Vitamin A

Why vitamin A is good for you

Vitamin A is essential for healthy eyes as it helps the eyes to function properly in all conditions, even the dark. Vitamin A is essential in preventing night blindness.

Vitamin helps to prevent a leading case of blindness in the elderly called age-related macular degeneration (ARMD).

Vitamin A helps the immune system fight infection and illness by helping the epithelial tissues (the cells that make up the skin, line the mouth, nose, eyes, throat, lungs, digestive and urinary tracts and which keep out infective agents) grow and repair themselves. Without enough vitamin A, these cells become stiff, dry and much more likely to let their guard down and when that happens, germs can easily pass through them and into the body.

All humans (especially children and teenagers) need vitamin A for a wide range of body functions, including to help the body cells repair, grow properly and to keep bones and teeth strong.

Important vitamin A facts

• Vitamin A is a fat-soluble vitamin
  Since vitamin A is a fat-soluble vitamin, it requires some fat to be eaten at the same time, to enable it to be digested and absorbed properly so that it can be used by the body as required.
• Vitamin A is a potent antioxidant
  Vitamin A’s antioxidant properties are very potent – it acts to scavenge free radicals in the body that may otherwise do damage to DNA and raise risk of cancer and heart disease. Vitamin A reduces the oxidative damage that may otherwise occur in the cells of the body, from free radicals causing damage to them, if it was not available to neutralise and remove them.
• Vitamin A exists in the epithelial and mucous tissues, as well as the retina
  Vitamin A is found in the mucous (respiratory, gastrointestinal) and epithelial (urinary) cells of the body. The vitamin A in these cells helps to keep these cells moist and flexible, so that when any foreign substance (pathogen such as virus or bacteria) enters, these cells and tissues are able to eject the pathogen easily and resist infection. Without vitamin A, these cells may become stiff and dry, thus not providing the correct defense and allowing in the pathogen and enabling infection.
• Vitamin A is only found in animal food sources
  Vitamin A is only found in animal and animal product food sources. Vitamin A in animal foods (and animal products such as egg yolks, milk, fish, cheese) comes pre-formed, so that the body does not have to process it in order to be able to absorb it – the vitamin A simply goes to the intestines where it is absorbed and used as required (including some storage in the liver).
• There are three forms of preformed vitamin A
  The forms are – retinol, retinaldehyde and retinoic acid
• Retinol is easily destroyed
  Retinol is destroyed by light, high temperatures as well as when using copper or iron cooking utensils.
• The highest source of vitamin A is the polar bear liver
  It has 13,000IU-18,000IU per gram of liver!! More than enough to give vitamin A poisoning, even if only a tiny bit was eaten.

Vitamin A works best with

• Vitamin B1
• Vitamin B2
• Vitamin B3
• Vitamin B5
• Vitamin B6
• Vitamin B12
• Vitamin C
• Vitamin D
• Vitamin E
• Choline
• Essential fatty acids
• Calcium
• Phosphorus
• Zinc

Vitamin A and health

• Boosting the immune system fight off infection – vitamin A has an enhancing effect on the immune system due to its powerful antioxidant properties
• Helps with respiratory illnesses – many studies show that people who suffer from asthma, sinusitis and bronchitis improve significantly and have less incidence of infection and severity of symptoms when they are given vitamin A supplements. Studies also show that vitamin A builds resistance to the respiratory infections and illness
• Reduces hay fever and associated allergies – many studies show that people who suffer from allergic rhinnitis (or hayfever, which can happen all year-round, not just in spring) get major relief from their symptoms when they are supplemented with vitamin A.
• Necessary for good eyesight – Vitamin A is found in the mucous cells of the respiratory system and it helps to keep these cells moist and flexible, so that when any pathogen such as virus or bacteri) enters, these cells and tissues are able to eject the pathogen easily and resist infection
• Helps with night blindness – vitamin A helps you see better in the dark, because it tops up all the Vitamin A in your retina
• May prevent cataracts – vitamin A (and betacarotene) help mop up the free radicals which damage the lens of the eye and cause cataracts
• May prevent macular degeneration – vitamin A (together with vitamin C and vitamin E) is so vital for preventing or slowing down the development of progression of macular degeneration, which is the leading cause of blindness.
• Prevents heart disease – research shows that people who eat foods high in vitamin A (and betacarotene) have a much lowered risk for developing any type of heart disease (high blood pressure, high cholesterol levels, high triglycerides) and this reduces the risk for heart attack or stroke.
• Preventing heart attacks and heart disease – people who eat foods high in Vitamin A (and betacarotene) have fewer heart attacks and strokes

