Diet can affect mood, behavior and more

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Summary: Researchers assess how our diet choices can affect our moods and behavior, and explain how certain diets can help treat certain neurological disorders.

Source: The conversation

During the long sea voyages of the 15th and 16th centuries, a period known as the Age of Discovery, seafarers reported experiencing visions of sublime foods and green fields. The discovery that these were nothing more than hallucinations after months at sea was agonizing. Some sailors cried with longing; others threw themselves overboard.

The cure for these staggering mirages turned out not to be a concoction of complex chemicals, as once thought, but a simple lemon juice antidote. These sailors suffered from scurvy, a disease caused by a lack of vitamin C, an essential micronutrient that people get from eating fruits and vegetables.

Vitamin C is important for the production and release of neurotransmitters, the brain’s chemical messengers. Without them, the brain cells don’t communicate effectively with each other, which can lead to hallucinations.

As early explorers show in this famous example, there’s a tight connection between food and the brain that researchers like me are working to unravel. As a scientist studying the neuroscience of nutrition at the University of Michigan, I am particularly interested in how components of food and their breakdown products can alter the genetic instructions that control our physiology.

In addition, my research also focuses on understanding how food can affect our thoughts, moods, and behaviors. Although we can’t yet prevent or treat brain diseases through diet, researchers like me are learning a lot about the role diet plays in the everyday brain processes that make us who we are.

Perhaps not surprisingly, a delicate nutrient balance is key to brain health: deficiencies or excesses of vitamins, sugars, fats and amino acids can affect the brain and behavior in negative or positive ways.

Vitamin and mineral deficiencies

As with vitamin C, deficiencies in other vitamins and minerals can also trigger nutritional diseases in humans that adversely affect the brain. For example, low levels of vitamin B3/niacin in the diet – typically found in meat and fish – cause pellagra, a disease in which people develop dementia.

Niacin is essential for converting food into energy and building blocks, protecting the genetic blueprint from environmental damage, and controlling how much of certain gene products is made. In the absence of these critical processes, brain cells, also called neurons, fail and die prematurely, leading to dementia.

In animal models, reducing or blocking brain production of niacin promotes neuronal damage and cell death. Conversely, increasing niacin levels has been shown to mitigate the effects of neurodegenerative diseases such as Alzheimer’s, Huntington’s and Parkinson’s. Observational studies in humans suggest that adequate amounts of niacin may protect against these diseases, but the results are not yet conclusive.

Interestingly, niacin deficiency caused by excessive alcohol consumption can lead to effects similar to those of pellagra.

Another example of how nutrient deficiencies affect brain function can be found in the element iodine, which like niacin must be obtained from the diet. Iodine, found in seafood and seaweed, is an essential building block for thyroid hormones – signaling molecules important to many aspects of human biology, including development, metabolism, appetite and sleep. Low iodine levels prevent the production of sufficient amounts of thyroid hormones and impair these essential physiological processes.

Iodine is particularly important for the developing human brain; Before table salt was supplemented with this mineral in the 1920s, iodine deficiency was a leading cause of cognitive disability worldwide. The introduction of iodized salt is believed to have contributed to the gradual rise in IQ scores over the past century.

Ketogenic diet in epilepsy

Not all nutritional deficiencies are bad for the brain. In fact, studies show that people with drug-resistant epilepsy — a condition in which brain cells fire out of control — can reduce the number of seizures by following an ultra-low-carb diet known as a ketogenic diet, in which 80% to 90% of Calories are obtained from fat.

Carbohydrates are the body’s preferred source of energy. When they’re not available – either because of fasting or a ketogenic diet – cells get fuel by breaking down fats into compounds called ketones. Using ketones for energy causes profound changes in metabolism and physiology, including the levels of hormones circulating in the body, the amount of neurotransmitters produced by the brain, and the types of bacteria that live in the gut.

Researchers believe these diet-related changes, particularly the higher production of brain chemicals that can calm neurons and decrease levels of inflammatory molecules, may play a role in the ketogenic diet’s ability to reduce seizures. These changes may also explain the benefits of a ketogenic state — either through dieting or fasting — on cognitive function and mood.

Credit: Brainy Can

Sugar, saturated fats and ultra-processed foods

Excess amounts of some nutrients can also have adverse effects on the brain. In humans and animal models, increased consumption of refined sugars and saturated fats — a combination commonly found in ultra-processed foods — promotes eating by desensitizing the brain to the hormonal signals known to regulate satiety.

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This shows a box of macaroons
What we eat matters, and just the right amount of essential nutrients is key to our overall health. The image is in the public domain

Interestingly, a diet high in these foods also desensitizes the taste system, causing animals and humans to perceive foods as less sweet. These sensory changes can affect food choices as well as the rewards we receive from food.

For example, research shows that eating ice cream every day for two weeks dampens people’s responses to ice cream in brain areas important to taste and reward. Some researchers believe this reduction in food reward signals may increase cravings for even more fatty and sugary foods, much like smokers crave cigarettes.

High-fat and processed foods are also associated with lower cognitive function and memory in humans and animal models, and a higher incidence of neurodegenerative diseases. However, researchers still don’t know if these effects are due to these foods or to the weight gain and insulin resistance that develop with long-term consumption of these diets.

timescales

This brings us to a critical aspect of how diet affects the brain: time. Some foods can affect brain function and behavior acutely—say, over hours or days—while others may take weeks, months, or even years to show an effect.

For example, eating a piece of cake quickly shifts a person with drug-resistant epilepsy’s fat-burning, ketogenic metabolism to a carbohydrate-burning metabolism, increasing the risk of seizures.

In contrast, it takes weeks of sugar consumption for the brain’s taste and reward pathways to change, and months of vitamin C deficiency to develop scurvy.

Finally, in diseases such as Alzheimer’s and Parkinson’s, risk is influenced by years of dietary exposure combined with 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, not too much, just enough of each nutrient.

About this news from nutrition and psychology research

Author: Monica Dus
Source: The conversation
Contact: Monica Dus – The Conversation
Picture: The image is in the public domain

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