What Deficiency Makes Fingernails Brittle? A Comprehensive Guide

November 20, 2025 •

3 min read

According to dermatological studies, significant improvements in nail strength have been observed in individuals with brittle nail syndrome after supplementing with biotin. Understanding what deficiency makes fingernails brittle is the first step toward restoring their strength and overall health.

Quick Summary

This guide explains the common nutritional deficiencies, such as biotin and iron, that can lead to brittle nails. It also covers external factors and lifestyle changes to restore nail strength.

Key Points

Biotin and Iron are Key Culprits: Deficiencies in biotin (Vitamin B7) and iron are two of the most commonly cited nutritional causes for brittle nails.
Keratin Production Relies on Nutrients: Nail strength depends on keratin, a protein whose production is supported by adequate intake of protein, zinc, and B vitamins.
External Factors Often Contribute: Frequent exposure to water, harsh chemicals, and acetone-based nail polish removers can strip the nail's natural oils, leading to brittleness.
Medical Conditions Can Be a Factor: Brittle nails can be a symptom of underlying health issues, including thyroid disorders and anemia, so a doctor's consultation may be necessary.
Holistic Care is Essential: Improving nail health involves a combination of dietary improvements, proper hydration, gentle nail care techniques, and protecting your nails from environmental stressors.
Supplements Need Medical Guidance: While supplements like biotin can help those with a deficiency, it's crucial to consult a healthcare provider before starting any supplement regimen to ensure it's appropriate for your needs.

Primary Nutritional Deficiencies That Cause Brittle Nails

Fingernails are primarily made of keratin, a fibrous protein. Maintaining healthy keratin requires a balanced diet of vitamins, minerals, and protein. A lack of these nutrients can weaken the nail plate, causing brittleness, splitting, and peeling.

Biotin (Vitamin B7)

Biotin is a B-complex vitamin crucial for cell growth and metabolizing amino acids, which build keratin. It is often associated with brittle nail syndrome. While biotin deficiency is uncommon, insufficient dietary intake or genetic conditions can affect its metabolism.

Biotin deficiency can manifest as:

Splitting and peeling nails
Increased fragility
Slow nail growth

Studies show that biotin supplementation can improve nail thickness and reduce brittleness in deficient individuals over several months. Good dietary sources include eggs, salmon, sweet potatoes, nuts, and seeds.

Iron

Iron is vital for oxygen transport to the nail matrix, where new nail cells develop. Low iron levels reduce this oxygen supply, leading to weaker, thinner nails and slower growth. Severe iron deficiency can result in koilonychia (spoon-shaped nails), characterized by thin, brittle, and concave nails.

Signs of iron deficiency in nails include:

Brittle nails that break easily
Pale nail beds
Concave or spoon-shaped nails (in severe cases)

Protein

As nails are mainly keratin, adequate protein intake is fundamental. Protein deficiency can cause weaker nails with visible ridges or slower growth. Lean meats, poultry, fish, eggs, dairy, and legumes are excellent protein sources.

Zinc

Zinc supports cell growth and division, which are rapid in nail cells. Deficiency can cause white spots, nail plate degeneration, and overall weakness. Zinc is found in beef, fish, eggs, and legumes.

Other Micronutrients

Other nutrients also impact nail health:

Vitamin C: Necessary for collagen, which gives shape and strength to nail tissue.
Magnesium: Involved in protein synthesis for nail growth.
Calcium: A key mineral for nail structure; low intake may contribute to soft nails.

External Factors and Lifestyle Choices

Brittle nails can also result from external damage and moisture loss.

Moisture Exposure: Frequent wetting and drying, like from handwashing or dishwashing without gloves, dries out and weakens the nail plate.
Chemical Exposure: Harsh chemicals in cleaning products, detergents, and acetone removers strip natural oils, causing softness and brittleness.
Aging: Nails naturally become more brittle and grow slower with age.
Excessive Nail Products: Frequent use of gel polishes, acrylics, and aggressive filing weakens the nail plate.

Underlying Medical Conditions

Brittle nails can sometimes indicate a medical issue.

Hypothyroidism: Can cause dry, brittle nails along with other symptoms.
Anemia: Iron deficiency anemia is a known cause.
Raynaud's Syndrome: Affects circulation to the extremities, impacting nutrient delivery to nails.
Psoriasis and Eczema: These skin conditions can also affect nails.

Comparison of Deficiency Symptoms

Identifying specific deficiency symptoms can help pinpoint the cause, but professional medical advice is recommended.


Nutrient	Primary Role	Associated Nail Symptoms	Food Sources
Biotin (B7)	Keratin production	Splitting, peeling, fragile nails	Eggs, nuts, seeds, sweet potatoes
Iron	Oxygen transport	Pale nail beds, slow growth, spoon-shaped nails	Red meat, spinach, beans, fortified cereals
Protein	Keratin formation	Weak nails, visible ridges	Meat, fish, eggs, dairy, legumes
Zinc	Cell growth & division	White spots on nails, weakened nail plate	Beef, poultry, eggs, legumes
Vitamin B12	Red blood cell production	Discoloration, slower growth	Meat, poultry, fish, eggs, dairy

Strategies to Improve Nail Health

A combination of approaches is often best for restoring nail strength.

Hydrate: Drink enough water. Use hand and nail cream or oil regularly.
Protect Hands: Wear gloves during chores.
Balanced Diet: Eat whole foods, including leafy greens, lean proteins, and healthy fats.
Limit Nail Polish: Take breaks from polish and use acetone-free removers.
Gentle Filing: File in one direction.
Seek Medical Advice: Consult a healthcare provider if nail health doesn't improve with lifestyle changes.

Conclusion

Brittle fingernails typically result from nutritional deficiencies like biotin or iron, combined with external factors and potentially underlying health conditions. A balanced diet, protection from harsh elements, and gentle nail care can make a significant difference. For persistent issues, professional medical advice is crucial to determine the specific cause and treatment. For further general guidance, the Mayo Clinic offers helpful tips on daily nail care.

Frequently Asked Questions

Biotin (Vitamin B7) and iron deficiencies are among the most common nutritional causes of brittle nails. Biotin helps produce keratin, while iron ensures oxygen delivery to the nail bed.

Yes, dehydration can impact nail health. Just as skin needs moisture, so do nails. Frequent wetting and drying of the hands can strip moisture, making nails dry and brittle, so staying hydrated is crucial.

Beyond nutrition, common non-nutritional causes include aging, repeated exposure to water, harsh chemicals like acetone, and underlying medical conditions such as hypothyroidism, psoriasis, or anemia.

For individuals with a diagnosed biotin deficiency, supplements can be highly effective in strengthening nails. However, for people with adequate biotin levels, the evidence is less conclusive. Always consult a doctor before starting supplements.

Brittle nails caused by iron deficiency may be accompanied by paleness in the nail beds, fatigue, or shortness of breath. A severe deficiency can also cause koilonychia, or spoon-shaped nails.

While often caused by common lifestyle factors, brittle nails can sometimes indicate a more serious underlying health condition like a thyroid disorder or anemia. If your nails don't improve with lifestyle changes, it's best to see a doctor.

To prevent brittle nails, wear gloves when cleaning or doing dishes, use acetone-free polish remover, moisturize your hands and cuticles regularly, and adopt a balanced diet rich in vitamins and minerals.