We take the case of betel nut use in Bangladesh to investigate the relationship between betel quid and chronic health outcomes, and to consider local disease ecology and evolutionary explanations for consumption of this psychoactive substance.<h4>Methodology</h4>We analyzed data from a random sample of 765 women and 499 men in Matlab, Bangladesh, to assess associations between betel quid use and anemia, type 2 diabetes (T2D), hypertension, and inflammation (C-reactive protein, CRP).<h4>Results</h4>Betel quid use was associated with all health outcomes investigated. The gene discussed is CRP; the disease is anemia (phenotype).