Dairy Products and Breast Cancer - Essay Example

1. Dairy Products and Breast Cancer: A Literature Review of Three Epidemiological Research Studies Introduction: The purpose of epidemiological evidence is to relate causes to the effects they produce; all three pieces of research can be said to partially achieve this outcome. That such evidence is insufficient on its own to establish causality becomes obvious in these particular studies, and in the final analysis, the links in humans between dairy products and their positive or detrimental effect on breast cancer development, appear somewhat tenuous. After close examination of each report, the conclusion must stand that there are too many biases, variables and possible areas for misinformation to prove categorically the good or bad impacts of dairy food on breast cancer development or its prevention. In their literature review of this topic, Moorman and Terry, (2004) put it in a nutshell, 溺ost of the studies reviewed showed no consistent pattern of increased or decreased breast cancer risk with a high consumption of dairy products and as a whole or when broken down into high-fat and low-fat dairy products, milk, cheese or butter.(Moorman & Terry, American Journal of Clinical Nutrition) This would seem to be an accurate assessment, despite having been published slightly before two of the studies under present scrutiny, and alongside this, they need to be looked at with a view to determining how well they inform and whether, after reading, a better understanding of the topic is achieved. Critical Reviews: This section will summarise, in chronological order, each of the studies and include comments on their effectiveness and accessibility for learning purposes. 1. Intake of Dairy Products, Calcium, and Vitamin D and Risk of Breast Cancer, (2002) (Shin, Holmes, Hankinson, Wu, Colditz & Willett, September 2002.) Summary: This is an example of a longitudinal cohort study, where researchers evaluated data from the Nurses Health Study, with 88,691 participants over a period from 1980 till May 1996. 2. Using food frequency questionnaires, the purpose was not to identify risks from high intake of dairy foods, calcium and vitamin D, but, somewhat confusingly is stated as 鍍o evaluate whether high intake of dairy products, calcium or vitamin D is associated with reduced risk of breast cancerand to 電isassociate the effects of calcium and vitamin D from those of milk and dairy products.(Shin, Holmes, Hankinson, Wu, Colditz, & Willett, 2002). After identifying 3,482 pre-post- and indefinable- menopausal- status women, with 妬ncident invasive breast cancer(Shin et al) they examined and compared high and low daily intakes, high and low fat dairy products and milks, intake of calcium in dairy foods and vitamin D, not clearly connected but absorbed in other ways such as via supplements. They used two year time increments and two sided statistical tests. The researchers concluded that there was 渡o association between intake of dairy products and breast cancer in post menopausal women.(Shin et al). With premenopausal women, a high intake of low fat dairy foods, in particular low-fat milk, was linked to reduced risk of breast cancer, as were calcium and vitamin D, but these were difficult to link as independent factors in breast cancer. Critical Review: Most of the study is easy to interpret, even for non-professionals, giving a clear picture of what happened and how. The statistical analysis, because of the numbers, timespan and variables involved, seem complex at first. But the examples cited help to make it understandable. 擢or example, the incidence of breast cancer from 1980 through 1984 was related to the dietary information from the 1980 questionnaire, and the incidence of breast cancer from 1984 through 1986 was related to the average intake from the 1980 and 1984 questionnaires. (Shin, et al) The tables included are well laid out, with accompanying notes to clarify the meanings. But the study appears to rely heavily on the reported intakes by participants of the foods and supplements under scrutiny. Once breast cancer sufferers were identified, all variables which are considered to contribute to the disease, such as the use of contraceptive pills, hormonal imbalances, obesity, eating disorders, were not fully explored. The exclusion of those 登f uncertain menopausal status 3. ( 310 women) seemed based on a need for tidy outcomes and no explanation as to reasons why is given. Other relevant variables not fully considered or explained were, numbers of children, possible vitamin deficiencies, why sunlight and residential areas impact; they are only mentioned in passing. The biggest problem with the study is the reliance on self-reporting, and although scientific statistical analysis is used, (e.g. Pooled logistical regression to estimate multivariable relative risks) Shin et al, and attempts made to quantify portion size, the fact remains that such reliance means data may be inaccurate. Omitting, or not fully exploring all potential cancer risk factors missed useful scientific links. On the positive side, the numbers and length of time taken, are strong support for the consistency of the research, however inconclusive the final evidence may be. “their independent associations [...]are difficult to distinguish.