Vitamin A
vitamin
ApprovedGeneral information about nutrients. No diagnosis, no medical advice. If you take medication, are pregnant or have a medical condition, talk to your doctor before taking supplements.
Overview
Fat-soluble vitamin, including the retinol form. Vitamin A contributes to the maintenance of normal vision. Vitamin A contributes to the normal function of the immune system.
Interactions
Retinol (vitamin A) and calcitriol (active D3) compete for RXR nuclear receptors. High-dose vitamin A can antagonize vitamin D signaling, impairing calcium absorption and bone health.
Research status
Vitamin A has a role in the process of cell specialisation.
Top 5 food sources
Expert opinions
Bryan Johnson Blueprint
Johnson deliberately avoids high-dose preformed retinol supplements and meets intake through his prescribed 'Green Giant' and 'Nutty Pudding' meals, which include sweet potato, carrots, kale, and spinach and yield well over 20,000 mcg RAE of beta-carotene daily. Because beta-carotene conversion is self-limiting, this approach carries no risk of vitamin A toxicity. He tracks retinol and RBP (retinol-binding protein) in quarterly blood panels to confirm sufficiency. No isolated vitamin A pill is included in the Blueprint stack.
Source: Blueprint Protocol
NIH
The NIH sets a Tolerable Upper Intake Level of 3,000 mcg RAE (3 mg) preformed vitamin A (retinol/retinyl esters) per day for adults to prevent hepatotoxicity, bone loss, and teratogenic effects. Chronic intake above this raises risk of intracranial hypertension and osteoporotic fractures, and exposure above 10,000 IU in early pregnancy is linked to birth defects. Plant-based beta-carotene has no UL because conversion to retinol is tightly regulated. RDA is 900 mcg for men and 700 mcg for women. Deficiency is seen mostly with malabsorption and strict low-fat vegan diets.
Recommended dose: 0.7–0.9 mg
Source: NIH
Expert profiles summarise publicly available statements. The named people do not cooperate with Stackwell and have not authorised these summaries. Not medical advice.
Broad agreement on RDA. Supplementation rarely needed with balanced diet.