By Densie Webb, Ph.D., R.D.

Thanks to the late Dr. Robert Atkins, there’s been a low-carb diet revival over the last several years. Carbs are in the dietary dog house it seems, blamed for everything from obesity and acne to diabetes and heart disease. Stores and even restaurants featuring low-carb foods are popping up across the country—testimony to this new religion.

   But is it accurate to lump all carbs in the same bread basket? It turns out it’s not that simple. The reality is that there are good carbs and bad carbs, just as there are good fats and bad fats.

The Trouble With Carbs. Most low-carb gurus focus on the fact that eating high-carbohydrate foods raises blood sugar levels, risky for diabetes and heart disease. But the reason diet doctors have latched onto the low-carb bandwagon is that limited evidence suggests that elevated blood sugar and insulin levels—from eating a lot of carbohydrate-rich foods—may contribute to obesity.

   However, to leap from that to shunning nearly all carbs, regardless of their source, is misguided. Here’s why.

Good Carbs, Bad Carbs and Some In Between. All carbohydrates, whether from a slice of whole-wheat bread, a teaspoon of sugar or a serving of white rice, provide the same four calories per gram. But there are important differences in the foods that supply those calories.

   While whole-wheat bread provides fiber, vitamins, minerals and a healthy collection of disease-preventing phytonutrients, sugar provides nothing more than calories. White rice provides carbs in the form of starch rather than sugar, but because it’s refined, most of the nutrients have been lost.

   Compounding the issue are differences in how the body processes carb calories from different foods. The attempt to measure these differences has led to what’s known as the glycemic index of foods, a measure of a food’s effect on blood sugar. One glycemic index table, from the University of Sydney, shows that white rice and table sugar have amazingly similar effects on blood sugar. Combine that failing grade with the few nutrients either one provides and they are easily dubbed “bad carbs.”

   But hold on. One difference is that rice is generally eaten as part of a meal, with perhaps vegetables, nuts, lentils or whole-grain bread—foods that likely blunt the potential blood-sugar-raising effect of rice. Sugar, on the other hand, is often eaten alone as a soft drink, as candy, or in coffee or tea. Or it’s the major ingredient in low-fiber, low-nutrient, high-fat desserts or snacks. Sugar, it seems, is an even “badder” carb. Even then, there’s a distinction.

Added Sugars Are the Real Villains. If you boil down the effects of carbs on blood sugar to a basic level, it’s not simply sugar that’s the problem. It’s mostly added sugars. Sucrose—table sugar—is present in foods almost totally as added sugar in desserts and snacks. Likewise, high-fructose corn syrup, a chemically altered form of the natural sugar fructose, is added to soft drinks and sweets that have little or no redeeming nutritional value.

   Fruits and milk products contain a lot of naturally occurring sugars—as fructose and lactose—which most low-carb diets also limit or shun completely. But, unless you have a metabolic problem that prevents you from digesting one of these two sugars, few experts suggest cutting back your intake of either, except perhaps juice because it’s so concentrated. Most health experts urge us to eat more fruit and low-fat dairy products, not fewer.

   That’s because fruits, despite consisting almost entirely of carbs, are excellent sources of vitamins, minerals and phytonutrients, as well as fiber. Low-fat milk and unsweetened yogurt are good sources of nutrients as well. That’s a far cry from foods with a lot of added sucrose or high-fructose corn syrup, which are typically low in or even devoid of fiber, vitamins, minerals and phytonutrients.

   Research backs the logic that added sugar means fewer nutrients. Data from a national nutrition survey reveal that as added sugar increases in the diet, intakes of calcium, vitamin A, iron and zinc decrease. It stands to reason that if sugar calories replace fruits and vegetables, phytonutrient intake suffers as well.

How Much Sugar Is Too Much? Here, experts differ. But EN likes the recommendation from the World Health Organization, which advocates limiting intake of “free” sugars (added sugars and the concentrated sugars in fruit juice) to no more than 10% of daily calories. If you consume 1,800 calories a day, that translates into 180 calories a day from sugar. Not much, when you consider a single 12-ounce can of soda provides 150 calories of added sugar. No wonder researcher Wim Saris, Ph.D., at the Nutrition and Toxicology Research Institute at the University of Maastricht in the Netherlands, says, “Soft drinks are probably the biggest sugar issue in the U.S.”

   Does that mean sugar is forbidden fruit, so to speak? Not at all. The goal isn’t to eliminate sugar from your diet. That’s not realistic.

   “Appropriate amounts of sugars and fat make food palatable,” says Suzanne Murphy, Ph.D., of the Cancer Research Center of Hawaii at the University of Hawaii. “I don’t think we should scare people into thinking that they can’t ever have some added sugars.”

   Research shows that sugar becomes a health issue only when it pushes nutritious foods out of your diet. That means the occasional dessert after a healthful meal is okay. So is the occasional piece of candy. It’s when sodas, cakes, cookies and doughnuts become menu mainstays that your diet—and possibly your health—is in trouble.

Carbohydrate Calculations. So how much and what kind of carbs should you eat? The Institute of Medicine, as well as most nutrition experts, still recommend a diet that provides 45% to 65% of calories from carbohydrates.

   The key is to be sure they are mostly healthful, high-fiber complex carbs. Once you choose the right carbs, the amount becomes less of an issue.

   What about the effect on body weight? Saris says the real issue for weight control is calories, not carbs. Many other experts agree. In his research, two groups of people received the same number of calories from a diet high in either simple (refined) carbohydrates or complex carbohydrates. There was little difference in weight loss between the two groups.

   Saris’ assessment: “The type of carbohydrate doesn’t matter, as long as calories are restricted.”

The Bottom Line. Still can’t figure out what to eat? Go for whole, minimally processed foods, with the fiber intact.

   That means opting for whole fruit over fruit juice. For a side dish, serve brown rice or mix white rice with vegetables, lentils or nuts. For breakfast, reach for unsweetened whole-grain cereal topped with fresh fruit instead of a low-fiber cereal and fruit juice. The carb content and calories may be similar, but the nutrient profile and effects on your blood sugar—and possibly weight and health—are decidedly different.