Final answer:
Pellagra is a disease caused by a deficiency of niacin (vitamin B3) and tryptophan, largely affecting the poor in the early 1900s, especially in areas where corn was the main diet. Wealthier individuals had a more varied diet and were less prone to the disease. The identification and fortification of food with niacin helped reduce pellagra cases.
Step-by-step explanation:
Pellagra is a disease caused by a deficiency of niacin (vitamin B3) and tryptophan. It commonly affected people in the early 1900s, particularly in rural areas of the southern United States, Italy, and parts of Africa. The disease was more prevalent among the poor due to their limited diet that typically lacked niacin-rich foods.
In the early 1900s, pellagra was often seen in communities where corn was the staple food because corn is low in niacin and tryptophan, unless properly treated with lime to release the niacin. People from higher social classes (nobles and gentry) were less affected by pellagra because they had a more varied and nutritious diet, which included niacin-rich foods like meat, poultry, fish, and fortified breads.
Those who lived in poverty, therefore, had a greater risk of developing pellagra due to their limited access to these essential nutrients. It wasn't until niacin was identified as the preventive element and fortification of foods began that the prevalence of pellagra significantly decreased.