Serum selenium and serum lipids in US adults: National Health and Nutrition Examination Survey (NHANES) 2003-2004

Abstract

Objective: High selenium has been recently associated with several cardiovascular and metabolic risk factors including diabetes, blood pressure and lipid levels. We evaluated the association of serum selenium with fasting serum lipid levels in the National Health and Nutrition Examination Survey (NHANES) 2003-2004, the most recently available representative sample of the US population that measured selenium levels.

Methods: Cross-sectional analysis of 1159 adults>or=40 years old from NHANES 2003-2004. Serum selenium was measured by inductively coupled plasma-dynamic reaction cell-mass spectrometry. Fasting serum total cholesterol, triglycerides, and HDL cholesterol were measured enzymatically and LDL cholesterol was calculated.

Results: Mean serum selenium was 136.7 microg/L. The multivariable adjusted average differences (95% confidence interval) comparing the highest (>or=147 microg/L) to the lowest (<124 microg/L) selenium quartiles were 18.9 (9.9, 28.0) mg/dL for total cholesterol, 12.7 (3.3, 22.2) mg/dL for LDL cholesterol, 3.9 (0.4, 7.5)mg/dL for HDL cholesterol, and 11.5 (-7.6, 30.7) mg/dL for triglycerides. In spline regression models, total and LDL cholesterol levels increased progressively with increasing selenium concentrations. HDL cholesterol increased with selenium but reached a plateau above 120 microg/L of serum selenium (20th percentile). The triglyceride-selenium relationship was U-shaped.

Conclusion: In US adults, high serum selenium concentrations were associated with increased serum concentrations of total and LDL cholesterol. Selenium was associated with increasing HDL cholesterol only at low selenium levels. Given increasing trends in dietary selenium intake and supplementation, the causal mechanisms underlying these associations need to be fully characterized.

Figure 1

Adjusted differences (95% CI) in serum lipids by serum selenium concentrations. Serum selenium was modeled as restricted quadratic splines with nodes at the 5^th, 50^th, and 95^th percentiles. The multivariable linear regression models were adjusted for sex, age, race, education, body mass index, smoking, cotinine, postmenopausal status, cholesterol, total fat, saturated fatty acids, and selenium intakes, and use of vitamin and mineral supplements (Model 2). Lipids concentrations at the 10^th percentile (115 µg/L) of the serum selenium distribution were used as reference. The histogram shows the distribution of selenium concentrations in the study population.