An abundance of scientific research demonstrates that overconsumption of added dietary sugar is harmful to physical health, but research on its long-term effects on cognitive health is lacking. Findings from a recent study in mice indicate that overconsumption of added sugar during adolescence contributes to the risk of becoming obese, hyperactive, and cognitively impaired as adults.

Current public health guidelines recommend that children between the ages of two and 19 years limit their intake of added sugars to less than 10 percent of their total daily calories – roughly 12 teaspoons per day. Despite these recommendations, the average child living in the United States consumes 15 to 18 teaspoons of added sugar every day, primarily from sugar-sweetened beverages, desserts, and sweet snacks.

The authors of the study conducted two experiments involving four groups of young (adolescent) mice. All mice could eat freely from their standard mouse food. In the first experiment, water was always available to two groups of mice, but one group had access to only plain drinking water, while one group had a choice between plain water or water containing a 25 percent sugar solution. In the second experiment, both groups had access to only plain drinking water, but one group was given restricted access (two hours per day, five days per week) to water containing a 25 percent sugar solution. At the end of the 12-week intervention, the authors of the study subjected the mice to a battery of behavioral and memory tests and assessed neurogenesis (the foundation for memory) in the animals' brains.

They found that the mice that consumed high quantities of sugar became hyperactive when they were exposed to a new situation and had impaired memory formation – phenomena commonly observed in attention deficit and hyperactivity disorders. They also demonstrated impaired neurogenesis in their brains, especially within the dentate gyrus area of the hippocampus, a region associated with memory formation. About four weeks into the 12-week intervention, the mice began to gain weight, and by the end of the study, they were about 10 percent overweight. Mice whose access to sugar was restricted consumed four times less sugar than those who had full access. They did not gain weight, and they experienced fewer neurocognitive deficits.

These findings suggest that overconsumption of sugar in mice promotes weight gain, behavior problems, and memory impairments. Although this was a mouse study, many of these findings are translatable to humans. Learn more about the harmful effects of sugar on the brain in this episode featuring Dr. Rhonda Patrick.

• Link to full study.