Published: Nov 5, 2013 | Updated: Nov 6, 2013
By Cole Petrochko, Staff Writer, MedPage Today
Reviewed by Zalman S. Agus, MD; Emeritus Professor, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner
- On an isocaloric diet, overweight men who were on a high-fructose or a high-glucose diet did not develop any significant changes in hepatic triacylglycerol concentration or serum levels of liver enzymes.
- Note that on a hypercaloric diet, both high-fructose and high-glucose diets produced significant increases in these parameters without any significant difference between the two groups.
Sugar intake was not associated with nonalcoholic fatty liver disease (NAFLD) in a population of overweight men who were otherwise healthy, researchers found.
Overweight men who consumed high-fructose or high-glucose diets did not see significant increases in insulin resistance (increase of 0.8 in a homeostasis model assessment versus 0.1), serum concentration of uric acid (22 mu-mol/L versus 23 mu-mol/L), concentration of hepatic triacylglycerol, or body weight, according to Ian MacDonald, PhD, of the University of Nottingham in England, and colleagues.
However, significant increases in weight and concentration of hepatic and serum triacylglycerol occurred when the patients were transitioned to a high-calorie diet with high glucose or high fructose, they wrote online in the journal Gastroenterology.
"Based on the results of our study, recommending a low-fructose or low-glycemic diet to prevent nonalcoholic fatty liver disease is unjustified," MacDonald said in an accompanying statement. "The best advice to give a patient is to maintain a healthy lifestyle with diet and exercise."
Past research in the association between fructose consumption and fatty liver disease has shown a significant association between daily consumption with increased hepatic fibrosis.
A mouse study showed that those whose diet contained 10% glucose, but was otherwise the same, had an increase in energy intake, body weight, visceral obesity, fatty liver, elevated insulin, and hyperlipidemia.
Researchers have shown a link between liver fat and worse metabolic profiles in twin studies.
The authors looked at hepatic outcomes in 32 overweight but healthy men ingesting a high- fructose diet compared with those receiving a high-glucose diet.
Participants were randomized to receive either high glucose or high fructose in their diets over 2 weeks, which was followed by a 6-week washout period, a second baseline assessment, and a second 2-week period where their calorie intake was also increased.
Those enrolled were ages 18 to 50, had a body mass index of 25 to 32 kg/m2, and had a waist circumference greater than 94 cm (around 37 inches).
Participants were excluded if they drank more than 21 units of alcohol weekly, had weight change of more than 3 kg (about 6.6 lbs) in the last 3 months, had regular high-intensity physical activity, were vegetarian, or drank more than 25 g/day of fructose (500 mL), which is roughly the same as a 16 oz bottle (480 mL) of soda daily.
Roughly a quarter of participants' energy intake was given through monosaccharides mixed into four times daily doses of 500 mL of water in the initial 2-week study period. During the second study period, participants were subject to habitual food consumption with the same quantities of monosaccharides.
Sweetened drinks were forbidden during both study periods, while exercise was encouraged.
The primary outcome was hepatic steatosis, while secondary endpoints were hepatic adenosine triphosphate content, insulin resistance, and enzymes. Also collected were weight, satiety, insulin resistance, nonhepatic triglycerides, inflammatory cytokines, and adipokines.
Between-group differences were significant for measures of insulin resistance (P=0.03) and uric acid concentration (P<0.01).
During the hypercaloric period, participants in both groups had similar increases in:
- Weight: 1.0 versus 0.6 kg (P=0.29)
- Absolute concentration of hepatic triacylglycerol in the liver: 1.70% versus 2.05% (P=0.73)
- Serum: 0.36 versus 0.33 mmol/L (P=0.91)
"The outcomes were less influenced by the type of monosaccharides than by energy status," they wrote.
There was an increase in abdominal and diarrheal symptoms among participants in the fructose group.
They noted that the study was limited by the large quantity of each monosaccharide in participants' diets relative to the average sugar consumption in England (25% versus 14.6%), lack of crossover between groups, short-term of the study, lack of regulation in food intake during the hypercaloric period, and lack of liver biopsy data.
Nonetheless, "our study serves as a warning that even short changes in lifestyle can have profound impacts on your liver," MacDonald said.
The study was supported by a grant from Core charity, the National Institute for Health Research Biomedical Research Unit in Gastrointestinal and Liver Diseases, the Nottingham University Hospitals NHS Trust, and the University of Nottingham.
MacDonald reported serving on scientific advisory boards for Mars and Coca Cola.
Primary source: Gastroenterology
Source reference: MacDonald IA, et al "No difference between high-fructose and high-glucose diets on liver triacylglycerol or biochemistry in healthy overweight men" Gastroenterology2013; 145: 1016-1025.