"[To prevent bone loss,] topping every list, of course, are good health habits: regular weight bearing exercise (such as walking, running, or weight training), an adequate intake of calcium (1,500 mg a day for postmenopausal women) and vitamin D"

"Behavior of young adults has a major impact on the chance of developing osteoporosis later in life. Risk of osteoporosis depends on peak bone mass which develops when young. Exercise reduces the risk for osteoporosis by increasing bone mass."

"Dietary factors are significant. High protein intake may cause excretion of calcium, and the high amount of protein in most American's diets is probably a major cause of osteoporosis."

"High sodium intake also leads to loss of calcium."

The last RDA for calcium was 800-1,200 mg per day, but the recent consensus conference of the National Institutes of Health increased the recommendation to 1,000-1,500 mg daily (NIH Panel urges increase in adult calcium intake. Pub Health Repts, 109:715-6, 1994). But though most people agree on the need for calcium in the diet, the debate on the value of calcium supplementation continues, even as the daily requirement for calcium has increased. When I sought good reviews about the value of calcium supplements, I was surprised to find two reviews, published at nearly the same time, in the same distinguished journal, reviewing the same data, and reaching opposite conclusions. Anyone who tells you there is one obvious correct answer is blind to the controversial reality of calcium supplements.

Two factors are important to consider in this debate. In favor of supplementation, it is well established from dietary surveys such as those presented in the RDA report that most of the U.S. population does not obtain sufficient calcium from the diet. On the other hand, calcium supplements with high dosages may be hazardous, cause unpleasant side effects, and not be effectively absorbed.

Except for young men, most of us get less calcium in the diet than the RDA. But there are many exceptions, especially among supplement users, and few people seem to realize that too much calcium may be as harmful as too little.

"10% of the adult population reports calcium intakes already exceeding 1000 (women) and 1400 (men) mg/day." "Adverse effects of high-calcium diets may occur at intakes greater than 2000 mg/day." "Very high intakes of calcium have been reported to cause osteochondrosis, renal failure, and death...soft tissue calcification, irritability, headache, ...risk of kidney stone formation"

Another serious risk associated with calcium is that calcium in supplement form may interfere with zinc uptake from the intestine, leading to zinc deficiency. Anyone taking calcium supplements should take an appropriate amount of zinc at the same time.

"Our findings suggest that high-calcium diets [or supplements] can reduce net zinc absorption and balance and may increase the zinc requirement in adult humans." "Zinc deficiency has many untoward effects, including loss of appetite, growth retardation, skin changes, and immunologic abnormalities."

This interference has been quantitated, so that one can properly blend the correct amount of calcium and zinc in a supplement, though few calcium supplements do this.

"researchers found that in women and men who took a 600-mg calcium pill with a meal containing about 7 mg of zinc, zinc absorption was reduced by 50%. However, adding about 8 mg of zinc to the calcium supplement offset the decline."

On the other hand, the answer is not to go out and buy a zinc supplement to go with your calcium supplement, for zinc supplements too have hazards.

"Zinc supplements of 50 mg per day can cause a decrease in the important enzyme superoxide dismutase. Excessive intakes of zinc have also caused low levels of high- density lipoproteins, increasing the effects of low-density lipoproteins that in theory contribute to atherosclerosis and heart disease."

The RDA for zinc is 12 mg, but most women get less than 10, with elderly getting about 9. Note the ratio in the previous report indicates about 8 mg of zinc compensates for about 600 mg calcium. Review of the available studies attempting to quantitate this relationship and interference have led me to the conclusion that about 2 mg of zinc should be taken for each 100 mg of supplemental calcium, as long as you never take too much calcium at once. So how much should one take? Any at all?

We are not drinking milk like we used to, and that decreases calcium consumption. Some believe that this contributes to osteoporosis, although there are others who believe that the high protein content of milk is likely to contribute to osteoporosis, because the protein in milk may leach calcium from bone. I have spoken with researchers who believe that this is another highly politicized area of research, with the milk lobby supporting the message that milk reduces the risk of osteoporosis.

"One possible problem is that dairy products are rich in protein, and a high protein intake slightly increases calcium excretion in urine, which might reduce bone density."

Univ. Of California-Berkeley Wellness Newsletter 15: 10 (July, 1999)

"Per capita milk consumption in the United States has declined every year for the past 20 years" "at least one-third of all osteoporotic fractures have a nutritional basis...pill-takers maintained a significantly elevated calcium intake."

