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Thursday, November 1, 2007

The Calcium Debate

Osteoporosis in the United States has been called an epidemic. It has also been called a myth, a normal part of aging rather than a disease. In the middle of this debate is calcium. Experts recommend supplementation as a way to prevent osteoporosis and bone fracture, but worldwide population studies have shown that people who consume the most calcium (like those in the United States and Scandinavian countries) also have the highest rates of fracture, while people who consume the least (like those in Asian and Mediterranean cultures) have the lowest fracture rates. If bone loss is the problem, is calcium really the answer?
   
Bone Mineral Density

Bones are composed of protein matrix and minerals like calcium, and they continuously regenerate themselves. Cells called osteoclasts break them down and cells called osteoblasts build them back up. The balance between bone destruction and bone growth determines bone density. The body favors growth during younger years while the skeleton is developing and maturing, but after the age of 30, the balance shifts toward bone loss. Around age 50, declining levels of estrogen and testosterone may speed the process.

Below average bone mass is known as osteopenia when the deficiency is slight and osteoporosis when it becomes more advanced. Low mineral density makes bones more fragile and increases the risk of fracture. For older adults, hip fracture is often a life-changing event. Only 25 percent of elderly individuals who sustain such an injury are able to return to their pre-fracture activity level. Most require specialized long-term care in a rehabilitation facility or nursing home and 25 percent die within one year.

Calcium

Researchers have found that a high intake of calcium does improve bone mineral density, but long-term observational studies have not found lower rates of bone fracture with high calcium intake. Some studies have even suggested that too much of the mineral may increase the risk of kidney stones, prostate cancer and ovarian cancer.

The National Osteoporosis Foundation recommends 1000 milligrams (mg) of calcium each day for adults until age 50, and 1200 mg per day thereafter. Because these routine recommendations do not take dietary sources into account, many people get more calcium than they need. The average adult in the United States consumes about 300 mg of calcium per day from non-calcium-rich foods. Each serving of dairy products (one cup of milk or yogurt, or one and a half ounces of cheese) and each cup of cooked spinach add approximately 300 mg of calcium. Three ounces of sardines (with bones) or one cup of cooked collard or turnip greens accounts for an additional 400 mg. When considering supplementation, these estimations make it easy to calculate true calcium needs.

Calcium should always be taken with magnesium in a 2:1 ratio. Calcium citrate is the most easily assimilated form, which is optimal for older adults who tend to have less stomach acid. Studies have also shown that unlike other forms, calcium citrate inhibits kidney stone formation.

Other Influences

Calcium is not the most important factor in bone health. Studies have shown that weight-bearing and resistance exercises, as well as impact activities like walking, jogging and dancing, are the best protection against osteoporosis and bone fracture. The reason behind the research is simple: force applied to bone triggers growth and the absence of force leads to deterioration. Exercise not only makes bones stronger and more resistant to breaking, it strengthens muscles and improves balance and coordination so falls are less likely. Walking at least two hours each week can reduce the risk of hip fracture in elderly adults, but choosing a variety of activities that apply force to a variety of bones gives the best results.

Other factors found to have a positive affect on bone mass include vitamins D and K; both are necessary for the absorption and utilization of calcium. Researchers in Germany who studied black cohosh found that the herb had positive effects on bone metabolism equal to estrogen replacement therapy, but without increasing the risk of breast cancer, heart disease, blood clots and strokes.

In contrast, factors that negatively impact bone density include smoking, diets high in protein and/or sodium, and consumption of saturated fat, caffeine, soda and excessive amounts of alcohol. Osteoporosis can also result from chronic kidney disease, hyperthyroidism, certain kinds of cancer, stomach surgery and medications such as corticosteroids, anticonvulsants, antidepressants, tetracyclines, some cancer drugs, thyroid hormones and antacids containing aluminum.

The Bottom Line

The bottom line for stronger bones is regular exercise, outdoor activities and a healthy, balanced diet that includes foods high in calcium and at least one daily serving of dark green vegetables, rich in vitamin K, such as broccoli, turnip greens or spinach.

People who don’t spend enough time in the sun to generate adequate levels of vitamin D (determined by a simple blood test) can compensate by adding sardines, herring, salmon and/or cod liver oil to their diets.

To reduce the risk of falls and fracture, older adults should live in clutter-free environments with good lighting, have their sight and hearing tested annually, wear rubber-soled shoes and always use caution when walking on slippery or uneven surfaces.