Last reviewed and revised by Faculty of Harvard Medical School on August 28, 2012
By Caitlin Hosmer, M.S., R.D., L.D.N.
Brigham and Women's Hospital
The fat vs. carbohydrate debate remains a hot topic. You may have heard the terms "net carbs," "effective carbohydrate count" and "impact carbohydrates" as carbs replaced fat as the "bad" macronutrient.
Food producers and packagers respond to diet trends with changes in ingredients and labels. For example, for years Americans were told that fat is bad and, as a result, manufacturers produced cholesterol-free and fat-free foods with enticing promotions on the packages. Total calories took a back seat to the number of calories from cholesterol and fat in a particular product. Currently, food manufacturers have switched to carbohydrates as the enemy; as expected, consumers assume that the fewer the better.
In order to make the percentage of carbohydrates in a food item appear smaller, manufacturers subtract the grams of partially or undigested carbohydrates from the total carbohydrate grams. The result is what they term "net carbs." Ingredients that typically get subtracted out include fiber, sugar alcohols and glycerin. The assumption is that these subtracted carbohydrates do not "count" because they have no influence on blood sugar and insulin production.
But this may not work for diabetics trying to control their blood sugars. The kinds of carbohydrates consumed make a difference not just the total calories. Reading and understanding food labels and portion sizes is enough of a challenge. Add the complexity of new terms and obscure calculations, and the task becomes even more difficult.
Interpreting Food Labels and Carbohydrate Content
Depending on the food, carbohydrate labeling can be broken down into "Dietary Fiber," "Sugars," "Sugar Alcohols" and "Other Carbohydrates."
The largest group of these partially digested carbohydrates is sugar alcohols, which are sweet-tasting but are not absorbed as completely as sugar and have fewer calories. Sugar alcohols include maltitol, isomalt, erythritol, mannitol, sorbitol, xylitol, lactitol and a more encompassing term called hydrogenated starch hydrolysates. Sugar alcohols can be voluntarily listed collectively as "sugar alcohols" or listed individually underneath Sugars in the Nutrition Facts Box. In addition, the U.S. Food and Drug Administration standards require that sugar alcohols be listed by name in the ingredients.
Glycerin is another ingredient that has a minimal effect on blood-sugar levels. It is used to add moisture and improve texture to a product. It is fully absorbed and contributes calories.
Fiber refers to the portion of plant material that humans are not able to digest. There are two kinds of dietary fiber, soluble and insoluble. Both are important for proper bowel function, and help to prevent weight gain, regulate blood sugar, and may decrease colon-cancer risk. Over age 50, men should eat 30 grams daily and women 21 grams. Under age 50, men need 38 grams daily and women 25 grams.
To most accurately reflect the effect of a food on blood sugar, look at the total grams of carbohydrates listed and where they come from. If there are more than 5 grams of fiber per serving, this number can be subtracted from the total grams of carbohydrate. Make sure you look at the serving size listed on the Nutrition Facts label of the product, not just your personal serving size.
For example, if the total carbohydrate in a serving is listed as 25, and the product also contains 6 grams of dietary fiber per serving, you may subtract the fiber grams from carbohydrate to get the total number of carbohydrates affecting blood sugar (19 grams).
All other sources of carbohydrate should be counted.
The bottom line is that not all carbohydrates are "bad." Low-carb packaged foods with eye-catching labels and enticing slogans might seem healthy, but actually have little nutritional value. Although it's not as flashy a message, look for healthier, old-fashioned "whole foods" instead. For example:
- Choose whole, high-fiber grains that supply healthy servings of vitamins and minerals and have a smaller impact on blood sugar than their refined relatives. These include bulgur, barley, quinoa, brown and wild rice, oats, whole-grain breads and cereals.
- Eat all kinds of colorful vegetables. Healthy starchy vegetables such as sweet potatoes, beets, turnips and parsnips are preferable, but diabetics still need to keep quantity in check.
- Explore dried beans and peas, the carbohydrate sources that are also sources of plant protein and are packaged along with high fiber and lots of vitamins and minerals.
- Don't forget the convenience and pleasure of several pieces of fruit throughout the day.
Caitlin Hosmer, M.S., R.D., L.D.N., is the manager of the Nutrition Consultation Service at Brigham and Women's Hospital. Caitlin earned a Bachelor of Science degree with honors from Cornell University. She completed her dietetic internship at Frances Stern Nutrition Center and New England Medical Center, and received a master's degree in nutrition at Tufts University.