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Think about it. Your brain is always “on.” It takes care of your thoughts and movements, your breathing and heartbeat, your senses — it works hard 24/7, even while you’re asleep. This means your brain requires a constant supply of fuel. That “fuel” comes from the foods you eat — and what’s in that fuel makes all the difference. Put simply, what you eat directly affects the structure and function of your brain and, ultimately, your mood.
Like an expensive car, your brain functions best when it gets only premium fuel. Eating high-quality foods that contain lots of vitamins, minerals, and antioxidants nourish the brain and protect it from oxidative stress — the “waste” (free radicals) produced when the body uses oxygen, which can damage cells.
Unfortunately, just like an expensive car, your brain can be damaged if you ingest anything other than premium fuel. If substances from “low-premium” fuel (such as what you get from processed or refined foods) get to the brain, it has little ability to get rid of them. Diets high in refined sugars, for example, are harmful to the brain. In addition to worsening your body’s regulation of insulin, they also promote inflammation and oxidative stress. Multiple studies have found a correlation between a diet high in refined sugars and impaired brain function — and even a worsening of symptoms of mood disorders, such as depression.
It makes sense. If your brain is deprived of good-quality nutrition, or if free radicals or damaging inflammatory cells are circulating within the brain’s enclosed space, further contributing to brain tissue injury, consequences are to be expected. What’s interesting is that for many years, the medical field did not fully acknowledge the connection between mood and food.
Today, fortunately, the burgeoning field of nutritional psychiatry is finding there are many consequences and correlations between not only what you eat, how you feel, and how you ultimately behave, but also the kinds of bacteria that live in your gut.
How the foods you eat affect how you feel
A new expert review confirms that diet significantly influences mental health and wellbeing, but cautions that the evidence for many diets is comparatively weak.
Lead author, Professor Suzanne Dickson (University of Gothenburg, Sweden) said:
“We have found that there is increasing evidence of a link between a poor diet and the worsening of mood disorders, including anxiety and depression. However, many common beliefs about the health effects of certain foods are not supported by solid evidence”.
The researchers found that there are some areas where this link between diet and mental health is firmly established, such as the ability of high fat and low carbohydrate diet (a ketogenic diet) to help children with epilepsy, and the effect of vitamin B12 deficiency on fatigue, poor memory, and depression.
They also found that there is good evidence that a Mediterranean diet, rich in vegetables and olive oil, shows mental health benefits, such as giving some protection against depression and anxiety. However, for many foods or supplements, the evidence is inconclusive, as for example with the use of vitamin D supplements, or with foods believed to be associated with ADHD or autism.
“With individual conditions, we often found very mixed evidence”, said Suzanne Dickson. “With ADHD for example, we can see an increase in the quantity of refined sugar in the diet seems to increase ADHD and hyperactivity, whereas eating more fresh fruit and vegetables seems to protect against these conditions. But there are comparatively few studies, and many of them don’t last long enough to show long-term effects”.
The study confirms that while certain foods can be associated with a mental health condition, this tells us little about why the food causes this effect. It concludes that the need to link mental health effects with provable dietary causes needs to be the main focus of future research in nutritional psychiatry.
Professor Dickson continued:
“There is a general belief that dietary advice for mental health is based on solid scientific evidence. In reality, it is very difficult to prove that specific diets or specific dietary components contribute to mental health.
The scientists confirmed that some foods had readily provable links to mental health, for example, that nutrition in the womb and in early life can have significant effects on brain function in later life. Proving the effect of diet on mental health in the general population was more difficult.
Suzanne Dickson said “In healthy adults, dietary effects on mental health are fairly small, and that makes detecting these effects difficult: it may be that dietary supplementation only works if there are deficiencies due to a poor diet. We also need to consider genetics: subtle differences in metabolism may mean that some people respond better to changes in the diet than others.
There are also practical difficulties that need to be overcome in testing diets. Food is not a drug, so it needs to be tested differently from a drug. We can give someone a dummy pill to see if there is an improvement due to the placebo effect, but you can’t easily give people dummy food. Nutritional psychiatry is a new field. The message of this paper is that the effects of diet on mental health are real, but that we need to be careful about jumping to conclusions on the basis of provisional evidence. We need more studies on the long-term effects of everyday diets”.
Nutritional psychiatry: What does it mean for you?
Start paying attention to how eating different foods makes you feel — not just at the moment, but the next day. Try eating a “clean” diet for two to three weeks — that means cutting out all processed foods and sugar. See how you feel. Then slowly introduce foods back into your diet, one by one, and see how you feel.
When some people “go clean,” they cannot believe how much better they feel both physically and emotionally, and how much worse they then feel when they reintroduce the foods that are known to enhance inflammation.