Groups at risk of vitamin A deficiency

There are many people who may be at risk of vitamin A deficiency:

• People who are on a very low fat diet
  People that are on a very low fat diet may not be eating enough foods that are rich in vitamin A, because most foods high in vitamin A tend to be high in fat also. This type of low fat diet could contribute to a deficiency of vitamin A and supplementation may be required.
• People that drink alcohol excessively
  People that drink excessive amounts of alcohol may be deficient in vitamin A because the alcohol prevents the body from transporting and using vitamin A properly. In addition, people who drink excessive amounts of alcohol may not be eating enough food, so may not get enough vitamin A from their foods anyway.
• People who have recently undergone surgery
  People that have undergone surgery may be deficient in vitamin A, as all the reserves will be used to help the body heal from the surgery, so may need vitamin A supplementation.
• People who smoke cigarettes
  Tobacco reduces the amount of vitamin A that is absorbed from foods eaten, so people who smoke cigarettes may become deficient in vitamin A and need supplementation.
• People who take certain medications
  Many prescription as well as over-the-counter (OTC) medications cause a decreased absorption of vitamin A, which could cause a deficiency (while some medications cause an increased absorption of vitamin A). People who take any type of medication should seek advice from their doctor before trying any vitamin A supplements to ensure it is suitable for their individual circumstances.
• People under a lot of stress
  People who experience physical or physiological stress, such as overwork, fatigue, not eating enough/properly, exercising too much all create free radicals which lower vitamin A levels. If the stress is constant and prolonged, this uses up most of the vitamin A reserves. Vitamin A helps to combat free radicals that are produced at times of stress and could be deficient and may need supplementation.
• People with certain illnesses
  People with certain illness may have low vitamin A levels – illness such as cystic fibrosis, liver disease and chronic diarrhoea. People with any type of illness should seek advice from their doctor before trying any vitamin A supplements to ensure it is suitable for their individual circumstances.
• People with chronic infections
  People with chronic infections (such as bronchitis) usually have low levels of vitamin A due to the infection and may have used up most of their vitamin A reserves to combat the free radicals that are produced at times of infection, so could be deficient and may need supplementation. Illness or chronic infection produces free radicals, which lower vitamin A levels
• People with recent severe burns
  People that have recent severe burn may be deficient in vitamin A, as all the reserves will be used to help the body heal from the severe burns, so may need vitamin A supplementation.
• Strict vegetarians and vegans
  Vitamin A only exists in food that is of animal origin – meats and meat products such as milk, cheese, eggs and butter. People that do not eat animal foods (or only very little animal products) may be at a high risk of being deficient in vitamin A and could need supplementation.
• Users of birth control pills
  May have high levels of vitamin A in their blood, but low levels stored in the liver (the pill does not have this effect on Vitamin A)

Talk to a medical professional about vitamin A supplements before taking them.

Symptoms of vitamin A deficiency

Deficiency of vitamin A occurs when blood levels are less than 10mcg / litre of blood.

General symptoms of deficiency

• abscesses forming in the ear
• diarrhoea
• dry hair, scalp, rough skin, dry itchy eyes
• fatigue
• frequent cold and respiratory infections, such as asthma, allergic rhinitis (hay fever), bronchitis
• insomnia
• skin disorders, such as acne, eczema, boils and a bumpy skin
• slow healing from injuries
• sinusitis

People with any of these symptoms should seek advice from their medical practitioner.

More severe symptoms of vitamin A deficiency include:

• Blindness
• Eyesight problems
• Lack of tear secretion
• Night blindness
• Poor bone growth
• Reproductive problems
• Slowed growth
• Ulcerated cornea and blindness
• Weakened tooth enamel
• Weight loss

People with any of these symptoms should seek advice from their medical practitioner.

