Dietary fructose and glucose differentially affect lipid and glucose homeostasis

Authors: SCHAEFER, ERNST - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; GLEASON, JOI - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; DANSINGER, MICHAEL - Tufts University

Submitted to: Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2009
Publication Date: 4/29/2009
Citation: Schaefer, E.J., Gleason, J.A., Dansinger, M.L. 2009. Dietary fructose and glucose differentially affect lipid and glucose homeostasis. Journal of Nutrition. 139(6):1257-1262.

Interpretive Summary: The average American consumes approximately 50% of calories as carbohydrate. Dietary carbohydrates are eaten mainly as starch (glucose polymer), glucose, and fructose. Both table sugar (or sucrose) and high fructose corn syrup contain approximately equal amount of glucose and fructose. The purpose of this review was to examine all published studies in which these different types of carbohydrates have been examined. In animal studies it is now clear that dietary glucose is primarily taken up by many different cells in the body, while dietary fructose is primarily taken up by the liver and is converted to triglyceride, where it is released on very low density lipoproteins which can be converted to low density lipoproteins or LDL. Elevated LDL cholesterol levels are a major risk factor for heart disease. In animals dietary fructose is also more likely to lead to diabetes than is dietary glucose. However in human studies at 30 – 60 grams per day dietary fructose had no significant deleterious effects on markers of heart disease risk. Moreover direct comparisons between sugar and high fructose corn syrup indicate no major differences between these two dietary constituents in effects on fasting and fed levels of various heart disease risk factors including levels of cholesterol carrying particles in the blood, and levels of blood glucose and insulin. The overall data indicate that for heart disease risk reduction the focus should be on restricting the intake of excess energy, sucrose, high fructose corn syrup, and animal and trans fats and increasing exercise and the intake of vegetables, vegetable oils, fish, fruit, whole grains, and fiber.

Technical Abstract: Absorbed glucose and fructose differ in that glucose largely escapes first-pass removal by the liver, whereas fructose does not, resulting in different metabolic effects of these 2 monosaccharides. In short-term controlled feeding studies, dietary fructose significantly increases postprandial triglyceride (TG) levels and has little effect on serum glucose concentrations, whereas dietary glucose has the opposite effects. When dietary glucose and fructose have been directly compared at approximately 20-25% of energy over a 4- to 6-wk period, dietary fructose caused significant increases in fasting TG and LDL cholesterol concentrations, whereas dietary glucose did not, but dietary glucose did increase serum glucose and insulin concentrations in the postprandial state whereas dietary fructose did not. When fructose at 30-60 g (approximately 4-12% of energy) was added to the diet in the free-living state, there were no significant effects on lipid or glucose biomarkers. Sucrose and high-fructose corn syrup (HFCS) contain approximately equal amounts of fructose and glucose and no metabolic differences between them have been noted. Controlled feeding studies at more physiologic dietary intakes of fructose and glucose need to be conducted. In our view, to decrease the current high prevalence of obesity, dyslipidemia, insulin resistance, and diabetes, the focus should be on restricting the intake of excess energy, sucrose, HFCS, and animal and trans fats and increasing exercise and the intake of vegetables, vegetable oils, fish, fruit, whole grains, and fiber.