Osteoporosis: Calcium matters--but how?


Osteoporosis is a modern plague, one that is found almost entirely in industrialized, Westernized societies. Conventional medical wisdom tells us that the causes of osteoporosis are calcium deficiencies and deficiencies of estrogen in women. But the areas of the world where there is large-scale usage of dairy products and estrogen therapy for women are those with the highest incidence of osteoporosis. Extensive use of dairy products, it would seem, does not prevent osteoporosis.

What about sources of calcium other than dairy products? Is calcium important at all? You may be amazed to know that a number of investigators now believe that intake of calcium is largely unrelated to the rate of bone loss after growth has been achieved. There is not a simple deficiency state for calcium as may exist with, say, iron in an iron deficiency anemia. The World Health Organization (WHO) has studied this question for decades and has never recorded non-starving populations with clinically apparent calcium deficiencies.

In the mid-1970s, the National Academy of Sciences, which formulates the recommended daily allowances (RDA's), suggested a daily intake of 800 milligrams of calcium, even though the WHO said that only 400 to 500 milligrams a day was sufficient to prevent disease. I understand that the Food and Nutrition Board has proposed to increase the RDA to 1,000 milligrams a day; 1,500 milligrams a day is the recommendation for pregnant women. We are increasing the calcium recommendation and experiencing an increasing incidence of osteoporosis while other women in the world are doing well on as little as 200 milligrams a day. The problem is that you simply can't force oral calcium into bones. The intestinal tract is not a passive funnel for minerals to enter your skeleton.

Why the discrepancy between intake of calcium and bone strength? It is simply because it is the calcium balance, not the calcium intake, that counts. A comparison to a bank account is fair. No matter how much money is deposited in the account, if more money is withdrawn than is deposited, the account will go into negative numbers. Similarly, if more calcium is being lost from the body than enters it, there will exist a negative balance, and osteoporosis will eventually result.

Let's imagine two individuals. The first ingests 1,100 milligrams of calcium a day, and the second ingests only 350 milligrams. If the first person excretes 1,150 milligrams a day, that person will be in negative calcium balance, and, if the condition persists, will eventually become osteoporotic. If the 350-milligrams-a-day person excretes only 300 milligrams a day, that individual will be in positive calcium balance and will be at virtually no risk for osteoporosis. It's as simple as that. The intake matters little. What does matter is the output or, more importantly, the final balance.

This explains why people taking in small amounts of calcium may have healthy bones, while people taking in large amounts of calcium are often osteoporotic and have hip fractures.

What could possibly cause such severe calcium wasting? PROTEIN in excess of daily needs, that's what.

For many decades physiologists, but not medical doctors, have known that excessive protein intake is associated with a negative calcium balance. On a high-protein diet, more calcium is lost in the urine than can be deposited in the bones. On an extremely high-protein diet, you can take in as much calcium as you wish and you will still be in a negative balance. A considerable number of studies, at least one dating back to 1920, all agree that when dietary protein is sharply increased, urinary excretion of calcium goes up and the person goes into a negative balance for calcium. These studies are usually ignored when medical doctors write about osteoporosis.

How much protein is "enough" to cause the problem? Most Americans eat 2 to 5 times more protein than they need for maintenance, ingesting as much as 125 grams daily when 35 to 50 grams is the minimum requirement. As little as 75 grams of protein a day can be sufficient to put you into negative calcium balance.

It is easy to understand how a negative calcium balance maintained over years can cause osteoporosis. Unlike carbohydrates and fats, which can be stored, excess protein must be broken down daily into its component amino acids and then must be excreted by the kidneys. Proteins contain nitrogen, phosphorus, and, in the case of animal proteins, sulfur. When these substances are excreted, they create an acid condition. This requires the presence of an acid neutralizer, or cation. The only cation available in large amounts is calcium, and that calcium must come out of the skeletal bone.

And that is the essence of the osteoporosis riddle -- the answer to the question of why nations with the highest calcium and estrogen intake have the highest rates of bone loss. No other explanation fits the facts. The areas of the world with low calcium intake and little osteoporosis invariably have a low-protein intake.

How much protein is best? It depends on whether the protein is derived from animal or plant sources. Thirty-five to 50 grams a day seems reasonable and fits with the latest RDA recommendations of 0.75 grams per kilogram a day. The intake can be considerably more if the protein is plant based. Why? Because vegetable sources of protein have fewer sulfur-containing amino acids.

Milk and other dairy products are almost universally revered and recommended as the "best" sources of calcium and as a solution to the osteoporosis problem. Dietitians are in almost universal agreement with this advice. Even such highly informed sources as the Pritikin Institute and Dr. William E. Connor of the University of Oregon go along with these recommendations.

The scientific evidence, however, does not. It clearly shows that the protein/excess calcium pattern described above will negate the effect of added calcium, no matter how it is added. The result is net bone loss when measured after a year.

In a famous 1985 study (American Journal of Clinical Nutrition 41:254), women were given 24 ounces of low-fat milk daily for a year. This resulted in nearly 1,500 milligrams a day of calcium. That should have taken care of things! But they promptly went into negative calcium balance. In other studies using low calcium intake (500 milligrams a day) and a low protein intake, there was prompt establishment of a positive calcium balance, and, therefore, no likelihood of osteoporosis.

Protein is mightier than calcium, it seems!

See the next issue of Nutrition Health Review for the conclusion of Dr. Kradjian's series on osteoporosis: "A Misinformed Public."

PHOTO (BLACK & WHITE): Robert M. Kradjian, M.D.



By Robert M. Kradjian, M.D.

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