Vitamin A: Functions, Sources, deficiency, dosage, and side effects

Contrary to popular belief, Vitamin A is a class of fat-soluble chemicals that includes retinol, retinal, and retinyl esters. As a result, vitamin A is commonly regarded as a specific nutrient.

This vitamin comes in two forms: provitamin carotenoid found in plants and preformed vitamin found in animals. It is inactive and must be converted to retinal and retinoic acid before it can be helpful. In addition, it also dissolves in fat and stores it in the body’s tissues for later use.

The vast majority of this vitamin stored in our body is in the form of retinyl esters in the liver. Then, this ester dissolves into all-trans-retinol, which binds to retinol-binding protein.


  • It promotes cell growth, immune function, and fetal development and is beneficial to the eyes.
  • One of the most well-known benefits of this vitamin is that it helps maintain healthy eyes and vision.
  • It also aids in the maintenance of surface tissues such as the skin, intestines, lungs, bladder, and inner ear.
  • As a result of its antioxidant properties, carotenoids-rich fruits and vegetables may protect against cancer.
  • A study shows that retinoids can inhibit the growth of cancer cells, including bladder, breast, and ovarian cancer cells.
  • As it aids in forming sperm and eggs, vitamin A is essential for male and female reproduction.
  • It is essential for pregnant women’s health, developing children, and those trying to conceive.


Insufficient of this vitamin is not common in developed countries, unlike in developing countries where people have limited access to preformed vitamin and provitamin carotenoids in their diets.

  • Based on the World Health Organization, deficiency of this vitamin is the primary cause of preventable blindness in children worldwide.
  • A lack of this vitamin also increases the severity of illnesses like measles, diarrhea, and the risk of death.
  • A deficiency of this vitamin hurts the fetus by slowing growth and development, increasing the risk of anemia and death in pregnant women.
  • Skin problems such as hyperkeratosis and acne are less severe symptoms of vitamin A deficiency.
  • Premature infants, people with cystic fibrosis, and expecting or breastfeeding women in developing countries are all at risk of this vitamin deficiency.

Food resources

A variety of foods contain preformed vitamin and provitamin carotenoids. However, your body utilizes plant-based carotenoids less readily absorbed and used than preformed vitamins.

Genetics, food, overall health, and drugs influence your body’s ability to change carotenoids, such as beta carotene, into suitable forms of this vitamin. As a result, vegans and others who follow a plant-based diet should be cautious about consuming enough carotenoid-rich foods. The following foods contain preformed vitamins:

  • Eggs’ yolks
  • Bovine liver
  • Liverwurst
  • Butter
  • Liver oil from fish
  • A chicken’s liver
  • Salmon
  • Cheddar cheese
  • Liver-based sausage
  • King of the mackerel
  • Trout
  • Carotenoids in vitamins are given below:
  • Sweet potato
  • pumpkin
  • Carrots
  • kale
  • Spinach
  • Dandelions greens
  • Collards and greens
  • Cantaloupe
  • Papaya
  • Red bell peppers

 Dosage recommendation

 The required Dietary Allowance for vitamin A is 900 mcg for men and 700 mcg for women per day. If you eat a lot of natural foods, you can quickly meet this intake level. A well-balanced diet is an excellent way to ensure that your body receives adequate amounts of this essential vitamin. Conversely, it can have severe or even fatal consequences. If pregnant, do not take this vitamin without consulting your doctor.

Moreover, infants require it for normal development, but excessive amounts can result in congenital disabilities. Therefore, you may need to take a prenatal vitamin designed for pregnant women. Consult your doctor before using this medication if you are breastfeeding. The dose requirements may change while you are nursing.

Toxicity levels

To avoid toxicity, adults should not exceed the Tolerable Upper Intake Level of 10,000 IU (3,000 mcg) per day. Though consuming too much-preformed vitamins from animal sources such as the liver is possible, toxicity is more commonly associated with over-supplementation and treatment with drugs such as isotretinoin. In addition, this vitamin is fat-soluble, stored in our body, and can accumulate to dangerous levels over time. Acute toxicity develops quickly after ingesting a single extremely high vitamin. Chronic toxicity happens when more than ten times the RDA is taken over a long period. Although less common than chronic toxicity, acute toxicity is associated with more severe symptoms such as liver damage, elevated cranial pressure, and even death. To avoid toxicity, refrain from taking a high-dose supplement containing this vitamin. Ask a healthcare professional before taking the supplements because too much of this vitamin can be dangerous. The toxicity can cause liver damage, vision problems, nausea, and even death. If you’re taking high-dose supplements, make sure a doctor prescribes them.


How to consume

Follow the label’s instructions or the advice of your doctor. A vitamin A injection is given to a muscle. A healthcare provider can administer the injection if you cannot take the medication orally. Please read the information that came with the vitamin carefully and follow it. If you are unsure about something, consult your doctor or pharmacist. The recommended dietary amount of this vitamin increases with age. Ask a health professional if you have concerns about providing a child with this vitamin. The pill should not be crushed, chewed, broken, or opened; instead, it should be swallowed whole. Combining similar vitamin preparations may result in a vitamin overdose or other dangerous side effects. Store at room temperature, and keep moisture, heat, and light away.

Side effects

If you have hives, difficulty breathing, or swelling of your face, lips, tongue, or neck, seek medical attention immediately. When you notice these signs, call your doctor:

  • High fever
  • Excessive sweating
  • Extreme exhaustion
  • Swings in mood
  • Nausea, vomiting, and appetite loss
  • Changes in your menstrual cycle
  • Perplexity or irritability
  • The occurrence of double vision
  • Soreness in the mouth and bleeding gums
  • Convulsion,
  • Hair loss, peeling skin, and skin discoloration.

A high dose in children can result in:

  • Growth problems in children
  • Drowsiness, including loss of consciousness and vision problems.
  • High fever and chills
  • Mucus cough, chest pain, and breathing difficulty
  • Vomiting, nausea, or diarrhea
  • Blister

Where to Buy

You can find it at grocery stores, health food stores, and online.


This information is not meant to provide medical advice or replace a personal physician’s advice or treatment. All readers of this information, especially those taking prescription or over-the-counter medications, should check with their doctors before initiating any nutrition, supplement, or lifestyle program. In addition, the statements and goods on this website have not been evaluated by the Food and Drug Administration.

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