Sucrose, high-fructose corn syrup, and fructose, their metabolism and potential health effects: what do we really know?

Abstract

Both controversy and confusion exist concerning fructose, sucrose, and high-fructose corn syrup (HFCS) with respect to their metabolism and health effects. These concerns have often been fueled by speculation based on limited data or animal studies. In retrospect, recent controversies arose when a scientific commentary was published suggesting a possible unique link between HFCS consumption and obesity. Since then, a broad scientific consensus has emerged that there are no metabolic or endocrine response differences between HFCS and sucrose related to obesity or any other adverse health outcome. This equivalence is not surprising given that both of these sugars contain approximately equal amounts of fructose and glucose, contain the same number of calories, possess the same level of sweetness, and are absorbed identically through the gastrointestinal tract. Research comparing pure fructose with pure glucose, although interesting from a scientific point of view, has limited application to human nutrition given that neither is consumed to an appreciable degree in isolation in the human diet. Whether there is a link between fructose, HFCS, or sucrose and increased risk of heart disease, metabolic syndrome, or fatty infiltration of the liver or muscle remains in dispute with different studies using different methodologies arriving at different conclusions. Further randomized clinical trials are needed to resolve many of these issues. The purpose of this review is to summarize current knowledge about the metabolism, endocrine responses, and potential health effects of sucrose, HFCS, and fructose.

Figure 1

Temporal association between increased consumption of high-fructose corn syrup (HFCS) and prevalence of obesity. Adapted from (3) with permission.

Figure 2

Metabolism of fructose and glucose in the liver. Reproduced from (41) with permission.

Figure 3

Comparison of high-fructose corn syrup (HFCS) and sucrose effects on glucose (A) and short-term energy-regulating hormones (B, C, D) in normal weight females. Reproduced from (34) with permission.

Figure 4

Comparison of high-fructose corn syrup (HFCS) and sucrose effects on glucose (A), triglycerides (E), free fatty acids (F) and short-term energy-regulating hormones (B, C, D) in men and women. Reproduced from (36) with permission.

Figure 5

The metabolic fate of an oral fructose load in healthy subjects. TG, triglyceride. Reproduced from (41) permission.

Figure 6.

Metabolic pathways related to de novo lipogenesis. A liver cell is shown, with VLDL secretory pathway and fructose uptake; otherwise, the pathways also apply in adipocytes. Circled minus sign, inhibitory action. ACC, acetyl-CoA carboxylase; CF'T-1, carnitine palmitoyl transferase 1; CL, ATP:citrate lyase; FAS, fatty acid synthetase; OAA, oxaloacetate; P, phosphate; PDH, pyruvate dehydrogenase; TCAC, tricarboxylic acid cycle. Reproduced from (95) with permission.