Macronutrient Composition and Depressive Symptoms Among Working-Age Participants in a US National Health Survey: An Isocaloric Substitution Analysis.

BACKGROUND

Depressive symptoms are common among working-age adults, and diet may be a modifiable correlate. Macronutrient composition has been linked to depressive symptoms, but usually one macronutrient at a time, and the few analyses of exchanges between them were confined to restricted populations. Protein, fat, and carbohydrate together account for almost all dietary energy, so a higher share of one implies a lower share of another. This study aimed to identify which exchange of energy between protein, fat, and carbohydrate, if any, is associated with depressive symptoms in working-age adults.

METHODS

In a cross-sectional analysis of the National Health and Nutrition Examination Survey from August 2021 to August 2023, we analysed 2,125 participants aged 20-64 years with two complete 24-hour dietary recalls. Depressive symptoms were defined as a Patient Health Questionnaire-9 score of 10 or higher. Protein, fat, and carbohydrate were expressed as percentages of macronutrient-derived energy, summing to 100%. Logistic regression estimated odds ratios (ORs) across quartiles, and leave-one-out models estimated isocaloric substitution of 5% of macronutrient energy, adjusted for demographic, socioeconomic, and lifestyle factors and body mass index. Models were repeated by sex and employment status. Unweighted analyses were primary.

RESULTS

Depressive symptoms were present in 277 participants (13.0%). The OR for the highest versus lowest quartile was 0.42 (95% CI: 0.28-0.63; P for trend < 0.001) for protein and 1.81 (1.24-2.65) for carbohydrate; fat showed no association. Replacing 5% of macronutrient energy from carbohydrate with protein was associated with lower odds (OR: 0.70, 0.59-0.84; survey-weighted: 0.76, 0.61-0.95), as was the same exchange from fat to protein (0.74, 0.60-0.90; survey-weighted: 0.78, 0.58-1.05), whereas exchanging carbohydrate for fat was not. Substitution estimates were similar by sex and among participants who were currently working (0.73, 0.58-0.92) and those who were not.

CONCLUSIONS

Among working-age adults, replacing carbohydrate or fat with protein was associated with lower odds of depressive symptoms. The design is cross-sectional, and prospective confirmation is needed.