Micronutrients are vitamins and minerals needed in small amounts for normal growth and development. Micronutrient deficiencies affect over two billion humans worldwide,^[1] and have been shown to affect people’s physical health (e.g. iron deficiency causes anemia) and cognitive function (e.g. iodine deficiency negatively affects mental development and lowers IQ). Many farm animals appear to also be deficient in some micronutrients, because their diets are optimized for food production rather than overall health.^[2]

There are three ways to reduce micronutrient deficiencies: giving people micronutrient supplements directly (supplementation); enriching staple foods such as rice, flour, oil and salt with micronutrients (fortification); and breeding or genetically manipulating plants to increase their micronutrient content (biofortification).

Treating micronutrient deficiencies in humans is a very cost-effective intervention: it usually costs only a few cents per person per year to provide particular vitamins or minerals.^[3] One of Givewell’s top-rated charities—Helen Keller International's vitamin A supplementation program—focuses on reducing micronutrient deficiencies.^[4] In animals, the organization Healthier Hens focuses on feed fortification for egg-laying hens.