Abstract
BACKGROUND: Concern has been recently raised about possible adverse cardio-metabolic effects of high selenium status, such as increased risks of diabetes and hyperlipidaemia. However, most of the evidence comes from selenium-replete populations such as that of the United States. OBJECTIVES: To examine cross-sectional and longitudinal associations of serum selenium with cardiovascular risk factors in Finland where selenium levels were amongst the lowest in the world until the early 1980s before the implementation of a nationwide selenium fertilization programme. METHODS: Serum selenium was measured in 1235 young Finns aged 3-18 years at baseline in 1980 (prefertilization) and in a subgroup (N = 262) at the 6-year follow-up (1986, postfertilization). During the 27-year follow-up, serum lipids, blood pressure, body mass index and smoking were assessed five times (1980, 1983, 1986, 2001 and 2007). RESULTS: Mean (±SD) serum selenium concentrations were 74.3 ± 14.0 ng mL(-1) in 1980 and 106.6 ± 12.5 ng mL(-1) in 1986 (average increase 32.3 ng mL(-1); 95% CI: 30.3 to 34.3, P < 0.0001). In univariate and multivariable cross-sectional models in 1980 and 1986, increased serum selenium levels were consistently associated with increased total, HDL and Low-density lipoprotein (LDL) cholesterol. However, the average longitudinal changes in lipids were -0.20 mmol L(-1) (95% CI: -0.30 to -0.10, P < 0.0001) for total cholesterol, 0.06 mmol L(-1) (95% CI: 0.03 to 0.10, P < 0.0001) for HDL cholesterol, and -0.23 mmol L(-1) (95% CI: -0.31 to -0.14, P < 0.0001) for LDL cholesterol. Selenium measured in 1986 was not associated with lipids assessed in 2001 and 2007. CONCLUSIONS: Cross-sectional findings from the Young Finns study corroborate positive associations of selenium status with serum lipids. However, longitudinal evidence does not support the causality of this link.