How could Dr.Goldberger have provided more convincing evidence of the relationship between pellagra and nutrition?

Dr. Goldberger could have provided more convincing evidence of the relationship between pellagra and nutrition by conducting controlled dietary experiments with diverse populations, ensuring that one group received a diet rich in niacin and other essential nutrients while the other group maintained a diet deficient in these nutrients. Additionally, he could have documented the onset and resolution of pellagra symptoms in relation to dietary changes over time, alongside rigorous statistical analysis to establish a clear correlation. Including biochemical studies to measure niacin levels in affected individuals could have further strengthened his findings.