Coix seed intake also led to an increase of the intestinal Faecalibacterium, an abundant human gut microbe in healthy individuals.
In Japan, coix seed is used to treat viral infections of the skin such as warts.
However, the effects are not conclusive and the specific immune indicators upon which coix seed may act are still unidentified. In addition, the influence of coix seed on the gut microflora and skin infection has not been reported.
In this trial conducted by researchers from Juntendo University in Japan, coix seed intake was examined on immune markers and gut microbiota from blood and stool samples taken from healthy male adults.
“Our findings could provide a clue to a mechanism through which coix seed could promote the spontaneous regression of viral skin infections,” and promote baseline evidence for the development of herbal medicines, according to researchers.
So, in this study published in Nutrients, 19 healthy male adults between 20 to 64 years old were recruited.
They were divided into the coix seed group (n=11) and the control group (n=8). The first group consumed 160g of cooked coix seed daily for one week.
Stool and blood samples were collected on day one and eight, to analyse intestinal microbiota and abundance of immune cells.
One week of coix seed consumption resulted in a significant increase in the killer T cells, helper T cells, and regulatory T cells as well as memory T cell ratio.
“These cells are involved in the removal of virus-infected cells and therefore, the activation of these immune cells could account for the reported enhanced regression of viral infections as a result of coix seed consumption,” researchers explained.
The one week of coix seed intake also significantly increase intestinal Faecalibacterium abundance from 7.7% to 10.9%.
No significant changes was observed in the control group.
Research have suggested that reduced levels of faecalibacterium are associated with inflammation, development of type 2 diabetes and atopic dermatitis.
Researchers acknowledged the limitations of their study. “Diet directly affects the gut microbiota, but we did not control for the diet during the intervention period, so there is a possibility that several other dietary factors during the intervention might have confounded the obtained results.”
“The effects of coix seed consumption could be more clearly observed by conducting the same trial under controlled diet.”
In addition, this study was conducted with a limited number of male participants. Future research should be undertaken by recruiting a larger number of participants, including females.
Researchers said: “Coix seed has been suggested to promote spontaneous regression of viral skin infection. A systematic examination of the effects of traditional herbal medicines including their mechanisms could allow for their effective use and provide opportunities to develop new medicines.”
“Coix Seed Consumption Affects the Gut Microbiota and the Peripheral Lymphocyte Subset Profiles of Healthy Male Adults”
Authors: Minami Jinnouchi, et al.