4 star ingredients under the microscope

The jar is pastel pink, the gummies taste of strawberry, and the label lists four names in big letters: biotin, saw palmetto, collagen, ashwagandha. You’ve seen them all over social media, before-and-after shots included. But what’s really behind each of these names? And what are they worth for your hair once you step away from the ads?

We took them one by one. For the rest of the formula, B vitamins, zinc or selenium, everything is covered in our article on what’s in a hair supplement.

What the label is allowed to promise

In Europe, a supplement can’t say whatever it likes about hair. The regulation listing authorised health claims contains only four on the subject: biotin, zinc and selenium “contribute to the maintenance of normal hair”, and copper “contributes to normal hair pigmentation”¹.

Look at who’s missing: saw palmetto, collagen and ashwagandha. None of the three has an authorised hair claim¹. For ashwagandha, the claims submitted (stress, sleep, skin, vitality and more) are on hold at European level, and none has been validated². In other words, the three ingredients that get the most buzz have, in the eyes of the law, proved nothing for your hair.

Biotin

This is vitamin B7, the best-selling hair vitamin of all. A real lack of biotin makes hair fall out, but it’s rare: gut bacteria usually make enough³. Above all, no clinical trial has shown that it treats hair loss in someone who isn’t deficient³. To find out whether you’re short of something, you need a blood test, not a jar of gummies: we cover this in our article on deficiencies.

Biotin also has a downside. The French medicines agency (ANSM) warns about the growing use of high-dose supplements that can skew thyroid tests⁴. If you take it, read what to know before a blood test.

On an English-language forum, opinions go every which way⁵:

Posted on the HairLossTalk forum⁵.

Saw palmetto

Saw palmetto (Serenoa repens) is a palm extract. It has mostly been tested in hereditary hair loss, or androgenetic alopecia⁶. It’s the best-studied ingredient of the four, which isn’t the same as well studied.

A systematic review published in 2020 found 9 studies covering 381 patients in total: five randomised trials, two follow-up studies and two case reports⁶. The results point the right way, with modest improvements. But the authors conclude that solid data are lacking: most products mixed saw palmetto with other ingredients, some studies didn’t even state the amount, and measurement methods varied from trial to trial⁶.

The only trial that compared it directly with a prescription treatment followed 100 men for 24 months⁶.

As for side effects, the review mainly reports mild digestive problems, but also two girls aged 10 and 11 who had hot flushes that cleared up once they stopped⁶. Data on long-term use are missing⁶.

Collagen

Collagen is the protein that holds skin together. In supplements, it comes as peptides. A review published in 2026 gathered the trials on skin, nails and hair⁷. For hair, it cites four studies. In one placebo-controlled trial, hair gained shine, strength, thickness and density; in another, hair thickness improved in women⁷.

The authors stay cautious: few well-controlled studies, small groups, often subjective scores, and a good share of trials funded by manufacturers testing their own products⁷. One of the trials involved damaged hair, not hair loss⁷.

Online, the enthusiasm is real, and so is the doubt⁸:

Posted on the Mumsnet forum⁸.

In the same thread, others point out that collagen is digested like any other protein. Without a photographed starting point, there’s no way to settle it for you.

Ashwagandha

A plant from traditional Indian medicine, ashwagandha (Withania somnifera) is sold for stress. Its link with hair rests on an Indian trial published in 2026: 92 adults took a root-extract capsule morning and evening, or a placebo, for 75 days⁹. Measured hair density rose more with ashwagandha⁹. The limits: a single clinic, short follow-up, healthy participants, and an extract supplied by its manufacturer⁹. And these were capsules, not gummies.

Above all, the plant isn’t harmless. In April 2024, France’s food safety agency (Anses) issued an opinion after reviewing reported side effects, including cases of liver damage and an overactive thyroid (thyrotoxicosis)². It advises people to avoid it:

A thyroid disorder happens to be a classic cause of hair loss (see thyroid and hair). If that’s you, this gummy isn’t for you.

The sweet around it

A gummy is a vitamin dressed up as a sweet. To see what surrounds the active ingredients, read the ingredients list: the law requires them to be listed from most to least by weight¹¹. If sugar or glucose syrup comes first, it’s the main ingredient of your supplement. The WHO recommends keeping free sugars (added sugars, plus those in honey, syrups and juices) below 10% of the day’s calories, about 50 g for an adult eating 2,000 calories; going down to 5% may bring extra benefits¹⁰. The sugar in your gummies adds to the rest of the day’s, every day.

“Sugar-free” versions often use polyols. Above 10% polyols, the pack has to warn that excessive consumption may have laxative effects¹¹. And when you like the taste, it’s tempting to take more. Bad idea: too much selenium or vitamin A can actually make hair fall out³.

Judging your gummies by photos

The trials last from 75 days to two years. Your hair grows at the same slow pace. After three months in front of the mirror, you won’t know whether it’s the collagen, the season or your new haircut.

With Calvap, you take a photo before you start, then the same one every week: last week’s photo appears as a see-through overlay so you frame it the same way, on your parting, crown and temples. The journal records the day you opened the jar. After a few months, your timeline shows whether anything has changed, and you’ll know whether that jar is worth buying again.