Study: Supposedly Safe Amounts of Sugar May Be Toxic

Various kinds of sugar, brown, white and refined sugar

New information about sugar may leave a bitter taste in your mouth. Scientists at the University of Utah have discovered that feeding mice diets consisting of 25% added sugars – equivalent to about three sodas for humans – doubled mortality in female mice and significantly impaired male reproduction.

Added sugar, or any sugar added to foods during processing or preparation, makes up a significant proportion of the American diet. Since the 1970s, added sugars in the American diet have increased by 50%, due largely to the use of high-fructose corn syrup. Studies estimate that added sugars make up at least a quarter of calorie counts for 13-25% of Americans. In contrast, dietary guidelines recommend that solid fats and added sugars combined make up no more than 5-15% of total calories. For most Americans, sodas, energy drinks and sports drinks are the largest source of added sugar calories, followed by grain-based desserts.

Prior studies have generally given mice doses of sugar that are far higher than what is considered a safe level for humans. So in this study, the researchers limited the amount and type of sugar to levels that have widely been thought to be nontoxic for humans. In addition, they gave the mice a mixture of glucose and fructose that is very similar to the kinds of sugars you might drink in sodas and other sweet drinks.

What the researchers found should be enough to strike fear into the hearts of even the most avid soda lovers. Female mice fed the high-sugar diet died at twice the rate of the control mice. And male mice became much less virile. The little sugar-fiends were less competitive, controlling 26% less territory.

The male mice were also less fruitful, siring 25% fewer offspring than mice not doped up on sugar. This decrease in reproduction might be related to “reproductive impairments” triggered by the sugar intake, or it could be a result of the mice’s decreased ability to occupy and defend territory. Interestingly, the sugary diet initially increased female birth rates, but caused them to tank later in the study. No overall effect on female fertility was observed.

Sugar sounding scary? Learn more about how to kick your sugar habit.