Systemic inflammation involves the persistent activation of the immune system. Inflammation increases the risk of breast cancer, promotes breast cancer progression, and reduces survival. Inflammation has been shown to lead to the transformation of normal cells into breast cancer cells through the activation of distorted inflammatory signaling. Inflammation has also been shown to be important to the growth of breast cancer stem cells. Breast cancer patients tend to have high levels of markers of inflammation at diagnosis compared to the general population. Diet is believed to be a major contributor to inflammation. Now a new Italian population study has reported that a proinflammatory diet is associated with increased breast cancer risk, and the risk increases with the degree of the diet's inflammatory potential.

Causes of inflammation

Diet and lifestyle choices influence inflammation. Regular exercise can reduce inflammation. High consumption of dietary fiber has been shown to be associated with low levels of inflammation in breast cancer survivors. Generally speaking, a diet abundant in fruits, vegetables and healthy fats reduces inflammation. On the other hand, obesity increases inflammation, as does metabolic syndrome and elevated levels of LDL cholesterol (low-density lipoprotein, the "bad" cholesterol). Cigarette smoking also increases inflammation.

The typical U.S. diet results in a state of chronic inflammation. Undesirable foods include most of the oils used in cooking and baking, as well as more well-known unhealthy foods:

Alcohol
Bacon and other processed meats
Butter
Cheese, full fat
High fructose corn syrup
Lard (shortening)
Milk, full fat, and cream
Concentrated sources of omega-6 fats, such as corn oil, soybean oil, sunflower oil and safflower oil
Partially hydrogenated oil
Red meat such as beef, pork and lamb
Sugar
White bread, white flour pasta, and other highly refined wheat flour products
Well done or fried meat or fish of any type
In other words, some of the most frequently consumed foods in the U.S. (e.g., pizza, hamburgers, fried chicken, conventional pasta, donuts, ice cream, soda) are highly inflammatory. Adding healthy foods to a diet that otherwise tends to promote inflammation is not likely to be a successful strategy for reducing inflammation.

Latest research links proinflammatory diet to increased risk

The study referenced at the beginning of this news story was designed to investigate the association between proinflammatory diets and breast cancer risk. To conduct the study, the authors analyzed data from a large Italian case-control study conducted between 1991 and 1994. The study included 2,569 women with breast cancer and 2,588 cancer-free women (the controls). As part of the study, the women provided information about their diets using a validated 78-item food frequency questionnaire.

The authors assigned an inflammatory index score to the diets of each of the study participants. The women were then divided into five groups (quintiles) based on their scores. The analysis was adjusted for age, level of education, study center, body mass index, number of children, menopausal status, family history of hormone-related cancers and total calorie intake.

Breast cancer risk was found to be linked to the degree to which the women's diets were proinflammatory. Women in quintiles two, three, four and five had risks of breast cancer that were 33%, 37%, 41%, 75% higher, respectively, than women in quintile one. The authors conclude that a proinflammatory diet is associated with increased risk of breast cancer.

Please see our article on inflammation for more information.