The study referenced above was designed to investigate the links between specific dietary fat intake and risk of breast cancer. The study included postmenopausal (age 50 to 76) members of the VITamins And Lifestyle (VITAL) Cohort. The women completed a food frequency questionnaire upon enrollment in 2000-2002. A total of 772 of the participants developed breast cancer during follow up.
Among polyunsaturated fatty acids (PUFAs), intakes of the marine fatty acids EPA and DHA were found to be associated with reduced breast cancer risk. Overall intake of monounsaturated fats (MUFAs) was associated with increased breast cancer risk — women in the highest fifth of intake had 1.61 times the risk of breast cancer as those in the lowest quintile. High intake of the MUFAs myristoleic acid (biosynthesized from myristic acid, which is found in palm kernel oil, coconut oil, and butter fat) and erucic acid (mustard oil, rapeseed oil) conferred particularly high risk.
Overall intake of saturated fat appeared to be associated with increased risk of breast cancer (women in the highest fifth of intake had 1.47 times the risk), however this result barely reached statistical significance. High intake of the saturated fats (palmitic acid, palm oil, red meat, butter, lard), margaric acid (beef, lamb, high-fat dairy), and stearic acid (red meat, lard, butter) conferred significant high risk.
Total trans-fatty acid and polyunsaturated acid (a broad category of unsaturated fats that includes omega-3, omega-6 and omega-9 fatty acids) intakes were not associated with breast cancer. However, high intake of the trans-fatty acid linolelaidic acid (the trans fatty acid homolog of linoleic acid found in partially hydrogenated vegetable oils) was associated with increased risk. The authors conclude that different fats have different associations with postmenopausal breast cancer risk.
Note that while fatty fish such as salmon are recommended to protect against breast cancer and its recurrence, recent research suggests that fish oil supplements should not be used during chemotherapy.
Please see our article on fatty fish for more information.