Do Sugars Containing Fructose Increase Diabetes Risk?

Chatter about fructose, high-fructose corn syrup (HFCS), and sucrose is common these days, as the controversy has stepped up since Bray et al. published an article in 2004 indicating “the increase in consumption of HFCS has a temporal relation to the epidemic of obesity, and the overconsumption of HFCS in calorically sweetened beverages may play a role in the epidemic of obesity.” Now, James M. Rippe, MD, of the University of Central Florida Medical School, has published a review in Advances in Nutrition addressing many concerns and misperceptions of fructose.

Rippe reminds us that all 3 sugars contain fructose alone or as a component, and he indicates many investigators have suggested an association between fructose-containing sugars and various metabolic diseases, such as diabetes, metabolic syndrome (MetS), heart disease, nonalcoholic fatty liver disease, cancer, and dementia. However, those associations were often discovered using epidemiologic studies having low evidentiary value, animal studies, theoretical constructs, or experiments involving large doses of pure fructose compared with pure glucose.

Today, the general consensus among experts is that HFCS is not unique compared to sucrose or other nutritive sweeteners. The American Medical Association (AMA) and the Academy of Nutrition and Dietetics both indicate that all sugars have a potential association with obesity — a finding that seems simple and quite obvious.

Bray et al have publically stated that their original hypothesis was not meant to imply or establish causation. Regardless, they have reiterated their concern that fructose-containing sugars like HFCS and sucrose may be linked to a variety of adverse health consequences, particularly when they are consumed in sugar-sweetened beverages (SSBs).

Rippe’s paper explored fructose, HFCS, and sucrose metabolism and health consequences with an eye toward each study’s strengths and limitations. Using a series of questions, he presented results from recent randomized controlled trials (RCTs), with conclusions that can inform physicians whose patients have concerns.

In brief, Rippe indicated:

• HFCS and sucrose are metabolically similar, but metabolically different from pure fructose compared to pure glucose.
• Consumption of HFCS or sucrose at up to the 90th percentile human fructose consumption level does not appear to effect total cholesterol or low-density lipoprotein (LDL) adversely.
• High doses of the sugars appear to decrease high-density lipoprotein (HDL) a small amount, and increase triglycerides by 10% or more.
• Test subjects from the 90th percentile population of fructose-containing sugars showed no increase in risk factors for diabetes — including insulin, glucose, or insulin resistance — compared to glucose controls.
• In normal populations that consume moderate amounts of fructose-containing sugars, researchers saw no effect on uric acid or blood pressure, no increased risk for MetS, and no increase in fatty infiltration of the liver.
• Some difference in hypothalamic blood flow has been noted when fructose-containing sugars are compared with glucose in the context of mixed-nutrient meals.

“Clearly, further RTCs exploring real-world conditions in humans are urgently needed,” Rippe concluded. He noted that reducing intake of soft drinks is a prudent approach to better health, regardless of the sugar source.