The influence of meal composition on plasma serotonin and norepinephrine concentrations

Reports concerning changes in plasma neurotransmitter values that result from dietary manipulations have not been published so far. The influence of various meal compositions on platelet-poor plasma (PPP) serotonin (5-HT) and norepinephrine (NE) levels was investigated. Healthy volunteers were subjected to three test meals: a carbohydrate-rich meal (86% carbohydrates), a protein-rich meal (70% protein), and a fat-rich meal (92% fat). After a carbohydrate-rich meal, PPP 5-HT values increased significantly (4.47-fold, P less than .02), whereas a smaller increase (1.66-fold, P = NS) was observed after a fat-rich meal. These effects on PPP 5-HT values could be correlated with insulin plasma levels. A protein-rich meal significantly reduced (P = 0.0011) PPP 5-HT to 28% of initial values, despite an increase in plasma insulin levels. This study has shown that (1) changes in meal compositions influence PPP 5-HT and, to a lesser extent, NE values; (2) the resulting changes in PPP 5-HT levels parallel those reported for brain neurotransmitters; and (3) these results seem to indicate that PPP 5-HT levels may be a model for brain synthesis and release of 5-HT.