Amino acids, vitamins, and minerals: a panacea for healthy nails

EDITORIAL NOTE

This article was previously published and has been updated according to scientific and informative criteria to ensure clarity, transparency, and reference to verifiable literature. The content is for informational purposes only and does not replace medical consultation: for symptoms or therapeutic choices, consult a healthcare professional.

IN BRIEF

• Nails are keratinous structures primarily composed of keratin; their quality can reflect nutritional status and systemic conditions.
• Amino acids (especially sulfur-rich ones), proteins, and certain micronutrients (biotin, iron, zinc, selenium, vitamin C) are plausibly involved in nail health.
• Some supplementation (e.g., biotin in selected cases) has shown benefits in limited clinical studies; however, the general evidence is heterogeneous and contextual.
• Nail signs (e.g., brittleness, koilonychia, leukonychia) can indicate deficiencies or other conditions: diagnosis requires clinical evaluation and, if appropriate, laboratory tests.

Abstract: What does science say?

Nails are skin appendages primarily composed of keratin and corneocytes; their formation depends on the metabolic activity of the nail matrix and the availability of amino acids and micronutrients. Specialist literature summarizes that various deficiency states can alter nail growth, consistency, and color; at the same time, mechanical and environmental factors (repeated exposure to water, detergents, or solvents) are common causes of brittleness. Some nutritional interventions show biological plausibility and experimental data: for example, biotin has improved brittleness parameters in small clinical studies, and the role of vitamin C in collagen synthesis is well-established biochemically; sulfur-rich amino acids contribute to the formation of keratin's disulfide bonds. However, the strength of the evidence varies: there are limited reviews and clinical studies for individual nutrients, mechanistic studies on the role of proteins, and observational studies associating nail signs with iron or other mineral deficiencies. Interpretation requires attention to dose, duration, form of intake (foods vs. supplements), and clinical context: an improvement observed in a small study does not imply generalizable efficacy. In the absence of a confirmed deficit, the most robust approach remains a balanced diet, targeted medical evaluation, and avoiding exposures that damage the nail plate.

MAIN SECTION

What are nails and why can they weaken?

Nails are rigid structures formed by keratin proteins organized into horny layers; their growth depends on the activity of the matrix and the trophism of the nail bed. The chemical and physical composition of the nail plate influences strength, elasticity, and appearance: perturbations in the amino acid ratio, sulfur content, or trace elements can alter the structure. A recent review on nail biology and diseases summarizes the relationship between composition (keratins, lipids, minerals) and function. [1]

Common causes of brittleness and visual alterations

The causes of brittle nails are multifactorial: repeated exposure to water and detergents, trauma, onychomycosis, systemic diseases (anemia, thyroid disorders), medications, and nutritional deficiencies. Specialist literature emphasizes that almost any nutritional deficit can have a nail manifestation in certain clinical contexts; for example, iron deficiency is historically associated with koilonychia (spoon-shaped nails). [1] [8]

Structural nutrients: amino acids and keratin

Keratin is a polypeptide rich in specific amino acids, particularly sulfur-containing residues like cysteine, which promote disulfide bonds crucial for strength and rigidity. Chemical and spectroscopic studies describe how the amino acid composition and protein profile of the nail plate are correlated with its robustness; these biochemical bases explain the biological plausibility of the importance of adequate protein intake and individual amino acids for nail plate formation. [2] [3]

What research says about nutrients and supplementation

Biotin and specific supplements

Some clinical studies and case series report improvement in nail brittleness after biotin supplementation (typical studied dose: 2–2.5 mg/day), with a measurable increase in nail plate thickness in selected groups. However, the literature is limited in sample size and design, and broader reviews emphasize the need for caution: observed effects may be real in subgroups with undocumented deficiencies but are not proof of generalized efficacy for the healthy population. [4] [5]

Vitamin C, collagen, and supporting mechanisms

Vitamin C is an essential cofactor for enzymes that hydroxylate proline and lysine residues in collagen synthesis; dietary interventions combining protein sources rich in amino acids with vitamin C can promote the availability of precursors for matrix proteins. Experimental studies and small trials on collagen/gelatin enriched with vitamin C have shown an increase in indirect markers of collagen synthesis, suggesting a mechanism that could support the quality of horny structures under particular conditions, but direct translation to the nail requires further evidence. [6]

Minerals: iron, zinc, selenium, and copper

Minerals such as iron, zinc, and selenium have been associated with specific nail signs in clinical and observational studies. The presence of koilonychia is historically linked to iron deficiency states; other alterations (leukonychia, brittleness) have been observed in contexts of zinc or selenium depletion, sometimes improving after correction of the deficiency. However, much evidence comes from case series or observational studies: the link is biologically plausible but not always demonstrated as a causal relationship in general populations. [7] [8]

