Read The Protein Problem, Part 3: Protein and Strength.
Animal protein is often called high quality protein, whereas plant protein is described as low quality. The reason for this is that animal proteins have an amino acid profile similar to the one of the body's own proteins. This means that animal proteins are used more effectively than plant proteins by the body. Ironically, one should consume human flesh to obtain protein most similar to one's own, but that is another subject. Dr. Campbell explains that while animal protein makes the body grow faster than plant protein does, it also causes cancer cells to grow faster. That is also what he saw in his laboratory: cancer cells grew faster when fed casein, a protein found in milk, but not when fed plant proteins. Many studies show that casein makes cancer grow, while plant protein (soy and wheat) deters its growth. (1)
This situation can be illustrated by a builder, who is given all the material he needs for a construction. Because he has all the parts given, he does not need to reuse any of the old material from the old construction. But when his employer just keeps on dumping material off, the worker feels that he must use it for something – at least the body does. And the result is cancer cells. Dr. Campbell explains, "Increasing body growth may be useful for farm animal production and growing children faster, but it also means growing cancer cells faster, improving conditions for heart disease and speeding up aging—each of which has been documented. Growing young girls more rapidly means earlier sexual maturation, higher circulating levels of estrogen and, eventually, elevated breast cancer risk" (2). When comparing populations from different parts of the world, it is seen that those countries whose populations eat the most meat also have the highest rates of colon, breast, and prostate cancer, whereas those countries that do not use much meat have the lowest (3).
Not only does animal protein resemble the body's protein too much and can therefore cause cancer, but it also raises the IGF-1 levels in the body by raising the insulin level, which is raised by the uric acid, described in Part 2 of this series. IGF-1 is a hormone that stimulates the production and growth of cells while preventing the removal of old cells. It is what makes children grow and adults age. Studies have shown that IGF-1 makes cancer cells grow and spread, and that too high levels of IGF-1 increases the risk of cancer (4).
The effect of protein also depends on the amount consumed. In one experiment, the cancer cells in rats grew only when over 10-12% of the rats' food calories were from casein. The cancer cells did not grow when the rats were fed plant protein (soy and wheat), even at a level of 20%. (5) In another rat study, it was found that when the protein intake was decreased from 20% to 5%, even the strongest carcinogen aflatoxin could not cause cancer. Dr. Campbell comments on this, "Very simply, normal adjustment of protein intake was capable of enormously influencing the ability of a chemical carcinogen’s ability to promote cancer. Dietary protein trumped a very powerful carcinogen in a species that was exceptionally sensitive to this carcinogen" (6). One study was done on middle aged people whose protein was two thirdly from animal sources. It was found that those whose calories were 10-19% protein were three times more likely to get cancer than those who ate under 10% total protein. Furthermore, Dr. Campbell concludes from his China study that even relatively small amounts of animal protein can be harmful (7). It has also been found that plant proteins, such as those from beans, do not have the same deadly effects as animal proteins (8). However, plant proteins should not be consumed at too high levels either. Goldhamer says, "Just because our bodies have a vital need for a substance does not mean that twice or three times our need is even better. In the case of protein, the concept that more is better is dead wrong" (9).
Clearly, there is a link between animal protein and cancer, but it seems to depend on the amount of protein ingested. However, since animal protein generally is very concentrated, it is extremely hard not to get too much of it. Plants, on the other hand, naturally have a very dilute concentration of protein so that it would be hard to eat too much unless the protein has been artificially concentrated. Thus, it seems like plant proteins are safer to eat than animal proteins.
It would be nice to hear your response on this!
Look forward to The Protein Problem, Part 5: How to Get Enough Protein From a Vegan Diet!
(1) Campbell, T. Colin. "The Mystique of Protein and Its Implications." January 19, 2014. http://nutritionstudies.org/mystique-of-protein-implications/ (Accessed May 13, 2014)
(3) Young, Robert O., D.Sc., Ph.D., ND. "But Where Do I Get my Protein!?" March 28, 2012. http://articlesofhealth.blogspot.com/2012/03/but-where-do-i-get-my-protien.html (Accessed May 14, 2014)
(4) Fuhrman, Joel, M.D. "Animal Protein, IGF-1 and Colon Cancer." http://www.drfuhrman.com/library/Animal_protein_IGF-1_colon_cancer.aspx (Accessed May 13, 2014)
(5) Campbell, T. Colin, Ph.D. "Casein Consumption." October 29, 2013. http://nutritionstudies.org/casein-consumption/ (Accessed May 13, 2014)
(6) Campbell, T. Colin, Ph.D. "Animal Protein as a Carcinogen." October 29, 1997. http://nutritionstudies.org/animal-protein-carcinogen/ (Accessed May 13, 2014)
(7) Campbell, T. Colin, PhD. "The Protein Puzzle: Picking up the Pieces." August 1, 1995. http://nutritionstudies.org/protein-puzzle-picking-pieces/ (Accessed May 12, 2014)
(8) Young, Robert O., D.Sc., Ph.D., ND. "Dr. Robert O. Young's Research Validated in New Study - A High-Protein Diet Increases Risk of Cancer and Death." March 5, 2014. http://articlesofhealth.blogspot.com/2014/03/dr-robert-o-youngs-research-validated.html (Accessed May 13, 2014)
(9) Goldhamer, Alan, D.C. "Where Do You Get Your Protein?" October 15, 1997. http://nutritionstudies.org/get-protein-where/ (Accessed May 12, 2014)
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