Dietary factors in relation to rheumatoid arthritis: a role for olive oil and cooked vegetables?

BACKGROUND: Although several studies showed that risk of rheumatoid arthritis (RA) is inversely associated with consumption of n-3 fatty acids, the one study showing that olive oil may have a protective role has not yet been confirmed.
OBJECTIVE: We examined the relation between dietary factors and risk of RA in persons from southern Greece.
DESIGN: We studied 145 RA patients and 188 control subjects who provided information on demographic and socioeconomic variables, prior medical and family history, and present disease status. Subjects responded to an interviewer-administered, validated, food-frequency questionnaire that assessed the consumption of >100 food items. We calculated chi-square statistics for linear trend and odds ratios (ORs) for the development of RA in relation to the consumption of olive oil, fish, vegetables, and a series of food groups classified in quartiles.
RESULTS: Risk of developing RA was inversely and significantly associated only with cooked vegetables (OR: 0.39) and olive oil (OR: 0.39) by univariate analysis. A significant trend was observed with increasing olive oil (chi-square: 4.28; P = 0.03) and cooked vegetable (chi-square: 10. 48; P = 0.001) consumption. Multiple logistic regression analysis models confirmed the independent and inverse association between olive oil or cooked vegetable consumption and risk of RA (OR: 0.38 and 0.24, respectively).
CONCLUSIONS: Consumption of both cooked vegetables and olive oil was inversely and independently associated with risk of RA in this population. Further research is needed to elucidate the underlying mechanisms of this finding, which may include the antioxidant properties or the high n-9 fatty acid content of the olive oil.