Manager, Nutrition Services
Joslin Diabetes Center
You are wise to be concerned about getting enough calcium. Inadequate intake of calcium can increase the risk of postmenopausal osteoporosis as well as possibly play a role in weight gain and high blood pressure. The recommended amount of calcium for adults through middle age is 1,000 mg per day. This increases to 1,200 mg for those over age 51. Dairy products such as milk and yogurt, at 300 mg per serving, are a major source of calcium in the diet, but vegans as well as those with lactose intolerance can consume adequate calcium from other dietary sources with a little planning. Fish eaten with bones, such as sardines and canned salmon, provide almost as much calcium as dairy products. Other excellent sources of calcium are soy beverages, juices and cereals that are fortified with calcium and tofu that has been processed with calcium sulfate or nigari (magnesium chloride). Leafy green vegetables, such as collards, bok choy, kale and turnip greens, are also a good source of this important nutrient. Many of the leafy greens provide between 80 and 180 mg of calcium per serving. Although most leafy greens contain calcium, the calcium in some varieties is not readily absorbed during the digestive process. The calcium in vegetables such as spinach, rhubarb, Swiss chard and beet greens is largely unavailable due to the presence of oxalic acid, which binds calcium, reducing its absorption. For those who are don't eat a lot of vegetables, supplements may be the answer. Supplements containing calcium carbonate or calcium citrate are well absorbed and tolerated. It is best to take no more than 500 mg of calcium at a time because absorption declines with greater amounts. Whether you obtain your calcium from dietary sources or from supplements, reducing your sodium intake can help you decrease calcium losses in the urine. And regular weight-bearing exercise such as walking or running helps strengthen bones.