Evidence suggests that fructose is detrimental to the health when consumed in its refined and crystalline form. Fructose is part of the sugar molecule, and is also present in high fructose corn syrup (HFCS), and these are the two main routes for fructose consumption in humans. Fruit does not appear to show the same detrimental effects, perhaps because of the low concentration of fructose combined with the presence of essential factors and fibre. Increasing levels of refined dietary fructose concomitantly increases production of fatty acids in the liver through the de novo lipogenesis pathway, and evidence suggests that these fatty acids form lipids which accumulate in tissues and are a primary driver of insulin resistance. High intakes of both sugar and fructose are able to cause insulin resistance in animals in a few weeks, and human studies confirm that this effect is also present in humans. High fructose corn syrup is used as a sugar substitute largely in the United States of America in soft drinks.
As with most substances, the poison is in the dose, and as levels of fructose increase, the detrimental effects become increased also. In this regard, recent evidence suggests that high fructose corn syrup produces a dose response effect in terms of triglyceride productions. For example, in one study1 researchers used a double-blind study to investigate the effects of soft drinks sweetened with 0, 10, 17.5 and 25 % high fructose corn syrup on triglyceride production in healthy young adults. The results showed that there was a significant dose response production of triglycerides and low density lipoproteins in the subjects. Therefore high fructose corn syrup appears to detrimentally affect lipoprotein levels in such a way as to increase the risk of cardiovascular disease. The authors also observed a dose response increase in uric acid levels in the subjects. High intakes of fructose may therefore be a risk factor for cardiovascular disease and recommendations to limit intakes of fructose are based on sound nutritional science.