How Does Sugar Affect the Brain?


Satisfying sweet tooth cravings are notoriously hard to ignore, but recent research offers one more motivational push to pass on those chocolate-chip cookies and Snickers bars. A new study has linked sugar to side-effects outside the realm of diabetes and weight gain: compromised brain health. Researchers have found that high levels of blood glucose are associated with structural abnormalities and functional deficits in the brain, with the former thought to contribute heavily to the latter.

The effects of sugar on cognitive function have been popular research topics in the past. Sugar has been shown, for example, to modify brain chemistry sufficiently to have addictive qualities similar to those of hard drugs, although less intense. Recent animal studies have linked fructose (and low dietary omega-3 fatty acids) to an increase in insulin resistance in the brain, which impacts glucose metabolism (and energy production) and subsequently leads to impaired cognition and a reduced capacity for synaptic plasticity.

The new study, published in the January 2014 issue of the journal Neurology, aimed to identify the effects of sugar on the brain’s structure and function, with memory as the primary endpoint. It has long been known that diabetes, a condition that results in chronically elevated levels of sugar in the blood, is associated with a structurally smaller hippocampus (the part of the brain heavily involved in forming and storing memories) and an increased risk of dementia, an umbrella term referring to a significant decline in mental ability. What about non-diabetics? Would sugar have similar effects on memory in otherwise healthy adults?

The study analyzed short- and long-term glucose markers in 141 healthy, nondiabetic adults, who were subsequently challenged with a memory test and underwent brain imaging to assess structural changes. The results: participants with higher short- and long-term blood glucose measures were more likely to perform worse on memory tests and also recorded smaller hippocampal structure. The researchers suggest that the structural changes in the hippocampus can at least partially explain the sugar-induced memory deterioration. While this study suggests a direct link between sugar consumption and hippocampal atrophy, researchers warn that it does provide a definitive cause-effect relationship between high sugar intake and memory deficits.

This study provides further evidence that sugar may negatively impact health 1) outside the realm of weight gain and, more importantly, 2) even without preexisting sugar-related disease. It is generally a good idea to limit sugar consumption, especially of the processed variety, and to consume it in moderation. The Institute of Medicine (IOM) recommends that otherwise healthy adults limit consumption of added sugars to 25% of total daily calorie intake.