Keratin supplements are capsules, powders or gummies containing hydrolysed or solubilised keratin, usually sourced from sheep wool or poultry feathers. You cannot swallow keratin and have it arrive intact in your hair. Digestion breaks it into amino acids exactly like any other protein, and your body then builds its own keratin from scratch. The evidence for them is thin, and where people notice a change it is usually a nutrient they were short of rather than the keratin itself.

What are keratin supplements, and what is actually in them?

Keratin is the structural protein your hair, nails and the outer layer of your skin are made from. It is unusually rich in cysteine, a sulfur containing amino acid, and it is the sulfur bonds between those cysteines that give hair its strength and its shape.

These supplements take that protein from an animal source, most often wool or feathers, and process it so it can be swallowed. You will see two descriptions on labels. Hydrolysed keratin has been broken into short fragments. Solubilised keratin has been processed to keep more of the original structure while staying dissolvable. Both end up in the same place once they reach your stomach.

Read the back of almost any bottle and the keratin is rarely alone. Biotin, zinc, vitamin C, copper and sometimes iron or selenium are standard companions. That matters enormously when you try to work out what any effect is coming from, and most marketing is careful not to draw your attention to it.

Do keratin supplements work?

The honest answer is that they have not been shown to do much on their own, and the mechanism people imagine is not how digestion works. Protein you eat, whether it is keratin, chicken or lentils, is broken down into individual amino acids in the gut. Those amino acids go into a common pool, and your body draws on that pool to build whatever it needs, including new keratin in the follicle. Nothing about eating keratin specifically directs those amino acids to your hair.

That is why the interesting question is not whether keratin supplements contain keratin, but whether you were short of the raw material to begin with in the first place. If your overall protein intake is adequate, adding a small amount of processed wool protein is unlikely to change anything. If your intake is genuinely low, as it can be during very restrictive dieting or illness, then more protein of any kind helps, and a supplement is an expensive way to get it.

What does the evidence actually say?

There is research on these products, and it is worth being precise about its quality rather than dismissing it or overselling it.

• The trials are small. Typically a few dozen participants over three to six months, which is enough to detect a large effect and not enough to be confident about a modest one.
• They are usually funded by the ingredient supplier. That does not make them wrong, but industry funded nutrition trials report positive findings far more often than independent ones, so the result deserves more caution, not less.
• The products tested are mixtures. When a capsule contains keratin plus biotin plus zinc plus vitamin C, a positive result cannot be attributed to the keratin.
• The outcomes are often self reported. Questionnaires about how hair feels are useful, but they are highly susceptible to expectation, which is exactly what a supplement purchase creates.

The picture for the nutrients that ride along inside these capsules is much better documented. A 2019 review of vitamins and minerals in hair loss found reasonable evidence that iron and zinc shortfalls are associated with hair shedding, and much weaker support for supplementing people who are not short of anything. A 2017 review of biotin specifically found that reported benefits clustered in people with an underlying deficiency or an inherited metabolic condition, and that there is no good case for it in people with normal levels.

Who is most likely to notice a difference?

Four groups, and none of them for the reason on the packaging.

1. Anyone with low iron stores. Low ferritin is one of the best documented nutritional links to hair shedding, and it is common in menstruating women. This is worth a blood test through your GP rather than a guess.
2. Anyone genuinely low in zinc. Less common in the UK, but it happens with restricted diets and some gut conditions.
3. Anyone eating very little protein. Extended low calorie dieting, illness or a poorly planned vegan transition can drop protein intake far enough to show up in hair.
4. Anyone whose real problem is breakage. These people often feel a supplement helped, when what changed was that they also started conditioning properly at the same time.

Are keratin supplements safe, and what should you watch for?

Keratin itself is a food protein and is not the concern. The additions are, and three deserve naming.

• Biotin and blood tests. This is the big one. High amounts of biotin interfere with a wide range of laboratory immunoassays, including thyroid function and the troponin test used to assess chest pain, and it can push results high or low depending on the test. It is a documented cause of misleading results. Tell your GP, and anyone taking your blood, that you take a hair supplement.
• Vitamin A. Too much vitamin A is itself a recognised cause of hair loss, which is a bleakly ironic way to end up. Check the label, particularly if you take a multivitamin as well.
• Selenium. Excess selenium causes hair loss and brittle nails. The NHS advises keeping supplemental selenium well below the level where harm starts, and stacking several products makes that easy to breach without noticing.

The general rule is that stacking a hair supplement on top of a multivitamin on top of a fortified drink is how people quietly exceed safe amounts. Pick one product, read the label, and if you are pregnant, breastfeeding or taking regular medicines, check with a pharmacist first.

How do keratin supplements compare with food, topical care and a salon keratin treatment?

Four different things get sold under roughly the same promise. They are not interchangeable.

If your interest in keratin supplements really comes from hair snapping rather than hair falling, the topical row is where your money does more. Our guide to what actually causes hair damage covers the four culprits, and six habits that genuinely improve hair condition is the routine version. If your question is really about which nutrients matter rather than about capsules of wool protein, the vitamins your body uses to build keratin, and the foods that supply them is the companion page.

Hair loss, hair shedding and hair breakage: which one are you dealing with?

