I know this post will make me a lot of new enemies among the anti-retinol crowd, but the findings are too important not to share with my readers since the study was not only with humans, but humans in a very compromised state of health (heart failure). This suggests that in healthier humans the anti-depressant effects may be even more pronounced. While the study did not opine on the main mechanism of action, it does mention the crucial role of vitamin A in dampening inflammation, as well as its crucial role in steroidogenesis (including thyroid). Both of those pathways are very important in depressed patients, who are almost always found to have chronic inflammation and reduced levels of thyroid hormones as well as “neurosteroids” such as pregnenolone, progesterone, DHEA, testosterone, etc while also both reducing cortisol (a known causative steroid in depression) synthesis and blocking its effects at the receptor level.
https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/
https://onlinelibrary.wiley.com/doi/10.1002/ehf2.14935
“…The researchers observed that approximately 85% of participants with depression reported daily vitamin A intake of less than 731.38 µg. Wang and colleagues found that compared with patients with low daily vitamin A intake, depression was less likely in patients at increasing daily intake levels of vitamin A, which became significant above 731.38 µg daily. Moreover, daily vitamin A intake of 731.38 µg or more compared with low intake was significantly associated with lower odds for depression among participants with HF aged 65 years or older, men and participants with hyperlipidemia or chronic kidney disease. “Vitamin A acts as an antioxidant, protecting against oxidative damage and reducing inflammation by inhibiting the production of pro-inflammatory cytokines. By mitigating these processes, vitamin A may contribute to reduce the incidence of depression in HF patients,” the researchers wrote. “Vitamin A is involved in the regulation of various hormones, including cortisol and thyroid hormones, which have been implicated in depression. Chronic stress, commonly experienced by patients with HF, can dysregulate the hypothalamic-pituitary-adrenal (HPA) axis, leading to elevated cortisol levels,” they wrote. “Adequate vitamin A intake may contribute to optimal thyroid function and reduce the risk of depression in patients with HF.”
