Vitamin A Deficiency

What vitamin A does

Vitamin A is a fat-soluble vitamin stored mainly in the liver. It comes in two forms:

• Preformed vitamin A (retinol): in liver, fish oils, eggs, milk, cheese and fortified foods.
• Provitamin A carotenoids (mostly beta-carotene): in orange and dark green vegetables and fruit, such as carrots, sweet potatoes, spinach, kale, mango and cantaloupe. The body converts them to vitamin A.

It is needed for:

• Vision: forming rhodopsin, the light-sensitive pigment in the rod cells that let you see in dim light
• Surface tissues: keeping the cornea, conjunctiva, skin and the linings of the airways and gut moist and healthy
• Immunity: supporting barriers and immune cells
• Growth and reproduction

Because the liver stores months' to years' worth, deficiency develops slowly.

Symptoms of vitamin A deficiency

Eyes (xerophthalmia)

Eye changes progress in stages:

1. Night blindness: difficulty seeing in dim light, at dusk or after entering a dark room. This is the earliest and most common symptom.
2. Conjunctival dryness: the white of the eye becomes dry, wrinkled and dull.
3. Bitot spots: foamy, cheesy, gray-white patches on the white of the eye.
4. Corneal dryness: a hazy, dry cornea.
5. Corneal ulcers and keratomalacia: the cornea softens and melts, causing permanent blindness.

Skin and hair

• Dry, rough, scaly skin
• Small, hard bumps around hair follicles (follicular hyperkeratosis), often on the arms and thighs
• Dry, brittle hair

Immune system

• More frequent and more severe infections, especially diarrhea and respiratory infections
• More severe measles, with higher risk of complications and death

Growth and other effects

• Poor growth in children
• Anemia, as vitamin A helps the body use iron
• Infertility and, in pregnancy, higher risks to mother and baby

Causes

Low intake

The main cause worldwide, in regions where diets are low in animal foods and colorful vegetables. Young children, and pregnant and breastfeeding women, have the highest needs. In wealthy countries, very restricted diets, eating disorders, alcohol use disorder and food insecurity can cause it.

Poor absorption

Vitamin A needs fat and bile to be absorbed. Deficiency can result from:

• celiac disease and Crohn's disease
• cystic fibrosis and chronic pancreatitis, which reduce fat-digesting enzymes
• liver disease and blocked bile ducts, including primary biliary cholangitis
• weight-loss surgery, especially malabsorptive procedures such as biliopancreatic diversion and, less often, gastric bypass
• long-term diarrhea and parasite infections

Other factors

Zinc deficiency impairs the transport and use of vitamin A. Measles and other infections use up vitamin A quickly.

How it is diagnosed

• History and examination: diet, gut or liver disease, surgery, night vision and an eye exam for dryness and Bitot spots.
• Serum retinol: a blood test. Levels below about 20 micrograms per deciliter (0.70 micromol/L) suggest deficiency; below 10 micrograms per deciliter indicate severe deficiency. Levels can be falsely low during infection or inflammation, and they do not fall until liver stores are very low.
• Dark adaptation tests or electroretinography in specialist eye clinics.
• Tests for the cause, such as celiac antibodies or fecal elastase.

Treatment

• Vitamin A supplements: for xerophthalmia, WHO protocols use high doses given on day 1, day 2 and 2 weeks later, adjusted for age. Milder deficiency is treated with lower daily doses over weeks. Doses must be set by a doctor.
• Measles: WHO and US guidelines recommend two daily doses of vitamin A for all children with measles, which reduces complications and deaths.
• Eye care: lubricating eye drops and ointments, and antibiotic drops if the cornea is ulcerated.
• Treat the cause: gluten-free diet for celiac disease, enzyme supplements for pancreatic insufficiency, and water-miscible vitamin forms for severe fat malabsorption.
• Zinc if levels are also low.

Night blindness usually improves within days of starting treatment. Early eye changes reverse, but corneal scarring and keratomalacia damage are permanent.

Prevention

Adults need about 900 micrograms (men) and 700 micrograms (women) of retinol activity equivalents a day. A diet including dairy, eggs, fish and plenty of orange and dark green vegetables and fruit meets this. People with malabsorption conditions or after weight-loss surgery need regular monitoring and specific supplements. In many low-income countries, high-dose vitamin A supplements every 4 to 6 months for children aged 6 to 59 months reduce child deaths.

For the other vitamins and how their deficiencies compare, see vitamin deficiency.

Frequently asked questions

What are the first symptoms of vitamin A deficiency?

Night blindness is usually first: difficulty seeing in dim light, at dusk or when walking into a dark room. Dry eyes, dry and rough skin, and more frequent infections often follow. In children, poor growth may also be an early sign.

What causes vitamin A deficiency?

Worldwide, the main cause is a diet low in animal foods and colorful vegetables. In wealthy countries it is usually caused by poor absorption, from celiac disease, Crohn's disease, cystic fibrosis, pancreatic or liver disease, or weight-loss surgery. Alcohol use disorder and very restricted diets can also cause it.

How long does it take to correct vitamin A deficiency?

Night vision often improves within a few days to 2 weeks of supplements. Dry skin and eye surface changes improve over weeks. Liver stores take longer to rebuild. Corneal scarring that has already formed will not reverse.

Can you take too much vitamin A?

Yes. Preformed vitamin A from supplements and liver can build up and cause headaches, nausea, blurred vision, bone and liver damage, and birth defects in pregnancy. The adult upper limit is 3,000 micrograms a day of preformed vitamin A. Beta-carotene from vegetables does not cause this toxicity.

Which foods are highest in vitamin A?

Beef and chicken liver, cod liver oil, sweet potatoes, carrots, spinach, kale, butternut squash, cantaloupe, mango, eggs, milk and cheese are good sources. Eating carotenoid-rich vegetables with a little fat improves absorption.