Micronutrients are vitamins and minerals needed in small amounts for normal growth and development. Micronutrient deficiencies affect billion people worldwide (Centers for Disease Control and Prevention 2020), 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). Treating micronutrient deficiencies is a very cost-effective intervention: it usually costs only a few cents per person per year to provide particular vitamins or minerals (Hillebrandt & Engelbert 2016).

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).

One of Givewell’s top-rated charities—Helen Keller International's vitamin A supplementation program—focuses on reducing micronutrient deficiencies (GiveWell 2020).