Natto is a traditional Japanese dish consisting of fermented soybeans and is known for its dense nutritional content.
However, as its slimy texture and distinctive odour can deter some people from consumption, Daiwa Pharmaceutical Co Ltd developed a functional food ingredient called bacillus natto productive protein (BNPP) and produced under the trade name NKCP.
BNPP contains Bacillopeptidase F., which reportedly improves blood flow and skin condition.
To investigate its effect on the skin, Japanese researchers performed in vitro tests and a small-scale, single-armed trial funded by the firm.
It was found that BNPP exhibited significant inhibitory activity on tyrosinase at 0.01% and 0.1%, on elastase at 0.00001% to 0.001%, and on active oxygen (DPPH) radical scavenging activities at 1% and 10%.
Notably, tyrosinase induces skin melanogenesis; elastase degrades elastin, which plays a key role in maintaining skin elasticity; and active oxygen is involved in pigmentation and photoageing due to ultraviolet rays.
The effect of BNPP on human skin was further evaluated via a trial conducted from October 2022 to January 2023, which included 15 healthy women aged between 40 and 65 years.
The participants were instructed to take two BNPP-containing tablets (125mg each) per day post-dinner over a six-week intervention period.
All outcome variables were assessed at baseline and at the end of the trial.
The results demonstrated that skin hue a* value significantly increased from 16.27 to 17.04, and skin hue b* value markedly decreased from 22.07 to 21.11, compared to baseline.
An increase in skin hue a* value indicates an increase in the skin’s red tone, whereas a decrease in skin hue b* indicates a reduced yellow tone.
Although not statistically significant, brightness value (L*) rose from 67.24 to 68.56, indicating an elevation in skin brightness. Other secondary endpoints, namely dark circles, stratum corneum moisture content, and skin texture, also showed improvement.
In a questionnaire, the participants reported positive effects of BNPP on areas such as skin tone and texture, skin elasticity and resilience, moist feeling, fine lines, dark circles, eye bags, and sagging skin around the cheeks and mouth.
“Our findings showed that the oral administration of BNPP may significantly enhance skin rosiness, and also achieve notable improvement in skin conditions. It is reasonable to suggest that BNPP has the effects of preventing brown spot formation, lightening the skin, and improving fine lines and wrinkles,” the authors wrote.
Safe and stable
BNPP is a white or light-yellow powder, with the odour and vitamin K produced by natto removed to negligible levels so that it is easier to ingest.
In previous studies, BNPP has displayed its effects in boosting blood circulation, raising skin surface temperature of the neck and shoulders, ameliorating neck muscle stiffness, shoulder stiffness, and low back pain, improving cold hands and feet, and reducing headaches and blood pressure.
In this study, skin irritation and stability tests were conducted to examine the potential use of BNPP in cosmetics.
“We found that BNPP is non-irritant and can be applied to the skin. In addition, its high stability was confirmed. Its properties (colour and odour), aerobic plate count, and coliform bacteria at the time of production, and after six months and three years of storage at room temperature were tested. The results did not reflect any quality problems.”
Nevertheless, it should be noted that the study has several limitations, including the small number of participants.
“The current results of the skin tests are difficult to be extrapolated to other skin types. Therefore, further large-scale trials involving various skin complexion types are required. More tests are also needed to validate its use in cosmetics,” the authors concluded.
“Effects of Dietary Bacillus natto Productive Protein on the Skin: In Vitro Efficacy Test and Single-Armed Trial”
Authors: Naoki Igari, et al