Distribution of toenail selenium levels in young adult Caucasians and African Americans in the United States: The CARDIA Trace Element Study
Research highlights
► Average of toenail Se levels in this cohort was 0.844 μg/g (95% CI, 0.840–0.849 μg/g). ► Toenail Se levels vary geographically depending on soil Se concentrations. ► Males, African Americans and less educated participants have low Se levels. ► Smoking status and alcohol consumption are two important indicators of Se status.
Introduction
Selenium (Se) presents a nutritional challenge because of its dual features as an essential trace element and a potential toxin. Severe deficiency of Se can lead to Keshan disease (a congestive cardiomyopathy) (Keshan Disease Research Group, 1979) and also contributes to Kashin–Beck disease (an endemic osteoarthropathy) (Diplock, 1987). Both were reported in areas of China and other countries until they were virtually eradicated with Se supplementation. The apparent benefits of Se may not be limited to alleviating overt deficiency. Low serum, plasma, erythrocyte and toenail Se statuses have been associated with increased risk of cardiovascular disease (CVD) and cancer in some epidemiological studies (Burguera et al., 1990, Flores-Mateo et al., 2006, Knekt et al., 1990, Knekt et al., 1998, Russo et al., 1997, van den Brandt et al., 2003, Willett et al., 1983, Yoshizawa et al., 1998, Young and Lee, 1999), illustrating Se's important role in human nutrition. Conversely, Se toxicity can occur in areas with elevated soil concentrations or from high-dose supplementation (Helzlsouer et al., 1985; Longnecker et al., 1991; MacFarquhar et al., 2010; Yang et al., 1989a, Yang et al., 1989b, Yang et al., 1983), though these scenarios are uncommon in the United States (US). Because deficient and excessive levels of Se can both be harmful to human health, the need for further study to assess individual Se intake and tissue levels is clear.
The primary dietary sources of Se are meat, poultry, fish, grains and cereals. Se levels in food are mainly determined by soil levels, which vary widely throughout the US (Shacklette and Boerngen, 1984). Accurate and adequate assessment of Se intake based on individual food consumption is exceptionally difficult because of the minute amounts and wide variations in the same foods grown in different areas (Willett, 1998). Also, estimating Se intake directly in meals is not feasible in large studies. Thus, assay of biological specimens, which reflects consumption, is preferred both as a measure of intake and as a means to validate other forms of exposure assessment (Willett, 1998). One drawback of using blood (including whole blood, serum and plasma) or urine samples to identify Se status in the human body is that they respond to and reflect only recent changes. Even Se levels in erythrocytes may not reflect long-term exposure to Se, as erythrocytes can only circulate for about 120 days in the body (Joliet, 1953). Se measured in human toenails is more reliable than other body measures because: (1) toenails can reflect a time-integrated measure of exposure and have successfully predicted Se intake (R2=0.52) (Longnecker et al., 1996); (2) they are less prone to superficial contamination than hair because of their lower surface: volume ratio; (3) they are environmentally sheltered in populations that wear shoes (Hunter et al., 1990a); (4) they are easily collected, transported, stored and cleaned (Morris et al., 1983). Toenail Se concentrations are highly correlated with Se levels in other critical organs; therefore they are very useful in large-scale epidemiological studies (Morris et al., 2004). Thus, toenail Se measurements are being increasingly used in human studies.
Previous studies have reported data on Se levels in the US and worldwide (Hunter et al., 1990a, Kotsopoulos et al., 2010, Yoshizawa et al., 2003). However, these studies were conducted among middle-aged or older populations or only in one gender group. In particular, data on African Americans are limited. Therefore, we aim to present toenail Se distributions in American young adults of both genders, including both Caucasians and African Americans; and to explore potential predictors of toenail Se levels using data from the Coronary Artery Risk Development in Young Adults (CARDIA) Trace Element Study.
