What you eat affects how you think suggests research which shows a diet high in sugar can slow the brain, hampering memory and learning.

  Too much sugar slows the brain

Research focussed on high-fructose corn syrup – an inexpensive liquid six times sweeter than cane sugar and often added to processed foods and soft drinks. Two groups of rats were fed a fructose solution as drinking water for six weeks. A second group also received flaxseed oil and docosahexaenoic acid (DHA) – omega-3 fatty acids – which protect against damage to the synapses.

“DHA is essential for synaptic function – brain cells’ ability to transmit signals to one another,” said Fernando Gomez-Pinilla from University of California – Los Angeles (UCLA) Health Sciences. “This is the mechanism that makes learning and memory possible. Our bodies can’t produce enough DHA, so it must be supplemented through our diet.”

The animals ate standard rat chow and trained on a Barnes maze – which contained numerous holes but only one exit – twice daily for five days prior to starting the experimental diet. The team tested how well the rats navigated the maze, placing visual landmarks in the maze to help rats learn and remember the way. After the diet, the rats were tested again.

“The second group of rats navigated the maze much faster than the rats that did not receive omega-3 fatty acids,” said Gomez-Pinilla. “The DHA-deprived animals were slower, and their brain showed a decline in synaptic activity. Their brain cells had trouble signalling each other, disrupting the rats’ ability to think clearly and recall the route they’d learned six weeks earlier.”

The DHA-deprive rats also developed signs of resistance to insulin, which has lost much of its power to influence brain cells. Gomez-Pinilla suspects fructose is the culprit – eating too much could block insulin’s ability to regulate how cells use and store sugar for energy required for the processing thoughts and emotions.

“Our findings illustrate that what you eat affects how you think,” said Gomez-Pinilla. “Eating a high-fructose diet over the long term alters your brain’s ability to learn and remember information. But adding omega-3 fatty acids to your meals can help minimise the damage.”