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.

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 θ, α-2, and β-L frequency bands after the ingestion of peptides.