In the eyes of neuroscientists, how does diet affect mood and behavior?

What we eat matters, and getting the right amount of essential nutrients is key to our overall health

As this famous example of early explorers illustrates, there is a strong connection between food and the brain, and it's a problem that scientists like me are trying to unravel

Beyond that, another goal of my research is to understand how food affects our thoughts, emotions, and behaviors

Perhaps unsurprisingly, a delicate balance of nutrition is key to brain health: deficiencies or excesses of vitamins, sugars, fats, and amino acids can affect the brain and behavior in beneficial or detrimental ways

Eating a complete diet that includes a balanced supply of all essential vitamins and minerals is important for brain health

vitamin and mineral deficiencies

As with vitamin C, deficiencies in other vitamins and minerals can lead to nutritional diseases that adversely affect the human brain

Niacin is essential for the body to convert food into energy and building materials, protect the genetic blueprint from environmental damage, and control the production of certain gene products

In animal models, reducing or blocking niacin production promotes neuronal damage and cell death

Interestingly, niacin deficiency caused by excessive alcohol consumption can cause similar consequences to pellagra

Another example of how nutrient deficiencies can affect brain function can be found in elemental iodine, which, like niacin, must be obtained from one's diet

Iodine is especially important for the developing human brain

A ketogenic diet can help people with drug-resistant epilepsy

ketogenic diet for epilepsy

Not all dietary deficiencies are bad for the brain

Carbohydrates are the body's preferred source of energy

The researchers believe that these diet-dependent changes, particularly the high production of chemicals in the brain that quiet neurons and reduce levels of inflammatory molecules, may play a role in the ketogenic diet's ability to reduce the number of seizures

Some foods can negatively affect your memory and mood

Sugar, saturated fat and ultra-processed foods

Excessive amounts of certain nutrients can also have harmful effects on the brain
.
In human and animal models, increased intake of refined sugar and saturated fat, a combination common in ultra-processed foods, desensitizes the brain to hormonal signals that regulate satiety and satisfaction, thereby promoting eating
.

Interestingly, diets rich in these foods also desensitize the taste system, making food less sweet in animals and humans
.
These sensory changes may affect food choices and the rewards we receive from food
.
For example, studies have shown that when people eat ice cream every day for two weeks, important areas of the brain responsible for taste and reward become less responsive to ice cream
.
Some scientists believe that this reduction in food reward signals may enhance cravings for more fatty and sugary foods, just as smokers crave cigarettes
.

Diets high in fat and processed foods have also been associated with poorer cognitive function and memory in humans and animal models, as well as higher rates of neurodegenerative diseases
.
However, scientists still don't know whether these effects are due to these foods, or the weight gain and insulin resistance associated with long-term consumption of these foods
.

This brings up a key aspect of diet's effect on the brain: timing
.
Some foods can seriously affect brain function and behavior, say for hours or days, while others take weeks, months, or even years to have an effect
.

For example, eating a piece of cake can rapidly switch the fat-burning, ketogenic metabolism to carbohydrate-burning metabolism in patients with drug-resistant epilepsy, thereby increasing the risk of seizures
.
On the other hand, it takes weeks of sugar intake to alter taste and reward pathways in the brain, and months of vitamin C deficiency to develop scurvy
.
Finally, when it comes to diseases like Alzheimer's and Parkinson's, risk is influenced by years of dietary exposure as well as other genetic or lifestyle factors such as smoking
.

In the end, the relationship between food and the brain is a bit like the delicate Goldilocks: We don't need too little or too much of every nutrient, just enough
.

By Monica Dus, associate professor of molecular, cellular and developmental biology at the University of Michigan
.