Blog | Tuesday, February 21, 2012

QD: News Every Day--No smoking gun shows that fructose is worse than other sugars

Better research is needed before fructose can be blamed for a role in the obesity epidemic, a study concluded. A meta-analysis found that pure fructose had no effect on weight compared with diets that provided the same calories using nonfructose carbohydrates.

Instead, in these studies, the extra calories that are characteristic of high-fructose diets and not to fructose itself caused weight gain.

It's still not clearly understood why or how fructose might cause more weight gain than other carbohydrates. Still, a 2009 American Heart Association statement recommended an upper limit of intake for added sugars equal to one half of the discretionary calorie allowance (less than 100 kcal/d for women and less than 150 kcal/d for men) to achieve and maintain a healthy body weight.

To further isolate the effects of fructose, researchers reviewed controlled feeding trials lasting 7 or more days that compared the effect on body weight of free fructose and nonfructose carbohydrate in diets providing similar calories or of diets supplemented with free fructose to provide excess energy and usual or control diets. Trials evaluating high-fructose corn syrup (42% to 55% free fructose) were excluded.

Results appeared in the Feb. 21 issue of Annals of Internal Medicine.

Thirty-one same-calorie trials with 637 participants and 10 excess-energy trials with 119 participants were included. Limitations included that studies tended to be fewer than 15 participants and lasted for fewer than 12 weeks. They were generally ranked as low quality because of problems describing randomization, and similar problems.

The meta-analysis could conclude that fructose had no overall effect on body weight in same-calorie trials (mean difference, -0.14 kg [95% confidence interval [CI], -0.37 to 0.10 kg] for fructose compared with nonfructose carbohydrates. High doses of fructose in excess energy trials (+104 to 250 g/d, +18% to 97% of total daily energy intake) lead to significant increases in weight (mean difference, 0.53 kg [CI, 0.26 to 0.79 kg] with fructose).

To clarify the role of fructose in the obesity epidemic, larger, longer and higher-quality studies are needed. Also, researchers need to conduct trials with fructose as it's typically consumed, the authors wrote.

"Because current dietary guidelines are recommending reductions in the intake of sugar-sweetened beverages and at the same time encouraging consumption of fruits and vegetables, it will be equally important to have high-quality feeding trials that reconcile differences in effect between added fructose in sugar-sweetened beverages and naturally occurring fructose in fruits and vegetables," they wrote. "These future trials will be necessary for answering the question of whether the consumption of fructose under real-world conditions leads to overconsumption of calories and weight gain."