Because milk and dairy foods supply so much of the calcium in the
typical diet, it's hard to tease them apart when using data from
epidemiological studies. With ovarian cancer, there's reason to
believe that dairy products are the culprit because of evidence
pointing to intake of lactose, the sugar in dairy foods, as a
risk factor. With prostate and colon cancer, the evidence points
to calcium itself.
Studies have repeatedly found that we're far better off getting
most of our nutrients from food rather than from pills. With
calcium, it's more complicated. In many ways, dairy products, and
milk in particular, are an ideal source of the mineral. The
calcium content is high and easily absorbed. But when dairy comes
into the diet, saturated fat comes with it, and high saturated
fat intake increases the risk of heart attack, stroke, and other
cardiovascular problems. A few studies suggest that dairy food
itself increases the risk of certain cancers (see the answer
above). Of course, people can easily get around the saturated fat
problem by buying nonfat products, but not everyone likes the
taste of those nonfat products. Many vegetables are a good food
source of calcium, but spinach, chard, and a few others also
contain oxalate, and the presence of oxalate interferes with the
absorption of calcium.
Food is still the best way to get calcium, with the best choices
being nonfat dairy products (in limited amounts), certain types
of fish (salmon, sardines), and certain vegetables (kale).
Whether you need to "top it off" with a supplement depends on
your diet and whether you're trying to adhere to the official
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