Can keratin supplements taken orally improve hair growth, or are they only useful topically?

Keratin has become one of the most recognizable buzzwords in the world of hair care. Shampoos, conditioners, and salon treatments promise stronger, smoother hair thanks to this protein. But in recent years, keratin has also entered the supplement market, raising an important question: can swallowing keratin in pill or powder form actually improve hair growth, or is it only useful when applied directly to the hair?

Keratin is a structural protein that makes up most of the hair shaft, as well as nails and parts of the skin. Because of its rigidity and protective qualities, it gives hair its strength and resilience. When hair is damaged—whether from heat, chemicals, or aging—keratin levels in the strand itself can decrease, making it weaker and more prone to breakage. This is why topical keratin treatments became so popular: by coating the hair with hydrolyzed keratin (a broken-down version of the protein), they can temporarily fill gaps and smooth the surface.

But hair growth is not the same as hair appearance. To grow new, healthy hair, the follicles inside the scalp must receive the right nutrients. This is where oral keratin supplements come in, though their usefulness is far from straightforward.

The promise of oral keratin supplements

The idea behind keratin pills or powders is simple: by ingesting the protein, your body will have more of the building blocks needed to make strong hair. However, proteins taken orally are digested into amino acids in the stomach and intestines before they are absorbed. This means the keratin you swallow does not travel intact to your hair follicles. Instead, your body breaks it down like any other dietary protein. Because of this, many researchers argue that oral keratin supplementation may not directly influence hair growth in the way that topical applications can alter the appearance of existing hair. Still, there is evidence worth examining.

What the research says about oral keratin

A 2014 study by Beer, Wood and Veghte, published in The Scientific World Journal, tested a supplement called Cynatine HNS. Each daily dose contained 500 mg of keratin plus vitamins and minerals. It was a randomized, double-blind, placebo-controlled trial in 50 women. Over the course of 90 days, participants received either the supplement or a placebo. Researchers measured hair loss, hair growth rate, and hair strength through standardized dermatological assessments and laboratory analysis.

The authors reported statistically significant improvements in hair loss, hair strength and other hair and nail measures compared with placebo. However, the sample size was small, and two of the three authors listed company affiliations, which raises concerns about bias. Moreover, because the capsule also contained vitamins and minerals, it is unclear whether the improvements were due to keratin itself.

Criticism of existing studies

The main criticism is that the evidence base is very limited. Most clinical trials on keratin supplements are small, short-term, and often funded by companies selling the product. Independent large-scale studies are lacking. Furthermore, even when benefits are observed, it is difficult to separate the effect of keratin from that of other nutrients added to the supplements. The digestive breakdown of keratin also complicates claims, since the body does not necessarily direct those amino acids specifically to hair follicles.

Topical keratin: effects on appearance, not growth

When keratin is applied directly to the hair fiber in treatments or shampoos, it does not influence new growth, but it does improve the appearance and strength of existing hair. Hydrolyzed keratin proteins are small enough to attach to damaged areas of the hair shaft, creating a smoother, shinier look. A review of hair cosmetics describes hydrolysed proteins depositing on the cuticle and helping to smooth it (Gavazzoni Dias, 2015).

But these are cosmetic, not biological changes. They do not prevent hair loss, nor do they stimulate follicles. Instead, they temporarily mask or repair surface damage.

So, can oral keratin actually improve hair growth?

One small, 90-day, industry-linked trial of a keratin-plus-vitamins capsule reported benefits for hair strength and shedding, but oral keratin cannot be considered a reliable or proven solution for increasing hair growth. That trial's limits—50 women, 90 days, company-affiliated authors and a capsule that also contained vitamins and minerals—mean that conclusions must be cautious. By contrast, topical keratin can improve the look and feel of hair but has no known effect on the rate of new growth.

For pattern hair loss, the treatments with the most trial evidence are medicines such as minoxidil and finasteride. They have their own side effects and should be discussed with a doctor; finasteride is not approved for women and must not be used by women who are or may become pregnant. Keratin supplements might help some individuals improve hair quality, but they should not be confused with medical treatments for hair growth.

One small industry-linked trial reported less shedding and stronger hair with a keratin-plus-vitamins capsule, but the research is too small and too limited to show a benefit from keratin itself or that it stimulates hair growth. Topical keratin, on the other hand, can improve hair appearance but does not influence new growth.

In short: oral keratin is not a proven hair growth treatment, while topical keratin is only cosmetic.

References

Beer, C., Wood, S., & Veghte, R. H. (2014). A clinical trial to investigate the effect of Cynatine HNS on hair and nail parameters. The Scientific World Journal, 2014, 641723. https://pubmed.ncbi.nlm.nih.gov/25386609/

Gavazzoni Dias, M. F. R. (2015). Hair cosmetics: An overview. International Journal of Trichology, 7(1), 2–15. https://pubmed.ncbi.nlm.nih.gov/25878443/

U.S. Food and Drug Administration (FDA). (n.d.). Hair loss treatments. https://www.fda.gov/consumers/consumer-updates/hair-loss-treatments