Although the recommended daily allowance is 1,000 mg for young men and women, and 1,500 mg daily for post-menopausal women and older men, the daily intake is substantially less. Reported by the U.S. Bureau of the Census (Statistical Abstracts Of The United States: 1995 (115th ed). Washington, DC, US Government Printing Office, 1995, pg. 146.), young women consume an average of 600 mg daily, and the recommended daily intake is 1,000 mg, a difference of 400 mg. For post-menopausal women, the average intake is 700 mg daily, the requirement 1,500 mg, so mature women fall 800 mg short per day. Young men generally consume as much calcium as the RDA suggests, and thus are unlikely to benefit, and may be harmed, by supplemental calcium. However for mature men, over the age of about 60, their metabolism changes too, and they begin to lose calcium, with senior men suffering osteoporosis just as women do. For this reason, supplemental calcium is also warranted for mature men.

The basic process of bone maintenance is known as remodeling. The calcium in our bones turns over on a regular basis throughout life. To maintain the strength of our bones, small divots are continually forming in bone, sites at which the calcium is removed. Then the divot is refilled with fresh calcium. Bone is remodeled at a rate of 5% per year. Remodeling is important to eliminate wear and tear. This remodeling occurs in 3 months in youth, and over 9-12 months in the elderly. Initial bone mass depends 80% on heredity, 20% on exercise at age 10, but after age 50, depends 60% on heredity and 40% on lifestyle, esp. calcium, exercise, weight, smoking, and alcohol consumption.

But some studies do suggest that supplements can help as we age.

"In women within the first 5 years after menopause, supplemental calcium does not reduce the rate of bone loss. Women beyond this age are more responsive to supplemental calcium, particularly if they have low usual dietary calcium intakes. ..Recent estimates of the calcium requirement range from 800 to 1,500 mg daily."

MY ANSWER: OUR STUDIES INDICATE 200 MG TWICE A DAY FOR YOUNG WOMEN; 400 MG TWICE A DAY FOR MATURE MEN AND WOMEN

After using the method of urinary excretion to determine a saturating dosage of vitamin C, my students and I conducted a similar study to determine a useful dosage of calcium (submitted to Journal of the American Aging Association). Previous studies have established that urinary excretion is proportional to intestinal absorption of calcium.

What about dosage? How much do we effectively absorb? I became interested in this because my mother was suffering from osteoporosis. She went to her physician and asked, "How much calcium should I take?" His response was "Take a lot." "How much is a lot?", she asked. "I don't know," he replied, "just take a lot." Amazingly, no studies had been done to determine how much is effectively absorbed. With all the calcium supplements in the marketplace, no one had studied whether they were absorbed. Below is a sample of our surprising results.

Post- menopausal women, with substantial variability depending on medications like Fosimax or estrogen, showed an average maximal absorption at a 400 mg dose twice daily. These dosages are substantially lower than many calcium supplements presently on the market, and are less likely to lead to unpleasant side effects like diarrhea.

What about men? Young men consume as much calcium as the RDA suggests, and thus are unlikely to benefit, and may be harmed, by supplemental calcium. However for mature men, over the age of about 60, their metabolism changes too, and they begin to lose calcium, with senior men suffering osteoporosis just as women do. For this reason, supplemental calcium is also warranted for mature men. Based on the 1,500 mg requirement and 700 mg daily intake, a dosage similar to that of post-menopausal women, 400 mg twice a day, is warranted.

As a final note on calcium, there is a possibility that calcium also may protect the colon from cancer:

"intake of calcium from foods and supplements [in mature men] was inversely associated with colon cancer risk"

In summary, adequate intake of calcium is likely to reduce the risk of osteoporosis, and may provide protection from colon cancer as well. However, high dosages of calcium, as found in many existing calcium supplements, may cause unpleasant side effects and long term health risks. For calcium, too much intake may be as hazardous as too little. Our studies show that young women should get 200 mg of supplemental calcium twice a day. Mature men and women should take 400 mg twice a day.

"For all women and men over 65, daily intake [of calcium] is recommended to be 1,500 mg/day... In men and women 65 years of age and older, calcium intake of less than 600 mg/day is common... vitamin D insufficiency has been detected and may contribute to reduced calcium absorption... The physiology of calcium homeostasis in aging men over 65 is similar to that of women..."