Biotin for Hair and Nails: What the Science Really Says

Biotin, also called vitamin B7, vitamin H or vitamin B8 according to the nomenclature, is a water-soluble vitamin of the B complex. Like all water-soluble vitamins, it is not stored in significant quantities in the body: the excess is eliminated in the urine and the intake must be relatively constant from the diet.

What biotin is: actual biological function

Its central biological function is to act as a coenzyme of five carboxylases - enzymes involved in the metabolism of carbohydrates, fats and amino acids, and in the synthesis of glucose and fatty acids. Without available biotin, these enzymes cannot function, which directly affects the processes of cellular energy production and structural protein synthesis.

Biotin's relationship to hair and nails comes from its role in the synthesis of keratin, the fibrous protein that forms the structure of all three tissues. Biotin does not build keratin directly, but its enzymatic activity is necessary so that the available amino acids can be assembled into functional protein chains. Without adequate biotin, keratin synthesis is compromised and keratinized tissues are the first to reflect this.

Where is biotin found?

Biotin is naturally present, in small amounts, in many foods of plant and animal origin. For example, it can be found in:

• Eggs (specifically in the yolk);
• In meats and offal, such as liver;
• In fish, seeds and nuts;
• In certain fruits, such as bananas, watermelon or strawberries;
• And in some vegetables, such as spinach, broccoli and sweet potato.

Biotin and hair: what's in evidence and what's not

This is the point where most articles on biotin fail: they conflate the documented effect of deficiency with the speculative effect of supplementation in non-deficient people, as if they were the same thing.

What is well documented: according to studies, when there is an actual biotin deficit, hair becomes brittle, thin and more prone to breakage and shedding. Supplementation in this context restores normal function and measurably improves hair condition. Biotin deficiency also causes scaly periorificial dermatitis, a characteristic skin manifestation - and brittle nails.

What is not documented is that biotin supplementation improves hair in people with normal biotin levels. The available clinical trials are scarce, heterogeneous and with small samples. The review of the available evidence does not allow us to conclude that biotin supplements produce accelerated hair growth or greater density in people without a deficit. The market of hair supplements with biotin is enormously overdimensioned with respect to what the evidence supports.

Actual deficiency is rare. Biotin is present in many commonly consumed foods and the intestinal microbiota also synthesizes it in modest quantities. True deficiency appears in specific contexts: chronic consumption of raw egg white (which contains avidin, a protein that blocks biotin absorption), prolonged use of certain antiepileptic drugs, severe inflammatory bowel disease that compromises absorption, and some inborn errors of metabolism.

The practical implication: before supplementing biotin for hair, it makes more sense to assess iron (ferritin), zinc and vitamin D status - the deficits with the highest actual prevalence in the general population and with the greatest documented impact on hair - than to assume a biotin deficit without analytical basis.

Biotin and nails: where the evidence is strongest

Nails are the territory where biotin has its most consistent studies. Several clinical trials with doses of 2,500 micrograms daily for periods of three to six months have documented improvements in nail thickness, strength and appearance in people with brittle and fragile nails - the condition called onychoschizia.

The mechanism is analogous to hair: biotin enhances the synthesis of hard keratin, which is the nail-specific keratin that is stiffer than that of hair. The effect on nails is more predictable than on hair probably because the nail structure is more homogeneous and the effect of keratin on its resistance is more direct. Learn more about hair and nail care.

The condition remains the same: the effect is clearer when there is a deficit or suboptimal levels. In people with healthy nails and normal biotin levels, supplementation is of marginal benefit.

Foods with biotin: how to cover the requirement with the diet

The adequate intake of biotin established by EFSA for adults is 40 micrograms per day - a threshold that most people with a varied diet reach without difficulty. Foods with the highest concentration of biotin are:

Cooked egg yolk. This is the most concentrated and bioavailable source. One cooked egg provides approximately 10 micrograms. Important: raw egg white contains avidin, which blocks biotin absorption. Cooking denatures avidin and eliminates this effect. Eggs should be consumed cooked to take advantage of their biotin.

Liver and offal. Pork and beef liver have very high concentrations of biotin between 40 and 100 micrograms per 100 grams. They are also rich sources of heme iron, zinc and vitamin B12.

Nuts and seeds. Hazelnuts, almonds, peanuts and sunflower seeds have relevant content. A handful of hazelnuts provides between 5 and 15 micrograms depending on the size.

Fatty fish. Salmon, tuna and sardines provide biotin along with omega-3, vitamin D and selenium - a combination especially favorable for connective tissue and skin health.

