Fructose, high-fructose corn syrup, sucrose, and nonalcoholic fatty liver disease or indexes of liver health: a systematic review and meta-analysis , , ,

Abstract

Background: Concerns have been raised about the concurrent temporal trend between simple sugar intakes, especially of fructose or high-fructose corn syrup (HFCS), and rates of nonalcoholic fatty liver disease (NAFLD) in the United States.Objective: We examined the effect of different amounts and forms of dietary fructose on the incidence or prevalence of NAFLD and indexes of liver health in humans.Design: We conducted a systematic review of English-language, human studies of any design in children and adults with low to no alcohol intake and that reported at least one predetermined measure of liver health. The strength of the evidence was evaluated by considering risk of bias, consistency, directness, and precision.Results: Six observational studies and 21 intervention studies met the inclusion criteria. The overall strength of evidence for observational studies was rated insufficient because of high risk of biases and inconsistent study findings. Of 21 intervention studies, 19 studies were in adults without NAFLD (predominantly healthy, young men) and 1 study each in adults or children with NAFLD. We found a low level of evidence that a hypercaloric fructose diet (supplemented by pure fructose) increases liver fat and aspartate aminotransferase (AST) concentrations in healthy men compared with the consumption of a weight-maintenance diet. In addition, there was a low level of evidence that hypercaloric fructose and glucose diets have similar effects on liver fat and liver enzymes in healthy adults. There was insufficient evidence to draw a conclusion for effects of HFCS or sucrose on NAFLD.Conclusions: On the basis of indirect comparisons across study findings, the apparent association between indexes of liver health (ie, liver fat, hepatic de novo lipogenesis, alanine aminotransferase, AST, and γ-glutamyl transpeptase) and fructose or sucrose intake appear to be confounded by excessive energy intake. Overall, the available evidence is not sufficiently robust to draw conclusions regarding effects of fructose, HFCS, or sucrose consumption on NAFLD.

Relevance of liver fat to the impact of dietary extrinsic sugars on lipid metabolism

“…The metabolic effects of dietary fructose and sucrose on lipid metabolism, body weight and NAFLD have been extensively reviewed recently (23)(24)(25)(26) . This has coincided with a furore over the link between sugar and health, and the adverse outcomes of short-term, mechanistic studies that intervened with excessive amounts of fructose or sucrose (>20 % total energy) from sugarsweetened beverages (27)(28)(29)(30)(31) .…”

“…disentangle the effects of body weight from the specific metabolic effects of sugar (25,26) . Likewise, the impact of habitual intakes of sugar on NAFLD also remains unresolved.…”

Fructose metabolism and metabolic disease

“…The average consumption of fructose in US populations accounts for approximately 9% of total energy intake, while consumers in the 95th percentile average approximately 15% of total energy from fructose (22). In contrast, many interventional studies are short in duration (less than 4 weeks) and include dietary intakes closer to 25% of total energy intake from fructose (23,24).…”

Research needs and prioritizations for studies linking dietary sugars and potentially related health outcomes

“…Several systematic reviews have been published focusing on the effects of fructose on cardiometabolic outcomes in controlled trials [4][5][6][7][8][9]. Other systematic reviews have examined the effects of dietary sugars on body weight [10,11], and non-alcoholic fatty liver disease or indices of liver health [12], including both controlled trials and observational studies. Due to the complex relationships between dietary sugars and health outcomes there is a need to review a large array of populations, outcomes of interest, and types of studies to identify and prioritize the research gaps in this research area.…”