The so - called «big four» are: protein - energy malnutrition (PEM), with 500 million people affected and 10 million dying every year; vitamin A deficiency,
causing xerophthalmia and blindness, which affect 6 million people a year and kill 750,000; endemic goiter, caused by iodine deficiency and affecting 150 million people a year; and nutritional anemia, affecting 350 million people a year.
This was the first paper suggesting that the factor that treated
xerophthalmia — an eye condition
caused by vitamin A deficiency — was a separate factor from that which treated rickets, due to their different distribution among foods.