Soyfoods, vegan diets and cognitive function

[Guest guest]

Back in 2000, an epidemiologic study involving Japanese men living in Hawaii

came up with an unexpected finding: those men who ate the most tofu in middle

age were more likely to have experienced sign of signs of mental decline in old

age.

 

The researchers recorded intake of 26 foods—including tofu—in 3,000 men in the

mid-1960s and again in the early 1970s. The study was actually looking for links

between diet and heart disease—but they also gave the men cognitive function

tests in the 1990s and looked at brain size in men who had died. Tofu

consumption was associated with poorer test performance and brain atrophy.

 

It's hard to understand how this could be. After all, people in Japan—who eat

tofu all their lives—have much lower rates of dementia in old age than people in

the United States. But it's tricky to compare rates of dementia across cultures.

For one thing, dementia is diagnosed differently—using different criteria—in

different countries. And second, there are so many profound differences between

western and Asian culture that it's nearly impossible to single out any one

factor.

 

What we really need is a study comparing two groups of people in Japan—those who

eat tofu and those who don't. While we don't have that study, we do have one

that looked at soyfood intake among people in Hong Kong. In contrast to the

Hawaiian study, there was no relationship between cognition and soy intake.

 

It's possible that, in the Hawaiian study, tofu was an innocent

bystander—occurring along with other factors that raised dementia risk. And

there is reason to believe this may be the case. Intervention studies—which

directly measure effects when soyfoods or isoflavones are fed to people –suggest

that soy may actually be beneficial for cognitive function. In one study, a diet

high in soy improved both long and short-term memory.

 

Finally, there is some suggestion that vegetarians could have lower risk for

dementia. In a study of Seventh-day Adventists, those who ate meat were more

likely to develop dementia. Vegetarians, and especially vegans, may have

additional protection against cognitive decline since they tend to have lower

blood pressure, lower cholesterol levels, and less risk of stroke. Antioxidants

may also protect health of the brain.

 

The best ways to protect against loss of cognitive function are to stay

active—both mentally and physically—and to eat a balanced diet that provides

plenty of the antioxidants found in whole plant foods. Vegans should be certain

to use vitamin B12 supplements regularly. But there is no reason to think that

vegans or anyone else need to avoid soyfoods.

 

Be sure to check yesterday's column for information on the different forms of

soyfoods, including isolated proteins, and their effect on nutrient status.

Tomorrow we'll look at soyfoods and chronic disease.

 

 

Author: Virginia Messina, MPH, RD

Virginia Messina, MPH, RD is an Examiner from Seattle. You can see Virginia's

articles on Virginia's Home Page.