Back in 1975 RJ Wurtman, an expert on diet and serotonin levels explained that our diets can affect our mood and depression by raising tryptophan (an amino acid) levels. It was found decades earlier that in autopsies of suicide victims showed markedly low levels of serotonin. Thus all the Serotonin Reuptake Inhibitors on the market (Prozac, Celexa, Trazodone, Paxil, etc.) for treating depression. In this article protein is said to interfere with tryptophan levels. Pure carbohydrate is said to increase tryptophan levels.

Dr. Eades in PPLP used this to show that people become chemically addicted to the mood altering affects of carbohydrates, a conclusion that Wurtman himself came to in 1989 Jan. Scientific American , "Carbohydrates and Depression".

However, others have used this to show that low-carbing is bad for you because you get low levels of serotonin and depression. However, you can supplement with Tryptophan (an amino acid). Plus on another thread I show another AJCN article showing that Whey Protein can itself increase tryptophan levels. Add to this the fact that the other AJCN study shown in this post shows that obese people are more likely to be depressed, then I think we can fairly conclude that when we used to eat carbohydrates we weren't less depressed.

American Journal of Clinical Nutrition, Vol 28, 638-647,

REVIEW ARTICLES

Control of brain monoamine synthesis by diet and plasma amino acids
RJ Wurtman and JD Fernstrom


The rates at which monoaminergic neurons in rat brains synthesize their neurotransmitters depend on the availability of the amino acid precursors tryptophan (for serotonin) and tyrosine (for dopamine and norepinephrine). The administration of tryptophan, the injection of insulin, or the consumption of a single protein-free high-carbohydrate meal all elevate brain tryptophan levels and, soon thereafter, the levels of serotonin and its major metabolite 5-hydroxyindole acetic acid. The addition of protein to the meal suppresses the increases in brain tryptophan and serotonin, because protein contributes to plasma considerably larger amounts of the other neutral amino acids (e.g., leucine, phenylalanine) than of tryptophan, and these other amino acids compete with tryptophan for uptake into the brain. The elevation of brain tyrosine (by injection of the amino acid or consumption of a single 40% protein meal) accelerates brain catecholamine synthesis, as estimated by measuring brain dopa accumulation after decarboxylase inhibition, or brain catecholamine accumulation after inhibition of monoamine oxidase. These observations suggest that serotonin- and catecholamine-containing brain neurons are normally under specific dietary control.

-------------------------------------
American Journal of Clinical Nutrition, Vol 44, 772-778,
ORIGINAL RESEARCH COMMUNICATIONS


Changes in mood after carbohydrate consumption among obese individuals
HR Lieberman, JJ Wurtman and B Chew


Two groups of obese individuals who consume excessive calories primarily as snack foods have been identified. Carbohydrate cravers consume most or all snacks as carbohydrate-rich foods despite the equal accessibility of protein-rich snacks. Noncarbohydrate cravers consume about equal amounts of protein- and carbohydrate-rich snack foods. Using standardized self-report questionnaires, we measured mood before and 2 h after consumption of a high-carbohydrate lunch (104 g CHO). Responses to the meal differed significantly: noncarbohydrate cravers reported feeling considerably less alert, more fatigued and sleepy, while carbohydrate cravers described little or no change in these aspects of mood. Moreover, noncarbohydrate cravers experienced an increase in depression, while carbohydrate cravers reported feeling less depressed. Findings suggest that snacking habits of obese individuals may be related to subsequent mood states.