YOU MIGHT not call him a brainiac, but Dr. Neal Barnard is certainly brainy. He takes care of his gray matter and wants you to take care of yours. He'll be at the Ethical Society Friday night to talk about it.

Power Foods for the Brain (Hachette) is Barnard's latest book, and his thinking on food and health is worth paying attention to. Not just because he's a best-selling author, does nutrition research, teaches medicine at George Washington University School of Medicine and runs the nonprofit Physicians Committee for Responsible Medicine, all of which take mental acuity. It's more that he seems to think a decade or so ahead of the curve.

In addition to his own peer-reviewed research, Barnard points out trends among recent studies, pushing little-noticed issues into the mainstream conversation. Addictive junk food? Breaking the Food Seduction: The Hidden Reasons Behind Food Cravings - And 7 Steps to End Them Naturally was on it 10 years ago. Genes that can be triggered, or not, by lifestyle factors? Turn Off the Fat Genes: The Revolutionary Guide to Losing Weight came out in 2001.

Power Foods covers brain-boosting foods but also threats, such as excess metals. In a phone conversation, I asked Barnard if people should be paranoid about metal intake.

Well, yes, he said.

Iron and copper - meat's a big source of those - can be harmful when they oxidize in the brain, helping to release free radicals. Trace minerals are necessary nutrients, but whereas "you can eat a humongous amount of B6 or B12 without any adverse affects, with metals, if you tip even a little bit into excess, they can be harmful."

Multiple vitamins can be a concern, too, he said. "The vitamins themselves are fine, but the vitamin pill also includes metals that you don't need. So that's all part of the problem."

Better to be green?

But if we go plant-based, I wondered, are we walking a tightrope to get the right amount of iron? Barnard assured me that there's a wide berth: "A vegan diet makes iron balance really easy."

In clinical research, people going animal-free for some health goal have found that their iron intake slightly increases, on average. And it's all nonheme iron, "a form the body can absorb more of, if it needs more, or less if you're already in iron overload."

The heme iron that's in meat "tends to be too absorbable, so people tend to run into iron overload. And that's where you start talking about heart disease and Alzheimer's tied to iron excess," Barnard said.

A matter of fat

Some fats can be a problem, but others are essential for quality brain work. Most of us have heard about the omega-3s in fish, though they're also available in plant foods. But how does one strike a perfect balance?

Barnard, a longtime advocate for vegan diets, said that the first key is to "get away from animal products. They're very high in the saturated fats that have been, in my view, clearly linked to Alzheimer's disease, but also to brain problems . . . earlier in life."

He pointed out that "around 8 percent of the calories in a typical green leafy vegetable are fat, and much of that is omega-3s." Maximizing those power foods while minimizing added fats (like those used in frying) will help achieve the best brain balance.

If you want to supplement, there are DHA supplements made with algae, so "you can go ahead and have that if you want," Barnard said, "but I don't think most people need them."

He also talked about brain-friendly (free radical-fighting) vitamin E, plentiful in seeds and nuts, though a lot of us overdo it with those, even the good doctor.

"If I buy a bag of cashews I guarantee you it's gonna be gone in about 10 minutes," he said. His portion-control tactic? Pour an ounce of nuts or seeds into the palm of your hand - "once it hits your fingers that's more than an ounce" - and crumble them onto salad, "as an ingredient, not as a snack."

Barnard also cautioned against relying on vitamin E supplements: "There are 8 different forms of vitamin E in seeds and nuts, and they all have biological roles, but a pill has one or maybe two forms, and they tend to reduce the absorption of others from your diet."

Minding your mind

As baby boomers age, mental decline and what can be done to forestall it is a growing issue.

"At the University of Cincinnati researchers gave ordinary concord grape juice to people - their average age was 78 - . . . for three months they showed that it noticeably improved their memory and recall. They did the same thing with blueberry juice, same story."

Not that grapes and blueberries, which contain the anthocyanins that help learning and memory, are a magical antidote, but it can't hurt to bump them up in your eating routine. In another study, a brisk 40-minute walk three times a week was found to reverse natural brain shrinkage that occurs with aging.

Barnard is among a growing wave of doctors and scientists pushing for a bigger nutrition role in our health conversation.

There are still "a lot of folks like the smoker a generation ago, who knows that he or she should quit, but just isn't quite there yet," he said.

To help them along, he suggested experimenting with healthy, plant-based foods to find out what you like, then doing a three-week vegan test-drive.

After 21 days, "almost everybody is so delighted with it," he said, and "it's very easy to go forward at that point."

Barnard believes that we are in a place analogous to a generation ago, when doctors were themselves giving up smoking and getting serious about warning patients away from an established harm - cigarettes.

"Our generation," he said, "is doing the exact same thing with food."