Hair loss: understanding before treating.

6 min. read

10/07/2026

Perte de cheveux : comprendre avant de traiter.

Cellular beauty · Journal

Hair loss: understand before you act

Losing your hair is often experienced as inevitable. It rarely is. In the vast majority of cases, hair loss has an identifiable cause, and a cause you can act on.

The hair cycle: every hair has its own clock

A hair does not grow indefinitely. It goes through a life cycle in three distinct phases, controlled by precise hormonal, nutritional and cellular signals. Understanding this cycle means understanding where hair loss comes from, and why some approaches take several months before giving results.

The anagen phase is the active growth phase: the hair follicle produces the hair fibre at a rate of about 1 cm per month. It lasts from 2 to 7 years depending on genetics and nutritional status. At any given time, it concerns 85% of our hair. This is the phase we seek to prolong and strengthen.

The catagen phase is a short transition phase (2 to 3 weeks) during which the follicle shrinks and stops producing. It concerns about 1 to 2% of hairs at any given time.

Hair loss: the hair cycle (anagen, catagen, telogen) and the factors that disrupt hair growth, BIOLOGYST Journal — Fig. 1: The hair cycle and the main disrupting factors

The telogen phase is the resting phase: the follicle is inactive for 3 to 4 months, then the hair falls out naturally to make way for a new anagen cycle. It normally concerns 13 to 15% of hairs. Losing 50 to 100 hairs a day is therefore perfectly physiological: it is the normal consequence of this rotation.

Abnormal hair loss occurs when too many follicles switch to the telogen phase at the same time, or when the anagen phase gradually shortens. In both cases, the cause can almost always be identified.

Key figures of the hair cycle

50 to 100

Hairs lost per day = perfectly normal

2 to 3 months

Time between the triggering shock and visible hair loss

40 µg/L

Critical ferritin threshold for the follicle

90%

Of the hair fibre is made of keratin

Clinical study

Nutritional factors and hair loss

Rushton D.H. · Clinical and Experimental Dermatology · 2002 · Vol. 27(5) · pp. 396-404

This reference study established the direct link between serum ferritin levels and hair loss in women. The results show that a ferritin level below 40 µg/L: although considered “within normal range” by some laboratories: is enough to significantly weaken the hair follicle and reduce the duration of the anagen phase.

What this means in practice: iron deficiency is now recognised as the leading cause of hair loss in women of childbearing age. A ferritin test is the first test to ask for.

Read the publication →

“Hair loss is almost never inevitable. Most often it is a signal: nutritional, hormonal or emotional, sent by the body.”

The real causes: five mechanisms that trigger abnormal hair loss

The vast majority of hair loss is described as reactive or diffuse: that is, it has an identifiable cause and is potentially reversible once that cause is corrected. Here are the five most common mechanisms.

The most common causes of hair loss

Telogen effluvium

The most common cause of heavy hair loss. A triggering event (intense stress, fever, childbirth, surgery, a severe diet, stopping contraception) pushes up to 30% of hairs into the telogen phase at the same time. The hair loss occurs 2 to 3 months later: a delay that often makes the link hard to establish. Effluvium is reversible once the cause is corrected.

Iron deficiency (low ferritin)

Ferritin is the marker of iron storage. Below 40 µg/L, the hair follicle is weakened even if haemoglobin is normal. Iron deficiency affects between 30 and 50% of women of childbearing age and should always be investigated when hair loss occurs. Heavy periods and repeated pregnancies are the leading causes of depletion.

Nutritional deficiencies

Keratin, which makes up 90% of the hair fibre, requires sulphur amino acids (cysteine, methionine), zinc, selenium, B vitamins (biotin, B12, B9) and silicon to be synthesised properly. Any deficiency in these cofactors slows keratinisation, weakens the hair and shortens the anagen phase. Restrictive diets and digestive disorders are often to blame.

Hormonal imbalances

Dihydrotestosterone (DHT) is involved in androgenetic alopecia, gradually miniaturising the follicles. But other hormones play a role: drops in oestrogen (menopause, postpartum, stopping the pill), hypothyroidism, polycystic ovary syndrome (PCOS) and chronic stress via cortisol all disrupt the hair cycle.