(Shin et al) Because everything was collected using records, questionnaires and official input, this study seemed to operate at a distance from the human element, as if figures and not real people mattered most. Further study is needed, as stated by the researchers. They did not find enough evidence to support their hypothesis, and concluded with some ambiguity. 2.Dietary Intake of Conjugated Linoleic Acids and Risk of Premenopausal and Postmenopausal Breast Cancer, Western New York Exposures and Breast Cancer Study (WEB Study) (2004) (McCann, Ip, Ip, McGuire, Muti, Edge, Trevisan & Freudenheim, 2004) Summary: This case control research study set out to examine how specific fatty acid can be related to the causes of breast cancer. In animal studies, conjugated linoleic acids (CLAs) found in dairy foods and ruminant meats, appeared to be powerful anticarcinogenics, so the researchers wanted to examine the links between their intake and cancer links or otherwise, in pre- and postmenopausal women. They used 1,122 women with breast cancers, and 2,036 controls frequency, matching cases to age, race and country of residence, gathering data on diet from self administered food frequency questionnaires and personal interviews. Total CLAs and 9c, 11f 4. 18.2 isomer of CLA were studied in particular, alongside other cancer risk factors. They concluded that they found little association between CLA intakes related to overall breast cancer risk, but risks of ER-negative breast cancer among premenopausal women were reduced. In fact, they surmised that CLA intake might even reduce the risk as it may well retard the growth of certain types of tumours. Critical Review: As a whole, this study was very clear and easy to understand from the outset. The Introduction made sense of why the study was conducted, as well as offering excellent explanations on CLA , estrogen receptors, cancers and the life situations of the women studied. The comparisons with other studies are helpful in informing and rationalising their exact hypothesis. 哲o studies to date have included an examination of tumour characteristics; although previous studies do not strongly support an overall protective effect by CLA, tumour biology might be affected. (McCann, Ip, Ip, McGuire, Muti, Edge, Trevisan & Freudenheim) (2004) The Materials and Methods, and use of trustworthy professionals to conduct the research help to make it a credible study. The scientific and biological facts are clear and easy to understand. The Results clarify processes and findings, well supported by Table 1 which is easy to interpret. The Discussion expands the purposes, providing an honest explanation, clearly defining the findings and raising some important issues for future research, stated here: 滴igher CLA intakes could have important implications for reducing the burden of breast cancer by retarding the development of a less prognostically favourable tumour.(McCann et al) No definite links emerged 澱etween higher intakes of total CLA and 9, 11 CLA[...]to overall breast cancer risk, risks of ER-negative breast cancer among premenopausal women were reduced.(McCann et al). The research study provides good information on the topic in a way that anyone 5. could understand, despite limitations. These may be that numbers were low and concentrated in a relatively small geographical area and ethnic background. It might be hypothesized that larger random sampling would proved more universally applicable results. Again, the use of self-reporting over a period of five years could produce scientific inaccuracies, but the additional methods of in-depth data gathering by interviews and use of health professionals, gives the study more credibility than the larger cohort study, making it more relevant to sufferers and professionals alike. 3. Effects of milk fermented by Lactobacillus helveticus R389 on a murine breast cancer model (2005). (deLeBlanc, Matar, LeBlanc and Perdigon, 2005) Summary: The aim of this experimental study, using 5 groups of 25-30 mice, was to test the hypothesis that lactic acid bacteria had a positive effect in delaying or halting the development of breast cancer tumours. They used L. helveticus R389, and a variant thereof, L. 89, to carry out the experiment, feeding the mice with either of the treated milks, apart from one control group for between 2 7 days before injecting all with tumour cells. After four days, the mice were fed on a cyclical basis with the treated milks and monitoring of the results found that either bacterial strain delayed or stopped tumour development. Thus the study showed that after seven days of treatment, the antitumour immune response was triggered, and in particular, L. helveticus R389 deminished cytokines by its immunoregulatory capacity. The relationship between immune and endocrine systems were explored, and findings showed the effects on the cellular balance which impacts on the growth or retardation of breast and other cancers. They concluded that this was 砺ery important in oestrogen-dependent tumour and induced cellular apoptosis. (LeBlanc, Matar, LeBlanc, & Perdigon, 2005) In other words, the lactic acid bacteria in treated milk helped to achieve the homeostasis which prevents the growth