A new study to be published in late July 2008 announced that a high consumption of soy products in elderly Indonesians is associated with poor memory. The media will run with this premise without closely examining the rest of the study. That’s too bad, because soy may not be causing dementia. Declining memory may be due to low levels of a common nutrient.

In this study, researchers studied over 700 Indonesians and concluded that the oldest study participants who ate a lot of soy had increased dementia. The conclusion was: soy should be limited in people over 65.

Soy is high in phytoestrogens – estrogens that come from various plants like whole grains, beans, and flax seed. But you never hear that these foods could contribute to memory loss. The researchers of this study admitted that phytoestrogens may offer neuroprotection to some people – like the young and middle-aged. But it could be contraindicated in people over 65.

At the same time, they found that tempeh, a fermented soy product made from the complete soybean, is associated with improved memory. So they’re not saying that all forms of soy are harmful. Just those that are not fermented.

How could fermented soy foods be helpful and other soy products be harmful? The clue may simply be a common nutrient found to be high in fermented foods and low in older folks: folate (folic acid). “It may be that the interaction between high levels of both folate and phytoestrogens protects against cognitive impairment,” said Professor Eef Hogervorst, head researcher of this study.

Folic acid is found in dark green leafy vegetables and in many supplements. Until we have studies to confirm this connection between folate and soy, I suggest you simply make sure you’re eating plenty of green veggies, especially if you’re eating a lot of non-fermented soy (tofu, soy milk, etc).

Meanwhile, there’s another food group to consider if you want to avoid dementia: These same researchers found that a diet high in fruit lowered the risk for memory loss. No surprise there. Just make sure you’re eating plenty of fruit too.