Dietary Sugars: Not as Sour as They Are Made Out to Be

Over the course of evolution, Mother Nature preserved the ability of humans to make every sugar they need for metabolic functions. Glucose is the almost exclusive fuel preferred by the human brain. Human infants are born with sweet taste receptors, sugars are a significant energy source in human milk, and mammals have a direct gut-to-brain sugar-sensing system that enhances development of a preference for sugars. If sugars are as toxic as many postulate, what species advantage was conferred by this evolutionary progression? Observational studies have reported that sugar consumption is associated with various adverse health risks. However, observational studies can never prove causality, dietary intake records are known to be highly problematic, and the huge number of correlation interdependencies among environmental "exposome" variables makes it impossible to attribute causality to individual dietary components. Additionally, these studies overall have been graded as low quality, and many reported the small effect sizes are likely within the propagated methodological "noise." With several exceptions, data from randomized controlled trials that ensured isocaloric energy intakes have failed to confirm the causal implications of the observational data. Likewise, the comprehensive UK Scientific Committee on Nutrition Report on Carbohydrates and Health also failed to confirm the vast majority of widely postulated detrimental effects of sugar consumption per se. Current data on intakes of sugar-sweetened beverages and on the risks associated with high intakes of dietary fructose remain under debate.