The short answer
These supplements correct a deficiency; they do not treat hair loss. The systematic review on biotin, the central active ingredient of the market, finds only 18 published cases, and in every one the patient had an underlying condition. In a person with no deficiency, the research that would support an effect is, according to its authors, limited. Before buying, have your ferritin, zinc, vitamin D and TSH measured: that is the step that changes something.
What the literature says, ingredient by ingredient
Biotin: nothing for people who are not short of it
It is on every box, often promoted as “the hair vitamin”. A systematic review searched for all published cases and randomised trials on biotin and hair and nail growth. Result: 18 reported cases, and in each of them the patient had a condition explaining their poor growth. All improved on biotin. The authors conclude that despite the product’s commercial popularity, the research showing its effectiveness in healthy people is limited (Patel et al., Skin Appendage Disorders, 2017, PMID 28879195).
This is the most important sentence in this comparison: biotin works when you are short of it, and biotin deficiency is rare. Anses sets the adequate intake at 40 µg a day, a level that an ordinary diet covers with ease.
Iron, zinc, vitamin D: there is something there
A 2024 systematic review of 49 articles concludes that deficiencies in B vitamins, vitamin D, iron and zinc are associated with an increased risk of androgenetic alopecia, and that correcting them shows a potential benefit. The authors immediately add that the evidence is not entirely consistent, with several studies finding no significant association (Wang et al., Molecular Nutrition & Food Research, 2024, PMID 39440586).
The word that matters is deficiency. These studies do not say that adding zinc for someone who has enough will make their hair grow back. They say that a shortfall is a modifiable factor, which is a reason to test before supplementing, not the other way round.
Iron is the most common case in women, and the easiest to confirm objectively: our guide to iron and anaemia explains which tests to ask for, and our ranking of foods high in iron shows what to start with on your plate.
Keratin: the only ingredient with a trial of its own
Cynatine® HNS, a solubilised keratin, was the subject of a randomised, double-blind, placebo-controlled trial: 50 women, 25 per group, 500 mg a day for 90 days against maltodextrin. The results show statistically significant improvements in hair and nails (Beer et al., The Scientific World Journal, 2014, PMID 25386609).
That is more than biotin has ever had, and it should be said. Two reservations as well: one of the three authors is employed by Roxlor Global, which markets the ingredient, and it is a single trial of 50 people. The product tested also contained “keratin plus vitamins and minerals”, so the effect cannot be attributed to keratin alone.
The products, recorded on 24/09/2026
| Product | Actives per dose | Price | Cost per day | 3-month course |
|---|---|---|---|---|
| Nutri&Co, Complexe Cheveux | Cynatine® HNS keratin 500 mg + biotin 100 µg | 26.90 EUR / 60 caps. | 0.90 EUR | 80.70 EUR |
| Dynveo, Multi27 | Biotin 50 µg, zinc 10 mg (bisglycinate), selenium 22 µg, + 24 others | 27.90 EUR / 60 caps. | 0.93 EUR | 83.70 EUR |
| Nutri&Co, 3-month pack + brush | Identical to Complexe Cheveux | 94.60 EUR | 1.05 EUR | 94.60 EUR |
All three products fall within 15 cents a day. That is the first thing this table says, and it is unusual: on magnesium, whey or collagen, the gaps ranged from 50 to 98%. Here, price is not the deciding criterion. Composition is.
Two formula strategies, not to be confused
Complexe Cheveux bets on keratin, at the exact dose of the published trial: 500 mg. That is consistent, and it is the only product in the table whose main active ingredient has a randomised trial of its own. Its biotin at 100 µg is 2.5 times the Anses adequate intake, which achieves nothing more if you are not deficient.
Multi27 bets on broad coverage: 27 vitamins and minerals, including the zinc and selenium that the first one lacks. Its zinc at 10 mg as bisglycinate covers from 71% to 106% of the Anses reference, which depends on phytate intake: 9.4 mg a day for a low-phytate diet, up to 14 mg for a diet rich in wholegrains and pulses. This is a subtlety that labels ignore, since they all state “100% of reference intakes”.
In other words: if your tests show a shortage of zinc or vitamin D, the multivitamin is the right tool. If your tests are normal, keratin has the least poor data.
What none of these products will do
Treat androgenetic alopecia. It is the most common cause of lasting hair loss, it is hormonal and genetic, and it calls for medical treatment. A supplement does not slow it down.
Replace a diagnosis. Sudden or diffuse hair loss often has an identifiable cause: iron deficiency, thyroid disorder, after childbirth, a very restrictive diet, a medicine, acute stress. A ferritin, zinc, vitamin D and TSH test costs less than a three-month course and tells you what is going on.
Make up for a diet too low in protein. Hair is made of keratin, therefore of protein. An insufficient protein intake shows in your hair before it shows anywhere else: see our guide to how the body uses protein and our whey comparison if your intake really is low.
Our sources
- Official Nutri&Co and Dynveo pages, consulted on 24/09/2026: actives, doses, sizes and prices.
- Patel D.P. et al., A Review of the Use of Biotin for Hair Loss, Skin Appendage Disorders, 2017: PMID 28879195.
- Wang R. et al., Micronutrients and Androgenetic Alopecia: A Systematic Review, Molecular Nutrition & Food Research, 2024: PMID 39440586.
- Beer C. et al., A clinical trial to investigate the effect of Cynatine HNS on hair and nail parameters, The Scientific World Journal, 2014: PMID 25386609. One author employed by the ingredient’s distributor.
- Anses, nutritional reference values: biotin 40 µg/day (adequate intake); zinc from 9.4 to 14.0 mg/day depending on phytate intake, safety limit 25 mg/day.