The sweet and sour of sugar substitutes

Posted: Thursday, January 24, 2008

It's a common problem faced by folks with a sweet tooth: You want to eat healthier without giving up the taste of sugary desserts and drinks.

Darrell Wong / Fresno Bee
Darrell Wong / Fresno Bee

That means making sense of sugar alternatives. You're probably familiar with the artificial sweeteners Splenda, Sweet'N Low and NutraSweet, but what about the sweet substances found in health food stores, such as xylitol, agave nectar and stevia? Are they really healthier for you?

Before comparing them, remember why table sugar causes worry. Some don't like that it's a highly processed product. Others don't like its 15 calories per teaspoon. And still others monitor their blood sugar levels, which are affected by table sugar.

Here's a primer on how sugar (and other carbohydrates) affect the body: When ingested, carbohydrates cause blood sugar levels to rise. This means there's more glucose - a type of sugar that fuels the body's cells - in the bloodstream. The glucose triggers the release of insulin, a hormone that enables cells to take in glucose.

Problems occur when the body doesn't process glucose properly. Diabetics are plagued by high blood sugar levels caused by insufficient insulin or insulin resistance - a state in which the body produces enough insulin, but the cells don't respond well to it.

The opposite problem - low blood sugar, or hypoglycemia - is caused when "the body uses up glucose too rapidly, releases it into the bloodstream too slowly or calls upon your pancreas to manufacture too much insulin," Connie Bennett writes in "Sugar Shock! How Sweets and Simple Carbs Can Derail Your Life - and How You Can Get Back on Track" (Berkley Books, $14.95). Depending on the severity of hypoglycemia, symptoms can include heart palpitations, dizziness, mood swings, headaches, depression and extreme fatigue, she writes.

Xylitol, stevia and agave nectar can address some of these problems; none of them is a perfect substitute. Here's a closer look at the three.

Agave nectar

This nectar, a thin, honeylike substance harvested from agave plants, is noted for its low glycemic index - an indication that it may affect blood sugar levels less than sugar.

The glycemic index "measures the effect that a 50-gram serving of a particular food (eaten by itself) will have on your circulating blood glucose about two hours after you eat it," Bennett writes in "Sugar Shock." Foods with a higher glycemic index raise blood sugar more quickly than foods with a lower glycemic index.

Not everyone prefers it. Bennett, who also has hypoglycemia, won't touch agave nectar because it is "highly refined fructose," she says in a telephone interview.

Bennett's book points out the dangers of eating too much fructose. "Fructose is more readily metabolized to a form of fat known as triglycerides in the liver, and this can raise triglyceride levels in the blood," Peter J. Havel, a University of California at Davies nutrition and endocrinology researcher, says in "Sugar Shock." "Therefore, consumption of a diet high in fructose could not only lead to weight gain, but an increased risk of cardiovascular disease."

Stevia

The naturally sweet leaves of Stevia rebaudiana, a plant cultivated in South America and Asia, have been used for centuries as a sweetener in various countries, Bennett writes. But not so in the United States, where the Food and Drug Administration calls it a dietary supplement.

Look for this substance in the forms of white powder, yellowish liquid, whole leaf or ground-up leaves.

Stevia, which is up to 300 times sweeter than sugar, works best in drinks and desserts such as puddings and pie fillings, Catalano says. It won't lend cookies, muffins or cakes the proper texture.

In its pure form, it contains no calories and no carbohydrates, and it won't raise blood sugar levels. Just check the packaging to make sure your stevia isn't mixed with other sugars.

Xylitol

This white powder looks very similar to sugar, but it's actually a sugar alcohol made from plants such as corn.

Humans can't process xylitol completely, which makes it low in calories and less of a problem for blood sugar levels. But there's a price to pay: Eating xylitol or other sugar alcohols can result in cramps and diarrhea and other digestive problems.

"The reason we have side effects is because we don't absorb all of it," says Michelle Carrick, a registered dietitian at Saint Agnes Medical Center. She follows the American Diabetes Association's advice for calculating carbohydrates of foods with sugar alcohols: Subtract half of the sugar alcohol grams from the grams of total carbohydrates.

Xylitol works well in liquids such as tea but not everything else.



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