Contributions of Increased Dietary Linoleic Acid and Fructose to the Metabolic Syndrome

Abstract

Modern diets are characterized by an increase in fructose consumption largely facilitated by the propagation of high fructose corn syrup and the increased usage of all caloric sweeteners in a growing variety of food products. Accordingly, the human diet has seen a large increase in linoleic acid consumption over the last several decades, primarily coming from seed oils especially soybean and canola oil. It follows that the modern diet differs from the diet that was selected for by evolution and it has been suggested that the modern diet has contributed to the increased prevalence of chronic diseases currently observed. Fructose, once only found primarily in fruits, is now widely available and consumed to great excess. It is distinct from other sugars in the way it is absorbed, processed and metabolized. High levels of fructose intake have been correlated with various conditions of the metabolic syndrome, including hyperuricemia, hyperinsulinemia, hypertension, insulin resistance, leptin resistance, obesity and dyslipidemia. Likewise, linoleic acid consumption has increased with the advent of the industrial age. Modern industrial societies consume as much as 20:1 n to 6:n-3, whereas the consumption ratio of our Paleolithic ancestors has been predicted to be as low as 1:1. Radical change in our EFA profile has been associated with increased levels of atherosclerotic oxidized LDL-C and hypoadiponectinemia, which has been shown to be a strong indicator of metabolic syndrome. The studies covered in this review suggest that straying from the evolutionary selected diet has contributed to the increased prevalence of metabolic syndrome in industrialized societies worldwide. Accordingly a comprehensive effort would be advised, to restore the diet to that which humans were evolved to consume. This may suggest limiting fructose consumption to that found from natural sources and limiting linoleic acid consumption by avoiding overconsumption of seed oils for example.