Genetic and environmental influences on sodium intake determined by using half-day urine samples: The Healthy Twin Study^1-3

Background: Salt is essential in our diet, but excess intake is a well-established risk factor for hypertension. The presence and importance of genetic contributions to salt intake, however, are not well understood. Objective: The aim of this study was to examine whether a genetic predisposition and an environmental influence exist for sodium intake and salt habit. Design: In a twin-family cohort, half-day urine samples from 1204 individuals (133 pairs of monozygotic twins, 29 pairs of dizygotic twins, and 880 singletons) were collected to assess 24-h sodium intakes. Daily total sodium intake, sodium density per calorie (Na-D), and salt habit questions were analyzed with adjustment for other epidemiologic characteristics. We calculated heritability (h2) and intraclass correlations to examine the genetic and sha ed environmental contributions to total sodium intake traits. Results: The average sodium intake was 208.4 ± 107.0 mmol/d.Men had a higher absolute sodium intake (242.6 ± 117.4 mmol/d), but Na-D did not differ by sex. Moderate genetic influences existed (h2 = 0.31-0.34) for sodium intake and Na-D. We also found that sharing current residence rather than being a family member explained 22% of the variance in Na-D. Conclusion: Our findings suggest that both genetic predisposition and shared environment contribute to sodium intakes and salt habits alike. Am J Clin Nutr 2013;98:1410-6.