Vitamins are a group of substances needed in small amounts by the body to maintain health. Vitamin A cannot be made by the human body and so it is an essential part of the diet. Vitamin A is important for healthy eyes, good eyesight (vision), healthy skin and to help you fight infections. Vitamin A is sometimes also called retinol.
Foods that contain vitamin A include liver, milk, eggs and fish-liver oils. Another substance called beta carotene (which is found in green leafy and orange/yellow vegetables and fruits) can also be converted by your body to vitamin A.
Mild forms of vitamin A deficiency can usually be treated without any long-term problems. Vitamin A deficiency is much more common in low-income countries, where it is often very severe and can cause loss of vision and even death.
What is vitamin A deficiency?
Deficiency, or a lack, of vitamin A in your body happens because of a lack of sufficient amounts of vitamin A in your diet. Over time, a lack of vitamin A means that you may develop problems with vision and be less able to fight infections.
What symptoms are caused by vitamin A deficiency?
Mild forms of vitamin A deficiency may cause no symptoms. However, vitamin A deficiency may cause tiredness (fatigue).
Both mild and severe forms of vitamin A may cause an increased risk of:
- Infections, including throat and chest infections, and gastroenteritis.
- Delayed growth and bone development in children and teenagers.
More severe forms of vitamin A deficiency may also cause:
Eye and vision problems
- Poor vision in the dark (night blindness).
- Thinning and ulceration of the cornea on the surface of the eyes (keratomalacia).
- Dryness of the conjunctiva and cornea on the surface of the eye (xerophthalmia).
- Oval, triangular or irregular foamy patches on the white of the eyes (called Bitot's spots).
- Perforation of the cornea.
- Severe sight impairment (due to damage to the retina) at the back of the eye.
Skin and hair problems
- Dry skin
- Dry hair
- Itching (pruritus)
What are the causes of vitamin A deficiency?
Vitamin A deficiency may be caused by prolonged inadequate intake of vitamin A. This is especially so when rice is the main food in your diet (rice doesn't contain any carotene).
Vitamin A deficiency may also occur when your body is unable to make use of the vitamin A in your diet. This may occur in a variety of illnesses, including:
- Coeliac disease.
- Crohn's disease.
- Giardiasis - an infection of the gut (bowel).
- Cystic fibrosis.
- Diseases affecting the pancreas.
- Liver cirrhosis.
- Obstruction of the flow of bile from your liver and gallbladder into your gut.
Do you need any investigations?
If your doctor suspects you may have vitamin A deficiency then you will need to have blood tests to:
- Confirm whether you do have vitamin A deficiency.
- Check whether you have any other conditions, such as anaemia.
Other investigations will include tests of vision, especially how your vision adapts to the dark.
In children, X-rays of the long bones may be useful to assess bone growth, which may be delayed in vitamin A deficiency.
What is the treatment for vitamin A deficiency?
The treatment for mild forms of vitamin A deficiency includes eating vitamin A-rich foods - eg, liver, beef, oily fish, chicken, eggs, fortified milk, carrots, mangoes, sweet potatoes and leafy green vegetables.
For more severe forms of vitamin A deficiency causing symptoms, treatment includes taking daily oral vitamin A supplements.
How common is vitamin A deficiency?
Vitamin A deficiency is unusual in high income countries. However, it is very common in low income countries where it often develops because of intestinal infections and worms, and protein-energy malnutrition.
Vitamin A deficiency is the biggest cause of preventable blindness in children worldwide. It is the most common nutritional deficiency in the world.
An increased risk of vitamin A deficiency occurs in:
- People with illnesses affecting the way food is absorbed from the gut (bowel) into the body.
- People who have had weight reduction surgery.
- People who have a strict vegan diet.
- Prolonged excessive alcohol intake (alcoholism).
- Other forms of liver disease, as vitamin A is stored in the liver.
- Toddlers and preschool children living in poverty.
- Recent immigrants or refugees from low-income countries.
The most easily absorbed form of vitamin A is fat-soluble, and is absorbed as fat is broken down in the small bowel, so people who are on an extremely low-fat diet or are taking medication to reduce fat absorption, such as orlistat, may be at risk of vitamin A deficiency.
What is the outcome (prognosis)?
The outcome is very good if you have a mild form of vitamin A deficiency without any symptoms. However, more severe forms may cause permanent loss of vision if treatment with vitamin A supplements is not taken at an early stage. If you have early mild eye problems, treatment can result in full recovery without any permanent loss of vision.
Severe vitamin A deficiency with severe generalised malnutrition in low income countries often leads to death.
What is vitamin A?
Vitamins are a group of substances needed in small amounts by the body to maintain health. Most vitamins, including vitamin A, cannot be made by the human body and so they are an essential part of your diet. Vitamin A is sometimes also called retinol.
Can vitamin A deficiency be prevented?
A regular intake of vitamin A-rich foods will usually prevent vitamin A deficiency as long as you do not have any long-term condition preventing your body from using the vitamin A in your diet. Liver, beef, chicken, oily fish, eggs, whole milk, fortified milk, carrots, mangoes, orange fruits, sweet potatoes, spinach, kale and other green vegetables are among foods rich in vitamin A.
Eating at least five servings of fruits and vegetables per day is recommended.
Various foods, such as breakfast cereals, pastries, breads, crackers and cereal grain bars, are often fortified with vitamin A.
For people at increased risk, especially young children, vitamin A supplements can reduce the risk of symptoms, permanent loss of vision, and the risk of dying.
