Vitamin A and Night Vision: Science, Myths and Safety

Few nutrients are as closely tied to vision as vitamin A. The very first sign of a deficiency is often difficulty seeing in dim light, and in its severe form vitamin A deficiency can destroy the front of the eye. Around the world, it remains a leading cause of preventable blindness in children. Yet in countries where diets are varied, deficiency is rare, and the bigger risk can be taking too much in supplement form.

Vitamin A is also the subject of one of the best-known health myths: that eating carrots gives you exceptional night vision. This article explains how vitamin A works in the retina, who is at risk of deficiency, where the carrot legend came from, and why caution is needed with high doses, especially during pregnancy.

How vitamin A makes night vision possible

The retina contains two main types of light-sensitive cells. Cones work in bright light and let us see colour and fine detail. Rods are far more numerous, extremely sensitive to light, and responsible for vision in dim conditions such as at dusk or on a dark road. Our guide on how vision works describes these cells in more detail.

Rods contain a pigment called rhodopsin, sometimes known as visual purple. Rhodopsin is made from a protein (opsin) combined with a molecule derived from vitamin A called 11-cis-retinal. When a photon of light hits rhodopsin, 11-cis-retinal changes shape into all-trans-retinal. This tiny shape change triggers a chain of chemical events that sends an electrical signal to the brain. The used molecule is then released, transported to the neighbouring retinal pigment epithelium, recycled back into its original form and returned to the photoreceptor. This process is called the visual cycle.

Each time you walk from a bright room into darkness, your rods need to rebuild their store of rhodopsin. This is why it takes many minutes for your eyes to fully adapt to the dark. If vitamin A is in short supply, rhodopsin cannot be regenerated efficiently and dark adaptation slows down or fails, causing night blindness (nyctalopia).

Forms and sources of vitamin A

Vitamin A comes in two main forms in the diet:

• Preformed vitamin A (retinol and retinyl esters): found in animal foods such as liver, fish liver oils, eggs, dairy products and fortified foods. It is ready for the body to use.
• Provitamin A carotenoids, mainly beta-carotene: found in orange and yellow vegetables and fruits and dark green leafy vegetables. The body converts them into vitamin A as needed, which makes toxicity from food sources very unlikely.

For a wider look at eye-friendly eating, see our list of 15 foods that support eye health.

Vitamin A deficiency: a global problem

In high-income countries, vitamin A deficiency is uncommon and usually linked to conditions that interfere with fat absorption, such as coeliac disease, cystic fibrosis, chronic pancreatitis, liver disease, inflammatory bowel disease, or weight-loss (bariatric) surgery. Very restrictive diets and alcohol use disorder can also cause it.

Globally, the picture is very different. The World Health Organization describes vitamin A deficiency as a public health problem in more than half of all countries, especially in Africa and South-East Asia. Young children and pregnant women in low-income settings are most affected. The WHO estimates that hundreds of thousands of children become blind from vitamin A deficiency every year, and that half of them die within a year of losing their sight, because deficiency also weakens the immune system and makes infections such as measles and diarrhoea more severe.

To address this, the WHO recommends high-dose vitamin A supplementation for children aged 6 to 59 months in areas where deficiency is a public health problem. Food fortification, promotion of breastfeeding and diets rich in vitamin A are also key strategies.

Xerophthalmia: the stages of eye damage

The term xerophthalmia (literally dry eye) covers the spectrum of eye changes caused by vitamin A deficiency. Vitamin A is needed not only for the retina but also to maintain the moist, mucus-producing surface of the eye.

1. Night blindness: the earliest and most common symptom. Children may stumble at dusk or be unable to find things in dim light.
2. Conjunctival xerosis: the conjunctiva becomes dry, thickened and wrinkled.
3. Bitot spots: foamy, greyish or white patches on the white of the eye.
4. Corneal xerosis: the cornea becomes dry and hazy.
5. Keratomalacia and corneal ulceration: the cornea softens and can melt or perforate within days, leading to permanent blindness.

