Our bodies certainly need calcium. Most of it is used to strengthen bones and teeth, but it has other important functions. Calcium stabilizes cell membranes and aids the transport of compounds into and out of cells. It regulates neurotransmitters, substances that transmit nerve impulses, and helps initiate blood clotting. And without calcium, muscles, including the heart, don’t contract properly. So how much is the right amount?
Putting more calcium into your body doesn’t necessarily mean putting more calcium into your bones. Bones are constantly remodeling themselves and this complex process is controlled by a complex system of hormones. It is not controlled by the amount of calcium you take in (although calcium must be present in the blood before it can be incorporated into bone matrix).
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.
Osteoporosis
The number one reason that people take calcium supplements is to prevent bone loss and osteoporosis. But for most older people, osteoporosis is not a disease at all. It’s a natural aging process. The real problems are falls and fractures. Only one in four elderly individuals who sustain such injuries are able to return to their pre-fracture activity level. Seventy-five percent of older adults who survive falls require specialized long-term care in a rehabilitation facility or nursing home, and twenty-five percent die within one year.
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.
Calcium Supplements
Ideally, calcium should come from our diet. When it doesn’t, it must be supplemented. Our bodies probably need about 1000 milligrams (mg) of calcium each day, but before you start taking supplements, evaluate your diet and estimate your true needs.
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.
Other Important Nutrients
Individuals who take calcium supplements should supplement magnesium as well. The ideal ratio is 1:2 (half as much magnesium as calcium) so if you take 400 mg of calcium each day, balance it with 200 mg of magnesium.
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.
Plant-Based Diets
Remember that supplements are no substitute for a healthy diet and that calcium input is as important as calcium output. Excessive consumption of coffee or alcohol, and diets high in sodium, animal protein and grains can cause the kidneys to excrete more calcium. But plant-based diets high in vegetables and fruits, and low in sodium additives, cause the kidneys to retain more calcium. It’s a great reason to eat plenty of dark leafy greens and avoid processed foods.
References available upon request.
Dr Sarah Cimperman
is a naturopathic doctor in private practice in New York City. For more information, call 646-234-2918 or visit www.drsarah cimperman.com. Read her blogs online at www.adifferentkindofdoctor.blogspot.com and www.naturopathicgourmet.blogspot.com.
No comments:
Post a Comment