Sesame oil for hair growth?

A head of hair consists of approximately 100,000 to 150,000 hairs that renew cyclically. The hair shafts develop independently of each other within a hair follicle before falling out. Each hair follicle typically undergoes 25 to 30 cycles during its lifetime. A cycle unfolds in three stages. Firstly, the anagen phase, or hair growth phase, lasts between two and five years. It includes two major stages: the synthesis and pigmentation of the shaft. The second phase is called the catagen phase and extends over two to three weeks. Finally, the telogen phase constitutes the period during which the hair remains attached to the hair follicle for about three months before detaching and falling out.

Only a few cosmetic actives can genuinely influence the hair cycle. Regarding sesame oil, there are good reasons to believe that it could be an interesting ingredient to promote hair growth. Indeed, it has been shown that linoleic acid found in sesame oil has an activating effect on the Shh/Gli signalling pathway. This pathway promotes the transition from the telogen phase to the anagen phase, thus more quickly initiating the hair follicles into the growth phase. Linoleic acid, therefore, somewhat accelerates hair growth.

It would also appear that another molecule found in sesame oil could stimulate hair growth: sesamin. This molecule, part of the lignan family, has indeed demonstrated a significant ability to inhibit the 5α-reductase protein during in vitrostudies. This enzyme is responsible for catalysing the transformation of testosterone into dihydrotestosterone (DHT). Subsequently, DHT triggers an increase in the expression of interleukin 6 (IL-6), a cytokine that accelerates the transition between the catagen and telogen phases. DHT also acts by binding to the Dickkopf-1 (DKK-1) protein, leading to the apoptosis of the hair matrix cells and to the hair loss.

In a study, the effect of sesamin on 5α-reductase was compared to that of finasteride, an anti-androgen sometimes used to treat alopecia. According to the tests conducted, sesamin would be 1.54 times more effective than finasteride, suggesting that it could indeed stimulate hair growth. However, it is important to note that this is the only study to date on this subject. Further investigations would be necessary to assert that sesame oil promotes hair growth. Moreover, the study was conducted on sesamin, a constituent of sesame oil, and not on the botanical extract itself. Therefore, it cannot be ruled out that the concentration of sesamin in the oil may be too low to have the same properties.

The key takeaway : Even though they are promising, the scientific evidence available today is insufficient to conclusively state that sesame oil accelerates hair growth.