It's been implicated in the rise of obesity and Type 2 diabetes, not to mention other health concerns. On food labels you'll see it listed as glucose-fructose (a.k.a. high-fructose corn syrup), an inexpensive sweetener that's added to soft drinks, fruit drinks, breakfast cereals, baked goods, yogurt, canned fruit and condiments.
The potential health hazards of high-fructose corn syrup made headlines in 2004 when researchers in the United States published a report linking our increased use of corn syrup sweeteners over the past 20 years with rising obesity rates. Experts have argued that high-fructose corn syrup is processed differently than table sugar by the body. It's thought that fructose doesn't trigger hormone responses that regulate appetite and satiety, which could cause you to overeat.
Now, a new study published this week in the Journal of Clinical Investigation reveals that fructose-sweetened beverages can impair how the body clears blood sugar and handles fat - detrimental effects that can increase the risk of heart disease and heart attack.
Since its introduction in the 1970s, high-fructose corn syrup has been a boon to the food and beverage industry - it's cheaper than ordinary sugar, easier to blend into foods and tastes sweeter.
Table sugar (sucrose) is made from sugar cane or sugar beets. The body can't use pure table sugar for energy; it must first break it down into simple sugars.
During digestion, the body converts sucrose into an equal amount of glucose and fructose, its building blocks.
High-fructose corn syrup is made from corn that's been processed into syrup, then mixed with glucose. The end product is a sweetener that contains approximately 55 per cent fructose and 45 per cent glucose.
So, essentially the difference between table sugar and corn-based sweetening syrup is the ratio of glucose and fructose. In particular, the corn syrup leads to more fructose and less glucose in the bloodstream than table sugar does.
Once absorbed into the bloodstream, glucose and fructose make their way to the liver, where they're converted to energy or fat (triglyceride) compounds. Glucose metabolism turns off when there's an abundance of energy or fat in the liver. But that's not the case with fructose - as long as there's a steady supply of fructose, the liver keeps on making energy and fat.
In the study, researchers from the University of California, Davis, assigned 32 overweight and obese men and women to drink three daily servings (one with each meal) of a glucose- or fructose-sweetened beverage for 10 weeks. Participants followed their usual diet but were instructed not to consume other sugary beverages, including fruit juice.
During the study, individuals in both groups put on the same amount of weight. But that's where the similarities ended. Those drinking the glucose-sweetened beverage increased subcutaneous fat - the type of fat you can pinch - while participants in the fructose beverage group gained deeper intra-abdominal fat. (Intra-abdominal fat sits closer to the organs and increases the risk of heart disease and diabetes.)
Only those consuming fructose-sweetened beverages became less sensitive to insulin (the hormone that controls blood sugar) and had increased levels of blood fats. Consuming fructose increased fat production in the liver, elevated LDL (bad) cholesterol, and led to larger increases in blood triglycerides (fats) after meals which remained elevated during the day. (An impaired ability to clear triglycerides from the blood after eating is thought to boost the risk of heart attack.) These dramatic differences occurred despite comparable weight gain in the two groups.
Does this mean you should avoid beverages and foods that contain large amounts of fructose? Before I venture to answer, keep in mind that this study tested the metabolic effects of beverages containing 100 per cent pure glucose or 100 per cent pure fructose.
In Canada, beverages and foods are sweetened with sucrose (50 per cent glucose and 50 per cent fructose) or glucose-fructose (typically 55 per cent fructose and 45 per cent glucose). This study doesn't answer whether the detrimental health effects of sucrose or high fructose corn syrup are "diluted" by their lower fructose content.
What's more, the amount of sweetener consumed by individuals in this study - 25 per cent of daily calories - is considerably higher than 13 per cent, the estimated intake of added sugars by Canadians. (However, some children and teenagers may consume as many as 13 per cent of calories from sugary beverages alone.)
It seems pretty clear that a high-fructose diet has adverse health effects - on body weight, blood sugar and blood fats. The link between high-fructose corn syrup and obesity probably reflects the fact that we consume so much of it. Consuming too much sugar can lead to weight gain too - not to mention increased blood triglycerides.
Reducing your intake of added sugars - including high-fructose corn syrup - is wise. Added sugars come under many names including brown sugar, corn syrup, dextrose, fructose, fruit juice concentrate, glucose-fructose, honey, invert sugar, liquid sugar, malt, maltose, molasses, rice syrup, table sugar and sucrose. Read ingredient lists and you might be surprised to see how many different types of sugars are added to one product.
The "Nutrition Facts" box on packaging discloses the grams of sugars contained in one serving of food. (Four grams is equivalent to one teaspoon). But keep in mind the sugar content on nutrition labels include both naturally occurring sugars (e.g. fruit or milk sugars) and sugars added during processing.
Practising the following tips will help you curb your intake of sugars.
Avoid sugary drinks. Replace soft drinks, fruit drinks and sugar-laden vitamin water with plain water, low-fat milk, unflavoured soy beverage, vegetable juice or tea.
Go for natural sugars. Choose fruit, yogurt or smoothies over candy, cakes, cookies and pastries. Keep in mind that fat-free cookies, cakes and ice cream often have just as much - or more - sugar as their high-fat counterparts.
Choose breakfast cereals that have no more than eight grams of sugar per serving. Exceptions include cereals with dried fruit.
Sweeten foods with spices instead of sugar. Add cinnamon and nutmeg to hot cereals, a dash of vanilla to coffee and lattes, and grated fresh ginger to fruit and vegetables.
Reduce sugar in recipes. As a rule, you can cut the sugar in most baked goods by one-third.
Choose canned fruit in water or its own juice rather than syrup.
Limit your portion size of commercial salad dressings, ketchup and barbecue sauce.
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.