Media coverage of high fructose corn syrup (HFCS) and fructose increased sharply in early 2004 after publication of a hypothesis that they may play a role in the epidemic of obesity. The past several years have witnessed headlines such as “Fructose converts to fats faster than other sugars” “Is fructose making us fat?” “Limiting fructose may boost weight loss.” More recent hypotheses have attempted to link high intakes of fructose to the development of insulin resistance, metabolic syndrome, type 2 diabetes, abnormal blood lipids, and gout. As a result of confusing HFCS with pure fructose and mistakenly thinking that HFCS and sucrose (table sugar) are very different, some communities have considered bans on the sale of foods and beverages containing high fructose corn syrup (HFCS). Does the scientific evidence warrant the singular focus on the role of fructose—regardless of dietary source—in the development of obesity and chronic disease risk?
The widespread confusion over pure fructose, glucose, HFCS, and sucrose led the Agricultural Research Service of the United States Department of Agriculture (USDA/ARS) and the International Life Sciences Institute of North America (ILSI) to convene a roundtable of nutrition and health experts to address the state of the science on dietary sweeteners containing fructose. Held March 18 and 19, 2008 in Beltsville, Maryland, the workshop, “The State of the Science on Dietary Sweeteners Containing Fructose,” covered a range of topics including the chemical composition, properties, and food supply availability of dietary sweeteners that contain fructose; sources and amount of fructose in the diet; how the body metabolizes fructose; and research on the physiological effects of dietary sweeteners that contain fructose. According to Dr. David Klurfeld, National Program Leader of Human Nutrition at USDA/ARS, proceedings from the workshop will be published in a peer-reviewed journal and will help inform the scientific community of factors to consider when designing studies to evaluate the physiological effects of usual dietary intakes of fructose.
In the meantime, the workshop’s discussions suggest that consumers, nutrition communicators, and those who recommend nutrition policy should know the following five things about fructose and the sugars in which it is found.
1. HFCS is not the same as pure fructose
Pure fructose is 100 percent fructose and zero percent glucose. HFCS, on the other hand, refers to sweeteners that contain a mixture of fructose and glucose. The most commonly used types of HFCS are HFCS-55 which contains 55 percent fructose and 45 percent glucose and HFCS-42 which contains 42 percent fructose and 58 percent glucose. In comparison, sucrose—common table sugar—contains 50 percent glucose and 50 percent fructose.
2. HFCS is essentially the same as sugar (sucrose)
Sugar, which is technically called “sucrose,” is a combination of one fructose molecule and one glucose molecule. The two molecules are chemically linked, but when ingested sugar is digested to free fructose and free glucose. So in the intestine, sugar becomes 50 percent fructose and 50 percent glucose. This is almost exactly the same as HFCS. The only real difference is the HFCS does not need to be digested. It is basically pre-digested table sugar.
3. HFCS is similar to table sugar (sucrose) in its physiological effects
Sucrose (table sugar), honey, and many fruits, vegetables, and nuts naturally contain some fructose. Most contain 42 to 55 percent of total sugar content as fructose—which is similar to HFCS. Human studies that have directly compared sucrose and HFCS-55 show no meaningful differences in ratings of hunger and fullness, fasting or post meal blood levels of glucose, insulin, triglycerides, or leptin and ghrelin (hormones related to satiety) as would be expected based on the simple chemistry. Independent of this conference, the American Medical Association recently conducted a review of the literature and concluded that because the composition of HFCS and sucrose are so similar, particularly with regard to absorption by the body, it appears unlikely that HFCS contributes more to obesity or other conditions than does sucrose.
4. Experimental studies use atypical sources and amounts of fructose
Since at least the early 1980s several experimental studies have evaluated the effect of fructose on biomarkers of chronic disease risk, such as fasting and post meal blood lipids, glucose, insulin, and satiety hormone concentrations; insulin sensitivity; and glycosylated proteins that provide an indicator of overall glucose control in people with diabetes. More recent studies have focused on uric acid production which has been associated with the risk for metabolic syndrome and gout.
