Vitamin A (Retinol)

We need vitamin A for good eyesight, reproduction, immunological function, growth and development. 

The RDA for vitamin A for adults (according to the NIH) is 700µg RAE for non-pregnant/non-lactating females and 900µg RAE for males.

 RAE = retinol activity equivalent 

Conversion guide1 
1 mcg RAE = 1 mcg retinol 
1 mcg RAE = 2 mcg supplemental beta-carotene 
1 mcg RAE = 12 mcg beta-carotene 
1 mcg RAE = 24 mcg alpha-carotene 
1 mcg RAE = 24 mcg beta-cryptoxanthin 

Preformed vitamin A cannot be obtained from plants, but the body converts beta-carotene (and other carotenoids) to vitamin A. 

Colourful vegetables are good sources of beta-carotene, for example:  

SourcePortionAmount beta-carotene (RAE)
Mashed sweet potato (boiled without skin)1 cup 31000µg (2583 RAE)
Mashed sweet potato (baked with skin)1 cup27200µg (2275 RAE)
Bok choy (raw)1 head22500µg (1875 RAE)
Mashed carrots (cooked from frozen)½ cup9400µg (783 RAE)
Raw lettuce (cos or romaine)¼ head8175µg (680 RAE)
Cantaloupe melon ¼ large melon5675µg (473)

(Source: https://fdc.nal.usda.gov/ 

I recommend eating colourful vegetables and fruits plentifully every day. Ideally, they should be eaten alongside fat-rich foods, as this may increase conversion and absorption2-4.  

Consuming large amounts of preformed vitamin A can lead to chronic toxicity; but you do not need to worry about eating too much beta-carotene. 

Some individuals (due to their genetics) are low converters of beta-carotene to vitamin A5. Due to a lack of research on the subject, it’s not known whether vegans with such traits are at greater risk of deficiency. However, I have not found any convincing evidence that vegans that meet the RDA (via carotenoids) are at risk of a vitamin A deficiency.  

 
Recommendations: 

– Meet RDA via carotenoids-rich food. 

– Taking a preformed vitamin A supplement as a precaution is a reasonable choice. (But contact your doctor first, especially if you take other medications, due to potential interactions.)

– But women planning to become pregnant should discuss their requirements with their doctor: too much vitamin A in the first trimester of a pregnancy can cause birth defects. However, supplementing vitamin A with a recommended dose does not seem to increase this risk6,7 

References

1. Dietary Supplement Ingredient Database  
2. Kopec, R.E., Cooperstone, J.L., Schweiggert, R.M., Young, G.S., Harrison, E.H., Francis, D.M., Clinton, S.K. and Schwartz, S.J., 2014. Avocado consumption enhances human postprandial provitamin A absorption and conversion from a novel high–β-carotene tomato sauce and from carrots. The Journal of nutrition, 144(8), pp.1158-1166.
3. Muzhingi, T., Yeum, K.J., Bermudez, O., Tang, G. and Siwela, A.H., 2017. Peanut butter increases the bioavailability and bioconversion of kale beta-carotene to vitamin A. Asia Pacific journal of clinical nutrition, 26(6), pp.1039-1047.
4. Brown, M.J., Ferruzzi, M.G., Nguyen, M.L., Cooper, D.A., Eldridge, A.L., Schwartz, S.J. and White, W.S., 2004. Carotenoid bioavailability is higher from salads ingested with full-fat than with fat-reduced salad dressings as measured with electrochemical detection. The American journal of clinical nutrition, 80(2), pp.396-403.
5. Lietz, G., Oxley, A., Leung, W. and Hesketh, J., 2012. Single nucleotide polymorphisms upstream from the β-carotene 15, 15′-monoxygenase gene influence provitamin A conversion efficiency in female volunteers. The Journal of nutrition, 142(1), pp.161S-165S.
6. Oregon State University
7. Russell, R., Beard, J.L., Cousins, R.J., Dunn, J.T., Ferland, G., Hambidge, K.M., Lynch, S., Penland, J.G., Ross, A.C., Stoecker, B.J. and Suttie, J.W., 2001. Dietary reference intakes for vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. A Report of the Panel on Micronutrients, Subcommittees on Upper Reference Levels of Nutrients and of Interpretation and Uses of Dietary Reference Intakes, and the Standing Committee on the Scientific Evaluation of Dietary Reference Intakes Food and Nutrition Board Institute of Medicine. (nap.edu)
 

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