Regarding “Fertility and Agriculture Accentuate Sex Differences in Dental Caries Rates”

Abstract

The recent paper by Lukacs (2008) regarding the roles of fertility and agriculture in sex differences in dental caries rates is important in that it highlights the role of increased demands on women’s reproductive systems in the decline of oral health among women. However, the paper overlooked an important role of an additional factor related to increased fertility and decline of oral health: vitamin D. It was recently pointed out that the likely explanation for the correlation between parity and tooth loss among American women in Russell, Ickovics, and Yaffee (2008) could likely be attributed to inadequate vitamin D intake or production during pregnancy and lactation (Grant 2008). Dental caries are largely the result of oral bacteria (Nishikawara et al. 2006). One of the emerging health benefits of vitamin D is the induction of human cathelicidin, LL-37, which has potent antibacterial activities (Bikle 2008; Liu et al. 2007). For experimental support of the role of LL-37 in reducing the risk of dental caries, an old paper by East (1939) is very useful. In a study of 94,332 white boys aged 12–14 years, those living in regions with the greatest number of hours of sunshine per year had the lowest number of caries. The results were 13,000 hours/year, 2.91 caries/boy; 2,600–3,000 hours/year, 3.23 caries/boy; 2,200–2,600 hours/ year, 3.76 caries/boy; and !2,200 hours/year, 4.86 caries/boy. Another paper supporting this idea presents a summary of the mean rank by state of the prevalence of dental disease among U.S. military draftees in 1918, the U.S. Navy in 1934, and the U.S. Army in 1943 (Dunning 1953). The regression coefficient of mean rank with respect to summertime solar ultraviolet-B (UVB; Leffell and Brash 1996; see also http:// toms.gsfc.nasa.gov/ery_uv/dna_exp.gif) as used in an ecological study of cancer mortality rates in the United States (Grant and Garland 2006) is 0.71 ( ). P ! .001 Lukacs (2008, table 6) presents interesting data on dental caries prevalence in nine countries for males and females. These data provide an additional test of the role of diet and solar UVB. Simple indices for these two factors are latitude and the dietary supply of added sugar for 1979–1981 (FAO