Monkey tests suggest that eating soy may protect against Alzheimer's
　　TUESDAY, April 3 (HealthScout) -- Another reason older females should eat their tofu: It may help prevent Alzheimer's -- at least if you're an older female who is also a monkey, says a three-year study.

The plant-derived estrogens found in soy seem to cut down on the protein changes in the brain that foretell Alzheimer's, the researchers say. Although this proves nothing for women, further study may find similar changes in humans, they add.

"What I found, basically, is that the monkeys who ate soy isoflavones had a reduction in the protein modifications in the brain that are markers for Alzheimer's," says Helen Kim, a research associate professor at the University of Alabama at Birmingham. Isoflavones are chemicals a plant produces to protect itself against stress. "I have been studying the health effects of soy in brain tissue, and soy appears to protect against tau modifications, which is a protein marker for Alzheimer's disease."

Kim and researchers at Wake Forest University in North Carolina fed the 45 animals one of three diets: soy with isoflavones, soy without isoflavones and Premarin (a commonly prescribed female hormone replacement therapy). They used older female monkeys who had had their ovaries removed to simulate as closely as possible women who were past menopause. After three years of the diets, Kim examined the brain tissues of the monkeys.

Just as they expected, they found fewer Alzheimer's disease-linked tau protein changes in the brains of monkeys that received soy isoflavones, Kim says. Tau proteins that don't work well can cause nerve cells to collapse, she explains.

"What also was interesting was that these same effects were not detected in the primates who received estrogen replacement therapy," Kim adds. "I don't understand why the isoflavones did not have the same effects as estrogens, which we know from a lot of experiments is good for the brain. Isoflavones are similar structurally -- but not identically -- to real [animal] estrogen. There might be different mechanisms at work here."

The findings were presented today at the annual meeting of the American Chemical Society in San Diego.

The Alzheimer's Association calculates that 4 million Americans now have the disease and predicts that the number will hit 14 million by 2050 unless scientists find a cure.

But whether soy will have the same effect in humans is still the major question, says Zaven Khachaturian, the senior medical scientific advisor for the Alzheimer's Association in Washington, D.C. "For instance, people have looked at the effect of tofu on Alzheimer's from an epidemiological viewpoint, and none of the studies were conclusive. We don't know if there is less Alzheimer's in Japan or China, but we don't think so." Asians historically consume much more soy than Americans do.

Khachaturian says that the soy research is "an interesting observation that needs to be pursued." But people should not infer a cure here. "The problem is that soy is so readily available, and one could try to promote soy as an Alzheimer's therapy from the results of this study. That would be unfortunate and misleading, because it's still unproven, and self-medication could be dangerous."

"There are lots of open questions on the use of estrogen for the treatment of Alzheimer's that have yet to be resolved," he says.

　　By Neil Sherman
　　From HealthScout