Keen Cuisine: Ups, Downs,and Ins(ulin)

Fish, you already know, is brain food. But there's a lot more to feeding the brain than fish.

The brain needs glucose, its favorite fuel—yes, for energy, but also to build neurotransmitters for cell-to-cell communication. Since the brain can't store energy, it needs a steady supply of glucose. Small surprise, then, that boosting blood sugar stimulates the brain: Most people think and remember better after eating.

That is, after eating the right things. Wake up, pad into the kitchen, down some sugary confection and you'll get a swift lift in short-term memory. But consume a breakfast of more complex carbohydrates, from which the sugar is released more steadily, and there will be positive effects on long-term as well as short-term memory—even among the elderly with relatively poor recall. Retention of facts goes up as much as 25 percent.

Broadly speaking, two major factors regulate glucose supply to the brain. One is, obviously, how much fuel you consume and when. The other is how effectively that glucose has access to cells. And that is a function of the hormone insulin, produced by the pancreas and best known for its role in diabetes. One of the surprising stories in nutrition is how insulin is turning out to be a critical hormone for brain function, regulating both learning and memory, and possibly saving the brain from cognitive decline.

The Bagel Dip

Give type-2 diabetics a bagel and memory dips, not rises. It's long known that the disorder hastens cognitive decline and raises risk of Alzheimer's disease. Canadian researchers now find that foods with a low glycemic index—fruits, veggies, whole grains—protect against post-meal memory loss by modulating insulin levels. The response in diabetics is extreme, but not unique, say scientists.

Remember This: Fish

Insulin plays a big role in brain signaling pathways; to lay down memories you need insulin. Anything that messes with insulin function—loss of insulin sensitivity (insulin resistance), frank diabetes—messes up memory. But some foods aid insulin's brainwork, and the trail leads to omega-3 fats, found in canola oil and fish such as salmon. Omega-3 lipids called protectins and resolvins boost insulin tolerance.

Drat That Sat Fat

The typical American diet high in saturated fat does more than block arteries. It hinders insulin action in the brain and generates an excess of free radicals, leading to oxidative damage in neurons. Animals fed a diet of 39 percent fat have trouble navigating mazes, and their brains lack BDNF, a nerve growth factor needed for learning. The high-fat diet especially slows recovery of memory after trauma.

Avoiding Memory Lame

In addition to impacting memory via signaling pathways, insulin plays a direct role in preventing the memory loss of Alzheimer's disease. The hormone acts on memory-forming synapses to block the buildup of toxic amyloid-beta proteins associated with the disorder. Northwestern University researchers now view insulin as a possible treatment for the brain disorder.

Snooze News

Want to preserve brain function into old age? Get a good night's sleep tonight. Just three nights of poor sleep increases insulin resistance. And insulin activity doesn't rebound even after four days of sleep recovery. The altered response to insulin may explain why sleep loss is also linked to obesity. Lost snooze time boosts food consumption in animals. One result: They are on a fast track to diabetes.