Correspondence

Calcium Supplements and Nail Quality

N Engl J Med 2000; 343:1817December 14, 2000

Article

To the Editor:

There is a widespread belief among the general public that dietary calcium intake improves the quality of fingernails and toenails. Persons taking calcium supplements sometimes comment that their nails are less brittle or smoother, or that they grow faster. Presumably, the idea that dietary calcium improves nails has arisen because nails contain calcium, albeit at a much lower concentration (0.03 percent)1 than the skeleton (20 to 25 percent). Physicians are often asked questions on this subject by their patients, but information on which to base an informed reply is lacking. For example, in a search of Medline, my colleagues and I found no data on nail composition in relation to dietary calcium intake.

We assessed subjective changes in nail quality in 683 healthy postmenopausal women taking part in a randomized, placebo-controlled trial of calcium supplementation alone (1 g of elemental calcium per day as the citrate), for the prevention of postmenopausal osteoporosis. The mean (±SD) age of the women was 73±4 years, and the mean dietary calcium intake was 880±420 mg per day. After taking the study medication for 12 months, the women were asked to score the changes in the quality of their nails (including texture and brittleness) during that period, using a scale from –5 to 5, with scores of –5 to –1 indicating deterioration, a score of 0 indicating no change, and scores of 1 to 5 indicating improvement. Fingernails and toenails were scored separately.

The distribution of responses in the calcium and placebo groups with respect to fingernails is shown in Table 1Table 1Scores for Fingernail Quality Reported by Postmenopausal Women, According to the Treatment Assignment.. The majority of women in both groups noted no change. Among those who did note a change, more women in both groups reported improvement than deterioration. There were no significant differences in scores between the two groups (P=0.79). The results were virtually the same for toenails (P=0.36, data not shown).

These results provide no support for the idea that calcium intake alters self-reported nail quality in healthy postmenopausal women. The findings are consistent with limited laboratory evidence that the quality of nails is related to the arrangement of their cellular and protein components, not to their calcium content.2

Ian R. Reid, M.D.
University of Auckland, Auckland, New Zealand

2 References

1. 1

   Vellar OD. Composition of human nail substance. Am J Clin Nutr 1970;23:1272-1274
   Web of Science | Medline

2. 2

   Forslind B, Wroblewski R, Afzelius BA. Calcium and sulfur location in human nail. J Invest Dermatol 1976;67:273-275
   CrossRef | Web of Science | Medline