Food security and diet quality, not vitamin D status are significantly associated with depression: Results from NHANES 2015–2018

Observational research has suggested a link between vitamin D insufficiency and depression, while evidence from randomized trials examining the association have yielded inconsistent results. Food security and diet quality are also associated with both vitamin D insufficiency and depression. However, the potential interactions between these factors have not been well described. In order to examine the associations between depression, vitamin D status, food security, and diet quality, data from 8988 US adults (≥20 years) in NHANES (National Health and Nutrition Examination Surveys) 2015–2018 were analyzed. Questionnaire-assessed depression, food security, and diet quality and laboratory-analyzed serum vitamin D were used. Lack of full food security and a 10-point decrease in Healthy Eating Index 2015 score were independently associated with higher risk of mild to severe depression (OR 3.72 and 1.20, respectively, p < 0.001). The association between insufficient serum vitamin D (<75 nmol/L) and depression was fully attenuated after adjusting for food security and diet quality (p = 0.41). A major limitation of this paper, like all analyses of NHANES, is the inability to establish the temporality of the relationships between food security and diet quality with depression. Food security and diet quality, but not vitamin D status, were significantly associated with depression. This highlights how evaluating food security and diet quality are critical in research and public health interventions related to depression. Future interventions, especially into vitamin D insufficiency, as well as health policies should assess and address these factors.