Middle-aged adults with high dietary antioxidant capacity appear to be better protected against the risk of late-life depression, according to a Singapore study, bolstering the recommendation for an antioxidant-rich diet to prevent depression in ageing populations.
In a cohort of 13,712 Chinese in Singapore, the highest vs lowest quartile of dietary total antioxidant capacity (TAC) at a mean age of 52.4 years was associated with more than 20-percent lower odds of presenting with depressive symptoms at a mean age of 72.5 years. This was observed whether dietary TAC was measured using the Comprehensive Dietary Antioxidant Index (CDAI; Q4 vs Q1: odds ratio [OR], 0.73, 95 percent confidence interval [CI], 0.64–0.83; p<0.01 for trend) or the Vitamin C Equivalent Antioxidant Capacity (VCEAC) index (Q4 vs Q1: OR, 0.77, 95 percent CI, 0.68–0.87; p<0.01). [Antioxidants 2024;13:576]
“The results were robust and remained essentially unchanged in sensitivity analyses that excluded participants with pre-existing chronic diseases and those aged ≥65 years at baseline, as well as when applying inverse probability weighted regression models that addressed the potential influence of selection bias,” the investigators said.
Analyses of individual components of the dietary TAC showed that vitamin C, total carotenoids, and total flavonoids were particularly beneficial for reducing the likelihood of depression in later years.
Dietary TAC
The evidence on individual antioxidant nutrients and late-life depressive symptomology has yielded mixed results due to differences in study design and the specific targeted populations, as well as variations in antioxidant intake across diverse geographic regions and socioeconomic groups. [Eur J Nutr 2021;60:443-454; BMC Complement Med Ther 2020;20:315; J Nutr 2015;146:897S-904S]
“Based on these mixed findings, it has been suggested that isolated antioxidants may not fully reflect the collective antioxidant capacity present in our usual diet, thus leading to an underestimation of combined protective effects from a variety of antioxidant nutrients present in the diet,” the investigators pointed out.
In contrast, dietary TAC considers the synergistic interactions of the antioxidants present in the food matrix and, as such, has been proposed to measure the complex network of food-based antioxidants, they added. [Crit Rev Food Sci Nutr 2018;58:905-912]
Biological plausibility
The link between antioxidant-rich diets and lower depression risk may be explained by ageing’s effect on the brain, according to the investigators.
Research suggests that elevated oxidative stress and neuroinflammation contribute to the development of ageing-related depression and that the endogenous supplies for the antioxidant defense systems decline with age. [J Clin Biochem Nutr 2015;56:1-7]
“Dietary antioxidants can … counteract neurological damage from oxidative stress by mitigating inflammatory status in the brain [as well as] impact mood regulation and depressive symptoms through the gut-brain axis,” the investigators said. [Nat Commun 2022;13:7128; Redox Rep 2004;9:145-152]
“Future studies with repeated dietary assessments are still needed to confirm the associations and to elucidate the specific mechanisms through which dietary antioxidants may protect against ageing-related depression,” they added.