Food for Thought: How What You Eat Affects Your Brain
Optimal health depends upon careful calibration of opposing biological actions — contraction and relaxation of the heart, in breath and outbreath, wakefulness and sleep. If the heart repeatedly contracts too hard, or the breath is too deep, the body suffers.
And so it is with nourishment. After a meal, calories flow into the body, replenishing energy stores. A few hours later, the tide turns, and calories flow in the other direction, out of storage sites. Normally, this back and forth choreography occurs smoothly, with gentle, health-promoting effects on the body. But our modern industrial diet — loaded with highly processed carbs — has upset this natural rhythm, inundating the blood stream with excess calories immediately after eating, then leaving us deficient soon thereafter. Processed carbohydrates like white bread, sugary breakfast cereals, cookies, crackers and sweets cause blood sugar to surge soon after eating, and crash an hour or two later. The body copes with each extreme as best it can, by increasing insulin levels during the calorie flood and stress hormones during the drought. But these exaggerated swings in hormones and metabolism take a toll on the body. It stands to reason that they would also affect the brain.
In one particularly compelling study, researchers from the University of Wales in the United Kingdom gave 71 female undergraduate students slow or fast digesting carbohydrate-based breakfasts and then tested their cognitive functioning. They found that memory, especially for hard words, was impaired throughout the morning after the fast-digesting breakfast. This effect was most pronounced several hours after the meal (a 33% deficit). Similar results were obtained in Toronto among 21 patients with diabetes. Following a meal with fast-digesting carbohydrate, verbal memory performance, working memory, selective attention and executive function were worse compared to a meal containing the same amount of carbohydrate in slow digesting form.
These cognitive deficits in children and young adults, if persistent, may lead to a diagnosis of attention-deficient disorder (ADD). Of course, there are many reasons why kids today may have difficulty concentrating, ranging from too much screen time to too little sleep. But these and other studies suggest that overconsumption of highly processed carbohydrates could be contributing to the problem.
Suppose you gave your 12 year old son a “whole grain” bagel with fat-free cream cheese and a glass of 100% juice for breakfast, as was encouraged by the original Food Guide Pyramid of 1992. Though these foods might sound healthy, they’re highly processed, and contain little protein and fat to counterbalance the fast digesting carbohydrate. By mid-morning, the calories in his blood would probably crash, and stress hormones would surge — hardly a biological recipe for calm concentration and learning. Curiously, the stimulant drugs used to treat ADD have broadly similar biological actions to the stress hormone adrenaline. Could it be that these drugs help counteract the swings in blood sugar that occur on the highly processed diets children consume today? And might we reduce need for such drugs with the higher fat diet, slow digesting diet recommended in my book Always Hungry?
The right diet, and a few other simply lifestyle changes, can put biology back on your side, leading to long-term weight. But the first beneficiary will be your brain!