Legumes. Lentils and soybeans have moderate biotin content and are especially relevant in plant-based diets where animal sources are limited.

Dairy and cheese. They contribute modest amounts but contribute to the daily total in people with habitual consumption.

Biotin and silicon: why they work best together.

Biotin does not act in isolation on hair tissue. The most consistent results in hair and nail health studies appear when biotin is accompanied by other nutrients with which it shares metabolic pathways.

Organic silicon - specifically bioavailable orthosilicic acid - has complementary functions to biotin in hair tissue. While biotin acts in the enzymatic metabolism necessary for keratin synthesis, silicon acts as a cofactor in the synthesis and stabilization of hair follicle collagen and in the structural quality of the fiber. Studies with stabilized orthosilicic acid have documented improvements in hair fiber thickness and mechanical strength in nine-month trials - an effect that acts on the architecture of the new fiber growing from the follicle, not on the already formed fiber.

Zinc, vitamin C and quality proteins complete the nutritional framework for healthy hair. A deficiency of any one of these limits the performance of the others, regardless of dosage. Why hair looks better with silicon: mechanism and evidence

If you are looking for a supplement that combines real bioavailability and clinical support for hair and nails, Silicium's G7 Siliplant is formulated with collagen for hair tissue and organic silicon in a highly bioavailable liquid form.

Benefit from biotin and its qualities

In conclusion, it is important to maintain a healthy and balanced diet that covers all our nutritional needs, including those related to biotin.

However, its properties also make biotin an interesting option as a supplement, so that we can enjoy the benefits of this vitamin.

In situations of biotin deficiency and for some specific health conditions that we have mentioned throughout the article, supplementation may be especially advisable.

However, we can also resort to them to enhance our general well-being, either by providing the body with biotin alone or combined with other beneficial elements.

An example of this is Silicium G7 Neuro Health, a product that in addition to biotin providesuswith organic silicon to contribute to the normal functioning of the nervous system and psychological function, as well as to combat the harmful effects of aluminum that accumulates in the tissues.

Frequently asked questions about biotin

Is biotin fattening?

No. Biotin is a water-soluble vitamin with no effect on energy metabolism in a storage sense. It participates in the metabolism of fats, carbohydrates and proteins as a coenzyme, but does not alter the energy balance or promote fat storage. There is no biological mechanism or clinical evidence associating biotin supplementation with weight gain.

Can biotin interfere with blood tests?

Yes, and this is a clinically relevant caveat that biotin supplements often fail to communicate. Biotin in high doses (greater than 5,000 micrograms, present in some "high potency" supplements) can interfere with certain laboratory immunoassays that use biotin-streptavidin as a detection system. Assays that may be affected include TSH and thyroid hormones, troponin, estradiol, and some vitamin D determinations. The standard recommendation is to discontinue biotin supplementation at least 48-72 hours before a blood test.

External reference: Agencia Española de Medicamentos y Productos Sanitarios (AEMPS) - Informative note on biotin interference in analytical determinations.

How much biotin per day is the adequate dose in a supplement?

The adequate intake established by EFSA is 40 micrograms per day for adults. Supplements on the market vary greatly: from 100 micrograms to 10,000 micrograms (10 mg). There is no evidence that doses above 2,500-5,000 micrograms produce additional benefits on hair or nails compared to lower doses. It is the megadoses that generate the risk of analytical interference described above. For most maintenance purposes, doses of 300-1,000 micrograms are more than sufficient.

Does biotin in shampoo work?

Biotin applied topically in shampoos and conditioners does not penetrate the hair fiber or hair follicle in physiologically significant amounts. The hair fiber is a dead structure with no active metabolic absorption capacity. The effect of shampoos with biotin is purely superficial - it may improve hair texture and appearance in the short term through its conditioning effect, but it does not have the biological effect on keratin synthesis that ingested biotin does. It is marketing rather than science.

Can biotin be taken during pregnancy?

Biotin requirements increase slightly during pregnancy (EFSA states 40 micrograms also in pregnancy, although some studies suggest that requirements may be somewhat higher). Some animal studies have found that biotin deficiency during pregnancy may have effects on embryonic development, although actual deficiency in humans with normal diet is rare. As with any supplementation during pregnancy, consultation with a physician or gynecologist is the correct step before initiating or continuing supplementation.

External reference: NIH Office of Dietary Supplements - Biotin: Fact Sheet for Health Professionals