Section snippets
Study population
The CARDIA cohort was established in 1985 when 5115 American young adults, 18–30 years of age, participated in a study of the psychological and other lifestyle factors that might affect the evolution of coronary artery disease risk. Details of the study design have been published elsewhere (Friedman et al., 1988). Briefly, the cohort was enrolled from four US cities including Birmingham, Alabama; Chicago, Illinois; Minneapolis, Minnesota; and Oakland, California and was roughly balanced by age
Results
Geometric means and selected percentiles with 95% CIs for toenail Se levels, overall and from subgroups defined by selected variables, are shown in Table 1. The overall geometric mean concentration of toenail Se was 0.844 μg/g (95% CI, 0.840–0.849 μg/g). Median levels from lowest to highest quintile were 0.691, 0.774, 0.838, 0.913 and 1.037 μg/g. Average toenail Se levels from Birmingham were the lowest, while those from Minneapolis were the highest. Women, Caucasians, non-current smokers and
Discussion
These results extend recently released estimates of toenail Se levels in American young adults including African Americans and Caucasians using data from the CARDIA Trace Element Study (Xun et al., 2010b). In this study, toenail Se levels were associated with gender, ethnicity, study center, smoking status and alcohol consumption. Men, African Americans, those in Birmingham, current smokers and heavy drinkers were more likely to have low Se levels. In African American women, those who were
Acknowledgments
This study was supported by Grants R01HL081572 and P30ES10126, and Contracts N01-HC-48047, N01-HC-48048, N01-HC-48049, N01-HC-48050 and N01-HC-95095 from the National Institutes of Health. The authors thank Dr. Jared Reis for his valuable comments and Wang Xin for verifying the STATA programming. The authors also thank the other investigators and staff of the Coronary Artery Risk Development in Young Adults (CARDIA) Study for their valuable contributions.
References (56)
Trace elements in human health with special reference to selenium
Am. J. Clin. Nutr.
(1987)Selenium and acute alcoholism
Am. J. Clin. Nutr.
(1983)Diet, smoking, social class, and body mass index in the Caerphilly Heart Disease Study
Am. J. Clin. Nutr.
(1984)Selenium and coronary heart disease: a meta-analysis
Am. J. Clin. Nutr.
(2006)CARDIA: study design, recruitment, and some characteristics of the examined subjects
J. Clin. Epidemiol.
(1988)Establishing optimal selenium status: results of a randomized, double-blind, placebo–controlled trial
Am. J. Clin. Nutr.
(2010)Selenium in diet, blood, and toenails in relation to human health in a seleniferous area
Am. J. Clin. Nutr.
(1991)Effect of smoking and alcohol consumption on the serum selenium level of Lower Silesian population
Sci. Total Environ.
(2002)Dietary reference intakes for the antioxidant nutrients: vitamin C, vitamin E, selenium, and carotenoids
J. Am. Diet Assoc.
(2000)Selenium intake, age, gender, and smoking in relation to indices of selenium status of adults residing in a seleniferous area
Am. J. Clin. Nutr.
(1990)
Mapping soil micronutrients
Field Crops Res.
Prediagnostic serum selenium and risk of cancer
Lancet
Longitudinal association between toenail selenium levels and measures of subclinical atherosclerosis: the CARDIA trace element study
Atherosclerosis
Endemic selenium intoxication of humans in China
Am. J. Clin. Nutr.
Blood serum selenium in the province of Merida, Venezuela, related to sex, cancer incidence and soil selenium content
J. Trace Elem. Electrolytes Health Dis.
Plasma selenium concentrations in a Sikh population in Sydney, Australia
Analyst
A case–control study of toenail selenium and cancer of the breast, colon, and prostate
Cancer Detect. Prev.
Racial differences in free radical scavenging enzyme activity in children
J. Child Neurol.
Predictors of serum selenium in cigarette smokers and the lack of association with lung and prostate cancer risk
Cancer Epidemiol. Biomarkers Prev.
Mercury, fish oils, and the risk of myocardial infarction
N. Engl. J. Med.
Acute selenium intoxication in the United States
Fed. Proc.
Active and passive smoking and development of glucose intolerance among young adults in a prospective cohort: CARDIA study
Br. Med. J.
Distribution and functional consequences of nucleotide polymorphisms in the 3'-untranslated region of the human Sep15 gene
Cancer Res.
Predictors of selenium concentration in human toenails
Am. J. Epidemiol.
A prospective study of selenium status and breast cancer risk
J. Am. Med. Assoc.
Duration of the life span of erythrocytes
C.R. Hebd Seances Acad. Sci.
Association between toenail selenium and risk of acute myocardial infarction in European men. The EURAMIC Study. European Antioxidant Myocardial Infarction and Breast Cancer
Am. J. Epidemiol.
Serum selenium and subsequent risk of cancer among Finnish men and women
J. Natl. Cancer Inst.
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