A few years back, a friend gave me a book as a gift.
It was about the psychology of food cravings.
We think we crave certain foods because they taste good, but what we’re really after is how they make us feel.
The book didn’t teach me much I didn’t already know. Of course food affects mood!
Chocolate makes us happy. Wine makes us relaxed. Coffee makes us jittery.
But the science of nutritional psychology goes far beyond that.
It looks at how we can treat mood disorders with food.
It’s an area where more research is needed, because the way we usually medicate our feelings with food doesn’t work.
Comfort Food Isn’t All That Comforting
Food is the one thing we reach for to feel better, but it usually ends up making us feel worse.
For example, you’re feeling exhausted. You don’t want to cook, so you stop by McDonald’s on the way home. As you bite into your burger, you feel a rush of wellbeing. You drive off feeling good about your choice.
But then you get home, and you feel exhausted. Bloated. Depressed.
You assume the fast food gave you a temporary pick-me-up and the fatigue from before is just kicking in … but is that really the case?
Or is the fast food bringing you down?
There’s a strong link between eating fast food and depression.  Nowhere was that link more graphically illustrated than in the popular 2004 documentary Supersize Me, where Morgan Spurlock ate nothing but McDonald’s for an entire month.
Suffice to say, he didn’t feel all that great at the end.
Eating foods high in calories, sodium and saturated fat can bring you down for several days. And it’s not a chicken-or-the-egg thing. Although depressed people do tend to reach for high-calorie foods, at least one study has shown that the food comes first.
Your Brain on Food
Although we know nutrition affects physical performance, few of us realize how profoundly it affects mental performance.
The brain consumes 20% of your resting metabolic rate, which is around 200 to 300 calories a day. That’s a lot, for an organ that doesn’t even move.
And it needs high-quality calories. It wants antioxidants, healthy fats, vitamins and minerals. Broccoli, leafy greens, extra-virgin olive oil, salmon, turmeric, walnuts, and blueberries.
Yet we send our kids off to school with a bowl of cereal to tide them through until lunch. Maybe we should be throwing a handful of walnuts and blueberries into their bowl.
A poor diet doesn’t just hurt concentration and memory. It has been linked to dementia and cognitive decline as well, making those fruits and vegetables sound a lot more appealing.
Lest you think the answer is popping a bunch of supplements, the research on supplements isn’t as clear as the research on diet. Real food feeds your brain. Pills may help … or they may not.
Eating for Happiness
So what should you be eating, then?
Turns out that adults need different food to boost their mood, compared to young people.
A recent study found that young people should be eating “food that increases availability of neurotransmitter precursors and concentrations in the brain” (such as meat) at least 3 times a week, along with exercising, if they want to feel great. 
Adults, on the other hand, need rich sources of antioxidants (like fruits and vegetables) to feel their best.
And here’s the surprising bit:
Adults need to be particularly careful about foods that activate the stress response.
(Coffee, we’re looking at you.)
Head researcher Lina Begdache of Binghamton University explains that:
Our ability to regulate stress decreases [as we age], so if we consume food that activates the stress response—such as coffee and too much carbohydrates—we are more likely to experience mental distress.”
So that’s one view. We should be dialing back on the caffeine, eating breakfast, and avoiding foods with a high glycemic index.
But Begdache isn’t the only one to suggest that we can feel less distressed just by eating better.
Back in 2008, addictions expert Kathleen Desmaisons had a crazy idea. What if sugar sensitivity and depression were linked? Her book Potatoes Not Prozac suggested that getting blood sugar under control (by, among other things, eating a potato before bed every night) could balance serotonin levels.
An Australian study points to something even simpler:
Just eat more fruits and vegetables. 
It found that adding just one more portion of fruits or vegetables to your diet (up to a total of eight) can make you happier.
Yet most people don’t reach for the carrot sticks when they’re feeling down. Maybe they should.