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Calcium intake among Americans of all ages is significantly less than the amount recommended to assure normal bone health. In children and teenagers, this has led to a lower total amount of calcium in the bones in early adult life. From age 20 onward, about 1 percent of the total calcium is lost from bones each year. More is lost around menopause because of reduction in the levels of the female hormones estrogen and progesterone.
Over time as the bones become critically thin, osteoporosis develops, and that leads to loss of height, curvature of the spine (called a dowager’s hump) and serious fractures that can occur spontaneously or after a fall.
Particularly serious are fractures of the hip, after which fewer than 50 percent ever walk again; risk of death in the following year is 25 percent greater, and a large fraction require nursing home placement.
While osteoporosis is largely a disease in women, it also occurs in men but usually about 10 years later. In other words, the bones of an 80-year-old man are as likely to be osteoporotic as those of a 70-year-old woman.
Adequate lifelong intake of calcium and vitamin D, together with exercises such as impact aerobics and weight training, help build bone and protect against osteoporosis. Because of risks of breast and cervical cancer, blood clots, headaches and heart attacks and strokes, hormone replacement therapy is not recommended to prevent osteoporosis. In men and women over age 60, supplementing the daily diet with 500 mg of calcium plus 200 international units of vitamin D is recommended.
Concerns about calcium supplementation began when a German study published in the journal Heart in 2012 showed that some women taking calcium supplements had elevated levels of calcium in their blood, which in turn caused a substantially higher risk of heart disease. However an increase in blood levels is not related to the calcium absorbed from the bowel, either from the diet or supplements.
The calcium concentration in the blood is finely regulated by vitamin D, which promotes absorption of calcium from the bowel, and by a hormone called parathyroid hormone, produced by the parathyroid glands nestled within the thyroid gland in the neck.
A slight increase in calcium leads to a greater production of parathyroid hormone, which drives calcium into bone and maintains a normal level. Low serum calcium reduces parathyroid levels, and calcium leaches from bone to make the serum value normal.
Any increase in calcium entering the body is diverted into bone and does not raise serum calcium levels. But when there is an abnormally high level of either parathyroid hormone or vitamin D, the level of calcium in blood increases. In this circumstance, calcium deposits in arteries makes them thick and irregular and predisposes to blockage that can lead to a heart attack.
Nevertheless, many experts in the field have begun to argue that too much calcium in the diet may be bad for you and may adversely affect the heart. In an article just published in the Journal of the American Medical Association, researchers examined 388,229 men and women who were participating the National Institutes of Health-AARP Diet and Health Study. The subjects were followed for 12 years commencing in 1995.
The results showed that men (but not women) taking 1,000 mg calcium daily as a supplement were 20 percent more likely to die from heart disease than those not taking supplements. Based on this information, it seems prudent for men not to take calcium supplements.
The average American diet that is totally free of dairy products has approximately 800 mg of calcium. A 50- to 70-year-old man requires 1,000 mg of calcium daily, and over 71, the requirement is 1200 mg. Increasing calcium requirements to the recommended level can readily be met by drinking a glass of milk or eating an ounce of cheese or a cup of yogurt, all of which contain 300 mg of calcium. To date, calcium from food sources has not been shown to have any serious adverse effects.
We want to recognize disease risk and do everything possible to prevent it. With adequate dietary calcium in our diet, combined with appropriate exercise and screening, the risks of osteoporosis can be reduced. A calcium supplement that seems so harmless increases heart attack risk and should be avoided in adult men.
In medicine, nothing ever stays the same.