I've been researching around about carbohydrates, serotonin, mood changes, depression and tryptophan (5-HTP).

I came across this article that showed that tryptophan (a natural amino acid that is the precursor to serotonin--note: these are natural chemicals already in your body that prevent depression naturally and are low in clinically depressed people) tryptophan can be increased by using alpha-lactalbumin whey protein. This is found in several protein powders. Nature's Best Isopure Protein Powder contains 22% alpha-lactalbumin whey protein and personally I think it tastes like Hershey's Quik.

Other protein powders with alpha-lactalbumin (taken from a website that sells protein powder):

Whey protein isolates + concentrates
Ansi - protein by design
Champion nutrition-protein stack
Champion nutrition-pro score 100
Eas - simply whey
Gen - humanopro
Hi-tech generation - performance whey
Human development technologies - 5+1
Interactive nutrition - total whey
Iss - whey matrix
Labrada - proplete
Prolab - ion-x whey
Natures best - iso pure
Natures best - iso pure low carb
Sportpharma - actisyn



American Journal of Clinical Nutrition, Vol. 71, No. 6, 1536-1544, June 2000
© 2000 American Society for Clinical Nutrition

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Original Research Communications

The bovine protein -lactalbumin increases the plasma ratio of tryptophan to the other large neutral amino acids, and in vulnerable subjects raises brain serotonin activity, reduces cortisol concentration, and improves mood under stress

C Rob Markus, Berend Olivier, Geert EM Panhuysen, Jan Van der Gugten, Martine S Alles, Adriaan Tuiten, Herman GM Westenberg, Durk Fekkes, Hans F Koppeschaar and Edward EHF de Haan

Background: Increased brain serotonin may improve the ability to cope with stress, whereas a decline in serotonin activity is involved in depressive mood. The uptake of the serotonin precursor, tryptophan, into the brain is dependent on nutrients that influence the cerebral availability of tryptophan via a change in the ratio of plasma tryptophan to the sum of the other large neutral amino acids (Trp-LNAA ratio). Therefore, a diet-induced increase in tryptophan availability may increase brain serotonin synthesis and improve coping and mood, particularly in stress-vulnerable subjects.

Objective: We tested whether -lactalbumin, a whey protein with a high tryptophan content, may increase the plasma Trp-LNAA ratio and reduce depressive mood and cortisol concentrations in stress-vulnerable subjects under acute stress.

Design: Twenty-nine highly stress-vulnerable subjects and 29 relatively stress-invulnerable subjects participated in a double-blind, placebo-controlled study. Subjects were exposed to experimental stress after the intake of a diet enriched with either -lactalbumin or sodium-caseinate. Diet-induced changes in the plasma Trp-LNAA ratio and prolactin were measured. Changes in mood, pulse rate, skin conductance, and cortisol concentrations were assessed before and after the stressor.

Results: The plasma Trp-LNAA ratio was 48% higher after the -lactalbumin diet than after the casein diet (P = 0.0001). In stress-vulnerable subjects this was accompanied by higher prolactin concentrations (P = 0.001), a decrease in cortisol (P = 0.036), and reduced depressive feelings (P = 0.007) under stress.

Conclusion
The present study showed a significantly higher plasma Trp-LNAA ratio with an -lactalbumin–enriched diet than with a casein diet. Only in HS subjects did the -lac diet enhance plasma prolactin, decrease cortisol concentrations, and prevent depressive feelings during acute stress. Because increases in cortisol and depressive feelings may reflect low stress adaptation, the present data suggest that a diet composed of tryptophan-enriched whey proteins in healthy but stress-vulnerable subjects could improve the ability to cope with stress by enhancing brain serotonin function. We suggest that a diet either containing -lactalbumin–enriched whey protein of greater purity than that used in this study or combined with carbohydrates might cause an even greater increase in the plasma Trp-LNAA ratio and may lead to clinically important changes in vulnerable subjects under acute stress. Also, to search for direct evidence of diet-induced changes in serotonin neurotransmission in stress-vulnerable subjects, further research is needed on the effects of postsynaptic serotonin agents.


Conclusions: Consumption of a dietary protein enriched in tryptophan increased the plasma Trp-LNAA ratio and, in stress-vulnerable subjects, improved coping ability, probably through alterations in brain serotonin.