Current World Health Organization recommendation to reduce free sugar intake from all sources to below 10% of daily energy intake for supporting overall health is not well-supported by available evidence

Sugar is widely consumed over the world. Although the mainstream view is that high added/free sugar consumption leads to obesity and related metabolic diseases, controversies exist. This narrative review aims to highlight important findings and identify major limitations and gaps in the current body of evidence in relation to the effect of high sugar intake on health. Previous animal studies have shown that high sucrose/fructose consumption causes insulin resistance in the liver, skeletal muscle and consequent hyperglycemia, mainly because of fructose-induced de novo hepatic lipogenesis. Evidence from human observational studies and clinical trials was however inconsistent, where most if not all studies linking high sugar intake to obesity focused on sugar-sweetened beverages (SSBs), and studies focusing on sugars from solid foods yielded null findings. In our opinion the substantial limitations in the current body of evidence such as short study duration, use of supraphysiological doses of sugar or fructose alone in animal studies, lack of direct comparison of the effects of solid vs. liquid sugars on health outcomes, as well as the lack of appropriate control seriously curtails the translatability of the findings to the real-world situation. It is quite possible that "high" sugar consumption at normal dietary doses (e.g., 25% daily energy intake) per se, i.e., the unique effect of sugar, especially in the solid form, may indeed not pose a health risk for individuals apart from the potential to reduce the overall dietary nutrient density, although newer evidence suggests "low" sugar intake (<5% daily energy intake) is just as likely to be associated with nutrient dilution. We argue the current public health recommendations to encourage the reduction of both solid and liquid forms of free sugars intake (e.g., sugar reformulation programs) should be revised due to the over-extrapolation of results from SSBs studies.