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A Perspective on Sugars: Fructose, high fructose corn syrup, and sucrose

This week we also have the second article from Philip A. Wood, DVM, PhD. A Perspective on Sugars: Fructose, high fructose corn syrup, and sucrose which will review and compare features of three sweeteners because, as you may know, sugar gets in our diets from many sources.

A Perspective on Sugars: Fructose, high fructose corn syrup, and sucrose
Philip A. Wood

I want to review and compare features of these three sweeteners because, as you may know, sugar gets in our diets from many sources. Fructose, or fruit sugar, is a natural component of fruits and other foods. High fructose corn syrup (HFCS), on the other hand, is a synthetic product and is a commonly touted villain in our food chain, second only to trans fat. Sucrose is a naturally occurring disaccharide that is one part glucose and one part fructose. Although fructose and sucrose occur naturally in foods, most processed foods contain added sugars, predominately HFCS or sucrose.

Like glucose, fructose is a six carbon sugar commonly found in fruits and their juices. But unlike glucose, fructose alone does not elicit an insulin response (1-3), is not metabolically regulated and could be considered a “stealth” sugar. Furthermore, fructose does not require insulin for uptake by cells, it bypasses the first regulated steps in glycolysis, which glucose must traverse, and thus becomes a more ready substrate for fatty acid and triglyceride synthesis (1-3).

Today’s processed foods often contain HFCS, which is made from corn syrup. It was first introduced in the 1970’s as a 42% fructose (HFCS-42) product. Later, HFCS-42 was combined with HFCS-90, resulting in HFCS-55, which contains 55% fructose and is commonly used today (4). All three types of HFCS are presently found in different foods (4), but HFCS-42 and HFCS-55 are the main ones used. HFCS-42 is found predominately in baked goods, canned fruits and condiments, while HFCS-55 is in drinks, ice cream and frozen desserts. The name HFCS may be a bit misleading. Although the name says “high fructose,” and often interpreted as all fructose, HFCS has basically the same fructose content as sucrose. The non-fructose components of HFCS include glucose and polysaccharides. These components are free as part of the syrup rather than bound together as in the disaccharide structure of sucrose crystals.

Given the properties of these sugars, what should we consider as we eat and drink? Based on the properties I described and current research (2, 4), I am not convinced that HFCS is any more hazardous than sucrose. The real hazards are the unrecognized sugars that may be endogenous or “added sugars.” These sugars can represent significant hidden calories in many foods but are often ignored. Several clear examples can be found by scrutinizing our intake of fruit juices—especially calorie-rich fruit drinks that sound healthy (“Hey, let’s have a smoothie!”) and are often presented as promoting health.

In many cases, the only difference between cola and fruit juices, fruit drinks, or sport drinks is that the cola has fizz. Sugar-for-sugar, calorie-for-calorie, they’re all too often the same. Granted, fruit juices provide vitamin C, folate, and potassium. But it takes three to four oranges to make an 8 oz. glass of orange juice. That’s 24 grams of sugar—with fructose and glucose approximately equal (USDA)— from only 8 oz. of 100% orange juice. Still, that’s better than lemonade from concentrate, which is only 16% fruit juice, has HFCS and sugar (sucrose) as the first ingredients, and contains 27 grams of sugar per 8 oz. serving. There’s not much useful nutrition in that lemonade. Also beware of fruit juices sweetened by other fruit juices (e.g., apple or white grape); it is all still sugar in one form or another. I found 37 grams of sugar per 8 oz. serving in a popular cranberry-grape juice that was sweetened with concentrated fruit juice and labeled as 100% juice.

In comparison, 8 oz. of a common orange soda contains 34.6 grams of sugar (HFCS or sucrose). The soda comes in a 12 oz. can, a single serving, and thus provides 52 grams of sugar, about half of which is fructose. The 12 oz. can of orange soda contains 190 empty calories, so if you drink just over two cans each day for a week (18.5 cans), you end up getting the calorie content of 1 pound of fat (3,500 calories). I have demonstrated my points here with drinks; however, one can make the same points with other so-advertised “healthy” foods such as granola bars, breakfast cereals, sugared yogurts and others. Added sugars are in virtually all processed foods.

Perhaps a wiser choice than the fruit juice is the fruit itself. A single orange contains approximately a full day’s supply of vitamin C, a little fiber (2.8 grams), and 64 calories from 17 grams of sugar. At this rate, you would have to eat 55 oranges to consume the same calories as 1 pound of fat.

Current research indicates that basically HFCS equals sucrose (2, 4). Both contain fructose and glucose at approximately equal molar amounts, yet they have distinctly different properties than fructose alone. Large amounts of fructose are rarely found in foods without some accompanying glucose. The notion that increased consumption of HFCS, as compared to sucrose, is the “smoking gun” causing the obesity/diabetes epidemic is so far unfounded (4). We need to pay attention to all sweeteners—HFCS, sucrose, or fruit juices—as these sugars often represent excess, empty calories. Buyer beware: Read the nutrient labels on the cans, boxes, or packets (5) and avoid excess sugar intake depending on your health needs. One way is, eat the fruit and skip the juice that goes down so easily.

References:
1. Mayes PA. Intermediary metabolism of fructose. Am J Clin Nutr 58 (5 Suppl) 754S-765S, 1993.
2. Schorin MD. High fructose corn syrups, part 2-Health effects. Nutrition Today 41:70-77, 2006
3. Elliott SS, Keim NL, Stern JS, Teff K, Havel PJ. Fructose, weight gain, and the insulin resistance syndrome. Am J Clin Nutr 76:911-922, 2002.
4. Forshee RA, Storey ML, Allison DB, Glinsman WH, Hein GL, Lineback DR, Miller SA, Nicklas TA, Weaver GA, White JS. A critical examination of the evidence relating high fructose corn syrup and weight gain. Crit Rev Food Sci Nutr, in press.
5. Wood PA. Nutrient labeling in How Fat Works. Harvard University Press, Cambridge, Massachusetts, pp. 203-208, 2006.