Dietary fructose and metabolic syndrome and diabetes

Abstract

Studies in both healthy and diabetic subjects demonstrated that fructose produced a smaller postprandial rise in plasma glucose and serum insulin than other common carbohydrates. Substitution of dietary fructose for other carbohydrates produced a 13% reduction in mean plasma glucose in a study of type 1 and type 2 diabetic subjects. However, there is concern that fructose may aggravate lipemia. In 1 study, day-long plasma triglycerides in healthy men were 32% greater while they consumed a high-fructose diet than while they consumed a high-glucose diet. There is also concern that fructose may be a factor contributing to the growing worldwide prevalence of obesity. Fructose stimulates insulin secretion less than does glucose and glucose-containing carbohydrates. Because insulin increases leptin release, lower circulating insulin and leptin after fructose ingestion might inhibit appetite less than consumption of other carbohydrates and lead to increased energy intake. However, there is no convincing experimental evidence that dietary fructose actually does increase energy intake. There is also no evidence that fructose accelerates protein glycation. High fructose intake has been associated with increased risk of gout in men and increased risk of kidney stones. Dietary fructose appears to have adverse effects on postprandial serum triglycerides, so adding fructose in large amounts to the diet is undesirable. Glucose may be a suitable replacement sugar. The fructose that occurs naturally in fruits and vegetables provides only a modest amount of dietary fructose and should not be of concern.

FIGURE 1

Area increments in plasma glucose (mean ± SEM) after test meals indicated as follows: F = fructose, S = sucrose, P = potato, W = wheat, and G = glucose; 10 healthy, 12 type 1 diabetic, and 10 type 2 diabetic subjects were studied. The area increment after F was significantly less than the area increments after W and G in healthy subjects and significantly less than after P, W, and G in type 2 diabetic subjects. Reproduced with permission from Bantle et al. (14).

FIGURE 2

Mean plasma triacylglycerol (triglyceride) concentrations in 12 healthy women (A) and 12 healthy men (B) during the 24-h metabolic profiles on d 42 of the fructose (solid line) and glucose (dashed line) diets from 07:30 to 14:00; *significant difference between the 2 points, P < 0.006 (0.05/9, Bonferroni adjustment for multiple comparisons). To convert triglycerides to mg/dL, multiply by 88.5. Reproduced from Bantle et al. (28) with permission.