Deep dive · Hair at Health Royals · 7 min read
The strand you see in the mirror was finished weeks ago. Everything that decided how it looks happened out of sight, in a follicle a few millimetres under the skin.
The short answer
• The visible strand is keratinised cells with no metabolism of its own. The follicle underneath is living tissue, connected to blood vessels, nerves and hormones.
• Every follicle runs a cycle of growth, transition and rest. The hairs on one head sit at different points in it, which is why losing some hair every day is ordinary.
• Biotin and zinc contribute to the maintenance of normal hair, and vitamin B6 to normal cysteine synthesis, the amino acid at the heart of keratin. Those are the documented roles, and we do not stretch them.
How does hair actually grow?
It is often said that hair is dead. True of the part you can see: the strand above the skin is keratinised cells that have finished their work, which is why no product repairs it in the biological sense.
The living part sits below. Each hair grows out of a follicle, a small organ in the skin connected to blood vessels, nerves and hormones. At its base lies the dermal papilla, surrounded by a reservoir of stem cells. Together they decide when a strand starts and how long the follicle keeps building it.
The work is demanding. Cells divide quickly, assemble amino acids into keratin, cross-link them and push the finished material upwards at roughly a centimetre a month. The length you are looking at is a record of the months behind you. And it runs not continuously but in a cycle of three named phases.
Anagen
Growth
The follicle is actively building a strand. The long phase, measured in years, and its length sets how long hair can get.
Catagen
Transition
Building stops and the lower follicle regresses. A short phase, measured in weeks, and the one nobody notices.
Telogen
Rest
Still anchored, no longer growing. Measured in months. The strand is released as the follicle starts the next round.
Hair is not produced continuously. It is produced in rounds, and every strand on your head is somewhere different in that round.
How much hair is it normal to lose?
Because the cycle ends in release, shedding is not a failure of the system. It is the system finishing a round. A strand in the brush is usually a follicle that has completed its work and is preparing for the next.
This is also why counting is a poor instrument. What ends up in the brush depends on how often you wash, how you style and how long since you last brushed. The useful signal is not the amount but the change: shedding clearly heavier than your own normal, coming on suddenly, leaving defined patches, or continuing month after month.
And hair that feels thinner is not always hair that is leaving. It can be hair growing finer, or hair breaking before it reaches the length you want.
The question is never how many hairs you lose. It is whether that number has changed for you.
What shapes hair quality?
What people call hair quality is three separate properties. Density is how many hairs grow in a given area. Diameter is how thick each strand is. Durability is whether a strand survives long enough to reach the length you want. Hair can change in one and not the others.
Density and diameter are decided in the follicle, and so by everything the follicle is exposed to: age, hormones, circulation, inflammation and how well the body is supplied. Around hormonal transitions the balance of the cycle can shift, and new strands can emerge finer than the ones they replace. We cover that transition in the hidden rhythm of menopause and midlife vitality.
Durability is decided mostly above the skin, by heat, friction, tight styling and repetition. It is the part you control directly, and it usually responds fastest.
Stress and sleep sit across both. Prolonged load changes the environment the follicle works in, and hair is not the body's first priority when resources are short. That is one reason hair often registers a difficult period months after it has passed. More on that in the biology of stress.
Thinner-feeling hair, finer hair and breaking hair are three different problems. Naming which one you have is the first useful step.
Why does the scalp matter so much?
The scalp is skin. Same barrier, same pH balance, same sebum production, same microbiome logic as the skin on your face, and usually a fraction of the attention. The difference is that it is also the tissue every follicle sits in.
When the barrier is dry, irritated or out of balance, the environment around the follicle changes with it. Low-grade inflammation is the mechanism most often described here, and it is quiet by definition. Research has also connected the scalp microbiome, the microorganisms living on that skin, with dandruff and the host immune responses that come with it. Itching, flaking or a scalp that never settles are worth reading as information.
The practical answer is rarely a more complicated routine. It is a gentler one: milder cleansing, thorough rinsing, less heat, less tension. The barrier thinking in the biology of radiant skin applies here too.
You cannot treat the scalp as an afterthought and expect the follicle to behave as if it were not there.
What does nutrition actually do for hair?
The visible strand is largely keratin, structural proteins built from amino acids and cross-linked into something that bends thousands of times without snapping. One amino acid matters more than most: cysteine carries a sulphur atom, and the bridges between cysteine units give keratin much of its strength.
Assembling that structure is enzymatic work, and enzymes depend on specific micronutrients being available. This is where nutrition genuinely sits: you are not feeding the strand that exists, you are supplying the follicle building the next one.