What foods contain vitamin A?
There are two main groups of sources of vitamin A. The first is vitamin A itself, or retinol. This is found in animal products, especially liver, fish and cheese.
Liver is the richest source of vitamin A. A single helping of liver contains more than the recommended minimum intake of vitamin A for a week. For this reason it is not a good idea to eat liver more than once a week, as overdosing on vitamin A can be as dangerous as not getting enough.
Oily fish such as mackerel, herring, salmon and tuna are also rich in vitamin A. Tuna is the highest, with about three times as much vitamin A per 100 g as other fish. There is also vitamin A in shellfish. Cod liver oil contains quite a lot of vitamin A, so you need to be aware of this if you take it as a food supplement, so that you don't end up having too much vitamin A.
Dairy products are a good source of vitamin A. Because vitamin A is a fat-soluble vitamin, the amount in skimmed milk is very much lower than that in full cream milk. In some countries, milk is fortified by law with vitamins, including vitamin A, but currently in the UK this is not the case. Hard cheese such as cheddar has a higher level of vitamin A than soft cheeses.
Eggs also contain quite high levels of vitamin A.
Another substance called beta carotene can also be converted by your body to vitamin A. Beta-carotene is found in fruits and vegetables. However, you need to eat a lot more of these sources to get the vitamin A that you need than you do with animal sources.
Orange vegetables have the highest level of beta carotene: sweet potatoes, pumpkin, carrots and squash. Other coloured vegetables such as red peppers, have quite a bit in them. There is also quite a lot in green leafy vegetables such as spinach, greens and lettuce, although it is harder for the body to use the carotene from these sources. The body can use the vitamin A more easily in cooked or processed vegetables than in raw ones.
Fruits with the highest level of carotene are also generally orange: ripe mango, papaya, cantaloupe melon and apricots, dried or fresh.
Vitamin A is most readily absorbed in fat particles in the gut (intestine), so making sure there is some fat in your meal - for example, a little oil in your salad dressing - will help you to make use of the beta carotene.
In general, a healthy balanced diet will provide the vitamin A that you need.
How much vitamin A do I need?
The recommended daily amount of vitamin A an adult needs is 0.7 mg for men and 0.6 mg for women. A healthy diet that includes some of the foods listed above daily is sufficient for healthy adults. Therefore, otherwise healthy adults do not need to take vitamin A supplements.
Pregnant women need to eat a little bit more, and breastfeeding women need about 1.3 mg daily. Breast milk provides all the vitamin A that young babies need.
Any excess vitamin A can be stored by the body. Therefore, you don't need to eat the recommended amount of vitamin A every single day.
Supplements and fortification
Many people take a multivitamin which will contain a recommended daily amount of vitamin A. In higher income countries, it is not necessary for most people to supplement the vitamin A which is available through a balanced diet, but taking this small amount daily is unlikely to do any harm.
Vitamin A is included in Healthy Start vitamins for children, which are available for some babies and children in the UK.
Some foods are fortified with vitamin A. This means that extra vitamin A is added to them as part of the manufacturing process. These products include dried skimmed milk powder, breakfast cereals and hard spreads such as margarine. In the UK, this fortification is voluntary but in some countries it is a legal requirement.
What is vitamin A used for?
Vitamin A is important for healthy growth and development.
It is used in the immune system to help you fight infections.
It is also important for the eyes, where it is used to make chemicals needed for colour vision and also low light vision. It is also important in maintaining the health of structures at the front of the eye.
Vitamin A is important for pregnant women as it is essential for the development of the the baby's brain, limbs, heart, eyes and ears. Vitamin A deficiency in pregnant women is more likely to occur during the later part of pregnancy when the growing baby's requirement for vitamin A is highest, and it can cause night blindness and increase the risk of death. However, too much vitamin A in pregnancy can cause birth defects.
Can I take too much vitamin A?
If you regularly have more than 1.5 mg of vitamin A per day then you may develop problems because of high vitamin A levels.
Vitamin A poisoning in the short term (for example, 150 mg at once) can cause nausea and vomiting, headache and some nervous system (neurological) problems.
A very high intake of vitamin A over a long period of time can cause problems such as rough skin, dry hair and an enlarged liver. Taken over the long term it may weaken bones, increasing the risk of fractures.
High levels of vitamin A in pregnant women may also cause the unborn baby to develop birth defects. Therefore, women who are (or may become) pregnant are advised not to take any vitamin A supplements. Women who are (or may become) pregnant should also not eat liver or foods containing liver, such as liver pâté or liver sausage, because of the high levels of vitamin A in liver. The risk is thought to be highest in the first few weeks of pregnancy.
Further reading and references
; World Health Organization
; A global clinical view on vitamin A and carotenoids. Am J Clin Nutr. 2012 Nov96(5):1204S-6S. doi: 10.3945/ajcn.112.034868. Epub 2012 Oct 10.
; Vitamin A supplementation for preventing morbidity and mortality in children from six months to five years of age. Cochrane Database Syst Rev. 2017 Mar 113:CD008524. doi: 10.1002/14651858.CD008524.pub3.
; Prevalence of vitamin A deficiency in South Asia: causes, outcomes, and possible remedies. J Health Popul Nutr. 2013 Dec31(4):413-23.
; Review of the safety and efficacy of vitamin A supplementation in the treatment of children with severe acute malnutrition. Nutr J. 2013 Sep 1212:125. doi: 10.1186/1475-2891-12-125.
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