Losing weight should have a positive effect by mitigating health risks and improving overall well-being. And, of course, for anyone struggling with the consequences of being overweight, dropping those extra pounds restores energy, lowers both blood pressure cholesterol levels, and decreases stress on the bones and ligaments. But diets may take away more than pounds. There is evidence that diets can also take away bone strength.

A few years ago, a study from Rutgers University revealed some worrisome findings on bone health. After only six weeks, the bones of the women on a weight-loss diet were not absorbing as much calcium as women who were not dieting, even though the dieting women were taking an additional 1,000-mg calcium supplement. Since these women were post-menopausal, the researchers suggested that dieting itself might make older women more vulnerable to fragile and easily breakable bones.

Since many weight-loss plans don’t emphasize the need to consume calcium-rich dairy products (Weight Watchers is an exception), the obvious answer to the prevention of weakening bones is taking a calcium supplement. After all, haven’t women been told for years that supplements are a reliable source of calcium, especially for people who may not eat dairy products (like vegans or people who don’t like foods that come from milk)?

Now it looks like calcium supplements are out, and calcium-rich foods are in.

Jane Brody recently discussed the latest information about the benefits and risks of calcium supplementation in the New York Times Science Section. She reported that the United States Preventive Services Task Force reviewed over 130 studies on whether calcium and vitamin D supplements prevent bone fractures. Their conclusion: They don’t. It turns out that calcium from food is substantially more effective in promoting bone health than calcium taken as a supplement. Moreover, some reports have now pointed to a significant link between calcium supplements and an increased risk of heart attacks.

This information that calcium supplements are not as reliable as food in maintaining bone health removes the safety net that many women depend on. This is especially true for dieters because knowing that you, the dieter, could swallow a couple of calcium pills made you confident that you were getting enough of this vital mineral, even if you stopped eating dairy products to save some calories.

So now what do you do?

The first thing is to know how much calcium you should be taking into your body every day.
Women and men under 51 need 1,000 mg a day. Women need 200 more mg over 51, so their daily intake should be 1,200 mg. No one yet knows why weight loss should increase the need for calcium, but there is useful information about the best way to get your bones to absorb this mineral:

  1. You should not eat more than 500 mg of calcium at any one time, because that seems to be the maximum amount that a body can process per ingestion;
  2. Sunshine, or other sources of vitamin D, are necessary for calcium absorption. If your skin is not exposed to vitamin-D-enhancing sunshine, do take a supplement or eat vitamin-D-fortified foods (cod liver oil, of course the worst-tasting, is probably the best source);
  3. Caffeine in coffee and chocolate, as well as caffeinated energy drinks and sodas, increase the loss of calcium from the body. Don’t overdo it on the caffeine or else your bones may become too weak to support your energized body;
  4. Just because a food contains calcium doesn’t mean it will be absorbed by your body. Whole grains, peanuts, soybeans and most leafy green vegetables like spinach contain compounds that stick to calcium and prevent the mineral from entering your body.[1] Kale, mustard greens and collard greens are exceptions, as they don’t contain the calcium-grabbing compounds. (Tofu, which is made from soy, will yield up calcium if it is processed with calcium sulfate and nigari. FYI: Nigari is the Japanese name for magnesium chloride. Both compounds are responsible for the formation of the solid part or block or the tofu.)
  5. Read food labels. How else can you decide between cow, soy, almond, and rice milk? They all vary in calcium content and calories, and some of these dairy milk-like beverages are now fortified with more calcium than they were just a few years ago. Many foods that normally are calcium-free, such as orange juice and Total cereal, are also now calcium-fortified. If you put orange juice on your cereal in the morning (as my lactose-intolerant friend does), you may consume most of your calcium needs at breakfast; and to conclude,
  6. Convenience and calcium needs may conflict. Not all calcium-rich foods fit into your lifestyle, and dieting further limits what you can eat. Boiled kale and tofu burgers may not be foods you are going to prepare when you return from work at 8 p.m., so have alternatives available. Cottage cheese, yogurt and part-skim ricotta cheese are all low-calorie calcium sources, and can be blended into smoothies, pasta, soups, or used as toppings for calcium-fortified toaster waffles. Milk-based fish chowders are an excellent source of calcium, and if made with fat-free or low-fat milk, can easily fit into a dieter’s menu plan. Lasagna layered with low-fat ricotta cheese or cottage cheese and steamed kale can be made ahead of time, frozen in mealtime portions, and then heated up for a quick dinner. And if you can spare the calories, one-half cup of frozen Greek yogurt provides 15 percent of your daily calcium requirement (about 150 mg of calcium) and tastes good, too.

Even though dieting may make you vulnerable to bone loss if you don’t take these dietary precautions, remember that diets often have a beneficial effect on bone strength. Exercise, that other component of weight-loss programs, is essential in strengthening bones. Indeed, physical activity is essential to prevent, as well as reverse, bone loss. And if you do burn off enough calories, you really can eat that frozen Greek yogurt without guilt.


[1] Weaver, Connie & Proulx Heaney, Robert. Calcium in Human Health pp. 135-136

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