Objective Edible nuts are rich in unsaturated fatty acids, protein, vitamins, phytochemicals, and magnesium. Many studies have found that nuts play important roles in preventing chronic diseases related to oxidative stress, an important pathogenesis of fluorosis. However, no epidemiological studies on the relationship between nuts and coal-burning endemic fluorosis have been reported. Therefore, the present study aims to compare nuts intake among residents in coal-burning endemic fluorosis area.
Methods This cross-sectional study conducted in Zhijin County of Guizhou Province included 699 participants at 18-60 years of age. The participants with dental fluorosis and/or skeletal fluorosis were assigned into fluorosis group, and those without into non-fluorosis group. Structured questionnaires were delivered to collect general sociodemographic status, lifestyle, and coal-burning related lifestyle through face-to-face interview. A 75-item food frequency questionnaire was used to assess habitual dietary intake in the past year, especially nuts including peanuts, melon seeds, walnuts, almonds, pistachios, sesame, and cashews. Logistic regression was used to analyze the relationship between nuts intake and coal-burning endemic fluorosis.
Results There were 478 patients with fluorosis and 221 healthy residents without fluorosis in this cross-sectional study. The fluorosis group showed older age, higher urinary fluoride level, and more proportion of roasting gains by burning coal (P < 0.001), but nevertheless lower levels of household income, education level, and intakes of vegetables, fruits, total unsaturated fatty acids, magnesium, vitamin A, and vitamin E than the non-fluorosis group (P < 0.05). The average nuts intake of the fluorosis group (8.43 g/d) was lower than that of the nonfluorosis group (27.77 g/d) (P < 0.001). The univariate logistic regression analysis showed that nuts intake was inversely associated with coalburning endemic fluorosis (Ptrend < 0.001). After adjusting for general sociodemographic status, coal-burning related behaviors, nutrients, and food, a similar association was observed (Ptrend < 0.001). Compared with the lowest quartile of nuts intake, the ORs and 95% CIs of P50-P75 and P75-P100 were 0.27 (0.15, 0.49) and 0.19 (0.09, 0.39), respectively (P < 0.001). According to the sensitivity analysis on dental fluorosis and skeletal fluorosis, there was a significant dose-dependent inverse relationship between either dental or skeletal fluorosis and nuts intake (Ptrend < 0.001).
Conclusion In the coal-burning endemic fluorosis area, fluorosis patients' nuts consumption is remarkably lower than healthy residents'.
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