Tofu linked to dementia, study says
2 servings a week may be harmful
By Beverly Creamer
Advertiser Staff writer
Honolulu Advertiser newspaper
Eating tofu more than twice a week in midlife may diminish brain function in old age, and lead to Alzheimer's disease, according to ground-breaking new research by Hawaii scientists.
It's the first time scientists have labeled a dietary risk factor for the disease that affects 2 percent of the nation's 65 year olds and up to 16 percent of 80 year olds. The various forms of dementia cost the country as much as $180 billion a year in health care.
"It's big news," said Dr. Patricia Blanchette, president of the board of the
Aloha Chapter of the Alzheimer's Association and director of the Geriatric Medicine program at the University of Hawaii.
Hawaii researchers, led by Dr. Lon White, a scientist with the Pacific Health Research Institute at Kuakini Medical Center, are waiting for word on publication of their research in a scientific journal, offering further validation of their findings.
White's work has been viewed as some of the most important in the country, because it's based on a detailed, long-term database -- that of the 3,734 Japanese-American men in the Honolulu Heart Program study and the immense interest in finding causes for Alzheimer's.
The first word of White's findings came during a recent Washington, D.C. conference sponsored by the nation's soy industry at which White had been invited to speak.
White has been working on the tofu connection for several years as part of the Honolulu-Asia Aging study and the Honolulu Heart program, with financing by the National Institute on Aging. His work, comparing cognitive tests on the subjects with their dietary histories, has shown that more than two servings a week during the years of middle age (from 45 on) may affect cognitive function in older age.
Although Hawaii researchers don't really know what part of the tofu may be affecting cognitive function, they think that the plant estrogens it contains somehow block the brain's ability to use natural estrogens produced by the bodies of both men and women. Estrogen is necessary for healthy brain function.
"We don't know exactly. But there are different biochemical pathways in the
brain and (it) could possibly interfere with natural human estrogen binding in the brain," says Dr. Helen Petrovich, a co-investigator in the study.
"It's possible it could be slowing down the production of our estrogen, or
blocking it. Certain chemicals can block that."
White's work has sweeping implications for women who turn to plant estrogens as hormone replacement therapy after menopause, and for those hoping high levels of estrogens can improve their cognitive functioning.
"So many people have been touting tofu and its plant estrogen content as
possibly helpful with regard to maintaining cognition into old age," Blanchette said. "It's an example of how research is very important. Intuitively, you might think something is helpful, and then it turns out not to be."
But she said the public should view this the same way they should view the latest research on beta-carotene. "Just because excess amounts of beta-carotene are bad for you, I don't think I would tell people to stop eating carrots," Blanchette said. "Moderate amounts are good for you."
Same with tofu, she said.
"Everything in moderation, because there are such good things that tofu does
The journals Nature and Science have turned down White's findings for publications -- mostly because the study is not of wide appeal for their readers, said fellow researcher Petrovich. But it's now being considered for publication by The Journal of the American Nutrition Society.
White's data goes back to 1965 when the Honolulu Heart Program study began with 8,006 returning AJA veterans. The data collected over the years -- and continuing to be collected today -- is unusually detailed, and should produce more and more answers about causes of Alzheimer's.
"What we have here in Honolulu is a gold mine," White told the Advertiser
more than a year ago, as he pushed forward in his research, hoping for definitive results.
"It's one of the few large studies where people are moving into the age
where they're getting dementia, and lots of background information was recorded."
In comparing the dietary habits of 3,634 Japanese-American men whose tofu consumption ranged from zero to many servings a week, White found that those who ate the most scored lower than those who ate little on a standard cognitive function test for determining dementia.
"When you look at tofu consumption, there's a relationship between the
amount you eat and cognitive functioning in old age," Petrovich said.
In addition, examination of the brains at autopsy of the 300 who have died reveals that the brains of the men who ate more than two servings a week weighed less than those who consumed fewer than two servings of tofu a week.
In developing the research White factored out all other dietary items that could effect cognitive changes.
"He put into the model everything he could think of that could be another
cause," Petrovich said. "Green tea, black tea, rice, miso, meat, fish, milk, coffee." He also tried to compare data with Hawaii's sister study in Japan, but there wasn't the wide spectrum of tofu consumption available in Hawaii, Petrovich said. "Our study is one of the few that could show this kind of effect because most societies either eat a lot of tofu or none at all."
None of the other items showed any consistency in effect on cognitive function, she said. Only tofu.