High-Fat or High-Sugar: What’s Worse for the Brain?

high sugar and brainA recent study from Oregon State University asked whether diet differences could affect anxiety, memory, or cognitive ability.

The animal study found that the typical “Western” diet, usually high fat and high sugar, has negative effects on measures of cognitive flexibility. 

The Study

The study was done on young lab mice around two months old. The mice were randomly assigned a high fat diet (42% fat, 43% carb/sucrose), a high sugar diet (13% fat, 62% carb/sucrose), or a normal diet (13% fat/62% carb/sucrose).

Certain tasks and fecal microbiome tests were performed before starting the new diet and again two weeks after initiating the new diet.

After six weeks, the mice went through water-maze testing – a well-accepted measure of long and short term memory.

Even after this short amount of time on the new diet, the mice on the high sugar diets began to clearly lose mental and physical function including cognitive flexibility when compared with the mice on the normal diet. The high sugar diets appeared to have the most dramatic effect.

What is Cognitive Flexibility?

Cognitive flexibility is the ability to easily adapt to changing situations.

Kathy Magnusson, a Veterinary Medicine professor at OSU and top investigator at the Linus Pauling Institute, says, “The impairment of cognitive flexibility in this study was pretty strong. Think about driving home on a route that’s very familiar to you, something you’re used to doing. Then one day that road is closed and you suddenly have to find a new way home.”

A person with high cognitive flexibility could adapt the situation, find a new way home, and remember the road is closed and take the new route to work the next morning. A person without that flexibility would have a more stressful drive home and possibly forget and do the same thing on the way to work the next morning.

Why Does it Matter?

The Western diet characterized by high levels of processed sugars and fats have been linked to obesity, Alzheimer’s Disease, and many other chronic illnesses. Sugar is directly irritating to the body when in excess and processed fats tend to be unstable, especially when subject to cooking temperatures.

Now, we can see that Western diets directly affect the balance of healthy bacteria in your body – which may have deep implications for brain and cognitive health. “It’s increasingly clear that our gut bacteria, or microbiota, can communicate with the human brain,” said Kathy Magnusson.

These changes in the bacteria negatively affect physical and mental function.

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