Vision, skin and mucosa, immune function and gene regulation.
Switzerland age 18–65: 650 µg RE/day women, 750 µg RE/day men.
Retinol: liver, eggs and dairy. Provitamin A: carrots, sweet potato, pumpkin, spinach and kale.
Night blindness, dry eyes progressing to xerophthalmia and greater infection susceptibility; rare with a balanced diet in Switzerland.
Severe deficiency can permanently damage vision. Fat malabsorption increases risk.
Dry skin is nonspecific; night blindness and marked eye changes require medical assessment.
Fat malabsorption, very limited diets and liver/biliary disease.
Diet, symptoms and, when suspected, laboratory and clinical eye assessment.
Food first. Avoid high-dose retinol especially in pregnancy unless medically prescribed.
Chronic excess preformed vitamin A can harm liver, bone and pregnancy; food beta-carotene is different.