Vitamin A is a fat-soluble vitamin, which means it is found primarily in fatty foods and absorbed with fats into the body. Vitamin A is actually a family of compounds that have slightly different structures, including retinol and retinoic acid.... Read more
Vitamin A is a fat-soluble vitamin, which means it is found primarily in fatty foods and absorbed with fats into the body. Vitamin A is actually a family of compounds that have slightly different structures, including retinol and retinoic acid. Vitamin A’s functions include supporting good vision, normal immune system function, healthy skin and mucous membranes (the ‘inner linings’ of the body), and supporting iron metabolism. ‘Real’ or ‘preformed’ vitamin A is only found in animal foods such as organ meats, eggs and dairy products. Beta-carotene, a substance that can be converted to vitamin A in the body, is found in plant foods, especially orange, red and green vegetables such as carrots.
Primary functions of Vitamin A
Vitamin A is also said to have roles in cell differentiation, reproduction, bone growth, and formation of glycosaminoglycans (substances that form part of connective tissue), amongst others.
How much do we need?
The nutrient reference value for vitamin A is 800µg (2,666 iu). Nutrient reference values refer to the amount needed to ensure that the needs of nearly all the population (97.5%) are being met. The tolerable upper level for daily intake for adults is 3,000µg (10,000 iu).
Deficiency signs and symptoms*
More immediate deficiency signs may include the following:
Symptoms associated with severe deficiency may include:
*Note that many of these symptoms can be indications of other health conditions or deficiencies – please consult your doctor or health practitioner if you are concerned.
Forms and bioavailability
This is particularly important when it comes to vitamin A.
Beta-carotene found in vegetables and fruits is often called vitamin A, but it is not the same thing. Beta-carotene can be converted to vitamin A in the body, but this conversion rate can be very low – as little as 3 per cent! Conversion can be negatively affected by various factors, such as poor thyroid function, stress and other nutrient deficiencies. So we can get some vitamin A through beta-carotene in veggies and fruits (and beta-carotene in supplements), but it is not the body’s ideal source.
Pre-formed, or ‘real’ vitamin A refers to members of the retinoid family such as retinol as found in animal foods. In supplements, preformed vitamin A may be in the form of retinyl palmitate or retinyl acetate, which can be suitable for vegetarians and vegans. Preformed vitamin A can be used directly by the body for all its vital functions.
The best food sources of ‘real’ vitamin A include:
Beta-carotene is found in carrots (of course!) as well as other orange vegetables and fruits, and green and red vegetables too.
Adults: Dosages of preformed vitamin A in supplements for adults are typically between 2,500 iu (750µg) and 5,000iu (1,500µg). Levels of 10,000 iu or higher may be recommended by a practitioner for short-term therapeutic purposes in adults, but should not generally be used long-term. Beta-carotene may be used in higher doses without any risk of overdosing (the body will never convert more than it needs to vitamin A).
Children: Individual vitamin A supplements are not generally used for children other than under the guidance of a practitioner. A children’s multivitamin supplement may contain around 650–1300 iu (200–400µg) of preformed vitamin A, or more as beta-carotene.
Note: For women who are pregnant or planning pregnancy, it is advised not to take more than 2,000 iu (600 µg) of preformed vitamin A in supplement form.
What to look out for when buying a supplement
So what do you look for when buying a vitamin A supplement? Firstly, you need at least some of your vitamin A in its ‘real’ form, and not all as beta-carotene – as your body may not be able to convert a great deal of it.
The best source in supplement form is cod liver oil, which contains a completely natural form of vitamin A. However, make sure you choose a good quality product from a reputable brand, and that it actually lists vitamin A in the nutritional information.
For vegetarians or vegans – or anyone who can’t take cod liver oil – go for a supplement that contains some vitamin A in the form of retinyl palmitate or similar.
For women who are pregnant or planning pregnancy, it is advised not to take more than 2,000 iu (600 µg) of preformed vitamin A in supplement form. Supplements that contain more than this should state on the label that the product should not be taken in these circumstances. (Beta-carotene can be taken in higher amounts, however.)If you are taking any medications or have any medical condition, please consult your healthcare practitioner before taking vitamin A. Read less