Vitamin A Deficiency

Vitamin A deficiency means the body's vitamin A stores, held mostly in the liver, have run low enough to affect the tissues that depend on it. Vitamin A is part of rhodopsin, the light-sensitive pigment in the retina, and it keeps the cornea, the conjunctiva and the skin healthy. That is why the eyes show it first: night blindness is the earliest sign, followed by dryness of the eye surface (xerophthalmia), foamy Bitot's spots and, in severe cases, corneal ulcers and permanent blindness. Deficiency also makes infections such as measles and diarrhoea more severe. Worldwide it remains one of the leading causes of preventable childhood blindness. A pooled analysis of surveys from 138 low- and middle-income countries estimated that 29% of children aged 6-59 months were deficient in 2013, with the highest rates in sub-Saharan Africa (48%) and south Asia (44%). In the United States, fewer than 1% of people have a low serum retinol level. In high-income countries, deficiency is mostly secondary: fat malabsorption (cystic fibrosis, inflammatory bowel disease, coeliac disease, chronic liver disease), bariatric surgery, and very restrictive eating, which was the cause in three-quarters of 61 published childhood cases from high-income countries reviewed in 2026, often in autistic children. Because vitamin A is fat-soluble, the same conditions often cause vitamin D, E and K deficiency alongside it. Treatment is vitamin A given under medical supervision, with doses set by a clinician, because preformed vitamin A is toxic in excess and high intakes in early pregnancy can cause birth defects. In chronic liver disease the liver releases vitamin A poorly and excess can be harmful, so repletion needs particularly careful monitoring. Prevention is a diet with liver, eggs, dairy and oily fish or plenty of orange and dark-green vegetables, plus routine supplements for groups with malabsorption.

• •Night blindness: poor vision in dim light or darkness, usually the first sign
• •Dry, gritty eyes and dryness of the conjunctiva (conjunctival xerosis)
• •Bitot's spots: foamy, grey-white patches on the white of the eye
• •Corneal dryness, clouding, ulceration or scarring in advanced deficiency
• •Worsening vision, which can become permanent
• •Skin problems alongside the eye changes
• •More frequent or more severe infections, especially measles and diarrhoea in children
• •Anaemia in chronic deficiency

• •Low intake of animal-source foods and provitamin A-rich vegetables
• •Very restrictive or selective eating, including in autistic children
• •Cystic fibrosis with pancreatic insufficiency
• •Crohn's disease, ulcerative colitis or untreated coeliac disease
• •Chronic liver disease and cirrhosis
• •Malabsorptive bariatric surgery (gastric bypass, biliopancreatic diversion, duodenal switch)
• •Preterm birth, with low liver stores at birth
• •Frequent infections such as measles and diarrhoea, which lower blood retinol
• •Orlistat, which reduces absorption of fat-soluble vitamins

Vitamin A comes in two dietary forms. Preformed vitamin A (retinol and retinyl esters) from animal foods is absorbed efficiently, at 75-100%. Provitamin A carotenoids such as beta-carotene from plants are absorbed far less well, typically 10-30% from foods, and must then be converted to retinol in the gut; that conversion varies between people. Diets that rely on a few plant staples with little animal food can therefore fall short even when vegetables are eaten. Absorption depends on normal fat digestion, so anything that disrupts fat digestion cuts uptake: pancreatic insufficiency in cystic fibrosis, Crohn's disease and ulcerative colitis, untreated coeliac disease, cholestatic and chronic liver disease, and malabsorptive bariatric operations. The liver both stores vitamin A and makes retinol-binding protein, the carrier that releases it into the blood, so liver disease lowers blood levels in two ways. Blood retinol stays normal until liver stores are almost used up, which is why deficiency can build silently for years and then appear abruptly, sometimes decades after bariatric surgery. Infection also lowers serum retinol, and deficiency in turn makes measles and diarrhoea more severe.