Many of us guys pride ourselves on being logical and rational and look down on emotions and feelings. It is critical to recognize, though, the importance of this aspect of your life: any of us can become irritable and inefficient when our emotions peak or wane to an extreme. After all, there’s no such thing as a true Stoic (or Vulcan).
This is all important because our neurotransmitter levels, and therefore emotions, can be strongly effected by what we eat. And let’s face it: even Yoda would have trouble mastering his neurotransmitters. We ask the question, “Why not optimize your transmitter levels and be in a good mood instead of crappy one?” We think that’s a good question.
I. Seratonin:Let’s start with our good friend and confidant, seratonin. Seratonin is what most anti-depressants stimulate and for good reason: seratonin puts you in a good mood with a positive outlook. You just can’t help yourself with an abundant supply of this neurotransitter. It helps you sleep and night and be at peace during the day and just as important: it suppresses your appetite!
So how can you boost this little wonder worker? If you guessed “by eating right”, you would be spot on. Seratonin is actually made from the amino acid tryptophan and the more tryptophan that you get in your brain, the more seratonin you brain produces. Furthermore, tryptophan is in many of the high protein foods we eat and so it would seem that the more protein one eats, the more seratonin, right? Wrong! Unfortunately, Mother Nature is often counterintuitive.
As it turns out, tryptophan competes with many other amino acids to make it past the blood brain barrier and thus seratonin is actually decreased after a high protein meal. All those other aminos from a high protein meal basically crowd out tryptophan and says, “Wait your turn!” In other words, after a medium or high protein meal, tryptophan stays high in the blood but decreases in the brain where it is needed the most.
And here’s another even more counterintuitive twist: if you eat a low protein/medium (or high) carb meal, the rise in insulin pulls all the aminos except tryptophan into muscle and other body tissues leaving tryptophan at high levels in the blood. And because there are no competing amino acids, it is ushered directly into the brain and raises seratonin.
Therefore, a low protein, medium carb meal raises seratonin levels, boosting your emotions and producing a sense of peace and relaxation. All is well with the world. Yes, this is yet another reason to consider a Low Fat (or Ornish) Diet.
This has been verified by multiple studies which show that a low fat diet and high carbs boosts mood. For example, one study of obese women found that simple carbs were the prime mood booster. Subsequent work on healthy subjects revealed that “over 1 year, there was a favorable effect of an energy-restricted LF diet compared with an isocaloric LC diet on mood state and affect in overweight and obese individuals”.  Another study that we have mentioned elsewhere showed the Mediterranean Diet to be a depression healer.  And yet another study found that a low carb diet was much more worse for mood and outlook. Australian scientists placed participants on a low fat or low carb diet and, not surprisingly, found that both groups lost an equal amount of weight. However, the low carb group “felt more angry, depressed and confused” than the Low Fat.  The bottom line is that a Low Fat Diet has been found repeatedly to boost mood and improve outlook.
Ever wondered why some of the guys in the gym that can outlift you by a magnitude of ten are so overweight? During the bulking phase, they are eating tons of protein at every meal. This will trigger their appetite and encourage hunger. Unless they are very disciplined, they will very likely overeat. For example, one study found that “Protein…was found to suppress subsequent intake independent of its contribution to total calories. Fat was found to be the least effective of the macronutrients in suppressing future food intake”. 
So should you avoid protein like the plague? Not necessarily and that leads to the discussion of dopamine and diet below:
II. Dopamine:Dopamine levels are also dependent on an amino acid, tirosine. But, unlike tryptophan, tirosine does not get crowded out and so, in general, a higher protein meal will lead to increased dopamine levels. Furthermore, too many carbs will wash out some of the effects of the tirosine because insulin will ferry all amino acids out of the blood and into muscle and other tissue.
So who cares about dopamine? All guys should! Dopamine (and its cousin norepinephrine) are the feel good chemicals of sex and those rushes and highs that us guys experience are a direct result of increasing dopamine. In fact, dopamine is what is boosted by crack and other narcotics.
So to maximize mood throughout the day, try the Low Fat (or Ornish) Diet but supplementing with egg whites every other meal. This will alternate you between seratonin and dopamine throughout the day and preserve your arteries while you’re at it.
By the way, David Kessler, former head of the FDA, has recently documented in his book The End of Overeating how the food industry uses salt, sugar and fat to literally make you addicted to processed foods. This trinity – salt, sugar and fat – literally alter your brain chemistry, particularly by modifying dopamine levels, to make you pant and paw like one of Pavlov’s dogs.
If you eat anything out of a box, can or package, you are going to have a very tough time controlling your appetite. Food executives and engineers are not stuipd: they now how to keep you coming back for more. Again, stay out of the middle of grocery store – it’s the Tire Inflation Zone for us guys!
1) Arch Intern Med, 2009, 169(20):1873-1880, “Long-term Effects of a Very Low-Carbohydrate Diet and a Low-Fat Diet on Mood and Cognitive Function”
2) Br J Nutr, 2009, 101(12):1821-1827, “Adherence to the Mediterranean diet is associated with better mental and physical health”
3) Physiol Behav, 1987, 39(5):561-569, “Macronutrient relationships with meal patterns and mood in the spontaneous feeding behavior of humans”
4) Prevention, Apr 2010, p. 45.