of mutant cancer cells. Critical Review: There is excellent background, scientific information and references to other studies. It covers several disciplines of medical science, and identifies the links between 6. nutritional and medical research. But it appears aimed at professionals in many fields, including immunology, oncology, endocrinology and biochemistry, to name a few. This is important scientific information, not easy for the layman to interpret. As it is posted online at breast-cancer-research.com, explanations of terminology would make it more understandable. Detailed explanations of the Methods do help to clarify meaning. Sampling activity, is described in complicated and scientific ways; simplified explanations supporting the footnotes, would be more helpful. In fairness, the Statistical Analysis is short and concise, with Figure 1 and the explanations at the beginning of Results and Discussion not too hard to interpret. A shorter and simplified summary, included in the Discussion and Results would have been better. Figure 2 is not large enough to see the results clearly, enlarging it would help towards a better understanding of the technical data. The scientific detail in the section is difficult to understand, as it is technical and repetitive. References to other studies (pR482) should state whether these are human or animal. The Conclusion is particularly good, summing up and defining the outcomes. It highlights how important the results may be in the prevention and retardation of breast cancer. But the presentation of the research is one of its limitations. While it provides positive,scientifically proven results of the possibilities of the use of lactobacillus in enhancing the immune system, what needs to be honestly and more clearly stated throughout, is that the subjects were mice, and clearer links to implications for humans are required. What is also needed, is some indication of proportional intake of the lactobacillus for humans and the fact that the volume used in research may be insupportable in this form, to achieve effective positive effects. Because this research is freely accessible, this should be included to put its experimental nature into perspective. However, this research, using sound scientific methods, achieved what it set out to prove. Conclusion: In each of the studies, the qualifications, veracity and professional integrity of the researchers is in no doubt. Total confidentiality of participants is maintained throughout, and the acknowledgments of the work of others are consistently presented. The two studies involving 7. human subjects, while unable to reach definite conclusions, brought some rays of hope of finding ways to combat this dreadful disease, not least through the use of some dairy products. Unfortunately, the potential for mis-reporting on food and vitamin intakes, the different lifestyles and regional locations, and various other factors, suggest that the difficulties identified by researchers will not be easily overcome and that the evidence as a result of such studies to date, is not consistent enough. With regard to the mice study, the amount of treated milk fed to the animals, would be proportionately too great for most humans to consume in that form. But the findings suggest a more hopeful outcome, with the need for further research. On a personal level, the exercise has been a useful learning experience in various ways. It has provided insight into different models of research and how styles of presentation can assist or hinder understanding. There is a long way to go and a need for a wider vision in this field of study. Further learning has occurred when the need arose to investigate unfamiliar terminology or processes, which is a positive result from the exercise as a whole. Reference List Krishnakumar, V. (2001) Probiotic Cultures Opportunities and Threats p 3- 8. GIRACT Market Report. Retrieved October 20, 2006 from http://www.giract.com/presspapers/giractprobioticarticle-pdf Low Fat Diet Not a Cure-All. (n.d.) Nutrition Source. Harvard School of Public Health. Retrieved October 19, 2006 from http://www.hsph.harvard.edu/nutritionsource/low_fat.html McCann, S. E., Ip, C., Ip, M. M., McGuire, M. K., Muti, P., Edge, S. E., et al (2004) Dietary Intake of Conjugated Linoleic Acids and Risk of Premenopausal and Postmenopausal Breast Cancer, Western New York Exposure and Breast Cancer Study (WEB Study). Cancer Epidemiology, Biomarkers and Prevention, 2004, 13 (9) September 2004 Moorman, P. G. & Terry, P. D. (2004). Consumption of dairy products and the risk of breast cancer: a review of the literature. American Journal of Clinical Nutrition, Vol. 80, No. 1, 5-14, July 2004. Retrieved October 20, 2006 from http://www.ajcn.org/cgi/content/full/80/1/5 deMoreno de LeBlanc, A., Matar, C., LeBlanc, N., & Perdigon, G. (2005). Effects of milk fermented by Lactobacillus helveticus R389 on a murine breast cancer model. Retrieved October 19, 2006 from http://breast-cancer-research.com/content/7/4/R477 Shin, M-H., Holmes, M. D., Hankinson, S. E., Wu, K., Colditz, G. A., & Willett, W. C. (2002) Intake of Dairy Products, Calcium and Vitamin D and Risk of Breast Cancer. Journal of the National Cancer Institute. Vol. 94, No. 17, September 4, 2002. Read More