A few studies in humans have used sucrose and/or HFCS-55 in experimental diets but most studies have used pure fructose in the absence of glucose—and most studies have fed fructose (whether from pure fructose, sucrose, or HFCS) at abnormally high levels compared to usual dietary intakes. Humans rarely consume pure fructose in the absence of glucose as there are almost no sources of pure fructose in the diet, but many human experiments have fed pure fructose at 17 to 30 percent of total calorie intake. Such experimental conditions are completely irrelevant to the normal consumption of food and thus the results of those studies are of very little value.
The primary sources of fructose in the human diet are sucrose and HFCS—both of which contain a mixture of fructose and glucose in approximately a 50:50 ratio. A diet containing 17 to 30 percent of total calorie intake from fructose would equate to 34 to 60 percent of calories coming from sucrose and/or HFCS. Such diets are highly unusual, to say the least! In fact, estimates from dietary surveys actually show an overall mean fructose intake of about eight percent of calories from all food and beverage sources depending on age and gender, so these are 2- to 7-times more fructose than normally ingested. While exaggerating exposure can be good to identify some effects, these levels could change normal metabolism and therefore are not considered predictive of what occurs under typical circumstances.
Results from studies that have tested high intakes of fructose regardless of source provide information about how the body uses pure fructose under extreme conditions and help generate hypotheses for additional research. In order to be more meaningful to consumers, future research should examine physiological effects using typical intake levels and sources of fructose in the diet, which should include some glucose. Experimental diets should contain average amounts of fructose from a mix of fruits, vegetables, and foods and beverages sweetened with both sucrose and HFCS with a fructose/glucose ratio typically found in average diets.
5. Dietary advice should focus on energy balance, not fructose
The 2005 Dietary Guidelines recommend that Americans choose and prepare foods with little added sugars or caloric sweeteners in amounts recommended by the USDA Food Guide (MyPyramid). The primary concern is that diets high in added sugars tend to be higher in total calories and lower in vitamins and minerals. However, according to the 2005 Dietary Guidelines for Americans, discretionary calories (those calories which can be added after all nutrient needs are met but staying within individual calorie needs), can be consumed, which means some foods with sugar or HFCS can be eaten as part of a healthful diet. The amount of discretionary calories that fits with the Dietary Guidelines depends on age, gender, and physical activity level. The discretionary calorie allowance is the amount of calories remaining after selecting the recommended amount of nutrient-dense foods in each food group. Depending on a person’s caloric requirement and physical activity, additional discretionary calories can be added.
IFIC Foundation consumer research shows that consumers receive an abundance of dietary information, but not much clarity, from the media, government, and other sources including emerging science, popular diet books, and more. The resulting communication environment for sugars, including fructose and HFCS, is challenging for nutrition communicators and consumers alike. The intersection of science, dietary advice, and media coverage of complicated topics is one in which information clutter can override clarity.
Dr. Suzanne Murphy, University of Hawaii, who summarized “The State of the Science on Dietary Sweeteners Containing Fructose” workshop’s discussions, suggested that appropriate consumer messages should support the Dietary Guidelines. It is not helpful to offer potentially confusing recommendations about fructose when they are inherently misleading and current dietary guidance already advises that a healthful eating plan is one that is low in saturated fats, trans fats, cholesterol, salt (sodium), and added sugars.
The role of fructose in disease remains unclear; much more research is needed to fully understand: multiple dietary and lifestyle factors that influence obesity, insulin resistance, cardiovascular disease, and diabetes; and dietary advice based on the Dietary Guidelines for Americans.
Selected dietary sources of fructose and percent content of total sugars
- Crystalline Fructose (pure fructose) 100 percent
- Apples, pears less than 66 percent
- Raspberries, watermelon 56 to 65 percent
- HFCS-55 55 percent
- Bananas, grapes, oranges, peaches 42 to 55 percent
- Table sugar 50 percent
- Honey 48 percent
- HFCS-42 42 percent
What everybody needs to know about fructose
- High fructose corn syrup is not the same as pure fructose
- HFCS is similar to sucrose (table sugar) in its physiological effects
- Experimental studies use atypical amounts and sources of fructose
- Dietary advice should focus on managing discretionary calories and energy balance, not on one specific sugar such as fructose
