Hypertension is defined as a systolic blood pressure (SBP) of over 140 mmHg or diastolic blood pressure (DBP) of over 90 mmHg. Hypertension is widely known to be a factor affecting human health, so its prevention is considered important. We investigated the effect of casein-derived tripeptide Met-Lys-Pro (MKP) on blood pressure in a randomized, placebo-controlled, parallel-group study. Participants were healthy adults with SBP between 120 and 139 mmHg, and/or DBP between 80 and 89 mmHg. A total of 121 participants were randomly assigned to the MKP group or placebo group. Participants received either a test powder containing 100 μg of MKP or a placebo powder without MKP for 12 weeks. As a result, SBP and DBP were significantly lower in the MKP group than in the placebo group. No adverse events associated with the MKP intake were observed. This study showed that MKP has a beneficial effect on lowering blood pressure in healthy adults with high-normal and elevated blood pressure and can be safely used for continuous intake.

Lactulose is known to grow health-promoting bacteria, with an increase in the production of beneficial metabolites, such as lactic acid and short-chain fatty acids (SCFAs) in the colon. Ingestion of lactulose powder at a food dosage level is known to reduce the dermal emanation of ammonia, a typical human skin gas which potentially affects body odour. However, no study has reported the effect of lactulose on human skin gases other than ammonia. In this study, the influence of lactulose ingestion on the dermal emissions of γ-lactones, volatile cyclic esters with sweet smells, was investigated in healthy subjects. Healthy participants ingested the lactulose powder with a food dosage of 4 g d⁻¹ once a day for 2 weeks. γ-lactones emanating from the skin surface were collected from each participant’s forearm by using a passive flux sampler, and six kinds of γ-lactones, namely, γ-hexalactone (C6), γ-heptalactone (C7), γ-octalactone (C8), γ-nonalactone (C9), γ-decalactone (C10), and γ-undecalactone (C11), were determined by gas chromatography–mass spectrometry. Quantification of bifidobacteria in faeces collected before and after ingestion of lactulose for 2 weeks was carried out by using real-time PCR. The results showed a significant increase in the dermal emission fluxes of sweet-smelling C10 and C11 lactones as the number of bifidobacteria increased in the faeces, presumably mediated by SCFAs produced in the colon.