💇 Hair loss and brittle nails: from zinc deficiency to protein deficiency
Which deficiencies most often lie behind hair and nail problems
Hair loss and brittle nails are among the most common complaints that may point to a nutrient deficiency. Hair and nails are "low-priority" tissues for the body: when nutrients are lacking, the body first "takes" them for vital organs.
Deficiencies of zinc, iron, protein, biotin and vitamin D are frequent culprits. However, it is important to understand: hair loss can have other causes too (hormones, stress, thyroid disease), so diagnosis is needed. Below — what to check and how to replenish.
Main causes of hair loss
Hair loss occurs for various reasons: genetic (androgenetic) alopecia, telogen effluvium after stress, hormonal changes, diseases and deficiencies. Nutrition affects primarily telogen effluvium and hair quality.
Anemia and ferritin
Low ferritin is linked to increased shedding, even without obvious anemia.
Telogen effluvium
2–3 months after severe stress, hair mass transitions into the resting phase and falls out.
Thyroid gland
Hypo- and hyperthyroidism affect the hair growth cycle.
Protein and trace elements
A lack of protein, zinc, biotin and iron worsens growth and strength.
The role of zinc and iron
Growth and regeneration
Zinc participates in the cell division of hair follicles and protein synthesis. Deficiency leads to hair loss and brittleness.
Oxygen and ferritin
Iron carries oxygen to the follicles. Low ferritin (<30–40 mcg/L) is often linked to hair loss.
Protein and biotin: building material
Hair and nails are almost entirely made of keratin — a protein. Its synthesis needs amino acids as well as vitamin cofactors, including biotin (B7).
Vitamin D and other nutrients
Follicles
Vitamin D affects the hair growth cycle. Deficiency is linked to hair loss, although the data are mixed.
Thyroid gland
Supporting thyroid function indirectly affects hair.
Blood formation
B12 and B9 deficiency leads to anemia, and thus to oxygen starvation of follicles.
Collagen and keratin
Silicon participates in collagen and keratin synthesis, affecting the strength of hair and nails.
How to diagnose a deficiency
| Test | What it shows | Reference |
|---|---|---|
| Ferritin | Iron stores | Optimal 40–80+ mcg/L |
| Complete blood count | Anemia, hemoglobin | Hemoglobin norm depends on sex |
| Vitamin D (25-OH D) | D level | 30–60 ng/mL |
| B12 and folates | Blood formation | B12 400–900 pg/mL |
| Zinc (plasma/serum) | Zinc level | 70–120 mcg/dL |
| TSH | Thyroid gland | 0.4–4.0 mIU/L |
Food sources: table
| Nutrient | Product | Content (per 100 g) |
|---|---|---|
| Zinc | Oysters | ~30–90 mg |
| Zinc | Beef | ~5–8 mg |
| Zinc | Pumpkin seeds | ~7–8 mg |
| Iron | Beef liver | ~6–9 mg |
| Iron | Red meat | ~2–3 mg |
| Protein | Chicken breast | ~31 g |
| Protein | Egg (1 pc) | ~6 g |
| Biotin | Liver | ~30–50 mcg |
| Biotin | Eggs, nuts | ~10–20 mcg |
| Vitamin D | Fatty fish (salmon) | ~10–20 mcg (400–800 IU) |
Which deficiency causes hair loss?
Most often iron (low ferritin), zinc, protein, biotin and vitamin D. But there are many causes, including hormones and stress.
Does biotin help with hair loss?
Biotin helps with a confirmed deficiency. In most people with a normal level, there may be no noticeable effect.
What ferritin level is needed for hair?
Many dermatologists consider a ferritin level of 40–80 mcg/L and above optimal. Low ferritin is linked to hair loss.
Do I need a lot of protein for hair?
Yes. Hair consists of keratin (a protein). Chronic protein deficiency weakens hair and nails.
Can vitamin D affect hair?
Vitamin D deficiency is linked to hair loss, although the data are mixed. Maintaining a normal level is beneficial.
How quickly do hair recover after a deficiency?
Hair growth is slow (about 1 cm/month). Improvement after correcting a deficiency is usually visible after a few months.
Is excess zinc harmful?
Yes, high doses of zinc (>40 mg/day from supplements) can cause nausea and copper deficiency. Do not exceed the norm.
Which tests to take for hair loss?
Ferritin, complete blood count, vitamin D, B12, folates, zinc, TSH. A doctor will prescribe them.
Does collagen help for hair and nails?
Collagen provides amino acids needed for keratin and supports nails and skin. Data on hair are limited, but it may help.
Why do nails peel?
Causes: lack of protein, iron, zinc, biotin, as well as external factors (water, chemicals, trauma). Check your diet and tests.