osteoporosis. In particular, heavy alcohol use decreases bone density and weakens bones’ mechanical properties. These effects are particularly striking in young people (and animals), but chronic alcohol use in adulthood can also harm bone health. Further, animal studies suggest that bones do not overcome the damaging effects of early chronic alcohol exposure, even when alcohol use is discontinued.

The effect of moderate alcohol consumption on bone health is less clear. Some research in humans has indicated that moderate drinking may boost bone mass, whereas animal studies have contradicted that idea.

Research suggests that in addition to alcohol, other lifestyle factors, such as tobacco use and poor nutrition, might result in a lower peak bone mass and increase the likelihood of bone fractures. Other factors—such as weight–bearing exercise, increased body weight, and hormone replacement therapy—appear to have positive effects on bone development. To date, however, there has been little investigation into how alcohol interacts with these other factors to influence bone health and osteoporosis risk.

Current examinations of alcohol’s effects on bone health suggest numerous directions for further investigation. It is important to study the mechanism of alcohol’s effect on bone at many levels. Does alcohol work through growth factors, or does it affect osteoblasts directly in the young? How specifically does alcohol target osteoblasts? Does it act through receptors, signal transduction pathways, or through other mechanisms? Finally, additional research should examine whether alcohol’s negative effects on bone can be reversed.

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12 Frightening Facts About Milk

A large observational cohort study [ 1 ] in Sweden found that women consuming more than 3 glasses of milk a day had almost twice the mortality over 20 years compared to those women consuming less than one glass a day. In addition, the high milk-drinkers did not have improved bone health. In fact, they had more fractures, particularly hip fractures.

Interestingly, the study also found that fermented milk products (cheese and yogurt) significantly decreased mortality and fractures among these women. For each serving of these fermented dairy products, the rate of mortality and hip fractures was reduced by 10-15%. The researchers pin the negative effects of liquid milk on D-galactose, a breakdown product of lactose that has been shown to be pro-inflammatory. Milk has much more D-galactose than does cheese or yogurt.

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I am surprised that this study garnered so much mass media attention upon its release, as it highlights the deleterious side of milk, but I also think it is important to keep the findings in context. And when it comes to the health effects of dairy, the context is not so pretty:

  1. In observational studies both across countries and within single populations, higher dairy intake has been linked to increased risk of prostate cancer [2] .
  2. Observational cohort studies have shown higher dairy intake is linked to higher ovarian cancer risk [2] .
  3. Cow’s milk protein may play a role in triggering type 1 diabetes through a process called molecular mimicry [3] .
  4. Across countries, populations that consume more dairy have higher rates of multiple sclerosis [4] .
  5. In interventional animal experiments and human studies, dairy protein has been shown to increase IGF-1 (Insulin-like Growth Factor-1) levels. Increased levels of IGF-1 has now been implicated in several cancers [5] .
  6. In interventional animal experiments [6] and human experiments [7] , dairy protein has been shown to promote increased cholesterol levels (in the human studies and animal studies) and atherosclerosis (in the animal studies).
  7. The primary milk protein (casein) promotes cancer initiated by a carcinogen in experimental animal studies [8] .
  8. D-galactose has been found to be pro-inflammatory and actually is given to create animal models of aging [1] .
  9. Higher milk intake is linked to acne [9] .
  10. Milk intake has been implicated in constipation [10] and ear infections [2] .
  11. Milk is perhaps the most common self-reported food allergen in the world [11] .
  12. Much of the world’s population cannot adequately digest milk due to lactose intolerance.

So despite being very pleased that the public is glimpsing some of the evidence against milk in this recent study (though they also could be hearing about the benefits of cheese and yogurt from this same study), I think there is a far more powerful story a story that takes into account the largely hidden context of diet and dairy research. There is a wealth of indirect evidence of very serious possible harms of consuming dairy foods, and, on the flip side, the evidence that milk prevents fractures is scant.

As we look beyond the headlines, it is hard to think that we should continue to consume the lactation fluid that exists in nature to nourish and rapidly grow calves.