Shikwasa (Citrus depressa) is an evergreen shrub from the family Rutaceae (mikan) also called the hirami lemon, and grows widely across the southwestern islands south of the Amami Oshima Island to Taiwan. The fruit can be eaten but the unripe fruit is extremely sour, with the ripened fruit being somewhat sweet. In general, the unripe fruit is eaten as food. Various functions of flavonoids such as nobiletin contained in the unripe fruit have been reported. This trial is a randomized parallel group placebo-controlled trial with the purpose of investigating the effects for improving lifestyle-related diseases, such as decreasing abdominal fat or improving fat metabolism by drinking shikwasa juice. Subjects were healthy adult males and females with a body mass index (BMI) 23 or over, but less than 30 (shikwasa juice group: 9 subjects, placebo drink group: 10 subjects). Subjects drank the shikwasa juice drink (equal to 50g of juice) or the placebo drink for 12 weeks. The shikwasa group tended to have lower abdominal fat than the placebo group 8 weeks later（p=0.0812）. Furthermore, there was a significant difference between the shikwasa and placebo groups in adiponectin levels. These are negatively correlated with visceral fat mass and closely associated with fat metabolism, demonstrating that shikwasa stimulated adiponectin secretion. Furthermore, with regards γ-GTP and ALP testing, which are related with fat metabolism or accumulation, the shikwasa group had a significant lower γ-GTP than the placebo group, even though all the subjects in this trial were in the normal ranges for these parameters. There was a significant difference in ALP between the shikwasa and placebo groups as well. There were no adverse events that indicated safety issues in the long-term intake of shikwasa juice lasting 12 weeks. As such, the results suggested that shikwasa juice reduces visceral fat mass, and demonstrated that it stimulates adiponectin secretion.

Properties of Shikwasa (Citrus depressa) juice to improve lipid metabolism

256th National Meeting (2018)

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