Vitamin A in food

Vitamin A recommended daily intake (RDI)

The tolerable upper limits should only be taken for short periods and only under medical supervision.

Retinol equivalents (IU and mcg)

The above recommended dietary allowances of Vitamin A are given in Retinol Equivalents (RE) of vitamin A (in mcg).

The following shows the International Unit (IU) equivalents of Vitamin A:

One Retinol Equivalent (RE) of Vitamin A (in mcg) equals
6 International Units (IU) from beta-carotene
10 IU from other carotenoid-rich plant foods
4.10 IU from milk and yogurt
3.33 IU from animal sources and fortified foods

Toxicity

Vitamin A is toxic at doses greater than 22,500mcg (or 75,000IU) per day.

Vitamin A toxicity is known as also known as hypervitaminosis A.

Vitamin D supplementation helps to reduce vitamin A toxicity, so should be taken together.

Vitamin A is toxic in large doses. To avoid vitamin A toxicity, either take the recommended daily intake of Vitamin A or take betacarotene or eat foods rich in this vitamin.

Vitamin A toxicity can occur due to excessive intake of vitamin A over a short period (acute toxicity), or higher than normal intake of vitamin A over a long period, where levels of vitamin A build up over time and are not excreted by the body (chronic toxicity).

While acute vitamin A toxicity can be far more dangerous than chronic vitamin A toxicity, both are bad for your health. If you suspect you have had too much vitamin A, see a doctor immediately.

Overdosage and toxicity symptoms

High levels of vitamin A should not be taken for long terms as it can cause adverse health effects. Higher than the tolerable upper limit should only be taken for a short term and only under medical supervision. Overdosage and toxicity is more likely to occur from taking too many supplements, whereas dietary intake of vitamin A is highly unlikely to cause overdosage.

To avoid vitamin A toxicity, eat foods rich in this vitamin.

Acute vitamin A toxicity

Taking over (> 75000IU per day) causes the following symptoms:

• Birth defects (in pregnant women)
• Elevated calcium levels
• Fatigue
• Headache
• Insomnia
• Irritability
• Lethargy
• Menstruation stops (usually temporarily)
• Nausea and vomiting
• Painful bones
• Skin rashes that peel off

Chronic vitamin A toxicity

Taking higher than the tolerable upper limit causes the following symptoms:

Symptoms of overdose in adults

• Abnormal bone growth
• Birth defects (in pregnant women)
• Blurry vision and headache
• Bone and muscle pain
• Drowsiness, lethargy and loss of appetite
• Hair loss
• Headache
• Increased blood lipid levels
• Irritability
• Itching
• Jaundice (yellowing of skin/eyes)
• Loss of appetite
• Menstruation stops (usually temporarily)
• Vomiting and diarrhoea

People who experience any of the above toxicity symptoms should discontinue their vitamin A supplements and seek the advice of their doctor.

Symptoms of overdose in children

• bone pain
• fontanelle bulging (the soft spot on an infant’s skull)
• irritability
• lethargy
• loss of appetite
• stunted growth

Certain people should not take high vitamin A supplements:

• Women who are pregnant
  Women who are pregnant should not take more than the upper tolerable limit of vitamin A due to the risk on the unborn foetus. High levels of vitamin A supplements could cause birth defects.  Women of child-bearing age should not take more than 8,000IU of vitamin A per day for this very reason.

Certain people should not take vitamin A supplements without first consulting their doctor for advice:

• People who drink excessive alcohol
  People who drink alcohol excessively are advised not to take high levels of Vitamin A as their liver may be too sensitive from the alcohol abuse and more susceptible to liver toxicity of vitamin A. The liver may not be able to metabolise and use the vitamin A properly causing toxicity effects.
• People with cystic fibrosis
  People with cystic fibrosis may have low levels of vitamin A (as this vitamin is needed for ensuring healthy mucous membranes and it is not healthy in people with cystic fibrosis) and could need supplementation.
• People with diabetes
  People with diabetes may have low levels of vitamin A due to their condition and could need supplementation.
• People with gastrointestinal disorders (with diarrhoea)
  People that have any type of gastrointestinal disorder that has associated diarrhoea may be excreting a lot of their vitamin A out in their diarrhoea and could need supplementation.
• People with kidney disease
  People with kidney disease may have low levels of vitamin A due to their condition and could need supplementation.
• People with liver disease
  People with liver disease may have low levels of vitamin A due to their condition and could need supplementation.
• People with overactive thyroid function
  People with an overactive thyroid may have low levels of vitamin A due to their condition and could need supplementation.
• People with disorders of the pancreas, including viral pancreatitis
  People with disorders of the pancreas (including viral pancreatitis) may have low levels of vitamin A due to their condition and could need supplementation.

Interactions with medications and supplements

The following are the medications and supplements that are more likely to cause a reaction with vitamin A supplements:

• Antacids – any type of antacids can reduce absorption of vitamin A (as well as any of the other fat-soluble vitamins too)
• Calcium supplements – high levels of vitamin A supplements can reduce the effectiveness of calcium supplements if they are taken at the same time
• Cholestyramine and Colestipol – the medications Cholestyramine or Colestipol, which are used to lower LDL (“bad”) cholesterol levels can reduce the rate of absorption of vitamin A from foods
• Neomycin – the antibiotic Neomycin, can reduce the rate of absorption of vitamin A from foods
• Oral contraceptives – the oral contraceptive can increases the amount of vitamin A in the body and could cause some toxicity, so excessive vitamin A supplementation is not recommended
• Retin-A – Retin-A, a medication used for treating facial acne is high in vitamin A, so people taking vitamin A supplements at the same time as this medication will increase their risk for vitamin A toxicity
• Vitamin E – vitamin E supplements work very synergistically with vitamin A supplements, but when the intake of vitamin E supplements is at very high levels, they can deplete the vitamin A stores in the liver and cause a deficiency

References

• Ambalavanan N, Tyson JE, Kennedy KA, et al. Vitamin A supplementation for extremely low birth weight infants: outcome at 18 to 22 months. Pediatrics 2005;115(3):e249-e254
• Barker ME, Blumsohn A. Is vitamin A consumption a risk factor for osteoporotic fracture?. Proc Nutr Soc. 2003;62:845-850
• Bates CJ. Vitamin A. Lancet. Jan 7 1995;345(8941):31-5
• Chang L-C, et al. Retinoic acid induced glandular differentiation of the oesophagus. Gut, Dec 2006 doi:10.1136/gut.2006.097915
• Cox SE, Arthur P, Kirkwood BR, et al. Vitamin A supplementation increases ratios of proinflammatory to anti-inflammatory cytokine responses in pregnancy and lactation. Clin Exp Immunol. 2006 Jun;144(3):392-400
• Fletcher AE, Breeze E, Shetty PS. Antioxidant vitamins and mortality in older persons: findings from the nutrition add-on study to the Medical Research Council Trial of Assessment and Management of Older People in the Community. AJCN, 2003; Vol 78(5): 999-1010
• Genaro Pde S, Martini LA. Vitamin A supplementation and risk of skeletal fracture. Nutr Rev. Feb 2004;62(2):65-7
• Griffith HW. Minerals, Supplements and Vitamins – The Essential Guide. 2000 Fisher Books, USA
• Hathcock JN, Hattan DG, Jenkins MY, et al. Evaluation of vitamin A toxicity. Am J Clin Nutr. Aug 1990;52(2):183-202
• Lieberman S, Bruning N. The Real Vitamin and Mineral Book – Using Supplements for Optimal Health. 3rd Edition. Avery Publishing, New York, 2003
• Office of Dietary Supplements USA – has the official USA RDI for all vitamins (these are also adopted by Australia), accessed 9 August 2005
• Osiecki, Henry, The Nutrient Bible 2002, BioConcepts Publishing
• Wolbach SB, How PR. Tissue Changes Following Deprivation of Fat-Soluble A Vitamin. The Journal of Experimental Medicine 1925, Vol 42, 753-777

Last reviewed and updated: 29 April 2025