Saturday, April 17, 2010

From Michigan State University

The Truth about Protein and Calcium
by Leena Isac

[Ed. Note: Leena Isac is a CSETA/AnimaLife alumnus who is now a medical student at SUNY at Buffalo School of Medicine. She wrote the following essay for her fellow students.]
Nutrition is an increasingly important aspect of health and medicine. Most of us will practice in the United States, a country whose leading killers are heart disease, cancer and stroke, diseases largely preventable by lifestyle changes. Unfortunately, due to the time constraints inherent in medical school, our nutritional education is focused more on the biochemical aspects of nutrition. The major health problems in this country are not protein deficiency or vitamin deficiencies, but diseases of excess. We need to educate ourselves about the real nutritional problems, such as obesity and atherosclerosis, that will affect our future patients.

What Every Future Physician Should Know About Protein

It is a common belief that protein is an important element in a sound diet, and that meat is high in protein. Both statements are true, but there are two other facts that are less well-known among people uneducated in nutrition. The first is that the average American eats much more protein than needed, and that this has severe health consequences. According to Dr. T. Colin Campbell, a professor in the Division of Nutritional Sciences at Cornell University and former senior science advisor to the American Institute for Cancer Research, there is "a strong correlation between dietary protein intake and cancer of the breast, prostate, pancreas, and colon."[1] The second thing to know about protein is that plant protein is equally nutritious as animal protein, and in many ways, it is far superior to animal protein. Though it is true that foods such as eggs and human milk have a high "biological value" in terms of amino acid composition, this does not in any way imply that they are good foods for adult human consumption. Plant foods contain a broad range of essential amino acids. An editorial in the medical journal Lancet reports, "Formerly, vegetable proteins were classified as second class, and regarded as inferior to first-class proteins of animal origin, but this distinction has now been generally discarded."[2]

A clinical study reported in the Journal of the American Dietetic Association compared the intake of the essential amino acids in the diets of meat eaters, lacto-ovo-vegetarians (those consuming dairy products and eggs) and vegans (no eggs or dairy products). The study set the protein requirements for each amino acid at a height that would easily cover the needs of even growing children and pregnant women. The researchers found that not only did all three diets provide sufficient protein, they were all well above sufficient: "Each group exceeded twice its requirement for every essential amino acid and surpassed this amount by large amounts for most of them."[3]

It is almost impossible to design a calorically adequate diet that does not include sufficient protein, including all of the essential amino acids. A member of a team of Harvard researchers commented, "It is difficult to obtain a mixed vegetable diet which will produce an appreciable loss of body protein without resorting to high levels of sugar, jams, jellies, and other essentially protein-free foods."[4]

In fact, a federal advisory committee's recommendation to the Secretaries of Agriculture and Health and Human Services cites vegetarian diets as a healthy choice for Americans. A host of leading nutrition experts joined in calling for a massive revision of the USDA's Dietary Guidelines for Americans, the blueprint for all federal nutrition programs. William Castelli, M.D. (Director of the Framingham Heart Study), Benjamin Spock, M.D., Henry Heimlich, M.D., Dean Ornish, M.D., William C. Roberts, M.D. (Editor of the American Journal of Cardiology) and many others proposed moving vegetables, fruits, grains, and legumes to the center of the plate, leaving meats, dairy products, and added oils strictly optional. They joined the Physicians Committee for Responsible Medicine in submitting a proposal with over a hundred scientific references, showing that vegetarian diets can lead to dramatic reductions in the risk of heart disease, cancer, obesity, and other health risks, something that "lean meat" diets cannot even approach. In response, the Dietary Guidelines Advisory Committee reported that vegetarians "enjoy excellent health." The Committee also reflected the American Dietetic Association's official statements that vegetarians easily get more than enough protein, even without careful planning or intentional "protein complementing."[5]

This means that one does not need a degree in biochemistry to have a healthy balanced diet consisting of grains, vegetables, fruits and legumes. Any person whose diet does not primarily consist of empty calories will be assured a proper protein intake, be it through a peanut butter sandwich on whole wheat, or rice with vegan chili. A completely vegan diet which includes sufficient, nutritious calories will provide everyone with all the essential nutrients for a healthy life.

What Every Future Physician Should Know About Calcium and Animal Protein

Experts agree that calcium is one of the central building blocks of bones and is essential for normal body functions. Several studies show that extra calcium beyond the minimum requirement of 400 mg does little or nothing to stave off osteoporosis. Americans, whose calcium intake is among the highest in the world, also have one of the highest rates of osteoporosis. In any given population, the greater the intake of protein, the more common and more severe the incidence of osteoporosis.[6] Osteoporosis is a condition caused by a number of factors, the most important of which is excess dietary protein.[7] Low-protein diets create a positive calcium balance, and high-protein diets create a negative calcium balance. This occurs in men and young women, as well as in post-menopausal women. The high protein content of milk may actually contribute to the very disease that the calcium in milk is alleged to prevent. In the United States, osteoporosis is not a problem of calcium intake, but of calcium loss.[8] Doubling your protein intake above that required results in a 50% increase in calcium losses in the urine, and protein intakes that are twice the RDA are quite common in typical Western diets.[9] According to an FDA report on the relationship between calcium and osteoporosis, the negative calcium balance that results is "quite sufficient to explain the 1% to 1.5% loss in skeletal mass per year noted in post menopausal women."[10] By consuming dairy products, you are increasing your urinary excretion of calcium.

