A high intake of fructose impairs the cognitive abilities of rats by interfering with insulin signaling, but omega-3 fatty acids (n-3) reduces those negative effects effects according to a study from the Department of Integrative Biology and Physiology UCLA published in Journal of Physiology.
Although headlines today, including my own, emphasize the study’s findings regarding the impairing effects of high levels of fructose, the study also highlights the importance of n-3 acids, specifically DHA, to cognitive function. The authors of the study conclude: “In terms of public health, these results support the encouraging possibility that healthy diets can attenuate the action of unhealthy diets such that the right combination of foods is crucial for a healthy brain.”
The study, conducted by Rahul Agrawal1 and Fernando Gomez-Pinilla, consisted of four groups of six rats:
- one group ate an n-3 deficient diet with a fructose solution
- one group ate an n-3 deficient diet without a fructose solution
- one group ate an n-3 sufficient diet with a fructose solution
- one group ate an n-3 sufficient diet without a fructose solution
Each group was tested on a Barnes maze, a standard measure of spatial learning and memory in rodents. Prior to beginning their special diets all of the rats had been trained in the maze for a five days were found to be of equal cognitive condition.
The study found that an n-3 deficient diet hampered the rats’ performance on the maze, and that adding high fructose intake to an n-3 deficient diet made things substantially worse. The rats with an n-3 sufficient diet but a high level of fructose did significantly better than those with a n-3 deficient diet and a high level of fructose, but still did worse than those with a deficient n-3 level but no fructose. Here’s an illustration of the latency in completing the maze (lower is better):
The study notes: “Although there was a preference towards fructose drinking in comparison to the food intake, no differences were observed in body weight and total caloric intake, thus suggesting that obesity is not a major contributor to altered memory functions in this model.”
Full Paper: The Journal of Physiology: ‘Metabolic syndrome’ in the brain: deficiency in omega-3 fatty acid exacerbates dysfunctions in insulin receptor signalling and cognition
This is a new study and has yet to be replicated, and so far its implications for human diets is unclear. “We’re not talking about naturally occurring fructose in fruits, which also contain important antioxidants,” Gomez-Pinilla said in a pres release. “We’re concerned about high-fructose corn syrup that is added to manufactured food products as a sweetener and preservative.”
Although studies have found positive benefits in taking DHA supplements (see Wikipedia for an overview), previous study by Nutritional Sciences Division at King’s College London on the DHA levels in vegans and vegetarians concluded that although those who don’t eat meat have significantly lower levels of DHA “There is no evidence of adverse effects on health or cognitive function with lower DHA intake in vegetarians.” However, there are now a number of algae based vegan DHA supplements.