Published August 13, 2013
New research suggests that consuming added sugars, such as those found in candy, may prove toxic – even within the recommended dietary limits for humans.
Currently, the National Research Council recommends that people consume no more than 25 percent of their daily calories from added sugars. In a study published in Nature Communications, researchers sought to test how mice responded when they consumed a diet matching this recommendation.
“One common criticism of animals studies is they look at doses irrelevant to the human condition, which makes them more difficult to translate,” first study author James Ruff, a doctoral graduate from the University of Utah, told FoxNews.com. “We wanted to pick something relevant to human health.”
Ruff and senior study author Wayne Potts, a professor of biology at the University of Utah, tested this theory using two groups of unaltered mice. For 26 weeks, one group of mice was fed a mixture of otherwise healthy food comprised of 25 percent added sugars, while the control group of mice ate the same mixture of food with no added sugars. Both groups consumed roughly the same number of overall calories each day.
The mice were then released into a “mouse barn” designed to be similar to a mouse’s natural environment. There, the researchers observed the mice for 32 more weeks, which comprised the remainder of their life spans.
During this time, they used microchip technology to compare how long the sugar-fed mice lived in contrast to the control mice, how well they reproduced and how well they were able to acquire territory. According to Ruff, these factors make up a “Darwinian measure of an animal (and) its fitness.”
Overall, nearly twice as many female sugar-fed mice died within 32 weeks when compared to the control mice. Additionally, male sugar-fed mice produced 25 percent fewer offspring compared to control mice, and they gained control of 26 percent fewer territories.
“The odd things is our mice passed their physicals. They really didn’t look any different from control animals,” Ruff said. In fact, no differences were found between the two groups in terms of rates of obesity or fasting insulin, glucose or triglyceride levels.
The only noticeable differences between the groups of mice were that both male and female sugar-fed mice experienced higher levels of cholesterol, and female sugar-fed mice experienced an impaired ability to clear glucose from their blood.
Ruff described these results as, “statistically significant but clinically minor.” As a result, the study authors believe that consuming a diet of just 25 percent added sugars impaired mice just enough to hinder their ability to compete effectively in a natural environment. These types of small health declines are often difficult to detect in humans, according to Potts.
“We all know that every other month you turn on the news and something you’re exposed to all your life is found to be toxic after 20 years of epidemiology,” Potts told FoxNews.com. “It indicates we really do not have a reliable way to detect toxicity if it’s not gross toxicity. If health declines just by 10 or 20 percent, we’re often missing that kind of toxicity.”
Notably, Potts and Ruff have done similar studies measuring the effects of inbreeding in mice, and they noticed nearly identical outcomes in inbred and sugar-fed mice.
“The mice are telling us it’s a toss-up,” Potts said. “In both cases they lose about 30 percent of fitness and reproductive output.”
Though researchers would like to test the toxicity of low levels of sugar consumption in humans, they point out that this would be a difficult endeavor as human lifespans are much longer. However, they maintain that their findings should still raise an alarm among humans. If something makes a mouse sick, the researchers ask: Do people really want it in their bodies?
“Our specialty is detecting health declines that are 10 to 20 percent performance degradations, which never show up as something you can overtly see in people,” Potts said. “But we think there’s a sizable portion of the population that if they knew they were losing some of their health and performance, would be upset that these things are in our food supply and environment.”