Many of Dr. Greenwood Sr.'s papers refer to pellagra, a disease caused by a lack of the vitamin niacin. Recognized for its symptoms beginning with the letter D, diarrhea, dermatitis, dementia, and sometimes death, its etiology was poorly understood when it was epidemic in the American South in the early 1900s. Poverty and corn consumption were linked as related factors, but it wasn't until the 1920s that Dr. Joseph Goldberger established a diverse diet as preventative, and until the 1930s that niacin deficiency was identified as a cause.

What We Know About The Cause and Treatment of Pellagra

MS029 James Greenwood Sr. and Jr., MD's papers (Series 1, Box 2, Folder 17), John P McGovern Historical Collections and Research Center, Houston Academy of Medicine-Texas Medical Center Library