Is Calcium Safe?

Many factors are involved in bone density: bone cell growth, bone cell destruction, mineralization (adding more minerals like calcium to bone matrix) and resorption (removal of minerals like calcium from bone matrix). In childhood, when bone cell growth exceeds bone cell destruction, our bones and our bodies become bigger. Once we’re fully grown, bone growth balances bone destruction. After the age of 30, bone cell destruction slowly begins to exceed growth and we gradually lose bone mass as we age. After 50, declining levels of estrogen and testosterone can speed the process.

But age isn’t the whole story. Physical activity can slow or even reverse bone loss at any age. Simply put, our bones stay strong when we stay active. Weight-bearing exercises and activities that place forces on bones stimulate their growth, ensuring that the body will be able to withstand future forces. When we become sedentary, because the forces that stimulate bone growth no longer exist, we lose bone mass.

Regular exercise not only keeps bones strong as we get older, it also improves balance and coordination, making falls and fractures less likely. In a study published in the Journal of the American Medical Association, researchers at Harvard found that walking at least four hours per week was associated with a 41 percent lower risk of hip fractures in elderly adults, compared to those who walked less than one hour per week. For best results, I recommend participating in a variety of activities that apply forces to a variety of bones. People who do not exercise regularly should talk to their doctor before they start.

Each day, the average person usually consumes 300 mg of calcium from foods that are not especially rich in calcium. Add to that foods that are rich in calcium, including dark green leafy vegetables like spinach (300 mg per cup) and collard or turnip greens (400 to 500 mg per cup), dairy products like yogurt (350 mg per cup) and cheese (300 to 400 mg in 1.5 oz), and tinned fish with soft bones that you eat, like wild salmon or sardines (400 mg in 3 oz). Adults who consume at least three daily servings of dark green leafy vegetables, fish (with bones) and/or dairy products have no need to supplement calcium at all.

For those who do need to supplement, calcium comes in several forms. Calcium carbonate is inexpensive to produce and widely available, but it is more difficult to digest. Better choices include calcium citrate, calcium malate and calcium aspartate. These forms are more costly to produce and take up more space inside capsules and tablets, but they are better tolerated and more easily digested and absorbed by the body.

Vitamin D is necessary for the absorption and utilization of calcium. Sunlight stimulates the skin to produce vitamin D (which is why deficiencies are most common in winter and in areas furthest from the equator) but vitamin D can also be found in food. Good sources include cod liver oil, fish (especially sardines, which are also a good source of calcium when consumed with the bones), mushrooms, egg yolk, lamb and beef.

Vitamin D is often added to calcium supplements. Small amounts are usually not worrisome, but larger amounts (1,000 IU per day or more) should only be taken if blood tests show that levels are low. Taking too much vitamin D in supplement form can cause it to accumulate in the body and reach toxic levels. If you aren’t sure if you need it, ask your doctor for the test. It’s worthwhile because low levels of vitamin D have been linked to an increased risk of osteoporosis, autoimmune disease, depression, heart disease and cancer. Vitamin D should always be taken with food or fish oil for optimal absorption.