Hair loss is only visible when approximately 40% of the initial mass of the hair has been lost. It increases with age and can have several causes:
- heredity: unfortunately nothing can be done about it.
- hormones: excess testosterone in men and menopause in women cause hair loss. When the cause is hormonal, dietary supplements have few indications.
- nutritional factors: deficiencies in certain nutrients, obesity, oxidative stress. They represent 11% of cases.
The approach can be external (shampoo, lotion, etc.) or internal (nutritional intake in the form of food supplements). The latter is a fairly recent idea and responds to the concept of “nourishing the hair from the inside”. It makes sense because, as such, the hair is an inert structure and not very sensitive to external stimuli. The only thing that can be expected from an external treatment is to make it cleaner, silkier, shinier. In fact, the living structure is the hair follicle which synthesizes the hair. The follicle is richly vascularized, allowing nutrients to reach where hair synthesis takes place. It is therefore this internal approach that can promote hair growth and limit hair loss. We thus understand that the two approaches, external and internal, should not be opposed, because they act in complement.
Some nutrients are more useful to the hair than others and these are the ones that should be favored in food supplements. We will detail here those which are most frequently used and/or which one can think could be useful.
Group B vitamins
Pantothenic acid or vitamin B5
Vitamin B5 is present in offal, brewer’s yeast, egg yolk, whole grains, avocado… Deficiency is rare and is manifested by fatigue and insomnia. This vitamin is essential for the renewal of our cells, which is why it is often present in food supplements for hair health. However, the claim that vitamin B5 is essential for healthy hair is not allowed due to lack of evidence. If it does no good, it does no harm: its toxicity is very low.
It should be noted that a simultaneous intake of vitamins B5 and B8 reciprocally inhibits their intestinal absorption. Food supplements that contain these two vitamins at the same time should therefore not be used.
Pyridoxine or vitamin B6
Vitamin B6 is present in many foods of plant origin (peas, cereals, soya) or animal (poultry, liver). Deficiency is therefore rare (except in cases of chronic alcoholism) and consists of peripheral neuropathies (damage to one or all of the nerves of the peripheral nervous system). Its main actions concern the metabolism of carbohydrates and lipids. It also plays a role in the synthesis of serotonin (a neurotransmitter that allows transmission between two neurons).
The main adverse effect of pyridoxine is (as with deficiency!) peripheral neuropathy (more often sensory than motor). Its appearance depends on the dose and the duration of supplementation (on average after two years of consumption at high doses, generally equal to or greater than 25 mg/day, i.e. more than ten times the recommended intake!). In the majority of cases, the damage regresses when supplementation is stopped.
All of what is mentioned above leads to not recommending vitamin B6 as a supplement to a normal diet to promote hair growth.
Biotin or vitamin B8
Biotin is important for cell growth and metabolism, including that of proteins. It is widely found in the diet (mainly in the liver, but also in meat and fruit), so that there is practically no deficiency among Europeans. Research has shown that with biotin deficiency, hair loss occurs, which regrows when the deficiency is corrected. This is why biotin, present in many food supplements for the hair, can be useful.
It should be known that high concentrations of biotin in the blood distort the results of biological analyses. Therefore, if you supplement with biotin, you must report it to the medical analysis laboratory at the time you are sampled.
Because the hair is made up of 95% of a protein, keratin, the amino acids that constitute it are very important, either because of their richness within the protein, or because they provide specific functions: they allow bonds in the protein (formed of four strands) which contribute to its solidity.
cystine and methionine
Cystine is not an amino acid per se, but it is made up of two molecules of cysteine. Once it has been absorbed by the intestine, cystine must therefore be cleaved into cysteine in order to be used in the protein synthesis which will allow the creation of hair. Within keratin, cysteine forms extremely strong bridges between the strands. Cysteine is also necessary for the synthesis of glutathione, which is known to have a powerful antioxidant action. Note in this regard that the synthesis of glutathione requires another amino acid, glycine. This amino acid can be found in some dietary supplements.
The process of cleavage of cystine into cysteine is poor in humans, but cystine is preferred over cysteine because the former is readily obtained by extraction (mainly from salvaged hair) and is much better tolerated than cysteine. second. Methionine is the natural precursor to cysteine but, like cysteine, only low doses are well tolerated. An overdose of methionine leads to digestive disorders and, in the long term, neurological problems. Methionine is present in many foods, including fish, meats and eggs.
The effectiveness of cystine on hair growth is in fact deduced from its use in livestock: it has been observed that a diet enriched with cystine makes it possible to obtain finer and more abundant wool in sheep. merinos in Australia.
The main sources of taurine are meat and shellfish (especially clams and oysters). It acts on the hair follicle through its antioxidant action. Its usefulness in food supplements for the beauty of the hair is however not demonstrated at the present time.
Proline is present in all proteins, especially those that make up supporting tissues (like skin). We therefore find a lot in certain cuts of meat. Proline is incorporated into procollagen (the precursor of collagen) and there it is transformed into hydroxyproline, which makes it possible to make bridges between the strands of proteins, which ensures their solidity. There are many similarities between collagen and keratin, and supplement manufacturers play on this fact to promote the supply of proline to promote beautiful hair.
Minerals and metalloids
Selenium is provided by fish, shellfish, crustaceans and, to a lesser extent, eggs, dairy products and meat. Present in very small quantities in the body, it is essential to it because it contributes to the functionality of many enzymes. Selenium can therefore be useful to your hair thanks to its antioxidant properties. Selenium deficiency is more common among vegetarians or vegans.
Zinc is contained in many foods: pulses, seafood, fish, meat and whole grains. It plays a major role in cell multiplication and as such, it is important for the growth of hair follicles. It inhibits an enzyme important in the action of testosterone. Normally, a varied diet is sufficient to ensure an adequate intake of zinc. Supplementation can nevertheless be useful in men producing too much testosterone. Beware of excessive intake (over 20 mg per day), which can cause abdominal pain.
There are different forms of iron; the most easily usable by the body is ferric iron, which is found mainly in meats. The deficiency exists especially in women who have heavy periods, or during pregnancy, and in vegetarians.
Many hair supplements contain iron. Prefer those that contain iron bisglycinate, because it has better bioavailability (it uses very efficient intestinal transporters).
There are many other active ingredients used in food supplements. These include silicon (obtained from nettle or horsetail decoction), blackcurrant seed extracts, vitamin D, copper, hydrolyzed collagen, etc. The problem is that the more ingredients you put in a dietary supplement, the more likely you are to have interactions between them (sometimes positive, but most often negative). For this reason, efficacy studies and the search for adverse effects must be carried out on the finished products, and not on this or that ingredient. This problem, of course, affects all segments of the dietary supplement market.
What you must remember
Ensuring the beauty of hair and preventing hair loss is a segment of the beauty market that is of great interest to consumers, and therefore to food supplement manufacturers.
There’s a lot of sense in nourishing the hair follicle (key structure that synthesizes hair) from within, i.e. orally, rather than topically.
However, there is a serious lack of well-done clinical studies (especially on finished products) that would justify the claims made by food supplements for the hair.
The useful ingredients are either those which limit oxidative stress (vitamins, minerals), or molecules (amino acids) having a functional role in the protein (keratin) which constitutes the hair.