Follicular oxidative stress

Free radicals build up in the scalp with age, pollution and an oxidising lifestyle. They damage the cells of the follicular matrix, shorten the anagen phase and accelerate the miniaturisation of the fibres. This is one of the mechanisms described in premature hair ageing. Vitamin E and selenium contribute to the protection of cells from oxidative stress; other compounds, such as glutathione, are the subject of research in this area.

What the hair follicle needs to function

The hair follicle is one of the structures with the fastest cell renewal in the body. It consumes a considerable amount of energy and nutrients to maintain its anagen phase. In the event of restriction: whether dietary, digestive or linked to a specific deficiency, the follicle is one of the first organs the body sacrifices in favour of vital functions.

Essential nutrients for hair health

Hydrolysed keratin (Cynatine® HNS)

Keratin is the structural protein of hair. A hydrolysed keratin provides the amino acids and peptides that make up the hair fibre. Cynatine® HNS is a patented keratin whose specific hydrolysis is described by its developers as promoting its bioavailability. Keratin is not the subject of an authorised health claim: the elements below describe a mechanism and published research, not a guaranteed effect.

L-cysteine and L-methionine

These two sulphur amino acids are the direct precursors of keratin. Cysteine forms the disulphide bridges that give hair its strength and elasticity. Methionine is involved in cellular protein synthesis and in methylation (epigenetic regulation of the hair cycle).

Zinc

Zinc contributes to the maintenance of normal hair and nails. It is a cofactor of more than 200 enzymes involved in cell division, protein synthesis and keratinisation. It is often lacking in people on restrictive diets or with intestinal malabsorption.

Iron (ferritin)

Iron contributes to the reduction of tiredness and fatigue and to normal cognitive function. It is also involved in cell division. In the available research, a ferritin level below 40 µg/L is associated with a shorter anagen phase. Lactoferrin (Lactoferrine Active+, No. 09) is a milk protein studied for its role in iron transport; it is not the subject of an authorised health claim. Adjusting iron intake should be discussed with a healthcare professional, based on a blood test.

Selenium and vitamin E

Selenium contributes to the maintenance of normal hair and, with vitamin E, to the protection of cells from oxidative stress. It also contributes to normal thyroid function. A note: a diagnosed thyroid disorder requires medical diagnosis and care, which no food supplement can replace.

Silicon (bamboo extract)

Silicon is a trace element of the extracellular matrix. The available research describes its role in the mechanical strength of the hair fibre and in hair elasticity; it is not the subject of an authorised health claim. Bamboo extract is one of the most concentrated natural sources of silicon.

“The hair follicle is a faithful indicator of overall nutritional status. What you see falling out in the shower often reflects what your body is no longer receiving.”

Hair & Nail Regenesis: an integrated approach to keratinisation

Hair & Nail Regenesis (No. 05) was formulated around two families of ingredients: structural substrates (keratin, sulphur amino acids, silicon) and enzymatic cofactors (zinc, selenium, iron, B vitamins), several of which have authorised health claims, listed below.

Key ingredients · Mechanisms of action

Ingredient	Role
Cynatine® HNS · 500 mg	A patented keratin hydrolysate. Provides amino acids and peptides that make up the hair fibre. A scientific study on this ingredient (Beer et al., 2014, 48 women analysed, 500 mg/day) reports a 46.6% reduction in hair loss at 90 days compared with the start of the study. This research describes study observations; keratin is not the subject of an authorised health claim and individual results vary.
L-cysteine · 200 mg	The main sulphur amino acid in keratin. Forms the disulphide bonds that give hair its cohesion and mechanical strength. A precursor in the synthesis of glutathione, a compound studied for its role in the cell's antioxidant defences.
Bamboo extract · 150 mg (including 112 mg of silicon)	A concentrated source of silicon. Described as being involved in the perifollicular extracellular matrix; the available research concerns the strength of the fibre, the strength of nails and hair elasticity. No authorised health claim to date.
L-methionine · 50 mg	An essential sulphur amino acid, precursor of cysteine. Involved in protein synthesis and in the cellular methylation that regulates the expression of genes involved in the hair cycle.
Zinc 10 mg · Selenium 50 µg · Iron 7 mg	A fundamental mineral trio: zinc and selenium contribute to the maintenance of normal hair, selenium contributes to the protection of cells from oxidative stress, iron contributes to the reduction of tiredness and fatigue and supports cell proliferation in the matrix. A balanced combination to cover the three deficiencies most often involved in hair loss.
Vitamins B, A and E	Vitamin B9 (folate) contributes to the process of cell division and to the reduction of tiredness and fatigue. Vitamin A contributes to the maintenance of normal skin and regulates keratinocyte differentiation. Vitamin E contributes to the protection of cells from oxidative stress.

