Downloaded from http://ebn.bmj.com/ on April 21, 2015 - Published by group.bmj.com
Adult nursing Findings
Cohort study
Higher red meat intake in early adulthood is associated with increased risk of breast cancer; substitution with different protein sources such as legumes and poultry may help 10.1136/eb-2014-101941
Cynthia A Thomson Division of Health Promotion Sciences, Mel & Enid Zuckerman College of Public Health and The University of Arizona Cancer Center, Tucson, Arizona, USA Correspondence to: Dr Cynthia A Thomson, Department of Health Promotion Sciences, Mel & Enid Zuckerman College of Public Health, 1295 N Martin Street, Drachman Hall, Room A260, Tucson, AZ 85721, USA; [email protected]
Commentary on: Farvid MS, Cho E, Chen WY, et al. Dietary protein sources in early adulthood and breast cancer incidence: prospective cohort study. BMJ 2014;348:g3437.
Implications for practice and research ▪ Advice suggests that less red meat and more plant proteins in the diet reduces risk for several chronic diseases, including cancer. Farvid and colleagues’ findings suggest a benefit in relation to breast cancer risk reduction. ▪ Subgroup analysis of protein–breast cancer associations for menopausal status and alternately subtypes of breast cancer could improve knowledge and ultimately how we advise our patients.
Context Evidence evaluating associations between protein consumption and breast cancer provides inconsistent findings and sparse evidence of elevated risk with red meat intake. The study by Farvid and colleagues used data from the Nurses’ Health Study II cohort to improve on earlier work by evaluating dietary exposures earlier in adulthood. The large sample afforded opportunities to elucidate associations by subgroups of menopausal status and also tumour subtypes, analyses that are important to advancing our understanding and possibly explaining prior inconsistencies in findings.
A 22% lower risk for breast cancer in relation to low red meat intake was shown and was also supported in relation to higher red meat intake in adolescence. Poultry intake was associated with a 27% lower risk of postmenopausal, but not premenopausal, breast cancer. No significant differences by tumour subtypes were reported. Evaluation of substitution of red meat for poultry, fish, egg and plant sources of protein suggested legumes and non-red meat proteins were associated with lower risk for breast cancer, an association largely driven by premenopausal disease.
Commentary Inconsistent findings from observational studies continue to challenge the development of dietary recommendations for breast cancer risk reduction. Yet, larger, longer term cohorts with repeated measures of diet during critical periods in breast development (in utero, puberty) and pathological transition ( pregnancy, lactation and menopause), hold potential to expand knowledge and possibly explain the inconsistencies that defy clear understanding. The work by Farvid and colleagues moves us in this direction by exploring earlier adulthood and adolescent diet as exposures of importance. However, even in this case concerns arise with regard to measurement error in self-reported diet and unmeasured confounding. There is high likelihood that the red meat classification assigned is a surrogate for other health behaviours. In fact, women who reported higher red meat intake had a higher body mass index, more frequently reported smoking and described higher energy intake. Aggregate less healthy lifestyle behaviours have been associated with higher breast cancer risk.1 The ‘substitution’ analysis suggested red meat alone may not explain risk, rather alternate proteins may characterise low red meat intake. The energy intake differences are particularly interesting given biomarker-driven analyses that show higher energy intake to be associated with a markedly higher breast cancer risk in postmenopausal women when diet report is not.2 Importantly, the ‘dose’ of red meat at the upper quintile in this cohort averaged 1.6 servings per day, a mean intake above the 0.7 serving-per-day limit suggested by the World Cancer Research Fund and the Association for International Cancer Research.3 In the larger context, there has been a significant reduction in population-level red meat intake over the past 40 years, despite a general rise in breast cancer rates during this era, although this rise is somewhat attributable to broader use of screening mammography. And so the challenge continues. Observational studies will continue to contribute to untangling these complex relationships; however, more rigour is needed in terms of integrating biomarkers, assuring ample sample size to evaluate relevant subgroups and robustly capturing confounders, in order to assure these efforts inform rather than complicate the message to our patients. Primary prevention is difficult to sell. More consistent evidence of a substantial increase in risk, in combination with standard clinical advisement for dietary change, will be critical to changing eating behaviours and reducing breast cancer risk. Competing interests None.
