Milk and Osteoporosis: The Calcium Myth
In 2009, I was part of a UCLA study of cyclists and triathletes that looked at how endurance exercise impacted bone density, testosterone, and the production of inflammatory cytokines produced during long, frequent periods of exercise. Some of my cycling teammates were enticed to sign up because the tests included a free body fat percentage scan, but it turned out that the DEXA scan’s most important feature for me was its ability to measure bone density. Of the 200 athletes tested, I had the worst (lowest) bone density. Having broken my pelvis twice in bike racing crashes prior to the DEXA scan, it wasn’t totally unexpected, but it did alarm the doctor conducting the study who urged me to see a doctor to get on prescription meds. I didn’t, and five months later, I broke my hip in another bike race and was forced to address the osteopenia weakening my bones that would devolve further into full blown osteoporosis. I grew up in a household that believed drinking cow’s milk several times a day was all we needed to build strong bones—so how did this happen to me?
Although some studies have reported the beneficial effects of milk and dairy product consumption on osteoporosis and risk of fracture, the findings are conflicting.Purpose: We summarized earlier data on the association between milk and dairy intake and risk of osteoporosis and hip fracture through a meta-analysis.Methods: A systematic literature search of relevant reports published in PubMed, ISI (Web of Science), EMBASE, SCOPUS, and Google Scholar until August 2018 was conducted.Results: Total dairy intake was protectively associated with reduced risk of osteoporosis based on cross-sectional and case-control studies (0.63; 95% CI: 0.55-0.73). Milk consumption was not associated with the risk of osteoporosis (overall RR = 0.79; 95% CI: 0.57-1.08). In non-linear dose-response meta-analysis, increase intake of dairy (at the level of 0 to 250 grams per day) was associated with a reduced risk of osteoporosis (Pnonlinearty = 0.005). Meta-regression of included studies revealed an inverse linear association between dairy and milk intake and risk of osteoporosis; such that every additional 200-gram intake of dairy and milk was associated with a 22% and 37% reduced risk of osteoporosis, respectively. In terms of hip fracture, milk consumption was associated with a 25% reduced risk of hip fracture only in cross-sectional and case-control studies (overall RR = 0.75; 95%CI: 0.57-0.99). In linear meta-regression, every additional 200-gram milk intake per day was associated with a 9% greater risk of hip fracture in cohort studies.Conclusion: Despite an inverse association between milk and dairy intake and risk of osteoporosis and hip fracture in cross-sectional and case-control studies, no such association was seen in cohort studies. Given the advantages of the cohort over case-control studies, we concluded that a greater intake of milk and dairy products was not associated with a lower risk of osteoporosis and hip fracture.
Osteoporosis: Who Is at Risk
Bone density issues often plague cyclists because it is a non-weight-bearing sport. Since cycling had been my primary form of exercise for the last several decades, the odds weren’t in my favor. Further, problems with bone density often occur with “small-boned” people, and since I weigh in at 132 pounds, that accurately describes my bone structure. So, I had a couple things working against me, but I trusted that the cow’s milk that I drank daily would counteract these pre-existing conditions. I was wrong.
The dairy industry preaches that we need to drink cow’s milk several times a day in order to get enough calcium and vitamin D to build and maintain strong bones. I drank plenty of it—often chugging a quart of chocolate milk after a workout because I saw professional and Olympic athletes in commercials and magazine ads doing it. But that ended up causing me gastric distress (I’ll spare you the intimate details), and my bones were weak and broke easily anyway.
Does Milk Help Prevent Osteoporosis?
According to a study published by the British Medical Journal, hip fracture rates are highest in countries with the highest calcium consumption. Women who drink the 3+ glasses of milk per day recommended by the US Department of Agriculture increased their risk of hip fracture by up to 60 percent. So why are we told to drink milk to build strong bones?
The British Medical Journal’s research indicates that the milk sugar D-galactose promotes oxidative stress and inflammation, which are linked to decreased muscle and bone mass. Also, too much phosphorus—necessary for calcium absorption—is not beneficial. Cow’s milk is high in phosphorous, which may lead to calcium resorption, according to the Indian Journal of Clinical Biochemistry.
What Other Foods Have Calcium?
Instead of relying on cow’s milk, Amy Joy Lanou—author and chair and professor at the North Carolina Center of Health and Wellness at the University of North Carolina Asheville—advocates getting calcium from plants. She points out that calcium ingested from a variety of plant-based sources is up to two times as bioavailable as calcium ingested from cow’s milk and dairy products such as yogurt and cheese. According to The American Journal of Clinical Nutrition, one cup of cooked kale has the same amount of absorbable calcium as one cup of cow’s milk. Lanou recommends eating calcium-rich foods such as kale, tofu, broccoli, turnip greens, mustard greens, bok choy, white beans, sesame seeds, tahini, kidney beans, and almonds.
