Vitamin A, also known as retinoid, is a fat-soluble vitamin. The retinoids are a class of chemical compounds that are vitamers of vitamin A, including retinol, retinal (also known as retinaldehyde), retinoic acid, and retinyl ester. Vitamin A is an essential nutrient, which has many significant functions in the human body, including but not limited to those listed below.
- Regulates the growth and differentiation of cells, and helps cells reproduce normally.
- Contributes to vision health and improves vision in dim light.
- Promotes the normal development of the embryo and fetus.
- Stimulates the production and activity of white blood cells and improves the function of the immune system.
- Maintains the normal growth and development of bones, participates in bone remodeling,
- Maintains the health of endothelial cells, including the skin and mucous membranes that line the nose, sinuses, and mouth.
Main Existence Form
Vitamin A exists in two main forms in food, as preformed vitamin A and provitamin A carotenoids
Preformed vitamin A include retinol and retinyl esters. The retinol forms can combine with fatty acids to form retinyl esters. These forms of vitamin A are found in animal-sourced foods such as beef, calf, eggs, oily fish, liver and liver products and dairy products.
Carotenoids include α-carotene, β-carotene, γ-carotene, and the xanthophyll β-cryptoxanthin. These carotenoids function as provitamin A in herbivore and omnivore animals. Provitamin A carotenoids mainly found in plant foods, such as spinach, carrots, apricots.
Deficiency
The lack of vitamin A can lead to vitamin A deficiency and it signs include the following:
- Tired easily
- Loss of appetite
- Eyes are susceptible to viral infections
- Dry skin or hair
- Impaired taste and smell
- Night blindness
- Xerophthalmia, which can lead to blindness if left untreated
Toxicity
Vitamin A toxicity can occur if an overdose of vitamin A is taken. Vitamin A not absorbed by the body will be stored in the liver or fat tissues, and excessive storage will result in toxicity. Signs of toxicity are blurred vision, headache, muscle pain, weakness, irritability, nausea and vomiting, among others.
Recommended Amounts
Biological activity of Vitamin A can be measured in International Units (IU) while the Recommended Dietary Allowance (RDA) for vitamin A is usually expressed as micrograms (µg or mcg) of retinol activity equivalents (RAEs), where 1 mcg of all-trans retinol is equivalent to 3.33 IU of vitamin A. The vitamin content required by different age groups is as following.
- For babies aged 0 to 6 months, RDA is 400 mcg RAEs/day.
- For babies aged 7–12 months, RDA is 500 mcg RAEs/day
- For 1–3 years old, RDA is 300 mcg RAEs/day
- For 4–8 years old, RDA is 400 mcg RAEs/day
- For 9–13 years old, RDA is 600 mcg RAEs/day
- The recommendation for men after age 13 is 900 mcg RAEs per day (equivalent to 3,000 IU).
- The recommendation for women after age 13 is 700 mcg RAEs per day (equivalent to 2,333 IU).
Common Form in Supplements
Vitamin A is very unstable and is easily destroyed when it encounters acid, air, oxidizing substances, high temperatures or ultraviolet rays while its esterified forms are more stable and non-irritating than vitamin A. Therefore, commercial vitamin A supplements are mostly in the form of vitamin A acetate and vitamin A palmitate. These two ingredients are increasingly in demand in vitamin A supplements due to their better stability and better pharmacology.
Did You Know?
The majority of people with a normal diet do not need additional supplementation of vitamin A, since it is readily available from a normal diet. Those who consume a poor diet or suffer from diseases that result in low levels of vitamin A in their bodies may need to supplement through supplementation. You should consult your doctor before taking dietary supplements in order to avoid vitamin A toxicity due to overdose.
Alfa Chemistry provides a wide range of ingredients for nutritional supplements, including vitamin A acetate and vitamin A palmitate, please do not hesitate to contact us with any questions.
Our products and services are for research use only and cannot be used for any clinical purposes.