A handful of nutrients carry health claims authorised in the EU, worth stating exactly as authorised rather than in a more flattering paraphrase. Biotin, zinc and selenium contribute to the maintenance of normal hair. Copper contributes to normal hair pigmentation. Vitamin B6 contributes to normal cysteine synthesis. Zinc also contributes to normal protein synthesis. Notice what those are about: maintaining what is normal, and the steps involved in building keratin. None is a claim about faster growth or about reversing a loss, and no food in the EU is permitted to make one.
The research literature is a separate matter, best described by what it measured. One study examined how VEGF-mediated angiogenesis, the growth of new blood vessels, related to follicle size and hair growth in an experimental model. Other work examined how remodelling of the extracellular matrix, the network holding tissue together, changes in skin and follicles. A review examined inflammation and oxidative stress in patterned hair loss. Mechanisms under study, not promises.
Nutrition supplies the machinery that builds hair. It does not repaint the hair you already have.
When should you see a doctor?
Most hair change is slow, undramatic and tied to age, hormones, seasons and habits. Some is not, and the difference is worth knowing before you spend six months experimenting.
Speak to a healthcare professional if hair loss is sudden or rapidly progressing, if it comes in defined patches, if the scalp is painful, sore or persistently inflamed, if it arrives alongside other symptoms such as marked fatigue or weight change, or if it begins after a new medication. Any loss that is distressing you belongs in a consultation rather than a search bar.
A supplement is not a diagnosis. Sudden, patchy or painful hair loss should be assessed by a doctor.
If you are looking at your own hair right now
This article is about how hair works. If your question is more specific, and about thinning hair in women in particular, we keep that in a separate guide with the practical side and the formulas alongside it.
Read the need guide on thinning hair
Go deeper
- Thinning hair in women: what changes
- Golden millet and the biology behind healthy-looking hair
- Biotin for hair, skin and macronutrient metabolism
- Zinc: a small mineral with a broad role
- The biology of radiant skin
- The biology of stress, sleep and recovery
- The hidden rhythm of menopause and midlife vitality
Frequently asked questions
What makes hair look fuller and shinier?
Several things at once: the state of the scalp, the diameter of each strand, how much damage the lengths have taken, and the conditions the follicle works under. Shine is partly surface, since a smooth outer layer reflects light better, and partly structure.
What does hair care from within actually mean?
Treating hair as part of the body rather than a fibre you decorate. The strand is built by living tissue that depends on being supplied, so diet, recovery and scalp balance belong in the same conversation as conditioner.
Which nutrients have a documented role for hair?
A varied diet is the base. On top of that, biotin, zinc and selenium contribute to the maintenance of normal hair, copper contributes to normal hair pigmentation, and vitamin B6 contributes to normal cysteine synthesis. Those are the authorised wordings, and they are deliberately narrow.
Is hair that feels thinner the same as hair loss?
No. Hair can feel thinner because fewer strands are growing, because each strand is finer, or because strands break before they get long. Only the first is about loss, and sudden or persistent loss is a medical question.
How long before a change in routine shows in my hair?
Hair emerges at roughly a centimetre a month and the cycle is measured in months, so anything you change today is recorded in hair that has not appeared yet. Twelve weeks is the minimum sensible period over which to judge anything.
Does the scalp need a routine of its own?
It needs to be included, which is not the same as adding steps. Massage gently while washing, rinse properly, and pay attention to dryness, tightness or itching. A calm scalp is the goal, not a squeaky one.
Sources
- Paus R, Cotsarelis G. The biology of hair follicles. N Engl J Med. 1999.
- Giesen M, et al. Hair follicle stem cells and regeneration. Trends in Cell Biology. 2021;31(9):713–726.
- Fujiwara H. Extracellular matrix remodeling in skin and follicles. Int J Mol Sci. 2022;23(1):385.
- Yano K, et al. Control of hair growth and follicle size by VEGF-mediated angiogenesis. J Clin Invest. 2001;107(4):409–417.
- Clavaud C, et al. Dandruff is associated with changes in the scalp microbiome and host immune responses. PLOS ONE. 2018;13(7):e0198485.
- Tosti A, et al. Role of inflammation and oxidative stress in patterned hair loss. Dermatol Ther. 2020;33(6):e13985.
Important information
This article is educational reading and general information. It is not medical advice, and it does not diagnose or treat any condition. Food supplements are not a substitute for a varied diet and a balanced lifestyle. Individual needs and experiences vary. If you have questions about supplements, medication, allergies or your health, speak to a qualified healthcare professional. Sudden, patchy or rapidly progressing hair loss should always be assessed by a doctor.
