Fats used in seasoning and breast cancer risk: a case-control study in Moscow, Russia.

Background: As part of a case-control study of breast cancer conducted in Moscow the relationship between consumption of fat in seasoning and risk of breast cancer was assessed.

Design: The study comprised 92 cases and 110 controls. Cases were newly diagnosed consecutive cases seen at the breast clinic of the Cancer Research Centre of the Russian Academy of Medical Sciences during the year 1990. None of the patients had been previously treated for breast or other cancers and none had distant metastases. Patient were interviewed in the Clinic within two days of admission. Controls were recruited from women visiting their friends and relatives treated in the same Cancer Centre.

Results: Four levels of frequency of use of butter and vegetable oils, and four levels for combined sources were created to evaluate the association between use of fat in seasoning and breast cancer risk. Compared to low use, a non-significant increase in risk was observed for the highest intake of butter (Odds Ratio (OR) = 1.5, 95% Confidence Interval (CI) (0.8, 3.0)). High frequency of use of vegetable oil in seasoning decreased the risk of breast cancer. For the highest category of use, the adjusted OR was 0.2 (95% CI (0.1, 0.5)). Frequent use of mayonnaise also appeared to be associated with a decrease in the risk of breast cancer (OR = 0.1; 95% CI (0.01, 0.4)). For total fat seasoning consumption (vegetable oil+mayonnaise), the adjusted OR for highest category of intake was 0.1 (95% CI (0.03, 0.3)).

Conclusions: The results of the study suggest a negative association between consumption of fat used for seasoning (except butter) and breast cancer risk. This may be a direct effect or due to increased consumption of salad-type vegetables by high consumers of these sources of fats. The topic should be addressed in other studies in different populations.