Vitamins and minerals: their role in nail health and disease

Journal of Drugs in Dermatology, August, 2007 by Noah Scheinfeld, Maurice J. Dahdah, Richard Scher

Abstract

Nail health and appearance are global concerns. We investigated the use of biotin vitamin E, alpha-tocopherol, vitamin C (ascorbic acid), vitamin A, retinoids, retinol, retinal, silicon, zinc, iron, copper, selenium, and vitamin [B.sub.12] (Cyanocobalamin) in nail health and disease. The evidence that we adduce in this paper suggests that: 1) proper nail care seems to help maintain nail health; 2) no evidence supports the use of vitamin supplementation with vitamin E, vitamin C (ascorbic acid), vitamin A, retinoids, retinol, retinal, silicon, zinc, iron, copper, selenium, or vitamin [B.sub.12] (Cyanocobalamin) for improving the nail health of well-nourished patients or improving the appearance of nails affected by pathologic disease; and 3) brittle nail syndrome appears to abate with supplementation with a 2.5-mg dose of biotin daily or a 10-mg dose of silicon daily, a useful form of which is choline-stabilized orthosilicic acid.

Introduction

The appearance of finger and toe nails is a major cosmetic concern worldwide. While the role of vitamins in nail health and disease has engendered its own literature and a cottage industry exists to distribute vitamins to enhance nail health and appearance, little systemic evaluation of the role of vitamin and mineral supplementation in nail health has been performed. This article systematically assesses the literature and research on the use of vitamins to enhance nail health and fight nail disease.

Vitamins in General Human Health

Vitamins and minerals are also referred to as micronutrients because of the very small quantities needed for normal physiological function (generally <100mg/day). The FDA has established the recommended daily allowance of vitamins and minerals. (1) Circumstantial evidence suggests that their adequate intake is essential for the maintenance of healthy nails. Hemodialysis patients, who develop micronutrient imbalances, have an increased incidence of nail changes. (2) Deficiencies in vitamins and minerals might cause the brittle nails observed with anorexia nervosa and bulimia. (3)

Biochemical Properties of the Nail Plate

Keratin makes up the bulk of the nail plate. The nail plate contains both hair type ("hard") (80%-90%) and epithelial type ("soft") (10%-20%) keratins. (4) The overall nail sulfur content is approximately 10% by weight, and the disulfide bonds of cystine in the matrix proteins are thought to contribute largely to nail hardness by acting as a glue that holds the keratin fibers together and by creating the nail plate's tensile strength. Contrary to common belief, calcium does not contribute to nail hardness and constitutes only 0.2% of the nail plate by weight. The nail plate also contains lipids, although the lipid content is low compared to that of the stratum corneum (<5% by weight), which explains the nail plate's water resistance although its water content is 10% to 15%. The mineral content of nails varies among populations (Table 1).

Vitamins and Nails

Studies and case reports have assessed nail health (5) and biotin (6) (a B-complex vitamin), vitamin E, vitamin [B.sub.12], vitamin A derivatives (retinoids), vitamin D derivatives (calcipotriol), and combinations thereof. (5) Haneke, in particular, has published an excellent review on "onychocosmeceuticals," which discussed the role of vitamins in nail health but eschewed a systemic compilation and analysis of the extant data. This article will compile the extant data on vitamin and nail health wherever possible in table form. To assess the role of vitamins, it is important to be aware of the recommended dietary allowances for vitamins and minerals. (1)

Biotin (Vitamin H)

Biotin is a water soluble B-complex vitamin that has been shown to alter the gene expression in more than 2,000 genes. (7) Biotin is required by carboxylases catalyzing the cellular metabolism of glucose, amino acids, and fatty acids. The recommended daily allowance of biotin in adults is 30 [micro]g daily. Unlike the biotin present in foodstuffs, which is largely protein bound and incompletely absorbed, pharmaceutical preparations of biotin possess 100% bioavailability. (8) Biotin use to abate pathologic horse hoofs suggested it could treat human nail disease. (9) Biotin effectively treats brittle nail syndrome (BNS) (Figure 1), a disease characterized by soft, dry, weak, easily breakable nails that show onychorrhexis and onychoschizia, but has not been shown to affect healthy nails. (10,11) The use of biotin for BNS has been buttressed by clinical studies and based on this data biotin can be helpful in ameliorating certain types of nail pathology (Table 2).

Vitamin E

Vitamin E has no reported role in enhancing healthy nails (Table 3). There are reports of yellow nail syndrome (YNS) responding to topical and high dose oral vitamin E (600-1200 IU). (17-19) Luyten noted a women suffering with YNS, bronchial hyperactivity, sinusitis, and onychomycosis who used vitamin E and itraconazole with good outcome. (20)

Retinoids