The answer may be that dairy isn’t the great source of calcium we thought it was. Evolutionarily speaking, dairy is a new food. For most of human history, only nursing young have relied on milk, and many cultures still exclude dairy from their diets, notably in Asia and Africa. In China, where dairy plays little to no role in the traditional diet, hip fracture rates are some of the lowest in the world, although as the nation continues to Westernize, this is changing. One reason might be that in order for your body to process calcium, magnesium must also be present. Fruits and vegetables are high in magnesium, so when they serve as primary sources of calcium, calcium/magnesium ratios are pretty even, around 1:1. When dairy is the primary calcium provider, as it is in the West, calcium is favored over magnesium in ratios closer to 12:1.
It’s all about balance; if you get too much magnesium, calcium absorption would also be affected. You can take calcium/magnesium supplements, but be careful—many women find that magnesium supplementation can cause diarrhea and uncomfortable loose stools. The best thing is probably to work at eating more natural food sources of the nutrient. We recommend eating magnesium-rich foods such as dark-green and leafy vegetables, nuts, legumes, and brown rice.
Not all dairy foods are created equal. Milk may be better and safer than processed cheese or acid-curd products such as cottage cheese. This is probably because these products are high in both sodium and acid, both of which influence calcium release and absorption. If you consume a lot of milk, we recommend you opt for organic, because the cows producing organic milk are raised without unnecessary antibiotics and other undesirable chemicals (organic milk is, unfortunately, more expensive and not accessible to everyone).
Beyond how you take in calcium, there are other controversies. Some people argue that calcium intake has been overemphasized and definitive evidence is lacking that either taking in a lot of it from food or supplementing it with pills provides any benefit. Gillian Sanson calls the belief that calcium alone can save bones “the myth of the magic bullet,” and she writes, “Because the amount of calcium in the blood is so carefully regulated, increasing calcium does not necessarily mean that the body will build more bone.” She adds that cultures with low calcium intakes haven’t been shown to have problems with bone formation, suggesting that perhaps only seriously calcium-deficient diets pose a problem. So while getting extremely small amounts of calcium may well cause bone problems, megadosing on the nutrient will not necessarily prevent or fix them.
Bantu women of Africa consume only about 350 mg of calcium a day. Compare that with our recommended average of 1,200 mg to 1,500 mg, and you would expect these ladies to be disabled and fractured in disproportionately high rates. Not only is this not the case, but Bantu women tend to lose a strikingly small number of teeth and break few bones.
Although no one is sure why this is, one theory is that the vegetable-based diet that Bantu women consume is low in animal protein as well as calcium. Although protein is necessary for building bone, excessive meat consumption of the sort rampant in the United States may cause higher acid levels in the blood and urine, which the body tries to balance out by releasing calcium. This may be increasingly true as we age and our kidneys are less able to handle high acid loads. Consuming protein through vegetable sources, like consuming calcium, seems to have advantages over animal foods. We aren’t recommending you give up steak or hamburgers, just that you balance your diet to include more vegetables and less meat.
Not everyone thinks losing calcium in the urine will hurt your bones. A Canadian study tested high-protein (from vegetable sources) diets and found that although greater amounts of calcium were excreted, there seemed to be no negative impact on the balance of calcium in the bones.
Another element of the Western diet that may hurt bones is our high salt intake. Kidneys have to let go of calcium in order to get rid of salt from the body. This might be a reason early humans, who ate very little calcium, had such good bone mass.
Many studies of older women and calcium have yielded disappointing results. In 2005, the Women’s Health Initiative (WHI) calcium and vitamin D trials found that women who took a calcium regimen prescribed by the National Institutes of Health (NIH) over a ten-year period showed no statistically significant improvement in their bone mass or reduction in their fracture rates.
Most of us accept as gospel that calcium will improve our bones, so were the WHI findings a radical revision of conventional wisdom? Or was the design of the study itself flawed?
There were some significant problems with the WHI study. For starters, it excluded women who had been taking calcium their whole lives. Researchers were really testing to see if calcium intervention at a later stage of life—postmenopause—would make a difference. Remember: all the WHI women were postmenopausal. Since we know that much of your bone mass is laid down in your teens, twenties, and even thirties, one thing the study may reinforce is the importance of getting calcium as a young woman. Some other problems: there were concerns about the length of the study—it might have been too short to show reliable results -- and it wasn’t careful about whether participants were also taking bisphosphonates or estrogens in addition to calcium, two things that could have had major impacts on bone mass.
The Nurses Health Study, which looked at various health patterns in 121,701 women, found that neither milk nor calcium consumption seemed to make a difference when it came to preventing broken bones. Intriguingly, the Nurses Health Study investigators also determined that milk and calcium consumption as a young woman didn’t significantly reduce their risk for fractures (although there was a nonsignificant reduction found in hip fracture rates; again, it may or may not have been a coincidence).
So why should older women bother with calcium? Among other reasons, because we know that the nutrient is important for so many reasons, and there are still too many unanswered questions. The Nurses Health Study results showed that continuing to drink milk and take calcium seemed to counteract the bad effects that a lifetime of caffeine drinking could have on the hip and spine. Also, the Archives of Internal Medicine reported that calcium and vitamin D intake were associated with reduced PMS. We know that women who have PMS are more likely to suffer from bad menopausal mood swings. Perhaps getting adequate amounts of calcium and vitamin D can help your mood.
And remember, getting calcium from food is better than from supplements. Dr. Robert Heaney, an endocrinologist and internist at the Osteoporosis Research Center at Creighton University in Omaha, Nebraska, says, “The five best sources of calcium are food, food, food, fortified food, and supplements in that order.”
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