Frontiers in Nutrition · 8 authors, 3 centres
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This cross-sectional study of 41,021 US adults from NHANES (2003–2018) found that a higher combined intake of 11 dietary antioxidant micronutrients was associated with a lower prevalence of obesity and abdominal obesity. Iron and vitamin C contributed the greatest weight to this protective association. Selenium was the only antioxidant positively associated with obesity, suggesting a complex, nutrient-specific relationship.
**Background:** Obesity is a global pandemic affecting 43.4% of US adults, driven by oxidative stress and micronutrient deficiencies. While individual antioxidants have been studied, the combined effect of multiple dietary antioxidant micronutrients on obesity had not been examined. This study aimed to investigate the association between a complex of 11 dietary antioxidant micronutrients and the prevalence of obesity and abdominal obesity in a nationally representative US sample.
**Methods:** Data were drawn from the National Health and Nutrition Examination Survey (NHANES) across eight consecutive 2-year cycles (2003–2018). After excluding participants with missing dietary recall data, those under 18, pregnant individuals, and those missing BMI or waist circumference data, 41,021 participants were included for obesity analysis and 39,947 for abdominal obesity analysis. Dietary intake of 11 antioxidant micronutrients (vitamin A, vitamin C, vitamin E, retinol, α-carotene, β-carotene, β-cryptoxanthin, iron, zinc, selenium, copper) was assessed using the average of two 24-hour dietary recalls. Obesity was defined as BMI ≥ 30 kg/m²; abdominal obesity as waist circumference >102 cm (men) or >88 cm (women). Multivariate logistic regression was used to assess individual nutrient associations across quartiles. Weighted quantile sum (WQS) regression evaluated the combined effect of all 11 antioxidants. Restricted cubic spline (RCS) regression assessed non-linearity and threshold effects. Models were adjusted for age, sex, education, race/ethnicity, poverty, smoking, alcohol use, total energy intake, sedentary time, total cholesterol, HDL-C, dietary supplement use, eGFR, SBP, DBP, and diabetes.
**Key Results:** The study population had a mean age of 47.98 ± 18.93 years (49.7% male). In fully adjusted logistic regression models (Model 3), higher intake of most antioxidants was associated with lower obesity prevalence. Comparing the highest vs. lowest quartile: vitamin A (OR 0.86, 95% CI: 0.80–0.92, p-trend <0.001), α-carotene (OR 0.90, 0.84–0.96, p-trend = 0.010), β-carotene (OR 0.91, 0.85–0.97, p-trend <0.001), β-cryptoxanthin (OR 0.93, 0.87–0.99, p-trend = 0.001), vitamin C (OR 0.83, 0.78–0.88, p-trend <0.001), iron (OR 0.78, 0.72–0.85, p-trend <0.001), and copper (OR 0.86, 0.79–0.94, p-trend <0.001). Conversely, selenium was positively associated with obesity (OR 1.38, 1.26–1.50, p-trend <0.001). Vitamin E, retinol, and zinc showed no significant association. Similar patterns were observed for abdominal obesity. The WQS index showed the combined antioxidant mixture was inversely associated with obesity (adjusted OR 0.88, 0.84–0.92, p < 0.001) and abdominal obesity (adjusted OR 0.87, 0.83–0.91, p < 0.001). Iron (40.2% weight) and vitamin C (37.6% weight) contributed most to the protective association. RCS analysis revealed non-linear associations for retinol (p-nonlinearity = 0.001), vitamin A (p < 0.001), α-carotene (p = 0.001), β-carotene (p < 0.001), β-cryptoxanthin (p < 0.001), vitamin C (p < 0.001), iron (p = 0.009), and copper (p = 0.003) with obesity. Threshold inflection points were: retinol 235.57 μg/day, vitamin A 374.81 μg/day, α-carotene 58.89 μg/day, β-carotene 891.44 μg/day, β-cryptoxanthin 30.70 μg/day, vitamin C 43,410.00 μg/day (43.41 mg/day), iron 11,240.00 μg/day (11.24 mg/day), and copper 990.00 μg/day.
**Clinical Implications:** This study provides evidence that a higher combined intake of dietary antioxidant micronutrients—particularly iron and vitamin C—is associated with lower obesity prevalence. The identified threshold values (e.g., vitamin C >43.41 mg/day, iron >11.24 mg/day) may serve as reference points for future dietary interventions. However, the positive association with selenium and null findings for vitamin E, retinol, and zinc highlight that not all antioxidants are protective, and nutrient interactions matter. As a cross-sectional study, causality cannot be inferred. Future research should investigate optimal intake levels and the role of circulating antioxidant concentrations, and validate findings in non-US populations.