Methods Beyond evaluation of relative risk for breast cancer in relation to red meat, poultry, fish, egg, legume and nut intake, this work evaluated the effect of ‘substitution’ of protein selections in relation to risk, using selfreported diet from Food Frequency Questionnaires. The more interesting attribute of this work was the assessment of early adulthood protein intake as well as retrospective recall of adolescent protein intake in relation to breast cancer risk. The authors interrogated associations by subgroup including menopausal status and tumour subtypes, building on earlier work demonstrating an elevation in risk in premenopausal women with hormone-receptor-positive disease.
44
References 1. Thomson CA, McCullough ML, Wertheim BC, et al. Nutrition and physical activity cancer prevention guidelines, cancer risk, cancer mortality in the Women’s Health Initiative. Cancer Prev Res (Phila) 2014;7:42–53. 2. Prentice RL, Shaw PA, Bingham SA, et al. Biomarker energy and protein consumption and increased cancer risk among postmenopausal women. Am J Epidemiol 2009;169:977–89. 3. AICR/WCRF Recommendations for cancer prevention. http://www.aicr.org/ reduce-your-cancer-risk/recommendations-for-cancer-prevention/ (accessed 12 Aug 2014).
Evid Based Nurs April 2015 | volume 18 | number 2 |
Downloaded from http://ebn.bmj.com/ on April 21, 2015 - Published by group.bmj.com
Higher red meat intake in early adulthood is associated with increased risk of breast cancer; substitution with different protein sources such as legumes and poultry may help Cynthia A Thomson Evid Based Nurs 2015 18: 44 originally published online September 2, 2014
doi: 10.1136/eb-2014-101941 Updated information and services can be found at: http://ebn.bmj.com/content/18/2/44
These include:
References Email alerting service
Topic Collections
This article cites 3 articles, 3 of which you can access for free at: http://ebn.bmj.com/content/18/2/44#BIBL Receive free email alerts when new articles cite this article. Sign up in the box at the top right corner of the online article.
Articles on similar topics can be found in the following collections Diet (215) Adult nursing (43) Breast cancer (63) Menopause (including HRT) (48) Childhood nutrition (125) Childhood nutrition (paediatrics) (71) Health effects of tobacco use (42) Child health (441) Tobacco use (youth) (48) Adolescent health (89) Health education (324) Pregnancy (240) Reproductive medicine (321) Smoking (161) Tobacco use (162)
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/
Adult nursing Findings
Cohort study
Higher red meat intake in early adulthood is associated with increased risk of breast cancer; substitution with different protein sources such as legumes and poultry may help 10.1136/eb-2014-101941
Cynthia A Thomson Division of Health Promotion Sciences, Mel & Enid Zuckerman College of Public Health and The University of Arizona Cancer Center, Tucson, Arizona, USA Correspondence to: Dr Cynthia A Thomson, Department of Health Promotion Sciences, Mel & Enid Zuckerman College of Public Health, 1295 N Martin Street, Drachman Hall, Room A260, Tucson, AZ 85721, USA; [email protected]
Commentary on: Farvid MS, Cho E, Chen WY, et al. Dietary protein sources in early adulthood and breast cancer incidence: prospective cohort study. BMJ 2014;348:g3437.
Implications for practice and research ▪ Advice suggests that less red meat and more plant proteins in the diet reduces risk for several chronic diseases, including cancer. Farvid and colleagues’ findings suggest a benefit in relation to breast cancer risk reduction. ▪ Subgroup analysis of protein–breast cancer associations for menopausal status and alternately subtypes of breast cancer could improve knowledge and ultimately how we advise our patients.
Context Evidence evaluating associations between protein consumption and breast cancer provides inconsistent findings and sparse evidence of elevated risk with red meat intake. The study by Farvid and colleagues used data from the Nurses’ Health Study II cohort to improve on earlier work by evaluating dietary exposures earlier in adulthood. The large sample afforded opportunities to elucidate associations by subgroups of menopausal status and also tumour subtypes, analyses that are important to advancing our understanding and possibly explaining prior inconsistencies in findings.
A 22% lower risk for breast cancer in relation to low red meat intake was shown and was also supported in relation to higher red meat intake in adolescence. Poultry intake was associated with a 27% lower risk of postmenopausal, but not premenopausal, breast cancer. No significant differences by tumour subtypes were reported. Evaluation of substitution of red meat for poultry, fish, egg and plant sources of protein suggested legumes and non-red meat proteins were associated with lower risk for breast cancer, an association largely driven by premenopausal disease.
