INTRODUCTION
Hair and scalp products containing rice bran extract (RB) are heralded to promote hair growth through maintaining anagen, inhibiting 5α-reductase, and promoting melanogenesis, allowing for improved hair growth, thickness, density, and color.1–4 (RB) derived from Oryza sativa are natural ingredients commonly found in hair and cosmetic products and have been used for centuries before its mechanism of action was elucidated. Historically, the use of derives from the Huangluo Yao Village in China where women wash their long black hair with fermented rice water prepared in a clay pot over heat using rice, water, and herbs.5–7
Rice bran, the outer hull of rice, is a major by-product of milling containing γ-oryzanol, tocopherols, tocotrienols, phytosterols, phenolic acids and their esters, saturated and unsaturated fatty acids (FA); and policosanols.1,2,8,9 Of note, γ-oryzanol and linoleic acid have been found to promote hair growth in an animal study,10 while phytosterols, policosanol, γ-linolenic, linoleic, and oleic acids have been found to inhibit 5α-reductase activity in vitro.3,11,12 Treatment with a mixture of tocopherols and tocotrienols known to exhibit antioxidant properties have yielded increased hair count numbers in androgenic alopecia (AGA) patients.13,14
RB exhibits its anti-inflammatory properties through the activity of bioactive molecules, such as anthocyanin polyphenols, which reduce the production of proinflammatory interleukins (IL)-6 and 8 and activation of nuclear factor kappa B (NFκB).15,16 RB ash mineral extract was found to increase melanogenesis, which may mechanistically explain the observed anecdotal historical evidence of rice water preventing hair graying.18–20 The aim of this review is to assess the scientific evidence regarding therapeutic efficacy, safety, and consumer availability of RB on hair health.
Rice bran, the outer hull of rice, is a major by-product of milling containing γ-oryzanol, tocopherols, tocotrienols, phytosterols, phenolic acids and their esters, saturated and unsaturated fatty acids (FA); and policosanols.1,2,8,9 Of note, γ-oryzanol and linoleic acid have been found to promote hair growth in an animal study,10 while phytosterols, policosanol, γ-linolenic, linoleic, and oleic acids have been found to inhibit 5α-reductase activity in vitro.3,11,12 Treatment with a mixture of tocopherols and tocotrienols known to exhibit antioxidant properties have yielded increased hair count numbers in androgenic alopecia (AGA) patients.13,14
RB exhibits its anti-inflammatory properties through the activity of bioactive molecules, such as anthocyanin polyphenols, which reduce the production of proinflammatory interleukins (IL)-6 and 8 and activation of nuclear factor kappa B (NFκB).15,16 RB ash mineral extract was found to increase melanogenesis, which may mechanistically explain the observed anecdotal historical evidence of rice water preventing hair graying.18–20 The aim of this review is to assess the scientific evidence regarding therapeutic efficacy, safety, and consumer availability of RB on hair health.
MATERIALS AND METHODS
A primary literature search was performed in May 2021 using
PubMed/MEDLINE with the following search terms: (hair OR hair
