LOS ANGELES — When mice were fed a diet that was 25 percent added sugars — an amount consumed by many humans — the females died at twice the normal rate and the males were less likely to reproduce and hold territory, scientists said in a study published Tuesday.
The study shows “that added sugar consumed at concentrations currently considered safe exerts dramatic impacts on mammalian health,” the researchers said in the study, published in the journal Nature Communications. “Many researchers have already made calls for re-evaluation of these safe levels of consumption.”
The study’s senior author, University of Utah biology professor Wayne Potts, said earlier studies fed mice sugars at levels higher than people eat in sodas, cookies, candy and other items. The current study stuck to levels eaten by people.
The mice lived in “seminatural enclosures,” and the experimental and control groups lived in direct competition with each other. After being fed the two diets for 26 weeks, the mice lived for 32 weeks in mouse barns — enclosures of 377 square feet ringed by 3-foot walls. There were some nesting areas that were more desirable than others.
“Added sugars” are those added during processing or preparation, not those that occur naturally in fruit or milk. The scientists fed the mice a diet that got its added sugars from half fructose and half glucose monosaccharides, which is about what’s found in high fructose corn syrup, or HFCS, Potts said. The study, he said, was not set up to differentiate between the effects of different forms of caloric sweeteners.
The Corn Refiners Association, a trade group, questioned the use of mice in the study, saying in a statement that the only way to know the effect in people would be to test people.
“Mice do not eat sugar as a part of their normal diet, so the authors are measuring a contrived overload effect that might not be present had the rodents adapted to sugar intake over time,” the group said.
The trade group for the sugar industry, the Sugar Association, said it was studying the research. But it maintained that the sweetener used in the study was crucial.
“Sugar and the various formulations of HFCS are molecularly different — they are not the same product, yet too often, and erroneously, HFCS is referred to as an ‘added sugar.’” the statement said. “Only sugar is sugar.”
In a statement, Potts said mice were “an excellent mammal to model human dietary issues” because they’ve been living with people and eating the same food for thousands of years.
The Utah researchers noted that consumption of added sugars increased in the American diet by 50 percent from the 1970s to about 2008, primarily because of the higher consumption of HFCS. (The intake has since been declining, and the Sugar Association said consumption of sucrose has decreased by 35 percent in the last four decades.)
The 2010 Dietary Guidelines for Americans advise us to limit our total intake of added sugars, fats and other “discretionary calories” to 5 percent to 15 percent of total calories consumed every day. The Centers for Disease Control and Prevention found that from 2005 to 2010, we got 13 percent of our total calories from added sugar.
The male mice controlled 26 percent fewer territories and produced 25 percent fewer offspring, the scientists said. The lower reproduction levels could be the result of a decreased ability to defend their territories, the researchers said. The diet did not affect weight.
Potts said he has reduced the amount of “refined sugar” he eats and has suggested his family do the same.