Vitamin A: What does it do and how does it work?

February 5, 2020
Vitamin A can be found in food such as fish, milk, and orange-colored fruit and vegetables. It maintains and strengthens your vision, your immune system, and promotes healthier skin. Continue reading to find out more about its health benefits and sources.

Vitamin A is a fat-soluble vitamin that occurs naturally in certain foods. It manifests as retinol in products of animal origin and the form of provitamin A in fruit and vegetables. Like all vitamins, humans need it in small amounts to remain healthy. Therefore, we must add it to our daily diet.

But what does it do?

The functions and health benefits of vitamin A

Vitamin A is necessary for the development of certain body functions. For this reason, it has various effects on multiple systems.

Immune system functioning

First, this vitamin is an anti-infective as it’s key to the normal functioning of the immune system. It prevents infections, especially the respiratory system. These include throat infections, pharyngitis, sinusitis, bronchitis, etc.

A close up of the immune system.
Vitamin A is involved in the functions of the immune system. Therefore, it is key to the prevention of some infectious diseases.

Reproduction and development

Vitamin A has an important role in embryonic development. This is one of the first functions science found out about. A deficit of vitamin A during pregnancy can lead to problems in the formation of the urinary tract, the diaphragm, and the kidneys of embryos. Also, scientific studies reveal it’s a must for proper reproduction in both sexes.

Eye protection

Vitamin A is a must for healthy vision. Adequate levels allow the light to convert into electrical signals that the brain can interpret. It also improves vision and prevents night blindness (reduced vision under low light conditions). Also, it helps prevent some eye diseases thanks to its antioxidant effect: presbyopia, macular degeneration, cataracts, glaucoma, farsightedness, myopia or retinal detachment.

Read: Avitaminosis: the lack of vitamins


Vitamin A is also a great antioxidant. As such, it can prevent the development of certain degenerative diseases such as Alzheimer’s, coronary heart disease and chronic lung diseases. Some scientists believe that it may also offer protection against the development of other noncommunicable diseases, such as cancer.

Skin and mucous membranes

This vitamin aids in the maintenance of the skin. Plus, it’s excellent at protecting the mucous membranes, especially those of the digestive and respiratory tract. Also, our body needs it for tissue regeneration so it’s a good remedy for healing wounds in the digestive tract, such as ulcers and diverticulosis.

Many cosmetic companies have been incorporating vitamin A as another ingredient in their products. This has led to positive results in the treatment of acne, and to a reduction in the appearance of wrinkles and the prevention of skin aging.

A woman looking in the mirror.
Today, many cosmetic products contain vitamin A, as it’s a nutrient that helps protect the skin against premature aging.

Where can you get vitamin A?

We’ve already seen how our body needs this kind of vitamin to fulfill important functions. Humans can’t synthesize it, and therefore we must obtain it from edible sources.

There are two different forms:

1. Preformed vitamin A

This one is present in the food of animal origin. The body can easily absorb and store it and hydrolyzes it to form retinol. The following stand out from within this group:

  • Beef liver
  • Cod liver oil
  • Egg yolk
  • Butter and whole milk
  • Bluefish such as sardines, herring, mackerel, tuna, and salmon

2. Provitamin A (vitamin A precursors)

Some plant carotenoids are precursors of vitamin A. This is the case with beta-carotene, which converted retinol through enzymatic action in the intestine.

Carotenoids are mainly present in yellow and orange vegetables but they’re also in some leafy greens, especially in dark green ones. The yellow and orange pigments of the carotenoids are “hidden” under the color of the chlorophyll. The best sources of carotenes are:

  • Red peppers, sweet potatoes, pumpkins, and carrots
  • Cantaloupes, mangoes, and also in peaches and nectarines but in smaller amounts
  • Spinach, broccoli, chard, and kale

To absorb them better, you should cook the vegetables and mix them with a little bit of olive oil.

A woman surrounded by fruit and vegetables that contain vitamin A.
Some fruits and vegetables, especially those of yellow and orange, are a source of beta-carotene.

The health effects of a deficit in vitamin A

A vitamin A deficiency is usually caused by a long-term poor diet. It isn’t common in developed countries but appears in some parts of Africa and Southeast Asia. This is mainly because foods rich in vitamin A are scarce there.

Also, certain disorders that affect the absorption of fats into the intestine may increase the risk of deficiency. Specifically, chronic diarrhea, celiac disease, some pancreatic problems, and bile duct obstruction all play a role in this.

Some of the signs of vitamin A deficiency are:

  • Overly dry skin, rashes, scaly appearance and wrinkles
  • Brittle nails
  • Poor vision, night blindness, and very dry eyes due to lack of lubrication
  • Lack of appetite and smell
  • Infections

Doctors make a diagnosis based on an assessment of the symptoms and the results of a blood test. Supplements are a good way to try to reverse it but always do so under the instructions and advice of your doctor so they can prescribe the amount required for your particular case.

Also read: Vitamin preservation: everything you need to know

Beware of excess

The excessive intake of vitamin A could be toxic. In fact, this is a condition known as hypervitaminosis A. Estimates indicate it could be dangerous to consume 10 times more than the recommended daily dose.

Generally, it’s hard to attain high quantities through food. Thus, poisonings mainly happen when a person takes a high amount of vitamin A supplements. So, always follow the advice of a health professional.

High consumption of vegetables rich in provitamin A doesn’t usually lead to toxicity problems. The body just absorbs what it needs and removes any excess. However, large amounts of beta carotene can give turn your skin orange!

Overall, it’s easy to fill your plate with green, orange and yellow vegetables during the fall. And if you incorporate milk, fish, and eggs to it you’ll have just what it takes to keep a vitamin A deficiency at bay.

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  • Okreglicka K, et al. The effect of the selected vitamins , minerals and antioxidants on age-related macular degeneration. Pol Merkur Lekarski Journal. Julio 2019. 29;47 (277) 35-39.