Expert estimates suggest that women eating more poultry, fish, nuts and legumes and less red meat might have lower risk
Higher red meat intake in early adulthood might be associated with an increased risk of breast cancer, and women who eat more legumes (such as peas, beans and lentils), poultry, nuts and fish might be at lower risk in later life, suggests a paper published on bmj.com today.
- Higher consumption of total red meat during early adulthood was associated with
an increased risk of breast cancer
- Higher consumption of poultry during early adulthood was related to
a lower incidence of breast cancer in postmenopausal women
- Substituting a combination of poultry, fish, legumes, and nuts as protein sources
for red meat during early life seems beneficial for the prevention of breast cancer.
So far, studies have suggested no significant association between red meat intake and breast cancer. However, most have been based on diet during midlife and later, and many lines of evidence suggest that some exposures, potentially including dietary factors, may have greater effects on the development of breast cancer during early adulthood.
So a team of US researchers investigated the association between dietary protein sources in early adulthood and risk of breast cancer.
They analysed data from 88,803 premenopausal women (aged 26 to 45) taking part in the Nurses’ Health Study II who completed a questionnaire on diet in 1991.
Red meat items included unprocessed red meat (beef, pork, or lamb and hamburger) and processed red meat (such as hot dogs, bacon and sausage); poultry included chicken and turkey; fish included tuna, salmon, mackerel, sardines; legumes included beans, lentils and peas; and nuts.
Nine categories of intake frequency were recorded from “never or less than once per month” to “six or more per day.”
Factors such as age, height, weight, race, family history of breast cancer, history of benign breast disease, smoking, menopausal status, hormone and oral contraceptive use were taken into account. Adolescent food intake was also measured and included foods that were commonly eaten from 1960 to 1980, when these women would have been in high school.
Medical records identified 2,830 cases of breast cancer during 20 years of follow-up.
Putting these real life data into a statistical model allowed the researchers to estimate breast cancer risks for women with different diets. They estimated that, for each step-by-step increase in the women’s consumption of red meat, there was a step-by-step increase in the risk of getting breast cancer over the 20 year study period.
This translated to an estimate that higher intake of red meat was associated with a 22% increased risk of breast cancer overall. Each additional serving per day of red meat was associated with a 13% increase in risk of breast cancer (12% in premenopausal and 8% in postmenopausal women).
In contrast, estimates showed a lower risk of breast cancer in postmenopausal women with higher consumption of poultry. Substituting one serving per day of poultry for one serving per day of red meat – in the statistical model – was associated with a 17% lower risk of breast cancer overall and a 24% lower risk of postmenopausal breast cancer.
Furthermore, substituting one serving per day of combined legumes, nuts, poultry, and fish for one serving per day of red meat was associated with a 14% lower risk of breast cancer overall and premenopausal breast cancer.
They comment that:
Legumes contain several components such as fiber and phytoestrogen, which have been
negatively associated with breast cancer incidence.
Interestingly, when looking at postmenopausal women, higher consumption of poultry was related to a lower incidence of breast cancer for this population group.
When taking all the factors (age, height, weight, race, family history of breast cancer, history of benign breast disease, smoking, menopausal status, hormone and oral contraceptive use) into consideration, only oral contraceptive use modified the findings. For each serving/day of total red meat, the risk of breast cancer was higher among women who currently used oral contraceptives and moderately higher in women who were former users.
However, this finding, with respect to oral contraceptive use, may or may not be statistically significant as a previous study reported in the Lancet* found that, all the studies were showing that oral contraceptive use seemed to increase the rate of diagnosis not the rate of occurrence, and this could be down to factors such as more frequent medical exams for women using oral contraceptives:
The relation observed between breast cancer risk and hormone exposure is unusual, and it is not possible to infer from these data whether it is due to an earlier diagnosis of breast cancer in ever-users, the biological effects of hormonal contraceptives, or a combination of reasons.
Interpretation: Women who are currently using combined oral contraceptives or have used them in the past 10 years are at a slightly increased risk of having breast cancer diagnosed, although the additional cancers diagnosed tend to be localised to the breast. There is no evidence of an increase in the risk of having breast cancer diagnosed 10 or more years after cessation of use, and the cancers diagnosed then are less advanced clinically than the cancers diagnosed in never-users. Source
However, the authors of this current study do conclude that higher red meat intake in early adulthood “may be a risk factor for breast cancer, and replacing red meat with a combination of legumes, poultry, nuts and fish may reduce the risk of breast cancer.”
Further study of the relation between diet in early adulthood and risk of breast cancer is needed, they add.
For further information:
Maryam S Farvid Takemi fellow, and associate professor, Eunyoung Cho associate professor,
Wendy Y Chen assistant professor, A Heather Eliassen assistant professor, Walter C Willett professor
Collaborative Group on Hormonal Factors in Breast Cancer