Calcium

Calcium is a mineral stored primarily in our skeleton and, along with fiber, magnesium, and potassium, found lacking in most American diets. Dairy is the number-one calcium source in the United States, but it’s also the number-one source of saturated fat and a top food allergen. Getting calcium from dairy (but not nondairy sources) also appears able to stimulate prostate cancer cell growth and increase total prostate cancer risk.

Don’t we need dairy for strong bones? A meta-analysis of cow’s milk intake and hip fracture studies showed no significant protection, and a recent set of studies involving one hundred thousand men and women followed for up to two decades even suggested milk may sometimes increase bone and hip fracture rates. Researchers also investigated milk intake and mortality, as well as fracture risk in large populations of milk drinkers. In addition to significantly more bone and hip fractures, they found higher rates of premature death, more heart disease, and significantly more cancer for each daily glass of milk women drank. Men with higher milk consumption also had a higher rate of death, although they didn’t have higher fracture rates. The lack of association with fermented milk products suggested the milk sugar galactose may be to blame.

What about kidney stones? Most are composed of calcium oxalate, which forms like rock candy when urine becomes supersaturated with calcium and oxalates. For many years, doctors assumed that because stones are made of calcium, they should counsel their patients to simply reduce calcium intake, but this changed with a landmark study that pitted the traditional, low-calcium diet against a diet low in animal protein and sodium. After five years, the study found that eating less meat and salt was about twice as effective as the conventionally prescribed low-calcium diet, cutting kidney-stone risk by half.

What about calcium supplements? Calcium from supplements, but not from whole food sources, appears to increase the risk of heart disease, stroke, and death.

Are there calcium sources available without health-related risks? Dark green leafy vegetables, like kale, broccoli, and bok choy, are relatively rich in calcium that is absorbed about twice as well as the calcium in milk. What’s more, they also contain fiber, folate, iron, and antioxidants, some of the very nutrients lacking in dairy. I recommend getting at least 600mg of calcium daily via calcium-­rich plant foods—preferably low-­oxalate dark green leafies, which includes all greens except spinach, chard, and beet greens (all very healthy, but not good calcium sources due to their oxalate content).

Image Credit: fdecomite / Flickr. This image has been modified.