During the long sea voyages of the 15th and 16th centuries, a period known as the age of discoveryreported sailors experienced 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. Those sailors suffered from scurvya 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 chemical messengers of the brain. In its absence, brain cells don’t communicate effectively with each other, which can lead to hallucinations.
As early explorers show in this famous example, there is an intimate connection between food and the brain that researchers like me are working to unravel. As a scientist who studies the neuroscience of nutrition at the University of Michigan, I am particularly interested in how components of food and their breakdown products can change genetic instructions that control our physiology.
In addition, my research also focuses on understanding how foods 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 pellagraa 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 known as neurons, fail and die prematurelyleads to dementia.
In animal models, reducing or blocking the production of niacin in the brain promotes neuronal damage and cell death. Conversely, increasing niacin levels has been shown to ameliorate the effects of neurodegenerative diseases such as Alzheimer’s, Huntington’s and Parkinson’s. Observational studies in humans suggest that adequate levels of niacin are present can protect against these diseasesbut 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 disabilities worldwide. The introduction of iodized salt is thought to have helped gradual increase 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 B. by adopting an ultra-low-carb regimen known as a ketogenic dietwhere 80 to 90 percent of calories come 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 has profound effects Changes in metabolism and physiologyincluding 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 think so these dietary changes, specifically 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 that Benefits of a ketogenic state– either through diet or fasting – on cognitive function and mood.
Sugar, ultra-processed foods
Excess amounts of some nutrients can also have adverse effects on the brain. Increased consumption of refinery in humans and animal models sugar and saturated fats— a combination commonly found in ultra-processed foods — encourages binge eating desensitization the brain on the hormonal signals known to regulate satiety.
Interestingly, a diet rich in these foods is also important desensitizes the taste system, causing animals and humans to perceive food as less sweet. These sensory changes can affect food choices as well as the rewards we receive from food. For example, research shows that people’s reactions to ice cream lie in brain areas important for taste and reward are deadened if they eat it every day for two weeks. Some researchers think this decrease in food reward signals may be the case Increase cravings for even more fatty and sugary foodsmuch like smokers crave cigarettes.
High-fat and processed foods are also associated with lower cognitive function and memory into people 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 weight gain and insulin resistance develop with long-term use of these diets.
timescales
This brings us to a critical aspect of how diet affects the brain: time. Some foods can acutely affect brain function and behavior – e.g. e.g. over hours or days – while others 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 factors 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.
-The conversation
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