The reason a maize-based diet predisposes to pellagra is that the proteins of maize are particularly poor in tryptophan, so that a diet in which there are few other sources of protein provides insufficient tryptophan for nicotinamide synthesis.

Why are maize eaters more likely to get pellagra?

Pellagra is common in poor parts of the world, such as Africa and India, where corn (or maize) is a staple food. This is because corn is a poor source of tryptophan and niacin.

Does maize contain niacin?

Pellagra can be common in people who obtain most of their food energy from corn, notably rural South America, where maize is a staple food. If maize is not nixtamalized, it is a poor source of tryptophan, as well as niacin.