The current study established a dose-response relationship between dietary niacin intake and COPD prevalence using a representative sample of adults residing in the United States.
The protective effect of dietary niacin intake on COPD incidence was independent of age, income, smoking, drinking habits, marital status, race, hypertension, and diabetes.
Study participants who reported the highest niacin intake were at a significantly lower risk of COPD than those with the lowest intake. In fact, a clear dose-response relationship was observed between dietary niacin intake and COPD prevalence, in which increasing levels of dietary niacin intake were associated with a consistent reduction in COPD prevalence.
Note the standard "more studies are needed" statement at the end of the results. Few papers about vitamins make it through to publication without this disclaimer..
Nevertheless, further studies are needed to elucidate the precise mechanisms by which niacin intake affects COPD.