There are many known risk factors that can increase the likelihood of developing breast cancer - including gender, age, family history, obesity and alcohol consumption. Now, a study published in BMJ has found that higher red meat intake during early adulthood could well be one of these risk factors.
There are two types of breast cancer: non-invasive breast cancer, which remains in situ within the breast tissue, and invasive breast cancer, which spreads to other parts of the body. Breast cancer is the most common invasive cancer among women worldwide.
The American Cancer Society (ACS) state that breast cancer is the second highest cause of cancer deaths in women.
And the National Cancer Institute (NCI) report that in 2014, the following new cases and deaths are estimated:
- 232,670 new cases (female); 2,360 (male)
- 40,000 deaths (female); 430 (male).
A different research focus
Most dietary studies in this area of research have focused on the diet of individuals during midlife and later, and have found no significant connection between the risk of breast cancer and consumption of red meat.
The new study, from a team of US-based researchers, set out to investigate the association of dietary protein sources in early adulthood with the risk of breast cancer, as other previous work has indicated that lifestyle factors, including diet, may have a greater impact during early adulthood on the chances of developing breast cancer.
Data from 88,803 premenopausal women (aged 26 to 45) was analyzed from a questionnaire on diet completed as part of the Nurses' Health Study II in 1991.
A previous analysis of this data made a positive association between red meat intake and the risk of breast cancer, but it was unclear whether these findings were a result of the early age at dietary assessment or the relatively early age of women upon breast cancer diagnosis.
High consumption of red meat such as steak during young adulthood could increase the likelihood of breast cancer.
The new study provides an updated analysis of this data, with a longer period of follow-up, approximately three times as many cases of breast cancer and additional paths of investigation. In addition to different types of red meat consumption, researchers also examined the association between breast cancer and other protein-rich foods.
The diet questionnaire listed different types of food against nine categories of intake frequency, ranging from "never or less than once per month" to "six or more per day." The foods included unprocessed and processed red meats, poultry, fish, legumes, nuts, as well as foods that were commonly eaten from 1960 to 1980 when the participants would have been in high school.
Along with adolescent food intake, other health factors were taken into account when compiling the results, such as height, weight, personal and family history, race and smoking habits.
During 20 years of follow-up investigation, the researchers identified 2,830 cases of breast cancer from their participants' medical records.
How diet affected the likelihood of breast cancer
The study found that a higher intake of red meat products during early adulthood was associated with a 22% increased risk of breast cancer.
Conversely, a higher intake of poultry during early adulthood was associated with a lower incidence of breast cancer in postmenopausal women.
Replacing one portion of red meat a day with a portion of another high-protein food such as legumes, poultry, nuts and fish was associated with a 14% lower risk of breast cancer overall and premenopausal breast cancer.
The researchers conclude that "replacing red meat with a combination of legumes, poultry, nuts and fish may reduce the risk of breast cancer."
This is also recommended by the ACS, who have the following nutritional advice:
- Eat a healthy diet, with an emphasis on plant foods
- Limit how much processed meat and red meat you eat
- Limit your intake of processed meats such as bacon, sausage, lunch meats and hot dogs
- Choose fish, poultry or beans instead of red meat (beef, pork and lamb)
- If you eat red meat, choose lean cuts and eat smaller portions
- Prepare meat, poultry and fish by baking, broiling or poaching rather than by frying or charbroiling.
Dr. Maryam Farvid, one of the researchers from the study, told Medical News Today that they will continue their research by "evaluating the association between other food items and nutrients intake in early adulthood as well as during adolescence, and risk of breast cancer before and after menopause."
Further research is needed into this area, but for now, this study suggests that we should emphasize the importance of early adulthood with regards to our health in the long-term, along with the impact of diet.
For more information about breast cancer, visit our comprehensive Knowledge Center article.