Dietary selenium in humans toenails as an indicator

Abstract

Mounting laboratory and epidemiologic evidence suggests that selenium may be important in the etiology of both cancer and heart disease. We explored the use of hair and nails as indicators of selenium intake by measuring their selenium levels using neutron activation analysis, a highly sensitive and precise nondestructive technique. Levels in duplicate samples of nails, hair, and blood were all reasonably reproducible. However, selenium-containing shampoos severely contaminated some of the hair specimens, suggesting that use of hair in epidemiologic studies could be misleading. The mean selenium level in toenails from South Dakota (a known high selenium area) was 1.17 ppm (1SE = 0.09). This was significantly higher than mean levels from Boston and Georgia (medium selenium intake area) of 0.74 ppm (0.04) and 0.81 (0.03), respectively. The mean selenium level in toenails from New Zealand (low selenium area) was 0.26 (0.02) and these levels did not overlap those of other areas. The South Dakota specimens showed marked familial aggregation, probably reflecting dietary differences. Since toenails vary in length, clippings from different toes represent different time periods of formation; clippings from all ten toes reflect selenium levels integrated over an extended period. As toenails are easily collected, transported, and stored, and reflect longterm intake, they can be useful in epidemiologic studies of selenium and chronic disease.

Selenium Toxicity from a Misformulated Dietary Supplement, Adverse Health Effects, and the Temporal Response in the Nail Biologic Monitor

“…The use of TNs and FNs to estimate Se intake and as a surrogate of Se status in epidemiological studies is well established [12,48,49,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81]. Collectively these papers demonstrate that the nail Se concentration reflects integrated intake over several weeks and is retrospective back 3 to 18 months [12,72,73]; is reproducible over several years [69,74]; is sensitive to determinants such as supplement use, cigarette smoking, race, alcohol consumption and geographic location [16,48,67,68,70,71,77,81]; and can be accurately and feasibly measured by instrumental neutron activation analysis in large cohort studies [42,49,75,76,78,79,80].…”

“…Collectively these papers demonstrate that the nail Se concentration reflects integrated intake over several weeks and is retrospective back 3 to 18 months [12,72,73]; is reproducible over several years [69,74]; is sensitive to determinants such as supplement use, cigarette smoking, race, alcohol consumption and geographic location [16,48,67,68,70,71,77,81]; and can be accurately and feasibly measured by instrumental neutron activation analysis in large cohort studies [42,49,75,76,78,79,80]. Se has been shown to be incorporated in keratinacous protein (hair and presumably nails) largely as selenocystine (91% ± 4%) by near-edge X-ray absorption spectroscopy [82].…”

“…Se was quantified in the nail and TBF product samples by neutron activation analysis (NAA) at the University of Missouri Research Reactor (MURR) Center using previously described methods [16,17,48,49]. Briefly, samples prepared in HDPE vials, as discussed in previous sections, are irradiated for seven seconds at a thermal neutron flux of 6.5 × 10 13 n/cm 2 /s using the pneumatic-tube irradiation facility at the MURR Center.…”

Toenail selenium levels and prevalence of dyslipidaemia among Korean adults

“…Although blood Se level has been used as a major biomarker in many studies, it represents only short-term Se exposure ( 31 ) . Se is stored in multiple locations, including blood, hair and nails.…”

“…Se is stored in multiple locations, including blood, hair and nails. Among these storage sites, toenails are more likely to represent long-term exposure to Se than other storage sites ( 31 – 33 ) . We provided participants the sample-collection protocol for collecting nail specimens for trace-element analysis.…”