It’s become popular to think of foods as either good or bad, something to eat or something to avoid. Carbohydrates are now being blamed in part for the epidemic of obesity, diabetes and heart disease. And a slew of diet books proposes that you’ll feel better and be healthier if you never eat bread, pasta or sugar again.
But are carbs really so bad? Science makes the answer pretty clear: no.
While bread, pasta and sugar are hard-to-resist sources of calories without much in the way of nutrition, other carbohydrate-heavy foods – whole grains, legumes and fruit – are nutrient-rich. Carbohydrates can play a healthful role in your diet or they can be your undoing, depending on which, and how many, you eat.
The biggest beef against carbs is that it’s easy to eat too much of them, which is a problem because it can lead to weight gain and because they can crowd out more-nutritious foods.
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There’s also speculation that the way our bodies digest sugar and certain processed grains such as those found in white bread and white rice makes us hungry again soon after eating.
“Carbs aren’t the enemy,” says Julie Jones, a professor emeritus of food and nutrition at St. Catherine University in St. Paul, Minn. “Over-consumption – of anything – is the enemy.”
Even so, the good-or-bad notion gets traction. “It’s easier for a lot of people to cut off whole categories of food than to eat moderately,” says Marion Nestle, a professor in New York University’s department of nutrition, food studies and public health.
And a lot of people report that they feel better and lose weight when they cut out sugar and refined carbohydrates, she says. Yet there’s no reason, she adds, that bread, pasta and plain old sugar should be completely off-limits. In moderation, they’ll do you no harm.
What you need to know
You don’t eat carbohydrates, you eat food, so it’s useful to categorize foods by the type of carbohydrates that predominate.
1 Simple-carb foods are those that your body breaks down quickly and easily, such as sweeteners (sugar, honey, maple syrup) and refined grains (white flour, pasta, white rice). These are the carbs that get the bad rap, because they cause spikes in blood sugar.
2 Complex-carb foods, which include whole grains and legumes, have large, complex molecules that are more difficult to digest and don’t cause the same rapid increase in blood sugar.
3 The simple/complex classification isn’t perfect. Many fruits and vegetables contain both types of carbohydrates: Some get broken down quickly, others more slowly. And it’s not always true that whole foods are digested slowly while refined foods are digested quickly.
Let’s look at some of the simple carbohydrates, starting with sugar.
4 Some doctors believe that the problem with sugar is that it’s empty calories – tasty empty calories that go down easily, particularly in sweetened drinks. Others believe that the ease with which our bodies turn sugar in soda into sugar in our bloodstream messes with our metabolism in a way that disposes us to overeat.
5 Because the carbohydrates in refined grains – bread, white rice, pasta – come packaged with some fiber, some protein and even a few other nutrients, their calories aren’t quite as empty, and the speed with which they’re digested varies.
6 White bread, for example, lets loose a flood of glucose, so your blood sugar spikes, but pasta, particularly if it’s not overcooked, doesn’t have that effect.
7 There is a measure for how much a particular food increases your blood sugar: the glycemic index, or GI. When carbohydrates in a food get converted quickly, that causes a spike in insulin, which your pancreas releases to prompt cells to absorb the glucose.
The hormones that your body releases in response can make you feel hungry. The higher the GI, the higher the blood sugar level. If you eat high-GI foods often, the repeated stressing of your insulin-producing machinery may have other effects, such as increasing your risk for diabetes.
8 There is disagreement about the importance of the glycemic index. While some scientists believe it’s an essential measure of diet quality and while many diets have been designed around it, Nestle isn’t sold. She points out that the GI measures foods eaten alone, and what you eat with your carbs affects subsequent blood sugar levels.
9 Another view: Susan Roberts, director of the energy metabolism laboratory at Tufts University in Boston, acknowledges the many factors that affect the GI of food but still pays attention to it. In “every study I’ve seen, the higher the GI, the greater the risk of Type 2 diabetes, cardiovascular disease and breast cancer.”
10 With so much information available, it’s often hard to know what to eat. But everyone agrees that limiting sugar is important, and Jones points to the simple rule: Make half your grains whole.