PRACTICAL SECTION

What this means in practice

For those noticing brittle, thin, or discolored nails, the first practical indication is a clinical evaluation: the doctor can assess related signs (e.g., fatigue, pallor, other skin changes) and, if necessary, prescribe targeted laboratory tests (complete blood count, ferritin, metabolic profile). Diet plays a fundamental role: quality protein sources (meat, fish, eggs) provide amino acids necessary for protein synthesis; fruits and vegetables provide vitamin C and antioxidants; nuts, whole grains, and legumes contribute zinc, copper, and other trace elements. The use of supplements can be considered when documented deficiencies exist or in specific clinical contexts: for example, biotin has limited but useful evidence in some selected cases. Avoiding harmful exposures (prolonged washing, aggressive solvents, overly invasive manicures) is a simple and often effective intervention to reduce brittleness. [1] [4] [6]

Topical remedies and home care

Emollient compresses with vegetable oils, regular application of moisturizing creams, and protection during wet work can reduce flaking and moisture loss from the nail plate. Some home remedies (extra virgin olive oil, aloe vera, compounds with egg and honey) have moisturizing and protective plausibility, but direct clinical evidence is scarce; they should be understood as complementary measures, not substitutes for medical evaluations. Avoiding aggressive treatments and favoring small environmental corrections is often more helpful than untargeted supplementation. [1]

KEY POINTS TO REMEMBER

• Nails reflect nutritional, metabolic, and environmental aspects: the cause is often multifactorial.
• Amino acids and proteins are essential structural elements for keratin; cysteine and other sulfur-containing residues contribute to the bonds that give the nail plate strength. [2] [3]
• Some supplements (e.g., biotin) can improve parameters in selected groups, but the evidence is limited and not generalizable. [4] [5]
• Vitamin C supports collagen synthesis biochemically and, in contexts of targeted protein supplementation, can contribute to precursor availability. [6]
• Specific signs (koilonychia, leukonychia) can indicate deficiencies such as iron or selenium: medical evaluation is necessary. [7] [8]

Limitations of the evidence

The literature on the direct effect of individual nutrients on nail health includes observational studies, case series, small trials, and some mechanistic studies. Observational studies show associations but do not establish causation; clinical trials are often small, not always controlled, or with subjective endpoints. Furthermore, individual variability (age, sex, medical conditions, occupational exposures) and the different forms of administration (whole foods vs. pure supplements) complicate interpretation. For these reasons, caution is needed in drawing conclusions and generalizing results: the presence of an improvement in one study does not authorize therapeutic claims for everyone. Where possible, diagnostic confirmation of a deficiency before starting supplementation is the most rigorous strategy. [1] [4]

Editorial conclusion

Nails are sensitive indicators of nutritional status and environmental exposures, but their appearance is influenced by multiple factors. Research suggests that a solid nutritional foundation — adequate protein, essential micronutrients, and a varied diet — is the safest prerequisite for nail health. The use of supplements can be useful in selected cases but requires diagnostic confirmation and supervision; topical interventions and behavioral modifications remain practical and low-risk components. The best approach combines clinical evaluation, targeted correction of any documented deficiencies, and daily protective measures.

Editorial note

Article updated with reference to peer-reviewed literature and informative guidelines. For further information, or for personal health reasons, consult your trusted doctor. The information reported here is general in nature.

SCIENTIFIC RESEARCH

1. Muddasani S, Lin G, Hooper J, Sloan SB. Nutrition and nail disease. Clin Dermatol. 2021 Sep-Oct;39(5):819-828. DOI: https://doi.org/10.1016/j.clindermatol.2021.05.009. [1]
2. Baswan S, Kasting GB, Li SK, Wickett R, Adams B, Eurich S, Schamper R. Understanding the formidable nail barrier: a review of the nail microstructure, composition and diseases. Mycoses. 2017;60(5):284–295. DOI: https://doi.org/10.1111/myc.12592. [2]
3. Roberts TC, et al. Sex-related chemical differences in keratin from fingernail plates: a solid-state carbon-13 NMR study. RSC Adv. 2017;7:28213–28223. DOI: https://doi.org/10.1039/C7RA03487C. [3]
4. Colombo VE, Gerber F, Bronhofer M, Floersheim GL. Treatment of brittle fingernails and onychoschizia with biotin: scanning electron microscopy. J Am Acad Dermatol. 1990;23(6 Pt 1):1127–1132. DOI: https://doi.org/10.1016/0190-9622(90)70345-I. [4]
5. Ständer S, et al. Biotin for the treatment of nail disease: what is the evidence? J Dermatolog Treat. 2017;28(4):xxx-xxx. DOI: https://doi.org/10.1080/09546634.2017.1395799. [5]
6. Shaw G, Lee-Barthel A, Ross ML, et al. Vitamin C–enriched gelatin supplementation before intermittent activity augments collagen synthesis. Am J Clin Nutr. 2017;105(1):136–143. DOI: https://doi.org/10.3945/ajcn.116.138594. [6]
7. True leukonychia in Crohn disease induced by selenium deficiency. JAMA Dermatol. 2014;150(3):xxx-xxx. DOI: https://doi.org/10.1001/jamadermatol.2013.6701. [7]
8. Koilonychia and iron deficiency: Association in clinical reports. Arch Dermatol. 1980;116(8):861. DOI: https://doi.org/10.1001/archderm.1980.01640320011002. [8]