Vitamin A

What the evidence says

Deficiency causes night blindness and childhood mortality, and correcting it in deficient populations is one of public health's clearest wins. In replete people, supplementing has no demonstrated benefit — and the beta-carotene arms of two large prevention trials (ATBC and CARET) found MORE lung cancer in smokers, which is why those formulations were changed.

What studies used

Requirements sit near 700–900 mcg RAE/day; the tolerable upper limit for preformed retinol is 3,000 mcg RAE. Fat-soluble; studies dosed it with meals.

Reported from published studies and product labelling — a record of what was used in research, not a recommendation. What is right for you is a conversation with a clinician.

Watch out for

• Preformed retinol is teratogenic — high intakes in pregnancy are associated with birth defects, which is why isotretinoin has the programme it has
• It accumulates: chronic excess causes liver damage, raised intracranial pressure and bone loss. Liver and organ supplements stack onto this without labelling it
• Beta-carotene supplements raised lung-cancer incidence in smokers in trial data

Evidence base

Research (12)

• The Role of Vitamin A in Wound HealingNutr Clin Pract · 2019
• Vitamin A and β-carotene in pregnant and breastfeeding post-bariatric women in an urban populationJ Perinat Med · 2019
• Chapter 29: historical aspects of the major neurological vitamin deficiency disorders: overview and fat-soluble vitamin AHandb Clin Neurol · 2010
• Alcohol, vitamin A, and beta-carotene: adverse interactions, including hepatotoxicity and carcinogenicityAm J Clin Nutr · 1999
• The contribution of β-carotene to vitamin A supply of humansMol Nutr Food Res · 2012
• Techniques for measuring vitamin A activity from β-caroteneAm J Clin Nutr · 2012
• Fenretinide inhibits vitamin A formation from β-carotene and regulates carotenoid levels in miceBiochim Biophys Acta Mol Cell Biol Lipids · 2022
• Effect of vitamin A, calcium and vitamin D fortification and supplementation on nutritional status of women: an overview of systematic reviewsSyst Rev · 2020
• Effects of prepartum supplementation of β-carotene on colostrum and calvesJ Dairy Sci · 2022
• Alleviation of vitamin A deficiency with palm fruit and its productsAsia Pac J Clin Nutr · 2003
• Effect of vitamin A supplementation on iron status in humans: A systematic review and meta-analysisCrit Rev Food Sci Nutr · 2019
• Vitamin A supplementation and retinoic acid treatment in the regulation of antibody responses in vivoVitam Horm · 2007

Where next