The bitter truth about sweet, sweet HFCS
By the faculty of Harvard Medical School for The Harvard Medical School Adviser

Q: I'm struggling to lose weight. Should I stay away from high-fructose corn syrup?

A: High-fructose corn syrup (HFCS) is now the most popular added sweeter in the American diet, which makes it pretty hard to avoid completely. But there are some good reasons to limit your consumption of soda, sports drinks and other beverages that include HFCS, especially if you're trying to lose weight.

Honey contains fructose (fruit sugar), as do most fruits and some vegetables. It's the sweetest naturally occurring sugar. Ordinary table sugar is a mixture of glucose (better known as the sugar in your blood) and fructose. HFCS is also a mixture of glucose and fructose and is made by a process that changes some of the glucose in corn syrup into fructose. It's available in three grades -- HFCS-42, HFCS-55 and HFCS-90. The numbers indicate the percentage of fructose content. High-fructose corn syrup is as sweet as sucrose but less expensive. That's why softdrink manufacturers switched over to using it in the mid-1980s.

Fructose once seemed like one of nutrition's good guys. Despite being among the simplest of simple carbohydrates, it has a very low glycemic index. The glycemic index is a way of measuring how much of an effect a food or drink has on blood-sugar levels. Low glycemic index foods are generally better for you.

But large amounts of fructose may have some drawbacks. It has a low glycemic index because our metabolisms aren't designed to handle a lot of it at one time. For thousands of years, the only fructose humans consumed came from fresh fruits in season. In the past 100 years or so, there's been a massive increase in our fructose intake. But we haven't gotten any better at metabolizing it.

Glucose, not fructose, is the mainstay of our energy production. Cells throughout our bodies burn glucose to power our metabolism. In contrast, fructose is broken down almost exclusively in the liver. That means it's more likely to create certain types of fats, especially those that increase the risk for heart disease. And recent work has shown that fructose may have an influence on hormones that affect how hungry or full you feel. The changes may blunt your normal sense of fullness, which could lead to overeating.

Fruit juices such as apple or white grape juice in concentrated form are widely used as sweeteners. They are used to replace fats in lowfat products because they retain water and provide bulk. This makes the product feel better in your mouth and look nicer, too.

Fruit-juice concentrates also have high levels of fructose. Concentrated apple juice, for example, is 65 percent fructose. That's higher than the 55 percent fructose content of HFCS-55 that is used in soft drinks. And fruit-juice-concentrate sweeteners don't have the vitamins, minerals and fiber of whole fruit. So fruit-juice concentrates are another way that empty calories get into our diets.

Sweeteners added to sports and juice drinks are particularly troubling because many people think those drinks are healthful. Between 1977 and 2001, our energy intake from sweetened beverages more than doubled. And studies have shown that people don't cut back on their overall calorie intake to offset the extra calories from these beverages.

Researchers are also noting other problems. Harvard scientists report that women who drink one or more sugar-sweetened soft drinks per day are 83 percent more likely to develop type 2 diabetes than women who drink less than one a month. Not surprisingly, they are also more likely to gain weight.

Kids who drink sweet beverages get hooked on a level of sweetness that could affect their habits for a lifetime. Diet surveys have found that average American adolescents drink two 12- ounce sweetened soft drinks per day -- the equivalent of 20 teaspoons of sugar and 300 calories.

One of the problems with sweetened beverages is that they are beverages. These watery but high-calorie drinks may trick your body. That's because your body doesn't register the calories as well as if you were to drink a thicker liquid, such as a milkshake or whole milk.

Some experts say drinking less of these sweetened beverages may be the best single way curb the obesity epidemic. Earlier this year, a Beverage Guidance Panel issued its proposed "guidance system for beverage consumption." The six-level system emphasizes beverages "with no or few calories" -- especially water -- over those with higher calorie content. It also recommends drinking no more than 8 fluid ounces of sweetened sodas, juice drinks or energy (or sports) drinks per day. For more tips on cutting back, see the attached box.

Copyright 2006 the President and Fellows of Harvard College. Developed by Harvard Health Publications (www.health.harvard.edu). Distributed by UFS. Submit q u e s t i o n s t o havard_adviser@hms.harva rd.edu.