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 developing countries, where it is often very severe and can cause loss of vision and even death.
What is vitamin A?
Vitamins are a group of substances needed in small amounts by the body to maintain health. Vitamins cannot be made by the human body and so they are an essential part of your diet.
Vitamin A is important for healthy eyes and to help you fight infections. Vitamin A is sometimes also called retinol. Good sources of vitamin A include:
- Milk, yoghurt and cheese.
- Oily fish.
- Fortified low-fat spreads.
Liver is a very good source of vitamin A. However, you will be at risk of having too much vitamin A if you eat liver more than once a week.
Another substance called beta-carotene can also be converted by your body to vitamin A. Good food sources of beta-carotene in your diet include:
- Vegetables such as carrots, sweet potatoes and red peppers, and green leafy vegetables such as spinach.
- Orange/yellow-coloured fruit - eg, mango, papaya and apricots.
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 daily diet that includes some of the foods listed above is sufficient for healthy adults. Therefore, otherwise healthy adults do not need to take vitamin A supplements.
Any excess vitamin A is stored by the body. Therefore, you don't need the recommended amount of vitamin A every day.
Can I take too much vitamin A?
A very high intake of vitamin A can cause problems such as rough skin, dry hair and an enlarged liver.
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.
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.
How common is vitamin A deficiency?
Vitamin A deficiency is uncommon in Western countries but very common in developing countries.
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, such as:
- Coeliac disease.
- Crohn's disease.
- Cystic fibrosis.
- Some diseases affecting the liver or pancreas.
- People who have a strict vegan diet.
- Prolonged excessive alcohol intake (alcoholism).
- Toddlers and preschool children living in poverty.
- Recent immigrants or refugees from developing countries.
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.
What symptoms are caused by vitamin A deficiency?
Mild forms of vitamin A deficiency may cause no symptoms. However, mild forms of 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
Dry skin, dry hair, and itching (pruritus).
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, 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.
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 the developing world often leads to death.
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, 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.
Dr Colin Tidy
Dr Colin Tidy
Dr Hayley Willacy