Reduced cancer risk in vegetarians: an analysis of recent reports

Cancer Management and Research Dovepress open access to scientific and medical research Review Cancer Management and Research downloaded from https://www.dovepress.com/ by 5.135.254.153 on 12-Jul-2018 For personal use only. Open Access Full Text Article Reduced cancer risk in vegetarians: an analysis of recent reports This article was published in the following Dove Press journal: Cancer Management and Research 20 December 2010 Number of times this article has been viewed Amy Joy Lanou 1 Barbara Svenson 2 Department of Health and Wellness, Ramsey Library, University of North Carolina Asheville, Asheville, NC, USA 1 2 Introduction Correspondence: Amy Joy Lanou Department of Health and Wellness, CPO# 2730, University of North Carolina Asheville, One University Heights, Asheville, North Carolina 28804, USA Tel +1 828 250 2317 Fax +1 828 250 3856 Email submit your manuscript | www.dovepress.com Dovepress DOI: 10.2147/CMR.S6910 Powered by TCPDF (www.tcpdf.org) Abstract: This report reviews current evidence regarding the relationship between vegetarian eating patterns and cancer risk. Although plant-based diets including vegetarian and vegan diets are generally considered to be cancer protective, very few studies have directly addressed this question. Most large prospective observational studies show that vegetarian diets are at least modestly cancer protective (10%–12% reduction in overall cancer risk) although results for specific cancers are less clear. No long-term randomized clinical trials have been conducted to address this relationship. However, a broad body of evidence links specific plant foods such as fruits and vegetables, plant constituents such as fiber, antioxidants and other phytochemicals, and achieving and maintaining a healthy weight to reduced risk of cancer diagnosis and recurrence. Also, research links the consumption of meat, especially red and processed meats, to increased risk of several types of cancer. Vegetarian and vegan diets increase beneficial plant foods and plant constituents, eliminate the intake of red and processed meat, and aid in achieving and maintaining a healthy weight. The direct and indirect evidence taken together suggests that vegetarian diets are a useful strategy for reducing risk of cancer. Keywords: diet, vegan, prevention Despite widespread research efforts and increasing treatment options, cancer remains a leading cause of death worldwide. In 2004, cancer accounted for 13% of deaths worldwide (∼7.4 million people) with projections estimating an increase to 12 million deaths in 2030.1 Yet cancer is still considered a largely preventable disease with estimates of up to 90%–95% of the risk with roots in environment and lifestyle.2 Important lifestyle factors include tobacco use, diet, alcohol, sun exposure, environmental pollutants, infections, stress, obesity, and physical inactivity. Dietary factors were estimated to be responsible for 30%–35% of all cancers in the US in 1981.3 More recent estimates keep 35% as the overall impact of suboptimal dietary choices, but more specifically note that diet may be linked to as many as 70% of cases of colorectal and prostate cancer, 50% of cases for breast, endometrial, pancreatic, and gallbladder cancers, but only to about 20% of cases of lung, bladder, mouth, and esophageal cancers.4 While it is clear that dietary patterns and choices are important modulators of cancer risk, the question remains just what dietary pattern is optimal for primary prevention of cancer. The purpose, then, of this report is to review current evidence regarding the relationship between vegetarian eating patterns and cancer risk. Vegetarian eating patterns are defined as those that exclude all meats (beef, pork, lamb, poultry, fish, etc). Some vegetarians also exclude eggs but not dairy products, lacto vegetarians, some Cancer Management and Research 2011:3 1–8 © 2011 Lanou and Svenson, publisher and licensee Dove Medical Press Ltd. This is an Open Access article which permits unrestricted noncommercial use, provided the original work is properly cited. 1 Cancer Management and Research downloaded from https://www.dovepress.com/ by 5.135.254.153 on 12-Jul-2018 For personal use only. Lanou and Svenson exclude dairy products but not eggs, ovo vegetarians, and some exclude all foods from animal sources (all meats, dairy, eggs, and other animal derived foods including gelatin, honey, casein, lactose, etc), vegans. Many individuals worldwide for cultural or socio economic reasons consume diets that contain very small to modest amounts of meat from any source. Some individuals may exclude red meat or some but not all types of meat (for example fish). While these diets are clearly based on plant foods, and therefore often deemed “plant-based diets”, they are not vegetarian diets. Much of the evidence used to support the use of vegetarian diets for cancer risk reduction come from populations consuming plant-based diets and from studies that identify beneficial effects of specific foods or nutrients from plant sources. A brief overview of this literature is provided and then compared with the findings of studies specifically addressing the question of whether vegetarian dietary patterns reduce cancer risk. Plant-based dietary patterns and cancer risk Epidemiologic evidence from the Cornell–Oxford China Study conducted in the 1970s and 1980s demonstrated important relationships between dietary patterns and cancer risk and highlighted the importance of diets rich in whole plant foods for cancer prevention.5 The magnitude of difference in cancer risk within China ranges by more than a factor of 10 across the 65 counties studied. Campbell and colleagues found that a group of diseases (notably cancers of the colon, lung, breast, brain, as well as leukemia, cardiovascular disease, diabetes) were all associated with a diet of nutritional extravagance – meaning a diet that was associated with higher levels of blood cholesterol and blood urea nitrogen. These risk markers were directly associated with the intake of milk, meat, eggs, dietary fat, and animal protein and inversely associated with dietary fiber and legumes. In addition, breast cancer mortality increased with increasing dietary fat concentration and blood cholesterol levels. Higher blood levels of vitamin C and beta carotene, antioxidants provided by plant foods, were associated with lower rates of several cancers.5 In another report, Campbell and Chen make the strong statement that “there appears to be no threshold of plant food enrichment or minimization of fat intake beyond which further disease prevention does not occur”. And they add that in the context of diets in China the addition of small amounts of foods from animal sources is associated with increased risk of chronic degenerative diseases including cancer.6 2 Powered by TCPDF (www.tcpdf.org) submit your manuscript | www.dovepress.com Dovepress Dovepress Similarly, Carroll and col (...truncated)