In Reply to: high soy consumption= negative effects on brain posted by dana on January 29, 2005 at 6:13 pm:

I think people should be more concerned about ANIMAL protein than soy-- perhaps you should read Dr. T. Colin Campbell's new book "The China Project" (see vegsource homepage). Also, the people who are spreading these anti-soy myths around believe that you cannot be healthy unless you eat animal fat and animal protein.

This particlular myth has been trotted out again and again, despite the fact that it was very small epidemiological study. John Robbins writes (http://www.foodrevolution.org/what_about_soy.htm): “The study, conducted in Hawaii by Lon White, M.D., and his associates, was part of the Honolulu Heart Study. Looking at the diets and the risk of dementia of Japanese men residing in Hawaii, the study found that men who ate the most tofu during their mid-40s to mid-60s were more likely to have dementia and Alzheimer’s as they grew older… But that’s not all we know. We know, for example, that dementia rates are lower in Asian countries (where soy intake is high) than in western countries. We know that the Japanese lifestyle (with its high soy intake) has long been associated with longer life span and better cognition in old age. And we know that Seventh Day Adventists, many of whom consume soyfoods their whole lives, have less dementia in old age than the general population…The Honolulu Heart Study is far indeed from conclusive. It measured intake of only 27 foods, and there are many lifestyle factors for which it did not control. Researchers acknowledged that tofu consumption might be a marker for some other factor that affects cognitive function. And this would make tofu an innocent bystander. Results of other studies, say soy researchers Mark and Virginia Messina, ‘would suggest this is true.’

A number of clinical studies have shown that soy and isoflavones from soy are actually beneficial for cognition. In one study, published in the journal "Psychopharmacology" in 2001, young adult men and women who ate a high-soy diet experienced substantial improvements in short-term and long-term memory and in mental flexibility. Other studies have found that isoflavone supplements from soy improve cognitive function in postmenopausal women.

It is important to bear in mind that the Honolulu Heart Study is the ONLY study that has suggested a link between tofu consumption and dementia in old age. Having studied the literature, soy researchers Mark and Virginia Messina conclude that ‘there is no reason to believe that eating soyfoods is harmful to brain aging’.”

By the way, Dr. White later said: “It might be that this is totally wrong and the tofu has zip to do with it.” (Los Angeles Times, 3/23/2000)

John Robbins writes in the same article about animal studies:

"Animal studies are at the very foundation of many of the accusations against soy. But animals are not the same as humans, so foods that affect them in one way may well affect us differently. Protease inhibitors are substances that retard the action of digestive enzymes that cause the breakdown of protein. Fallon and Enig refer to studies that show that protease inhibitors isolated from soybeans can cause cancer in some animal species, but there is almost no evidence even suggesting that they have the same effect in humans. In fact, protease inhibitors found in soybeans appear to reduce the incidence of colon, prostate and breast cancer in humans.

Fallon and Enig make much of a 1985 study which showed that soy increases the risk of pancreatic cancer in rats. But researchers with the National Cancer Institute point out that the pancreas of a few species of animals, notably rats and chicks, are extraordinarily sensitive to dietary protease inhibitors such as those found in soy. This sensitivity has not been found in other species such as hamsters, mice, dogs, pigs, and monkeys, they say, and is "not expected to occur in humans." In fact, while rats fed nothing but soy run higher risks of pancreatic cancer, human populations consuming high levels of soy have decreased rates of pancreatic cancer.

Species, even those that seem quite closely related, often function quite differently at a molecular level. It is true, as Fallon and Enig point out, that baby rats fail to thrive on soy. But they also fail to thrive on human breast milk. This is because rats and humans have vastly different requirements. Human milk, for example, is 5% protein; rats' milk is 45% protein. The difference in nutritional requirements and responses for different species can be enormous. Foods that are highly nutritious for one species are often inedible or even poisonous to other species.

Fallon and Enig, however, build their case against soy upon animal studies. Soybeans are high in isoflavones - phytoestrogens, or plant substances that behave like weak forms of the hormone estrogen. K. O. Kline, M.D., of the Department of Clinical Science at duPont Hospital for Children in Delaware comments in a 1998 article in Nutrition Reviews. "It is clear from the literature," writes Kline, "that different species and different tissues are affected by (soy) isoflavones in markedly different ways." Fallon and Enig, however, do not agree. They denounce Kline's comments, fuming that "this is scientific double talk." To my eyes, in contrast, Kline's remark is the thoughtful humility of a scientist acknowledging the realities and limitations of animal research.

Remember thalidomide, the drug that caused horrendous birth defects in children born to mothers who took the drug during their pregnancy? Thalidomide had been widely tested on animals, where it appeared to be totally safe. Similarly, the combination of fenfluramine and dexfenfluramine, recently touted to be the answer to dieters' prayers, was extensively tested on animals and found to be very safe. Unfortunately it caused heart value abnormalities in humans. When the arthritis drug Opren was tested on monkeys, no problems were found, but it killed 61 people before it was withdrawn. Cylert was fine for animals, but when it was given to hyperactive children it caused liver failure."

Source: vegsource.com