Effects of soybean peptide on immune function, brain function, and neurochemistry in healthy volunteers

Objective: Soybeans, an excellent source of dietary peptides, have beneficial effects on health. We investigated the effect of the soybean peptide on immune function, brain function, and neurochemistry in healthy volunteers. Methods: Near-infrared spectroscopy (NIRS) was used to analyze brain cerebral blood flow. The A and DA levels in the serum were analyzed by ELISA kit. The total number of leukocytes was recorded with a standard counter. Flow cytometry was used to assess lymphocyte subset levels. Results: Cell numbers were upregulated in the group that had fewer leukocytes but downregulated in the group with more leukocytes. For the lymphocyte-rich type, lymphocyte counts tended to decrease, accompanied by an increase in granulocyte numbers. For the granulocyte-rich type, granulocyte counts tended to increase, but lymphocyte counts also increased. The numbers of CD11b(+) cells and CD56(+) cells increased significantly. Soybean peptide decreased the adrenalin level in plasma but increased the level of dopamine. Near-infrared spectroscopy showed significant increases in the amplitudes of theta, alpha-2, and beta-L frequency bands after the ingestion of peptides. Conclusion: Soybean peptides can modulate cellular immune systems, regulate neurotransmitters, and boost brain function. (C) 2012 Elsevier Inc. All rights reserved.