What Is Biotin, What Does It Do? The Role of Vitamin B7

Biotin is a small sulphur-containing molecule, and the body does not burn it for energy. Its job is to enable other enzymes to do their work. That is why the need is very small: the adequate intake for adults is defined as 30 micrograms per day, while daily intake on a Western diet is roughly 35-70 micrograms. Liver, cooked eggs, soy, yeast, fish and nuts are the main food sources. The link that gives this small molecule its reputation as a "hair vitamin" is weak; the reason is below.

What job does biotin do in the body?

In humans there are five biotin-dependent enzymes. Each one prepares molecules for the next metabolic step by adding a carbon.

It is also being investigated whether biotin can affect gene reading by binding to histones, but this area is still at basic science level. The link with keratin is more an assumption: in the lab, the growth and differentiation of normal hair root cells were not affected by biotin.

Why does tight binding to proteins matter?

The best-known property of biotin in chemistry is its extraordinarily tight attachment to certain proteins. The avidin in raw egg white is an example. Eating large amounts of raw egg white over a long period can therefore lead to deficiency; cooking neutralises this protein. The same binding is used as a tool in many laboratory tests. If there is a lot of biotin in the blood, a test can give false results. So the unexpected link between the "hair vitamin" and thyroid testing rests on the same chemical property.

What does biotin in shampoo and cream do?

It appears on labels under the name Biotin and is classified as a care ingredient. In cosmetic safety assessments, usage levels were found to be very low, reported at roughly 0,0001% to 0,6%. The same assessment concluded it was safe in 2001, and reconfirmed this conclusion with new data in 2023.

Being safe does not mean being effective. There is no solid clinical study measuring hair growth or shedding after applying biotin, and little reliable data measures how much of it penetrates the skin. New hair forms in the follicle beneath the scalp, while shampoo is rinsed off after a few minutes. It is more realistic to judge a product by its primary job, such as cleansing or easing combing, rather than by the biotin it contains.

Applied biotin and swallowed biotin are not the same thing

The two uses are often described in the same sentence, but they are separate matters in terms of quantity, evidence and risk.

The answers to questions such as who sees a deficiency, what studies show, and what to do before a test are in the does biotin help hair article. If you take supplements, do not forget to tell your doctor and the laboratory before a blood test.

Names confused with biotin on labels

• Panthenol: It is the precursor of vitamin B5. Its data on moisture in hair and skin is more extensive than for biotin.
• Niacinamide: It is vitamin B3 and has its own evidence base in skin. Being in the same B group does not mean it does the same job.
• Allantoin Biotin: A complex of allantoin and biotin. Usage data are scarce, and it is not regarded as the same ingredient as biotin itself.

How does deficiency look, and when should you see a doctor?

True biotin deficiency is rare. The picture is usually not hair loss alone: rash on the skin, seborrheic dermatitis, conjunctivitis and nervous system symptoms may also accompany it. Inherited enzyme problems, certain medications and the raw egg white described above are the best-known causes.

Sudden heavy shedding, hair loss in specific areas, or itching and sores on the scalp need to be investigated by a dermatologist. For brittle nails too, there is no strong data beyond small and old studies. If there is a change in the shape or colour of the nails, it should also be shown to a doctor.