The main lignan in flax seed may reduce 5-alpha-reductase. (Photo by AlishaV)
Flax seeds have several health benefits, but are they really helpful for hair growth? In this post, we'll look at the evidence behind the claims that flax seeds fight hair loss related to male-pattern baldness. And in case you decide to try it for yourself, the next post will deal with the subject of bioavailability and how to get the best bang for your buck.
Flax lignans and increased hair growth
The key ingredient in flax seed (sometimes spelled flaxseed and also known as linseed) are its lignans. Lignans are a group of phytoestrogens, which are found in grains, seeds and vegetables. The richest source of lignans is flax seed, the main lignan of which is secoisolariciresinol diglucoside (SDG).
So how do these phytoestrogens affect hair growth? Currently, there is only one (unpublished) study claiming hair growth benefits from flax lignans (link). This study was done by a company named Acatris and used a product called LinumLife EXTRA, which provides 50 mg lignans per one 250 mg capsule. The full paper is unavailable, so here's a quote from the press release:
Over a six-month period, 10 men, between the ages of 20 and 70 and in varying stages of AGA, consumed one 250 mg capsule of LinumLife EXTRA. Photographs were used to document hair loss conditions at the beginning of the study. At the end of the test period, eight men reported modest improvement of their hair loss condition, one reported much improvement and one subject reported no effect. Initial effects were noticed, on average, within one to two months of starting supplementation with flax lignans and no side effects were reported. Throughout the study, the daily number of hairs lost decreased and 50 percent of subjects noticed a decrease in oil secretion in their scalp. More noticeable improvements were noted in subjects with more severe conditions of AGA.
That would mean a 90% success rate after just two months, which sounds very good. However, claims like this have been made before, and since this study wasn't published in any journal, I'd take the results with a grain of salt.
SDG, benign prostate hyperplasia and hair loss
If we assume that flax lignans do indeed promote hair growth, what is the mechanism through which it works?
Many supplements that are sold as hair loss cures have much more evidence behind them as treatments for benign prostatic hyperplasia (BPH) than actual hair growth remedies. The logic behind the marketing is that since dihydrotestosterone (DHT) is a key factor in both BPH and hair loss, anything that works for BPH must also work for hair loss.
While there undoubtedly are drugs and supplements that treat both problems at once, it appears that the connection between BPH and hair loss is not as straightforward as one might think. Nonetheless, the fact that flax lignans seem to be effective for treating BPH gives us at least a hypothesis of how they might promote hair growth.
A randomized, double-blind clinical trial compared the effects of various doses (300 mg and 600 mg) of SDG on symptoms of BPH. This study found that levels of enterolactone and enteroldiol were significantly raised after supplementation, while prostate size was reduced (link). Notably, the authors conclude that the improvements in urinary symptoms from SDG were similar to those from androgen receptor blockers and more effective than 5-alpha-reductase inhibitors.
The authors offer several explanations for how SDG might reduce BPH symptoms: enterolactone and enteroldiol may inhibit the activity of 5-alpha reductase, or SDG may affect male hormone receptor binding, or other compounds in flax seed extract such as coumaric acid glucoside or ferulic acid glucoside may play a role.
In any case, it seems to me that whatever the exact mechanism, any potential hair growth effects from flax seed are probably due to the main lignan being a phytoestrogen. If there are other pathways, we don't know what they are yet.
Interestingly, in dogs, both flax seeds and sunflower seeds were shown to provide temporary improvement in skin and hair coat (link). The authors speculate that the result is most likely due to an increase in serum polyunsaturated fatty acid (PUFA) levels. This would probably not explain a reversal in hair loss in humans, however.
According to an unpublished study, 9 out of 10 men suffering from hair loss saw an improvement in their condition after taking a flax lignan supplement with 50 mg of lignans. Another study reported improvements in BPH symptoms from consuming 300-600 mg of SDG, the main flax lignan.
The mechanism through which flax lignans might work is not known, but a possible explanation is that SDG (a phytoestrogen) inhibits 5-alpha-reductase or androgen receptor binding.
For more information on hair growth, see these posts:
Bioactive Form of Silicon (BioSil) Improves Skin, Hair & Nails in Photoaged Women
Topical Ketoconazole (Nizoral) Increases Hair Growth in Mice
North African Plant Extract (Erica multiflora) Increases Hair Growth
Soy Protein Isolate Reduces DHT in Healthy Young Men