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Brittle, splitting or ridged nails

Nails split, peel and ridge for reasons that are mostly mechanical and environmental. Nutrition is in the conversation, but it is well down the list behind water, detergent, solvents and age.

General information only, not a diagnosis. A symptom is not proof of a deficiency — most symptoms here have many possible causes, and the common ones are rarely nutritional. Do not start a supplement to treat a symptom; the safe route is a blood test if one is warranted, and a doctor to interpret it. Use the red-flag list on each page, and see a clinician for anything that persists or worries you.

The dominant cause of brittle nails in adults is repeated wetting and drying. Water swells the nail plate; drying shrinks it; doing that many times a day — washing up, cleaning, healthcare work, gardening — separates the layers and produces the peeling and splitting people describe. Nail polish remover, particularly acetone, does the same thing faster. Age adds to it, because nail plates thin and grow more slowly over the decades.

Longitudinal ridges running from cuticle to tip are, in most people, simply a normal feature that becomes more prominent with age. They are so commonly interpreted as a deficiency sign that it is worth stating plainly: on their own, they usually mean nothing. Transverse ridges — grooves running across the nail — are different, because they record a systemic event around the time the nail was forming, and they are worth mentioning to a doctor.

The nutritional links that do exist are the same short list as for hair. Iron deficiency is associated with nail changes, including the spoon-shaped nails of long-standing deficiency. Frank zinc deficiency affects nails as part of a broader picture that includes skin and healing. Biotin has the best-known reputation and the same problems as it has for hair: deficiency is rare, evidence outside deficiency is weak, and high doses interfere with laboratory tests.

The practical measures that work are unglamorous and not nutritional: gloves for wet work and cleaning, less frequent polish removal, keeping nails short while they recover, and an emollient. If the nail changes are new, rapid, affecting one nail, or accompanied by pain or colour change, that moves out of cosmetic territory and into a medical appointment.

Nutrients commonly discussed for brittle nails

Each nutrient below is rated for how strong the evidence is that it relates to this symptom. "Relevant only if you are deficient" means it can matter when your level is genuinely low, but topping it up when it is not low does nothing.

Iron Relevant only if you are deficient

Long-standing iron deficiency produces recognisable nail changes, including thin, spoon-shaped nails. Suspecting it means asking for a blood test, not starting a supplement.

Full ranking: foods highest in iron.

Zinc Relevant only if you are deficient

Nail changes are part of the picture in frank zinc deficiency, alongside skin changes and slow healing. Isolated brittle nails in an otherwise well person are unlikely to be this.

Full ranking: foods highest in zinc.

Biotin Weak evidence

The one nutrient with a genuine, if small, literature on nail brittleness — and also the one with the laboratory-interference problem. If you take it, tell whoever orders your blood tests.

Protein Relevant only if you are deficient

Nails are keratin, so severe protein or energy deficit shows in them. Again, this is about real deficit rather than about optimisation.

Vitamin C Relevant only if you are deficient

Severe deficiency affects connective tissue, including around the nail folds. Scurvy is rare but not extinct, and it turns up in people with very restricted diets.

Full ranking: foods highest in vitamin c.

Source: Foods richest in each nutrient: USDA FoodData Central SR Legacy (public domain), per 100 g · checked 2026-09-02

Causes that are usually more likely

Before a nutrient, these are the explanations a clinician would normally consider first for brittle nails:

• Repeated wetting and drying — the commonest cause by far
• Acetone and other polish removers, and frequent gel or acrylic application
• Age: nail plates thin and grow more slowly
• Fungal nail infection
• Psoriasis and eczema affecting the nail
• Thyroid disease
• Trauma, including habitual picking
• Raynaud phenomenon and other circulatory conditions

When to see a doctor

Treat these as reasons to seek a professional opinion rather than to self-treat:

• A dark streak or band under a nail that is new or changing
• One nail behaving very differently from the others
• Pain, swelling or pus around the nail fold
• Nails lifting away from the bed, or thickening and crumbling
• Nail changes alongside tiredness, weight change or hair loss
• Clubbing — nails curving over rounded fingertips

This list is not exhaustive, and a symptom that is severe, persistent or getting worse always deserves a professional opinion. If you feel very unwell, seek urgent care rather than reading further.

Frequently asked questions

Other symptoms

All symptoms · Nutrient toplists · Blood test reference ranges