Nicotinic acid is also known as Niacin or Vitamin B3. A deficiency of which is known as Pellagra and is characterized as follows:
Pellagra defines systemic disease as resulting from a marked cellular deficiency of niacin. It is characterized by 4 “D’s”: diarrhea, dermatitis, dementia, and death. Diagnosis of pellagra is difficult in the absence of the skin lesions, and is often facilitated by the presence of characteristic ones. The dermatitis begins as an erythema. Acute pellagra resembles sunburn in its first stages, but tanning occurs more slowly than typically in sunburn.
Pellagra can be common in people who obtain most of their food energy from maize (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. Nixtamalization corrects the niacin deficiency.
The nixtamalization process was very important in the early Mesoamerican diet, as unprocessed maize is deficient in free niacin. A population depending on untreated maize(corn) as a staple food risks malnourishment, and is more likely to develop deficiency diseases such as pellagra.
See Wiki for the nixtamalization process: