Nutrient deficiences

=Parasites=

Hookworm
"Hookworm infestations seldom kill, but can cause severe anemia and cognitive defects. Combined with pellagra, the impact of a hookworm infestation could be devastating. Though the reach of pellagra was relatively limited, in the early 20th century up to 40% of population in the South carried the hookworm parasite. The worm’s complex lifecycle depended on access to humans, usually through bare feet, and transmission through untreated sewage. Sufferers could experience cognitive decline, lethargy, and strange urges to eat unusual things. They were often derided as “dirt eaters.” Hookworms were particularly successful in the kind of poor, sandy soils where landless whites and blacks were often relegated."

=Vitamins=

Pellagra (b3)
is what you get with a non-nixtamalized corn-based diet. . B3 (niacin) deficiency.

From Wikipedia: Nixtamalized maize has several benefits over unprocessed grain: It is more easily ground, its nutritional value is increased, flavor and aroma are improved, and mycotoxins are reduced by up to 97%–100% (for aflatoxins).2

B12

 * See: Vitamin B12: Who gets a B12 deficiency
 * See also: Pernicious_anemia

Scurvy
Vitamin C deficiency