CALCIUM, PHOSPHORUS, PROTEIN AND BONE LOSS

Based on my last post, a couple of folks have asked about calcium, phosphorus and bone loss, wondering about my assertion that too much meat and dairy can actually pose a problem in terms of osteoporosis.

Dummie.com has a good simple explanation of the biochemistry of the ongoing cycle of bone growth/bone loss. One excellent reference page on the balance between calcium and phosphorus is from University of Maryland Medical Center. They do a very good explanation and make this point:

"Nutritionists recommend a balance of calcium and phosphorus in the diet. The typical Western diet, however, contains roughly 2 - 4 times more phosphorus than calcium. Meat and poultry contain 10 - 20 times as much phosphorus as calcium, and carbonated beverages such as colas have as much as 500 mg of phosphorus in one serving. When there is more phosphorus than calcium in the body, the body will use calcium stored in bones. This can cause osteoporosis (brittle bones) and lead to gum and teeth problems. A balance of dietary calcium and phosphorus can lower the risk of osteoporosis."

So, what about milk? Well, it is very high in calcium but because it is very high in protein it ends up pulling calcium out of the bones. The issue is not eating calcium, its getting it into the bones AND then keeping it there. The website of Physicians Committee for Responsible Medicine  mentions the Harvard University Nurses' Health Study (I've been a proud subject in Nurses' Health Study II for over 20 years now!):

"...a 12-year Harvard study of 78,000 women, those who drank milk three times a day actually broke more bones than women who rarely drank milk.¹ Similarly, a 1994 study of elderly men and women in Sydney, Australia, showed that higher dairy product consumption was associated with increased fracture risk. Those with the highest dairy product consumption had approximately double the risk of hip fracture compared to those with the lowest consumption.^2"

A Harvard page admits that calcium alone won't do it but for some reason doesn't even mention the possible role of lower protein in the countries they talk about:

"Additional evidence further supports the idea that American adults may not need as much calcium as is currently recommended. For example, in countries such as India, Japan, and Peru where average daily calcium intake is as low as 300 milligrams per day (less than a third of the U.S. recommendation for adults, ages 19 to 50), the incidence of bone fractures is quite low. Of course, these countries differ in other important bone-health factors as well—such as level of physical activity and amount of sunlight—which could account for their low fracture rates."

When I look for stuff on the internet, I may browse certain sites but tend to discount what they say: quacks selling special diets, vitamin pushers, lobbying associations for dairy and beef industry and of course major pharmaceutical companies. If one of those sites happens to mention research findings, I search forward for a more neutral report of that research. I did find one page worth mentioning, that of a woman getting her Masters in Nutrition at Tufts who has summarized some findings with good citations at the end of her essay. She notes:
"What is undoubtedly clear is that the more PROTEIN a population consumes, the higher its prevalence of osteoporosis. That's correct- there is a direct correlation between protein intake and loss of calcium from the bone. This calcium-wasting effect by protein has been documented time after time in studies for over 70 years. Something to remember is that along with the calcium in your glass of milk there is also a sizable dose of protein. How strong is the effect of protein on calcium loss? If protein intake is doubled without changing intake of other nutrients, calcium in the urine increases by about 50%.

This argument does not go unchallenged, of course. For example, intake of the mineral phosphorus has been shown to decrease protein-induced urinary calcium loss. The problem with this reasoning is that phosphorus intake does not offset the negative effect of protein. It turns out that as phosphorus intake is increased, there is a subsequent increase in fecal calcium. In fact, when a phosphorus supplement is given along with a high protein load, urinary calcium is decreased but fecal calcium is increased. Scientists have taken this biochemical evidence one step further: many studies have found a strong, positive association between protein intakes and hip fracture rates among different populations around the world. In any given population, the greater the intake of protein, the more common the prevalence and more severe will be the osteoporosis. How about some examples?

The African Bantu consumes an average of 350 mg of calcium per day (current recommendations for Americans is about 1000 mg per day) yet do not have calcium deficiency, seldom break a bone, and rarely lose a tooth. (Plenty of Bantus live past age 65.) They consume very low-protein diets with sufficient calories. Osteoporosis among the Bantu is very rare until they migrate to the United States and begin to consume a typical, protein-laden American diet.

Native Eskimos have the highest dietary calcium intake of any other people in the world-- above 2000 mg per day from fish bones. Their diet is also the highest in the world in protein- up to 400 g per day primarily from fish (Americans rarely eat quite this much). Native Eskimos have the highest rate of osteoporosis in the world."