Early stages are reversible with treatment, which is why prompt recognition matters. Corneal scarring and perforation, however, cause permanent damage. Night blindness can also have other causes, such as inherited retinal diseases; our page on night blindness covers the full range.

The carrot myth

Many people grew up hearing that carrots help you see in the dark. The story is often traced to the Second World War. During the Blitz, Britain's Royal Air Force had begun using new airborne radar to locate German bombers at night. To protect this secret, it has been widely reported that British authorities encouraged the idea that pilots such as the night-fighter ace John Cunningham owed their success to eating lots of carrots. At the same time, the government promoted carrots to the public as a plentiful, home-grown food during rationing, suggesting they would help people see during blackouts.

Historians debate exactly how deliberate the deception was, but the core point stands: carrots did not give anyone super vision. If you are deficient in vitamin A, eating carrots or other sources will restore normal night vision. If you already have enough, extra carrots will not make your night vision better than normal. Our article on night driving and vision explains the real reasons many people struggle in the dark, such as glare, cataract and uncorrected prescriptions.

Too much vitamin A: toxicity

Because preformed vitamin A is stored in the liver, excessive intake can build up and cause toxicity (hypervitaminosis A). This is almost always due to high-dose supplements, fish liver oils or very frequent consumption of liver, not to fruit and vegetables.

• Acute toxicity after a very large dose can cause headache, nausea, vomiting, dizziness and blurred vision.
• Chronic toxicity from long-term high intake can cause dry skin, hair loss, bone and joint pain, liver damage and raised pressure in the skull, which can affect the optic nerves and vision.
• Long-term high intake of preformed vitamin A has been linked to reduced bone density and a higher fracture risk in older adults.

Health authorities set a tolerable upper intake level for adults for preformed vitamin A, and most people with a varied diet do not need supplements at all. Beta-carotene supplements carry a separate concern: in large trials, high-dose beta-carotene increased the risk of lung cancer in smokers and former smokers. This is why it was removed from the AREDS2 eye supplement formula, as discussed in our article on AREDS supplements.

Vitamin A and pregnancy

Pregnancy requires special care. Excess preformed vitamin A, particularly in early pregnancy, can cause birth defects affecting the face, heart and nervous system. For this reason, health services such as the NHS advise pregnant women, and those trying to conceive, to avoid liver and liver products such as pâté and to avoid supplements containing vitamin A (retinol) unless advised by a doctor. Pregnancy multivitamins are formulated with this in mind.

Medicines derived from vitamin A, such as oral isotretinoin used for severe acne, are strongly linked to birth defects and are only prescribed with strict pregnancy prevention measures. Such medications can also cause dry eyes and reduced night vision; our page on medications that affect the eyes has more information.

In contrast, in regions where vitamin A deficiency is common, the WHO recommends supplementation for pregnant women in specific circumstances to prevent night blindness. This difference shows why vitamin A advice depends heavily on context and must come from local health professionals.

Practical advice

• Eat a varied diet with orange and green vegetables, fruit, eggs and dairy; this covers vitamin A needs for most people.
• Do not take vitamin A supplements unless a doctor has diagnosed a deficiency or recommends them.
• Check the labels of multivitamins and fish liver oils so that you do not take several products containing vitamin A at once.
• If you are pregnant or planning pregnancy, avoid liver and retinol supplements and follow your midwife or doctor's advice.
• If you have a condition that affects fat absorption or have had bariatric surgery, ask your doctor about monitoring.

When to see a doctor

See an optometrist or doctor if you notice that your night vision is getting worse, you take much longer to adjust to darkness, or you have difficulty driving at night. Common causes include cataract and an outdated glasses prescription, but persistent night blindness can also signal vitamin A deficiency or an inherited retinal condition such as retinitis pigmentosa.