Dietary Calcium - Sources Of Calcium: Osteoporosis

Content provided by the Faculty of the Harvard Medical School

Dietary calcium

Luckily, if you want to increase your dietary calcium intake, you have plenty of calcium-rich foods from which to choose. Table 3 shows how much calcium is found in common foods. You may be surprised at how much you can accomplish by making a few substitutions, such as opting for firm versus regular tofu, or choosing ricotta instead of cottage cheese.

Dairy products are rich in calcium.

As the table reveals, dairy products provide the most concentrated sources of calcium. Moreover, they're often fortified with vitamin D, supplying the daily requirement of that nutrient in one serving. For these reasons, many osteoporosis experts favor dairy products as a source of calcium. But dairy products have their detractors. Critics argue that many dairy products are high in unhealthy saturated fats and that they can cause gas, bloating, and diarrhea in people with lactose intolerance. They also cite research suggesting that people who consume a large amount of dairy products may be at greater risk for prostate or ovarian cancer.

In response, proponents of milk and other dairy products point out that an increasing array of reduced-fat milks, yogurts, and cheeses makes it possible to cut fat and calories without skimping on calcium. In fact, many of these products contain slightly more calcium than their high-fat counterparts do. It's also true that if you're lactose intolerant and have trouble digesting dairy products, lactase — either taken as a pill or in liquid form — can help you enjoy these foods without worrying about unpleasant side effects. You can even find some dairy products on your grocer's shelves that already have lactase added. And both sides of this debate acknowledge that more research is needed before it's clear whether dairy products affect the risk for prostate or ovarian cancer.

While milk and other dairy products are certainly a rich source of calcium, other foods can also help you meet your daily requirements. Just a cup of fortified orange juice supplies about 300 mg of calcium, and a cup of some fortified cereals, such as Whole Grain Total, offers 250 mg of calcium. The plant kingdom is also calcium-rich, with spinach, dried beans, and nuts among the best sources. However, the calcium content can't always be accepted at face value; some vegetables and grains contain substances that undermine calcium absorption. For example, the oxalic acid in spinach and rhubarb combines with the calcium in these plants so that it isn't readily absorbed. Insoluble fiber, such as that in wheat bran, also reduces calcium absorption, but soluble fiber, such as that in fruit pectins, does not affect calcium absorption. To further complicate matters, there is no easy equation for determining how much of the calcium content of a fruit or vegetable is actually absorbed.

Food labels, although helpful, often require translating. Packaged foods list calcium content not in grams per serving, but as a percentage of the FDA's Daily Value, which is 1,000 mg for all adults. (However, if you are trying to fill the daily calcium requirement recommended by the National Academy of Sciences, you may need 1,200–1,300 mg a day.) To determine how many milligrams of calcium per serving a product contains, multiply the percentage figure on the package by 10. So, for example, if a product's food label says that one serving provides 20% of your daily calcium requirement, that means it contains 200 mg of calcium.

Last updated:	January 23, 2007