When a Carb's Not a Carb: The Net Carb Debate
Will counting net carbs help or hurt weight loss efforts?
What's in a Net Carb? continued...
Also in this category of largely indigestible carbohydrates are
sugar alcohols, such as mannitol, sorbitol, xylitol, and other polyols, which
are modified alcohol molecules that resemble sugar. These substances are
commonly used as artificial sweeteners.
In calculating net carbs, most manufacturers take the total
number of carbohydrates a product contains and subtract fiber and sugar
alcohols because these types of carbohydrates are thought to have a minimal
impact on blood sugar levels.
For example, the label on PowerBar's new double chocolate
flavor "ProteinPlus Carb Select" bar says it has
"2 grams of impact carbohydrates." The Nutrition Facts label on the
product says it has 30 grams of total carbohydrates.
Just below the nutrition facts box, the
"impact carb facts" box provided by the manufacturer explains,
"Fiber and sugar alcohols have a minimal effect on blood sugar. For those
watching their carb intake, count 2 grams." That's 30 grams minus the bar's
27 grams of sugar alcohols and 1 gram of fiber.
The Skinny on Sugar Alcohols
But researchers say the impact of sugar alcohols on blood sugar
levels and the body is not fully understood, and they may also cause problems
in some people.
"There are some sugar alcohols that can raise your blood
sugar," says Karmally. "Certain sugar alcohols do have a higher
glycemic index, and they still are not counted as carbohydrates by these
"When you tell a person 'net carbs' or 'impact carbs,' it's
very confusing," says Karmally. "A person with diabetes may think,
'It's fine for me to have as much as I want.'"
People with diabetes are advised to closely monitor their
intake of carbohydrates because their bodies can't produce enough insulin to
keep blood sugar levels within a safe range.
"I think we should not misguide people and make them aware
that these sugar alcohols also contribute calories," says Karmally.
"Too much of them can actually have a bad effect, and some of them can also
have a laxative effect."
Although sugar alcohols have been used in small amounts in
items like chewing gums for years, researchers say little is known about the
long-term effects of consuming large amounts of these substances.
Registered dietitian Jackie Berning, PhD, says she steers her
patients against products containing sugar alcohols for those reasons.
"I just don't know how they're going to react. We've never
put that much in," says Berning, an associate professor of nutrition at the
University of Colorado at Colorado Springs. "Some are going to get
diarrhea, and some are going to have gastrointestinal problems."