Why was the rate of pellagra lower in South America and Mexico as opposed to US early 1900s?

Pellagra was indeed less prevalent in South America and Mexico compared to the United States in the early 1900s. Several factors contributed to this difference:

Dietary Differences: The diets in South America and Mexico traditionally included foods rich in niacin (vitamin B3) and tryptophan, which are essential nutrients for preventing pellagra. Corn (maize) was a dietary staple in these regions, and it is naturally higher in niacin than the corn commonly consumed in the Southern United States. Additionally, South Americans and Mexicans often paired corn with beans, which provided complementary amino acids that enhanced the absorption of niacin and tryptophan.

Food Preparation Methods: In South America and Mexico, corn was often nixtamalized—soaked and cooked in an alkaline solution—before consumption. This process improved the nutritional value of corn by increasing the bioavailability of niacin and other nutrients. Nixtamalization also removed harmful substances, such as mycotoxins, which can contribute to pellagra.

Socioeconomic Factors: Poverty and inadequate access to nutritious food were major factors contributing to pellagra in the United States. In contrast, South America and Mexico had more diverse and equitable land distribution, which allowed for a greater proportion of the population to access a balanced diet.

Disease Awareness: Medical professionals and public health officials in South America and Mexico were more aware of pellagra and its causes compared to their counterparts in the United States. This awareness led to earlier diagnosis, appropriate treatment, and preventive measures, including nutrition education and fortification of staple foods with niacin.

It's worth noting that pellagra was not completely absent in South America and Mexico, but its prevalence was significantly lower than in the United States, where it reached epidemic proportions in the early 20th century.