Supplements are marketed at all three as if they were one problem. They are not.

Hair loss is a follicle problem. The follicle stops producing a normal hair, whether through pattern miniaturisation or an autoimmune condition. You see bare scalp, a widening parting or a receding outline. No supplement changes this.

Hair shedding is a cycle problem. A stressor pushes a wave of follicles into their resting phase and they release together about three months later. This is the one where a genuine iron or protein shortfall can be part of the story, and where correcting it can matter. Our guide to what causes telogen effluvium covers the timeline.

Hair breakage is a fibre problem. The follicle is fine, the hair grows, and the strand snaps from heat, bleach, tension or friction. Short broken pieces and split ends. This responds to what you put on your hair, not what you swallow.

Which Watermans products make sense here?

If you want the nutrient side handled without buying a wool derived protein you will digest anyway, and you want the fibre side handled properly, two products cover it.

GrowPro Hair, Skin and Nails Gummies

Sugar free and vegan, with biotin, zinc, bamboo silica, vitamin C, D3 and B12. Two a day. Nutrients that contribute to the maintenance of normal hair, in sensible amounts, rather than a mega dose of one ingredient. Remember to mention biotin to your GP before a blood test.

Masque Me Hair Mask

This is the topical protein route rather than the swallowed one. Hydrolysed lupine protein, provitamin B5, argan oil and rosemary, used weekly on the mid lengths and ends to reduce breakage so hair holds its length.

Condition Me Conditioner

The everyday version of the same idea. Shea butter, glycerin and lupine protein on the lengths after washing, which is what stops the ends snapping between masks.

Watermans products are 100% cosmetic and do not treat medical hair loss. Individual results may vary.

What should you look for if you decide to buy keratin supplements anyway?

• A full label with amounts, not a blend. A proprietary blend that hides how much of each ingredient you get is a reason to put it down.
• Micronutrients near reference intakes, not many multiples of them. More is not better, and for vitamin A and selenium more is actively worse.
• No vitamin A, if you already take a multivitamin. Stacking is where the risk lives.
• A realistic timeframe on the packaging. Scalp hair grows a little over a centimetre a month, so anything promising visible change in two weeks is selling you something other than hair.
• Vegan sourcing, if that matters to you. Keratin is animal derived by definition. Vegan hair supplements use plant amino acids or skip the keratin entirely, as ours do.

Frequently Asked Questions

Do they really work for hair growth?

There is no strong evidence that they do. The keratin is digested into amino acids like any protein and never reaches the follicle as keratin. Where people report a change, added biotin or zinc and a corrected shortfall are the more likely explanations.

How long would I need to take them to see anything?

Hair grows a little over a centimetre a month, so any nutritional change takes at least three months to become visible and closer to six to judge fairly. Anything promising results in weeks is not describing hair biology.

Are keratin supplements vegan?

No. Keratin is sourced from wool, feathers or horn, so it is animal derived by definition. Plant based hair supplements use amino acids or micronutrients instead.

Can I get keratin from food?

You get the building blocks from food, which is what actually matters. Eggs, fish, meat, dairy, soy, lentils and pulses supply the sulfur rich amino acids your body uses to make its own keratin.

Do keratin supplements interfere with blood tests?

The keratin does not, but the biotin that almost always comes with it can. High biotin intake distorts several common laboratory assays including thyroid and cardiac tests. Always mention any hair supplement before blood is taken.

Is a salon keratin service the same thing?

No. That is a cosmetic smoothing service applied to the outside of the hair with heat, and it changes how hair behaves rather than what it is made of. It has nothing in common with a capsule beyond the word on the label.

Can they cause side effects?

The keratin itself rarely causes trouble. The companions can: too much vitamin A or selenium is associated with hair loss and brittle nails, and iron can upset the stomach. Read the label and avoid stacking several products.

Should I take them if my hair is falling out?

Find out why first. Sudden shedding, a widening parting or bare patches all have different causes and different answers, and only some of them have anything to do with nutrition. A GP blood test is a better first purchase than a capsule.

Sources and References

• Almohanna HM et al., The Role of Vitamins and Minerals in Hair Loss: A Review, Dermatology and Therapy, 2019.
• Patel DP, Swink SM, Castelo-Soccio L, A Review of the Use of Biotin for Hair Loss, Skin Appendage Disorders, 2017.
• NHS, Vitamins and minerals, reference intakes and safe upper amounts.
• NHS, Other vitamins and minerals, including selenium and zinc.
• NHS, Iron, on intake and the risks of taking too much.
• NHS, Hair loss, on causes and when to seek advice.

Conclusion: The Short Version

Keratin supplements sound logical and fall apart on contact with digestion. Hair is made of keratin, but eaten keratin is broken down into amino acids like any protein, and nothing sends those amino acids to your scalp in particular. The trials are small, short and usually paid for by the people selling the ingredient, and the capsules almost always contain biotin and zinc, which makes any positive result impossible to attribute to the keratin. Sort out protein, iron and zinc through food, get a blood test if your hair changed suddenly, and put your product budget into conditioning the fibre, which is the part you can genuinely influence. If you take a hair supplement, mention the biotin before any blood test. Watermans products are 100% cosmetic and do not treat medical hair loss. Individual results may vary.