Nutrition

Don't Let Sugar Get You Down

Perhaps no single food affects stress hormones, mood regulators, and appetite signalers as negatively as excess sugar. Learn to control sugar, and you'll go a long way toward controlling how you feel throughout the day.

[ Updated: Jul 14, 2008 - 5:09:19 PM ]

To understand why sugar is more problematic than other forms of carbs, consider where it falls in the carbohydrate spectrum. Whole, unrefined carbohydrate sources such as whole grains, beans, nuts, seeds, vegetables, and fruits are packed with nutrients, dietary fiber, and phytochemicals—most with a long list of impressive health benefits to their name. They are also credited with helping you maintain steady blood-sugar levels. When your blood sugar stays consistent, your mood is elevated, and you don't feel terribly hungry. In other words, you feel good.

But sugar is at the very top of the Glycemic Index scale, and foods containing large amounts of sugar are right up there with it. These foods often offer virtually no nutrients along with the calories. What's worse, they often cause a rapid rise in blood glucose, which then causes a fast peak in insulin levels. Brain tryptophan rises and you feel energized for a bit, but the insulin moves blood sugar out of your system so fast that blood-sugar levels quickly fall, followed by lowering insulin levels. This roller coaster ride often leaves people feeling drained, in a foul mood, and, usually, uncomfortably hungry. Consumption has been associated with tooth decay, obesity, cardiovascular disease, and blood-sugar metabolism disorders such as diabetes and hypoglycemia—you have to wonder why our bodies crave it so much.

The answer lies in our evolutionary past. For thousands of years, Homo sapiens evolved to seek out sweet-tasting foods instinctively as a means of survival. Depending on the time of year and where they lived, people would scavenge for foods that were dense in energy and loaded with nutrients. Fresh ripe fruits on trees and vines, honey from combs, and sweet saps from trees and plants—all of which contain natural sugars—became the prehistoric chow of choice.

As an adaptive mechanism, sweet tastes triggered the brain to produce the chemical messengers I've already discussed that affect our brain function, memory, and behavior patterns. When a person eats food, the brain produces opioids, neurotransmitters that identify desirable sensations—in this case, sweet taste. Simultaneously, it triggers the production of dopamine, the neurotransmitter that helps you remember what brought on that desirable sensation, leaving you with the urge to feel it again in the future.

So the human sweet tooth became a kind of self-perpetuating phenomenon. Through memory and visual cues, neurotransmitters drove people to seek out sweet tastes, and once such food was eaten, the same neurotransmitters encouraged them to keep eating it.

During times of famine, this calorie-hoarding strategy could be a lifesaver, and for hunter-gatherer types, it was a sensible strategy even when they weren't in such dire dietary straits. It made sense to feast, even binge on huge amounts of sweet foods while they were in season in order to store up energy for the leaner times caused by natural seasonal variations in food availability.

That makes much less sense today. Food-processing technology has outrun natural selection. Most people in the United States, at least, have access to as much food as they want 24/7, eliminating the need for this adaptive survival instinct. But your body isn't very time-savvy, and the desire for sugar is hardwired. For example, babies tested at birth still prefer a sweet taste to alternatives—and probably will for a long time to come.