In an interview based, case control study of Rheumatoid Arthritis (RA) 168 cases and 137 controls were included. Patients and controls were interviewed with regard to a variety of socioeconomic, medical and dietary factors. During univariate analysis it was found that RA cases consumed significantly less olive oil and fish and adhered more rarely to the dietary restrictions traditional in Orthodox lent than controls. Applying multiple logistic analysis though (by which several variables were controlled for), only the association with olive oil consumption and lent adherence remained significant. More specifically; an increase in olive oil consumption by two times per week, resulted in a Relative Risk (RR) for development of RA of 0.49, whereas adherence to lent during the 27 weeks per year prescribed by the Orthodox Church, resulted in a RR of 0.33. We conclude that olive oil consumption and adherence to Orthodox lent may have a protective effect on the development and/or the severity of RA. This is a hypothesis generated by the present study that needs verification.