Lower protein diets lower your calcium requirement and reduce your need to eat high calcium foods. Plant proteins do not result in calcium loss in the same way that animal proteins do. Plant foods that are high in calcium include broccoli, tofu, chickpeas, almonds, cornmeal, soybean nuts, baked beans, and leafy green vegetables such as collard greens and kale, to name a few. Contrary to popular belief, the calcium contained in leafy greens (except spinach) and soybeans is at least as easily absorbed as the calcium in milk.[11]

Summarizing the medical research on osteoporosis, one of the nation's leading medical authorities on dietary associations with disease, Dr. John McDougall, says: I would like to emphasize that the calcium-losing effect of protein on the human body is not an area of controversy in scientific circles. The many studies performed during the past fifty-five years consistently show that the most important dietary change that we can make if we want to create a positive calcium balance that will keep our bones solid is to decrease the amount of proteins we eat each day. The important change is not to increase the amount of calcium we take in.[12]

Even conservative medical investigators no longer deny the connection between excess protein and osteoporosis. In a report published in Lancet, Drs. Aaron Wachman and Daniel Bernstein commented on work sponsored by the U.S. Department of Health and Harvard University. They called the connection between meat-based diets and the increasing incidence of osteoporosis an "inescapable" conclusion.[13] More than one hundred studies and research papers published in peer-reviewed scientific journals have found a direct and consistent association between animal protein consumption and calcium loss in the urine. These studies have shown that the best advice we can give young people with growing bones, as well as post menopausal women at risk for osteoporosis, is to limit protein intake, exercise three or more times a week (running, walking, high-impact aerobics) and consume more vegetables.

Even some of the studies funded by the dairy industry agree. In one Dairy Council-sponsored study, it was found that women who drank an extra three eight-ounce glasses of low-fat milk every day for a year showed no significant increase in calcium balance. The scientists who conducted the test said that the women continued to have a negative calcium balance because of the average 30 percent increase in protein intake during milk supplementation.[14] In 1984, the British Medical Journal published a report indicating that calcium intake is completely irrelevant to bone loss. The study tracked post-menopausal women for 2 years, and found that women who consumed less than 550 mg of calcium daily showed bone loss similar to those who took in as much as 2000 mg a day.[15] At the Mayo Clinic, Dr. B. Lawrence Riggs measured bone densities and calcium intake in women for more than four years. Reporting his findings in the August 1, 1986, issue of Science, he noted, "We found no correlation at all between calcium intake and bone loss, not even a trend."[16] The calcium loss of osteoporosis is aggravated by animal protein, sodium, caffeine, tobacco, and sedentary lifestyle; calcium intake is a much less important factor.

  1. Campbell, T.C., quoted in Lang, S. Diet and disease. Food Monitor, May-June 1983, p. 24.
  2. Editorial, Lancet, London, 2:956; 1959.
  3. Hardinge, M., et al. Nutritional studies of vegetarians, Part V, Proteins.... J Am Diet Assoc 1966; 48(1):27; and Hardinge, M., et al. Nutritional studies of vegetarians: Part I.... J Clin Nutr 1984; 2(2):81.
  4. Hegsted, M., cited in Register, U.D., et al. The vegetarian diet. J Am Diet Assoc 1973; 62:255.
  5. U.S. Government uses the v-word. Good Medicine 1996; 5(1):15.
  6. Chalmers, J. Geographic variations of senile osteoporosis. Journal of Bone and Joint Surgery 1970; 52B:667.
  7. Johnson, N., et al. Effect of level of protein intake on urinary and fecal calcium and calcium retention.... Journal of Nutrition 1970; 100: 1425; and Allen, L., et al. Protein-induced hypercalcuria: A longer-term study. American J Clin Nutr 1979; 32:741.
  8. Heaney, R.P., Evaluation of publicly available scientific evidence regarding certain nutrient-disease relationships.
  9. Heaney, R.P., Becker, R.R. Effects of nitrogen, phosphorus, and caffeine on calcium balance in women. J Lab Clin Med 1982; 99:46-55.
  10. Heaney, R.P., as per note 8.
  11. Heaney, R.P., Weaver, C.M., Calcium absorption from kale. American J Clin Nutr 1990; 51:656-7; Heaney, R.P., et al. Calcium absorbability from spinach. American J Clin Nutr 1988; 47:707-9; Heaney, R.P., et al. Soybean phytate content: Effect on calcium absorption. American J Clin Nutr 1991; 53:745-7.
  12. McDougall, J. McDougall's Medicine, New Century, Piscataway, NJ, 1985. p. 75.
  13. Wachman, A., et al. Diet and osteoporosis. Lancet May 4, 1968, p. 958.
  14. Recker, R., The effect of milk supplements on calcium metabolism, bone metabolism, and calcium balance. American J Clin Nutr 1985; 41:254.
  15. Nilas, L. Calcium supplementation and post menopausal bone loss. British Medical Journal 1984; 289: 1103.
  16. Kolata, G. How important is dietary calcium in preventing osteoporosis? Science 1986; 233: 519-20.

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