The Calcium Controversy: An Expert Warns That Supplements Are Not the Cure-All for Dowager's Hump
"Drink your milk" is no longer an admonition heard only by small children. In recent years most women have become concerned about getting enough calcium, fearing that if they do not they will join the 24 million Americans already suffering from osteoporosis, the disease that causes bone loss especially in women. Packagers of calcium-rich foods and supplements have played on these concerns with advertisements showing shrunken elderly women with bent spines, and sales of calcium supplements have surged in six years from $18 million to $240 million. Recent findings by doctors, however, indicate that this rush to calcium supplements may be premature for some. In fact, many women taking calcium supplements may be receiving little or no benefit.
Dr. B. Lawrence Riggs, 55, an endocrinologist at the Mayo Clinic in Rochester, Minn., has studied osteoporosis for more than 20 years. In his opinion calcium is not the easy fix for osteoporosis that most people believe. He spoke with Chicago bureau chief Giovanna Breu about the ongoing calcium controversy.
Who gets osteoporosis?
It's predominantly a woman's disease. Women of small stature and small bones are at greater risk than women with a larger build. Osteoporosis also tends to run in families.
Aren't men susceptible as well?
Men share with women the slow, age-related bone loss, but they have two advantages over women: They don't have a menopause and, regardless of stature, they start off with more bone mass than women.
Why the concern over osteoporosis now?
Osteoporosis involves more people than was thought. Our studies at the Mayo Clinic indicate that half of all elderly women eventually have bone fractures because of osteoporosis. Five years ago only 15 percent of Americans knew of the existence of osteoporosis, and now about 85 percent do. Although people are better informed, some have become needlessly frightened. I have young women coming to see me in their 30s who are afraid that if they don't have their five glasses of milk a day they're going to have a hip fracture in two or three years.
So what should we know about calcium?
Everyone needs a certain amount of calcium, probably 1,000 milligrams a day. But it's not established scientifically that calcium intake can prevent osteoporosis. There's evidence pro and con.
What did your studies at the Mayo Clinic indicate?
In a four-and-a-half-year project we measured bone density of 106 patients between the ages of 23 and 88. We did nor see a relationship between calcium intake and the rate of bone loss. We were unable to find a relationship between those who took a high amount of calcium and those who took a low amount of calcium.
If calcium is not the clear-cut and whole answer, what can prevent bone loss?
There's estrogen. For women in immediate postmenopause, estrogen is clearly most effective in preventing bone loss. Probably half of the fractures that occur as a result of osteoporosis can be prevented by prolonged estrogen replacement therapy.
When should estrogen treatment be started?
It is most effective during the eight to 10 years after menopause, when estrogen deficiency causes accelerated bone loss. If it is started after that period, there is little or no benefit.
What is the relation between calcium and estrogen?
If you take a high dose of calcium, the amount of estrogen required to prevent bone loss can be reduced. But many women take calcium thinking it can substitute for estrogen, and I believe everyone agrees that is not true.
But doesn't estrogen replacement therapy have risks?
Yes. Treatment must be monitored by a doctor and strictly regulated. To decrease the risk of endometrial cancer, you can take the hormone progestin, which blocks the excessive stimulation of the endometrium by estrogen. Although it is not a health risk, an added inconvenience is vaginal bleeding, similar to menstruation, caused by the combined estrogen and progestin. To reduce the risk of high blood pressure and blood clotting, administration of estrogen through the skin, by a dermal patch, may be effective.
Do you think people should take calcium supplements?
The advertisers are way out ahead of the scientific evidence. The need for calcium supplements is not as strong as the public has been led to believe, except during the extremes of life. Calcium supplements seem to be most beneficial in the young during growth and in the very old, when calcium absorption is impaired.
Then we should be concerned about calcium during the teenage years?
Yes. We put down 70 percent of our bone mass in about three or four years of our adolescent growth spurt. Even though you stop growing at 20 or so, you keep filling out bone until about 30. That's why it is important to have plenty of calcium during this entire period. It can come from either dairy products or calcium supplements.
When does bone loss start?
Bone loss begins at about 35, well before menopause. You continue to lose bone well up into the 80s and 90s.
Is a calcium supplement safe to take?
Except for a small percentage of people with high blood calcium or kidney stones, calcium is really quite safe. It's relatively inexpensive, so until the answers are in, why not take it?
How much calcium should a person take?
I advocate that everyone increase their total calcium intake to at least 1,000 milligrams a day. It's an open question after menopause, but at present I would say 1,000 milligrams—from food or supplements—are enough unless a woman has an increased risk of osteoporosis.
Which women are at increased risk?
Those who smoke or drink heavily, don't exercise, use drugs like cortisone, have osteoporosis in their immediate family, have undergone a premature menopause or are thin, small-boned white or Asian women. It would be reasonable for anyone with several of these risk factors to take up to 1,500 milligrams of calcium each day, including supplements.
How can you best get 1,000 milligrams of calcium a day from food?
If you eat a normal American diet, but never take any dairy products at all, you're going to be taking in about 250 to 300 milligrams of calcium, mostly in the form of leafy vegetables. If you add three servings of dairy products—a glass of skim milk, a dish of ice cream, cottage cheese or yogurt, or a thick slice of cheese—these will boost you to 1,000 milligrams. They're easy to absorb and, remember, food products have nutritional value, whereas calcium tablets have none.
When are calcium pills not well absorbed?
Most calcium supplements are calcium carbonate, which requires stomach acid to be absorbed. About 30 percent of middle-age and elderly women have acid in their stomach only during the ingestion of food. So it's important to take your calcium pills when you eat; otherwise, they don't do any good.
What prospect is there for progress in the fight against osteoporosis?
The main message is that there are so many new developments, so much is happening in the research area, that I really believe that in 10 years the disease can be brought under control. It is going to be possible to give a patient a certain combination of drugs and bring bone back to any given level. I am very optimistic about this.
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