“People don’t know that they don’t need to have dairy to get calcium in the body. I think that’s a misconception out there. In a whole-foods, plant-based diet, you get all your nutrients if you eat it correctly, and you can build strong bones just through a plant-based diet,” said Dr. Micah Yu, a rheumatologist, board-certified internal medicine doctor, and certified lifestyle medicine doctor based in Southern California.
Can You Get Too Much Calcium?
Dr. Yu does recommend taking a vitamin D supplement. “The building blocks of bones are calcium and vitamin D. I tell my patients that everyone should at least have a normal vitamin D level. Even though we get a lot of sun, it’s still hard to get normal vitamin D levels.”
What we don’t need is to increase our calcium intake to build strong bones, according to the World Health Organization. They advocate that countries like the US that have high rates of hip fractures from the overconsumption of calcium reduce the daily intake to 400-500 mg, which is far less than what the dairy industry has been telling us to get. The dairy industry recommends 1000 mg per day for adults, 1300 mg per day for adolescents, and 800 mg per day for children. The calcium in dairy products also comes with the added risks of heart disease, prostate cancer, and diabetes.
Can You Heal Osteoporosis?
A year after breaking my hip, I had to replace it, and a couple years later, I started a two-year course of daily injections to build back my bone density from osteoporosis to normal. Simultaneously, I added more weight-bearing exercise to my training program. It began with running and hiking, and eventually, I returned to the ice as a hockey player. And of course, I continued lifting weights several times a week as I did prior to breaking my hip. During that process is when I switched from vegetarian to vegan, hence removing all dairy from my diet. A session with a nutritionist put my mind at ease when he reassured me that I was getting more than enough calcium from my plant-based diet. Enough so that I do no longer need to take calcium supplements. It turns out that the best way to build strong bones is to eat more fruit and vegetables.
“Evidence collected during the past 20 years shows that we need to rethink our strategies for building and maintaining strong bones throughout our lives,” said Lanou. “Milk is unnecessary.”
Can Drinking Too Much Milk Make Your Bones More Brittle?
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If you drink milk to keep your bones strong, there’s good logic in it. Milk and dairy products are concentrated calcium sources, and we know calcium fortifies bones and prevents osteoporosis.
However, can drinking too much milk make your bones more brittle? Researcher and dietitian Gail Cresci, PhD, RD, walks through whether or not it’s safe to drink a lot of milk.
Should I cut back on my milk intake?
A Swedish study suggests that while milk may be good, more is not better.
This study found that too much milk – three or more glasses a day – was not only associated with mortality but also an increased risk of fracture and hip fracture.
Plus, it found that women who reported drinking three or more glasses of milk each day nearly doubled their risk of death in relation to women who drank less than one glass each day. Men were not as affected as women, but those who drank three or more glasses of milk each day still showed a significant increase in mortality.
A separate study reported that higher milk and dairy product consumption does not necessarily lower the risk of osteoporosis and hip fracture as noted in cohort studies versus looking at case-control and cross-sectional studies.
Does this mean you shouldn’t drink milk? Don’t go shunning the jug just yet.
One study found that milk contributes to meet nutritional recommendations and may help protect against chronic diseases. Although it’s true that milk and dairy are among the most calcium-rich foods you can eat, there are other substances in milk that may warrant some moderation.
“While the Swedish study raises interesting questions, there is not strong enough evidence to warrant a restriction on milk,” says Dr. Cresci.
The importance of vitamin D and diet
Vitamin D and a diet filled with calcium is key to strong bones.
“Calcium is linked with bone health, but vitamin D promotes calcium absorption and maintains adequate blood levels of calcium and phosphate to allow for normal bone mineralization,” says Dr. Cresci.
Without enough vitamin D, bones can become thin and brittle and the formation of strong new bone can be prevented. Vitamin D protects older adults against osteoporosis. Your doctor may suggest you get a blood test done to figure out your vitamin D level. However, no such test exists for calcium levels.
While milk contains 300 mg of calcium per cup, there are many other good dietary sources to keep in mind. Make sure you’re eating an adequate amount of calcium by including cheese, yogurt, greens (collards, kale), soybeans, figs, broccoli, oranges, sardines and salmon (with bones) and many fortified foods into your food rotation.
“If you want to drink milk for strong bones, I recommend no more than one glass a day,” says Dr. Cresci. “Do this in addition to a mixed diet rich in calcium. If you are unable to consume adequate amounts in your diet, consider supplementation with about 1200 mg of calcium and 600 to 800 IU of vitamin D daily, especially in winter months.”
Milk and dairy consumption is associated with reduced risk of some chronic diseases and had a beneficial effect on bone mineral density, but not risk of bone fracture. Milk consumption has some evidence to support against chronic diseases (type 2 diabetes), cardiovascular disease (stroke) and some cancers (colorectal, bladder, gastric, breast).
Consult with your doctor or dietitian before taking any new supplements.