Vitamin A is a fat-soluble vitamin that is important for normal growth, as well as for healthy skin, hair, and nails. It also plays a crucial role in the proper functioning of the eyes and the immune system.
There are different forms of vitamin A. Animal products contain vitamin A in the form of retinol, with liver being particularly rich in this vitamin. The body also produces vitamin A from carotenoids, which are found in plant-based foods.
Excessive vitamin A intake can be harmful, especially for pregnant women.
Different forms of vitamin A
Animal products contain vitamin A in the form of retinol or retinyl esters, while fruits and vegetables contain carotenoids. Carotenoids, often referred to as provitamin A, are substances the body can convert into vitamin A. There are various forms of carotenoids: alpha- and beta-carotene, and beta-cryptoxanthin.
Vitamin A in supplements is typically found as retinyl acetate or palmitate. Nowadays there are supplements that contain only beta-carotene and are therefore vegan.
How much vitamin A do you need per day?
In the Netherlands, the recommended daily allowance (RDA) of vitamin A for an adult (>18 years) male is 800 mcg/day, and for an adult female – 680 mcg/day.
The absorbtion of vitamin A?
Fat is necessary for the proper absorption of vitamin A in the body. The body absorbs 70 to 90% of retinol and 9 to 22% of carotenoids. Vitamin A is stored in the liver, with excess vitamin A also being stored in body fat.
Sources of vitamin A
Vitamin A is found in animal products such as meat, milk, dairy products, fish, and egg yolks, with liver being particularly rich in vitamin A. In the Netherlands, vitamin A is also added to margarine.
Carotenoid Beta-carotene is found in orange and yellow fruits and vegetables, such as carrots, pumpkins, yellow apples, apricots, peaches, and gala melons. Other carotenoids are found in leafy greens like kale, spinach, and endive.
The vitamin A content in foods is typically expressed in retinol activity equivalents (RAE):
1 RAE = 1 microgram retinol = 12 micrograms beta-carotene = 24 micrograms alpha-carotene = 24 micrograms beta-cryptoxanthin.
Main functions of vitamin A in the human body
Vitamin A serves several important functions in the body:
It supports vision and helps the eyes adjust to low light.
It contributes to the normal functioning of the immune system.
It plays a role in fetal development and child growth.
It is involved in the production of cells in skin, hair, gums, trachea, and lung tissue.
It helps maintain healthy skin.
A vitamin A deficiency can lead to skin problems (consider acne), dull hair, and night blindness. In extreme cases, it can cause total blindness.
Vitamin A advice for pregnant women
Excessive vitamin A intake increases the risk of birth defects. Particularly, excessive vitamin A intake increases the likelihood of congenital abnormalities (these are structural or functional anomalies that occur during intrauterine life in the baby). Therefore, it is advisable for pregnant women to avoid vitamin A supplements. It is also recommended to avoid consuming liver and liver-based products.
Vitamin A supplements
For many people, vitamin supplements (including vitamin A) are not necessary. If you choose to take a supplement, it is advisable not to exceed 100% of the recommended daily allowance (RDA). The reference intake (RI) on the label indicates the recommended daily amount. For vitamin A, adults should not take more than 800 mcg (men) or 680 mcg (women) per day from supplements.
Smokers are particularly advised against taking supplements containing provitamin A (beta-carotene). In smokers, high doses of beta-carotene (over 15 mg/day) may increase the risk of lung cancer.
What are the consequences of a vitamin A overload?
Too much vitamin A can occur if you consume liver frequently or take supplements with excessive amounts of vitamin A. This can lead to vitamin A toxicity, with symptoms such as:
Headache
Nausea
Dizziness
Fatigue
Issues with the eyes and skin
However, toxicity is primarily associated with excessive intake of vitamin A from animal products, rather than carotenoids (provitamin A) from fruits and vegetables. That said, high doses of beta-carotene supplements (over 15 milligrams per day) may increase the risk of lung cancer.
Due to the potential negative health effects of excessive vitamin A, the European Food Safety Authority (EFSA) has set a tolerable upper limit for vitamin A, which is a maximum of 3,000 mcg per day for adults.
Bottom-line recommendation
As supplementing vitamin A can be potentially harmful for health, I recommend obtaining this vitamin from food sources. Consuming a variety of colorful fruits and vegetables is essential to meet vitamin A needs. It’s also beneficial to pair these foods with healthy fats (e.g., avocado, olive oil) to improve vitamin A absorption.