Dosage and length of course

3 capsules per day, preferably in the morning or spread over the day at mealtimes. A course should last at least 2 to 3 months: a timeframe dictated by the hair cycle itself: a hair entering the anagen phase grows by about 1 cm per month and only becomes visible after 6 to 12 weeks of growth, whatever approach is chosen. Patience is part of the process.

Discover Hair & Nail Regenesis

Precautions. Plant-based capsule. Contains vitamin A: not recommended for pregnant women. Contains iron: if you have low ferritin or heavy periods, ask a healthcare professional for advice before combining several sources of iron.

Depending on your profile: the other formulas in the range

Depending on the context: proven iron deficiency, postpartum effluvium, a background of chronic stress, other BIOLOGYST formulas target different mechanisms. The choice is ideally made with a healthcare professional, based on a check-up.

Complementary combinations by profile

Low ferritin (below 40 µg/L)

Lactoferrine Active+ provides lactoferrin, a milk protein studied for its role in the transport and absorption of iron; it is not the subject of an authorised health claim. Note: Hair & Nail Regenesis already provides 7 mg of iron, i.e. 50% of the NRV. Any combination of iron sources should be decided with a healthcare professional, based on a blood test.

Post-stress or postpartum effluvium

Combine Magnesium Active+ and Serenity Flow to support nervous balance: magnesium contributes to the reduction of tiredness and fatigue and to normal functioning of the nervous system. A background of unmanaged stress keeps effluvium going even when deficiencies are corrected.

Hair loss linked to excess oxidative stress

Antioxidant Defense combines vitamin C, which contributes to the protection of cells from oxidative stress, with quercetin and Setria® glutathione, two compounds studied in this area, with no authorised health claim to date. A profile to consider in cases of smoking, urban pollution or intense physical activity.

Vitamin D deficiency (level below 30 ng/mL)

D3 Active+ (No. 11) provides vitamin D, which contributes to the maintenance of normal bones, to the maintenance of normal muscle function and to the normal function of the immune system. As far as hair is concerned, the available research describes VDR receptors in the follicle and observes an association between vitamin D deficiency and increased hair loss: a mechanism under study, not an established effect. A blood test and medical advice remain the starting point.

“Healthy hair is built over several months. Supporting hair during shedding means supporting the follicle, not forcing it.”

Frequently asked questions

How many hairs do we normally lose per day?

Losing 50 to 100 hairs a day is perfectly physiological. At any given time, 13 to 15% of hairs are in the telogen (resting) phase and fall out naturally to make way for a new growth cycle.

Why does hair loss occur 2 to 3 months after a shock?

Because a triggering event (intense stress, fever, childbirth, surgery, a severe diet) pushes up to 30% of hairs into the telogen phase at the same time. This phase lasts 3 to 4 months: hair loss therefore only becomes visible 2 to 3 months later, which makes the link hard to establish.

What ferritin level is associated with hair loss?

Below 40 µg/L, the hair follicle is weakened even when haemoglobin is normal (Rushton, 2002). Iron deficiency affects 30 to 50% of women of childbearing age: a ferritin test is the first test to ask for in the case of diffuse hair loss.

How long does it take to see a result?

Allow at least 2 to 3 months, whatever approach is chosen. A hair in the anagen phase grows by about 1 cm per month and only becomes visible after 6 to 12 weeks of growth: this timeframe is set by the hair cycle itself. If hair loss persists, the advice of a healthcare professional remains the first step.

Which nutrients are involved in keratin synthesis?

Keratin makes up 90% of the hair fibre. Its synthesis requires sulphur amino acids (cysteine, methionine), zinc, selenium, silicon and B vitamins (biotin, B9, B12). Further analyses of ingredients are available in the active ingredients blog and in the BIOLOGYST Journal.

BIOLOGYST. Food supplements should not be used as a substitute for a varied and balanced diet and a healthy lifestyle. Do not exceed the recommended daily dose. Keep out of the reach of young children. This article is for information only and does not replace medical advice: if hair loss persists, consult a healthcare professional.

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