Dietary fiber intake is inversely related to serum heavy metal concentrations among US adults consuming recommended amounts of seafood: NHANES 2013-2014

Heavy metals such as mercury (Hg), cadmium (Cd), and lead (Pb) have profound deleterious effects on human health, with seafood being the primary dietary source. Dietary fiber (DF) has been reported to bind heavy metals in animal models, thus promoting their excretion. However, little is known about such effect in human subjects. To examine the relationship between DF intake and blood heavy metal concentrations in adults consuming adequate amounts of seafood, a sample of adults (n = 422), with a mean age of 48 years (SE = 1.14), who consumed at least eight servings of seafood per month were selected from the National Health and Nutrition Examination Survey (NHANES, 2013-2014). Average intake of DF was computed from two 24-h recalls. Linear regression analyses were completed to assess the relationship between each of the three heavy metals and DF intake while adjusting for age, biological sex, race/ethnicity, and ratio of family income to poverty. Results showed that after adjusting for covariates, serum Cd and Pb levels were inversely related to DF intake among US adults meeting the recommendations for seafood consumption. Every 10 additional grams of DF intake is associated with 6.72% less serum Cd (p = 0.0010) and 5.65% less serum Pb (p = 0.0019) concentrations, respectively. Asian adults had significantly higher serum levels of Hg, Cd, and Pb (p < 0.0005) as compared to non-Hispanic White adults. Age was positively related to serum heavy metal levels (p < 0.0001). Future research is warranted to investigate the mechanism of action.

Automated summary

This study examined the relationship between dietary fiber intake and blood heavy metal concentrations in adults consuming adequate amounts of seafood. The results showed an inverse relationship between dietary fiber intake and serum cadmium and lead levels among US adults meeting the seafood consumption recommendations. Asian adults had significantly higher levels of mercury, cadmium, and lead in their serum compared to non-Hispanic White adults, and age was positively related to serum heavy metal levels. Further research is needed to investigate the mechanism of action.