Onychoschizia, nail plate splitting, and brittleness are common complaints: estimates suggest they affect approximately 20% of the adult population, with women affected three times more often than men [2]. Patients frequently seek solutions on their own — including at the pharmacy, where the selection of "nail beauty supplements" is vast and continues to grow. Yet the regulatory status of dietary supplements differs fundamentally from that of pharmaceuticals: manufacturers are not required to demonstrate efficacy, safety, or product quality before bringing a product to market. In this context, a systematic scientific assessment of the available data is particularly valuable for practicing specialists.

What the review covers

A narrative review published in Skin Appendage Disorders systematizes data on six categories of nail supplements [1]. For each, the authors examine the theoretical rationale, available clinical studies, and safety profile. The overall conclusion is unambiguous: the evidence base for all reviewed products remains limited, and significant methodological shortcomings burden existing studies.

Biotin: the most popular ingredient — and the most risky

Biotin (vitamin B7) is the undisputed favorite among nail supplements, and its use has a theoretical basis: the vitamin participates in five carboxylase enzymes involved in the metabolism of fatty acids, amino acids, and glucose, thereby indirectly supporting keratin synthesis. Among the clinical data, the most widely cited is the work of Floersheim: of 71 patients with brittle nails taking 2.5 mg of biotin daily, 41 of the 45 evaluated (91%) showed marked improvement in nail plate firmness over an average of 5.5 ± 2.3 months [3]. Hochman et al. reported clinical improvement in 22 of 35 patients. In a randomized study by Fanian et al. (60 healthy women, 90 days), nail growth in the group receiving a multivitamin formula containing biotin was significantly greater than in the placebo group: 5.23 mm vs. 5.15 mm (p < 0.001).

Nevertheless, the review authors note that none of these studies were fully blinded, that no rigorous randomized trials using biotin as the sole active ingredient exist, and that the available studies were conducted in small cohorts. Furthermore, biotin carries a clinically meaningful risk: supplementation at any dose can interfere with immunoassay results — particularly troponin, thyroid-stimulating hormone (TSH), and antithyroid antibody levels — potentially leading to diagnostic errors in the workup of cardiovascular or thyroid conditions.

Collagen peptides: promising data with caveats

Collagen peptides derived from type I collagen are theoretically expected to stimulate endogenous collagen synthesis and may influence the nail bed matrix. In the study by Hexsel et al., 25 women with brittle nails took 2.5 g of peptides daily for 24 weeks [4]. Nail growth rate increased significantly by week 12; by week 24, the increase reached 12%, and four weeks after the end of treatment, 15%. Satisfaction with results was reported by 80% of participants, 75% felt their nails were stronger, and 71% noted accelerated growth. The review authors, however, flag inadequate blinding as the key methodological limitation of this study. Reported adverse effects include diarrhea, abdominal fullness, and heartburn; anaphylactic reactions have been described in isolated cases with fish-derived collagen.

Solubilized keratin, ch-OSA, and MSM: rationale present, data scarce

Solubilized keratin is a highly bioavailable form of the nail's primary structural protein. In the only available randomized study, 50 women received 500 mg of solubilized keratin or a placebo for 90 days: the treatment group showed mild to moderate improvement in nail quality, while the placebo group showed no change. A single study is far too little to conclude.

Choline-stabilized orthosilicic acid (ch-OSA) acts through multiple pathways: it stimulates type I collagen synthesis, improves glycosaminoglycan cross-linking in the dermis, and strengthens keratin structure. In a double-masked, randomized study by Barel et al. (48 women, 10 mg ch-OSA daily for 20 weeks), VAS scores for nail brittleness declined significantly in the treatment group by the end of the observation period. In contrast, the placebo group showed no significant change [5]. The review authors describe the study design as relatively rigorous but note the small sample size.

MSM (methylsulfonylmethane) is an organic sulfur compound that reinforces the disulfide bridges of nail plate keratin. In the only available study, 63 women took 1 g or 3 g of MSM daily for 16 weeks: both dosage groups showed a statistically significant improvement in nail appearance. The review authors characterize the level of evidence as low.

Multivitamin formulations: virtually no data

Combination supplements containing amino acids, vitamins C, E, B6, biotin, and minerals (zinc, iron, copper) were examined in a single study involving just 8 patients with onychoschizia. After three months of use, nail plate strengthening and smoothing were reported. Drawing any evidence-based conclusions from this is not possible. Notably, the review authors also caution that multivitamin formulations with high levels of vitamins A, E, or selenium have been associated with elevated cancer risk in certain groups in some studies, and that excess vitamin A and selenium can themselves cause nail dystrophy.

Limitations and overall evidence assessment

The review authors conclude that none of the supplements examined has been evaluated in large, randomized, double-masked trials. Most studies enrolled small cohorts, had short follow-up periods, and lacked blinding or adequate standardization of outcome measures. Long-term safety data are virtually absent across all products, and particularly vulnerable groups — pregnant and breastfeeding women, children, the elderly, and patients with renal or hepatic impairment — are barely represented in the available research.

Practical takeaways and conclusions

Patient interest in nail supplements will only grow — and specialists should be prepared. The priority is to rule out systemic causes of nail changes: iron deficiency, thyroid disease, and nutritional disorders. If a patient is taking biotin, the laboratory must be informed before any immunoassay is performed — otherwise, false results may lead to a clinical error. Among all the options reviewed, collagen peptides and ch-OSA have the most compelling biological rationale and relatively better clinical data — though even for these, claiming proven efficacy in the strict sense remains premature. Nail supplements are occupying an increasing share of the nutricosmetics market, yet the scientific foundation for their use remains weak. Large, methodologically rigorous trials have validated none of the six categories reviewed by Zaraa and Richert. Biotin — the most studied ingredient — carries a real clinical risk tied to laboratory interference that many practitioners are unaware of. Future randomized controlled trials with adequate sample sizes and longer follow-up will be needed to clarify the picture. Until then, the specialist's role is to provide patients with balanced, honest guidance grounded in what science actually knows today.

References

1. Zaraa I., Richert B. Nail supplements: when, how, and why? Skin Appendage Disord 2025; 11(2): 176-181. 
2. Chessa M.A., Iorizzo M., Richert B. et al. Pathogenesis, clinical signs, and treatment recommendations in brittle nails: a review. Dermatol Ther 2020;  10(1):15–27.
3. Floersheim G.L. Behandlung brüchiger Fingernägel mit Biotin. Z Hautkr. 1989; 64(1): 41–8.
4. Hexsel D., Zague V., Schunck M. et al. Oral supplementation with specific bioactive collagen peptides improves nail growth and reduces symptoms of brittle nails. J Cosmet Dermatol 2017; 16(4): 520–526.
5. Barel A., Calomme M., Timchenko A. et al. Effect of oral intake of choline-stabilized orthosilicic acid on skin, nails, and hair in women with photodamaged skin. Arch Dermatol Res 2005; 297(4): 147–53.