Commentary Inconsistent findings from observational studies continue to challenge the development of dietary recommendations for breast cancer risk reduction. Yet, larger, longer term cohorts with repeated measures of diet during critical periods in breast development (in utero, puberty) and pathological transition ( pregnancy, lactation and menopause), hold potential to expand knowledge and possibly explain the inconsistencies that defy clear understanding. The work by Farvid and colleagues moves us in this direction by exploring earlier adulthood and adolescent diet as exposures of importance. However, even in this case concerns arise with regard to measurement error in self-reported diet and unmeasured confounding. There is high likelihood that the red meat classification assigned is a surrogate for other health behaviours. In fact, women who reported higher red meat intake had a higher body mass index, more frequently reported smoking and described higher energy intake. Aggregate less healthy lifestyle behaviours have been associated with higher breast cancer risk.1 The ‘substitution’ analysis suggested red meat alone may not explain risk, rather alternate proteins may characterise low red meat intake. The energy intake differences are particularly interesting given biomarker-driven analyses that show higher energy intake to be associated with a markedly higher breast cancer risk in postmenopausal women when diet report is not.2 Importantly, the ‘dose’ of red meat at the upper quintile in this cohort averaged 1.6 servings per day, a mean intake above the 0.7 serving-per-day limit suggested by the World Cancer Research Fund and the Association for International Cancer Research.3 In the larger context, there has been a significant reduction in population-level red meat intake over the past 40 years, despite a general rise in breast cancer rates during this era, although this rise is somewhat attributable to broader use of screening mammography. And so the challenge continues. Observational studies will continue to contribute to untangling these complex relationships; however, more rigour is needed in terms of integrating biomarkers, assuring ample sample size to evaluate relevant subgroups and robustly capturing confounders, in order to assure these efforts inform rather than complicate the message to our patients. Primary prevention is difficult to sell. More consistent evidence of a substantial increase in risk, in combination with standard clinical advisement for dietary change, will be critical to changing eating behaviours and reducing breast cancer risk. Competing interests None.
Methods Beyond evaluation of relative risk for breast cancer in relation to red meat, poultry, fish, egg, legume and nut intake, this work evaluated the effect of ‘substitution’ of protein selections in relation to risk, using selfreported diet from Food Frequency Questionnaires. The more interesting attribute of this work was the assessment of early adulthood protein intake as well as retrospective recall of adolescent protein intake in relation to breast cancer risk. The authors interrogated associations by subgroup including menopausal status and tumour subtypes, building on earlier work demonstrating an elevation in risk in premenopausal women with hormone-receptor-positive disease.
44
References 1. Thomson CA, McCullough ML, Wertheim BC, et al. Nutrition and physical activity cancer prevention guidelines, cancer risk, cancer mortality in the Women’s Health Initiative. Cancer Prev Res (Phila) 2014;7:42–53. 2. Prentice RL, Shaw PA, Bingham SA, et al. Biomarker energy and protein consumption and increased cancer risk among postmenopausal women. Am J Epidemiol 2009;169:977–89. 3. AICR/WCRF Recommendations for cancer prevention. http://www.aicr.org/ reduce-your-cancer-risk/recommendations-for-cancer-prevention/ (accessed 12 Aug 2014).
Evid Based Nurs April 2015 | volume 18 | number 2 |
Downloaded from http://ebn.bmj.com/ on April 21, 2015 - Published by group.bmj.com
Higher red meat intake in early adulthood is associated with increased risk of breast cancer; substitution with different protein sources such as legumes and poultry may help Cynthia A Thomson Evid Based Nurs 2015 18: 44 originally published online September 2, 2014
doi: 10.1136/eb-2014-101941 Updated information and services can be found at: http://ebn.bmj.com/content/18/2/44
These include:
References Email alerting service
Topic Collections
This article cites 3 articles, 3 of which you can access for free at: http://ebn.bmj.com/content/18/2/44#BIBL Receive free email alerts when new articles cite this article. Sign up in the box at the top right corner of the online article.
Articles on similar topics can be found in the following collections Diet (215) Adult nursing (43) Breast cancer (63) Menopause (including HRT) (48) Childhood nutrition (125) Childhood nutrition (paediatrics) (71) Health effects of tobacco use (42) Child health (441) Tobacco use (youth) (48) Adolescent health (89) Health education (324) Pregnancy (240) Reproductive medicine (321) Smoking (161) Tobacco use (162)
Notes
To request permissions go to: http://group.bmj.com/group/rights-licensing/permissions To order reprints go to: http://journals.bmj.com/cgi/reprintform To subscribe to BMJ go to: http://group.bmj.com/subscribe/
