These two papers caught my eye. The first is observational and uses very limited in data points but clearly suggests the hypothesis that sugar is a cause of major depression. The biochemistry is supportive of this, a high carbohydrate meal increases blood insulin, which increases blood tryptophan, which increases brain serotonin.
So you fall asleep after a high carb meal.
I used to be a standing joke in our family before I went LC. One of the joys of avoiding rice and pasta was getting my evenings back. The aftermath of sleeping through a serotonon spike is that about three to six hours later your brain serotonin plummets and you can't sleep. Ah, those nights of looking at the clock every five minutes from 2am to 4.30 am. The switch to LC not only gave a good night's sleep every night but I woke feeling good each morning. That's better.
So I find it highly plausible that sugar causes depression. Kick your serotonin system often enough and it will go on strike. Or develop "serotonin resistance" comparable to "insulin resistance".
The second paper looks at the effect of a low fat diet on mood. The abstract is self explanatory and here are the important lines:
"ratings of anger-hostility significantly increased in the intervention group after 1 month on the low-fat diet"
"The results suggest that a change in dietary fat content from 41 to 25% energy may have adverse effects on mood"
One month is VERY rapid for a mood disorder to emerge. Healthy volunteers are not usually prone to anger hostility episodes. This is an intervention study with the subjects acting as their own controls. It's good.
Next time you get carved up in a minor road rage episode, just ask yourself if the perpetrator will have had bacon and eggs fried in butter for breakfast. Alternatively perhaps a bowl of sugared cereals lubricated with skim milk followed by toast and jam lubricated with a low fat spread. Probably has a heart problem and is on a statin too. Anger hostility rating? Is this problem growing?
Dr Ancel Keys again?
Obviously what is missing from the second study is a period when the subjects ate 80% fat in their diet. I assure you it feels good.