I know I should have paid more attention in my college chemistry classes. Especially when it comes to understanding high fructose corn syrup and its effect on health.

Case in point: The respected Center for Science in the Public Interest (CSPI) recently sent a letter to the major of San Francisco opposing his proposal to tax beverages made with high fructose corn syrup but not drinks made with other forms of sugar. Scientific evidence, says CSPI, shows that high fructose corn syrup has no more detrimental effect on health than does regular sugar. How can this be? Let's put on our chemistry goggles and consider these facts:

High Fructose Corn Syrup (aka HFCS) is a natural sweetener made from corn. Corn kernels contain "corn starch" - glucose (sugar) molecules connected together in long chains. Enzymes - like the ones in our bodies that digest food - break these long chains into individual glucose molecules to make "corn syrup." Other enzymes convert about half the glucose in corn syrup to fructose (another sugar). And so is made "high fructose corn syrup."

HFCS is as sweet as sucrose or table sugar. But it is more stable and less expensive to make than sugar from cane or beets, which is why it is showing up in everything from sodas to spaghetti sauce.

High fructose corn syrup is chemically similar to sugar (sucrose). Sucrose - "table sugar" refined from sugar cane or beets - is a 50/50 mixture of fructose and glucose. High fructose corn syrup - made from corn - is 55 percent fructose and 45 percent glucose. Not much difference, which probably makes the guy who named it "high fructose" wish he had thought of another name such as "high in fructose when compared to corn syrup but similar in fructose content to sugar or honey."

Sugar from sucrose, honey or high fructose corn syrup adds taste, volume, tenderness, and texture to food. It is also a preservative which explains why most of us have at least one jar of jam in our refrigerator that has been there since the Stone Age.

Sugar, honey and HFCS are digested the same. Sugar is digested to fructose and glucose. Honey is digested to fructose and glucose. HFCS is digested to fructose and glucose.

It's the fructose part of sugar and HFCS that has scientists worried. Large doses of fructose may interfere with the body's ability to metabolize fats and may be related to our growing obesity problem.

Fructose has some redeeming qualities, too. It is the main sugar in fruit. It is less likely to cause tooth cavities than other sugars. It does not raise blood sugars or stimulate insulin as much as sucrose. And fructose is the main component of "fructans" - health-promoting substances in fruits and vegetables that feed the good bacteria in the gut. Fructooligosaccharides (FOS) and inulin are two of the better-known beneficial fructans.

Too much sugar - any sugar - can lead to health problems. A cup of apple juice, a cup of tea with 4 teaspoons of sugar, or a cup of soda sweetened with HFCS each contains about the same amount of fructose. If we avoid products that contain high fructose corn syrup like the plague and choose ones loaded with sugar instead, we've missed a very important point. "The real issue," says the Center for Science in the Public Interest, "is that excessive consumption of any sugars may lead to health problems." Amen.