This Is Your Brain on Food

Let’s get to the easy stuff first. Your brain loves it when you eat fat, salt, and sugar. Up until the last one hundred years, brains rarely came across fat, salt, and sugar in nature. When they did, the rule was simple: eat everything to completion. Brains evolved to release one or all of the neurotransmitters dopamine, endorphins, or endocannabinoids to thank you for eating fat, salt, and sugar. The reason for the euphoria these neurotransmitters induce is entirely related to the brain’s survival.

Some Foods Will Make You Temporarily Happier
The simplest answer to my subtitle is “yes,” some foods will make you happier, temporarily. Due to the way in which your brain evolved, the pleasure you experience from eating fat, salt, and sugar is ephemeral. The people who sell you foods with fat, salt, and sugar really love that aspect of brain evolution. The same is true for orgasms; the pleasure is short-lived by evolutionary design. Why? The answer is related to the brain’s two goals: survival and procreation. Brains prefer that we keep eating and having sex.

What about everything else you eat? For simplicity, let’s assume that you’re a normal healthy person; not all foods are always good or bad for all people. Let’s ignore fats, salt, and sugar. Are there any nutrients that you should eat to feel happier and healthier? No, absolutely no evidence exists to support such a claim. Indeed, the brain does not work that way. We become depressed or unhappy or cognitively impaired because of poor diets that contain too many fats and sugars (Front Nutr, 2021; 8: 656290). Popular claims that you can improve your mood and thinking rely upon changing the diet to make it less detrimental to your overall health. Simply stated: Poor diets are harmful to the brain. In contrast, do not expect that any specific food will make you happy all day long. Once again, brains do not work that way. Remember, brains only offer ephemeral pleasure.

A Bad Diet Can Impair Brain Function
Considerable evidence has linked an unhealthy diet to cognitive decline and depression associated with obesity, metabolic syndrome, diabetes, and cancer. These conditions lead to body-wide chronic inflammation that predisposes us to depression and cognitive decline.

Furthermore, being depressed or anxious can lead to poor dietary habits; conversely, poor dietary choices can lead to depression and anxiety. Although it can be difficult to determine which came first in some people, most relevant studies indicate that an unhealthy diet is a significant risk factor for future depressive symptoms (Br J Psychiatry 2009;195:408-413).

Unfortunately, there is very limited rigorous scientific evidence in humans that links specific nutrients to our mood. We do have a lot of evidence from animal studies, mostly rodents, but I have significant concerns about the validity of those studies and their applicability to humans because rodent chows have lots of unhealthy fats and usually get too many calories from soybean or corn oil and sugar. These diets aren't natural diets for rodents, or especially humans to consume. I should know, I spent the last 40 years feeding this diet to my rats.

Without a doubt, some dietary regimens are definitely more beneficial than others, for example, the Mediterranean diet has been associated with a lower risk of depression (BMC Med 2013;11:13). Notice the specificity of the conclusion: a lower risk of depression as compared to consuming a poor diet. An investigation of popular fad diets, such as those recommending either high protein or high carbohydrate intakes, found no relation between mood state and macronutrient content (Genes Brain Behav 2009;8:193-202). Thus, these diets are not likely to make someone more or less anxious or relaxed, as compared to being an omnivore.

Another study (Nutr Neurosci 2015;18:137-144) investigated for 23 months the association between diet and overall mood state in 84 adult humans with metabolic syndrome. The scientists carefully monitored the participants’ daily servings of cereals, vegetables, fruits, dairy products, and meat, and the percentage of energy provided by total and saturated fats, as well as the daily amount of cholesterol and sodium. The number of different foods consumed daily determined the variety of the diet. Daily mood was determined using a Visual Analogue Scale mood thermometer. Importantly, their results were corrected for the possible effects of caloric intake, age, and sex.

Saturated Fats and High-calorie Intake Can Lead to Depression
The results confirmed that a poor diet that was high in saturated fats and caloric levels lead to depression. Possibly more important, their analysis of the effects of specific nutrients indicated that people who consumed more water, fiber, ascorbic acid, tryptophan, magnesium, and selenium reported a better mood overall. A diet high in legumes, fruits, and vegetables, such as the Mediterranean diet, would provide these nutrients. One interesting finding was that a diet with a higher variety of fruits and vegetables was more effective than eating a diet that had a limited variety. It is unknown what role fiber plays in the control of mood and the finding in this study might be related to the presence of fiber in most legumes, fruits, and vegetables that were reported by the participants.

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Probably the most encouraging point to take away from this, and similar studies, was that it is never too late to take advantage of the benefits of a healthy diet (Am J Clin Nutr 2013;97:419-427; Front Nutr, 2021; 8: 656290). Just do not expect any particular food will make you happier or healthier. Nutritional deficiencies often result in impaired brain function, and, conversely, a healthy diet can only return you to baseline levels of brain function.