Vegans are less likely to develop overall and female-specific cancer; lacto-ovo diet confers protection from gastrointestinal cancers
By Barry Manembu
LOMA LINDA, Calif.– New research on the Seventh-day Adventist population suggests that, in comparison to non-vegetarian Adventists, vegans are less likely to be diagnosed with cancer overall (combination of all body sites) and also female-specific cancers (i.e., breast cancer, uterine cancer, ovarian and other genital cancers). It also shows that lacto-ovo-vegetarians are protected from cancers of the gastrointestinal tract (cancers such as colon, stomach, pancreas, etc, as a group).
Certain previous research studies have suggested that vegetarians are less likely to develop cancer as compared to non-vegetarians. Other studies,often from different countries, have not found such an advantage.This lackof clarity may result from the heterogeneity of vegetarian diets between subjectsand in different countries, as they may range greatly in the ratio of dairy foods to plant food eaten, the quality and identity of the plant foods, cooking methods, the limitations of measures used to quantify dietary intake, as well as other associated lifestyle factors that may produce an impact on the risk of cancer.
"These findings should give us a better understanding of the relationships between specific vegetarian subtypes with specific cancers," says Yessenia Tantamango-Bartley, MD, DrPH, a faculty at Loma Linda University's School of Public Health and postdoctoral fellow with the Adventist Health Study-2 (AHS-2). She is the lead authorof the research, recently published in the November online issue of Cancer Epidemiology Biomarkers Prevention.
The findings used prospective data (following persons over time) of 69,120Seventh-day Adventists participating in the Adventist Health Study-2 (AHS-2). AHS-2 began in 2002 as a study among Adventist church members throughout the USA and Canada. Thescope of this study is toinvestigate the role of various foods and nutrients, other lifestyle factors and metabolic risk indicators that maybe involved in cancer causation. All AHS-2 participants filled out a questionnaire that asked how often they consumed over 200 foods. Participants were then classified into a dietary category (vegan, lacto-ovo-vegetarian, pesco-vegetarian, semi-vegetarian, non-vegetarian) based on their responses.
There are at least three strong features of this research. First, researchers were able to categorize the dietary patterns into specific vegetarian subtypes. "Other studies may have used abroad category for vegetarian diet, namely plant-based diet. In our study, we divide vegetarians into vegans (consume no meat, poultry, fish, and dairy/eggs),lacto-ovo(consume no meat, poultry and fish), and pesco (consume no meat and poultry)," says Karen Jaceldo-Siegl, DrPH, head of AHS-2 nutrition section."By doing this we can study which specific diet has more or less protection from certain cancers."
Second, researchers were also able to validate incident cancers (2,939 found) with cancer registries in 38 U.S. states and Washington D.C. -- whereas many other studies match cancer cases in only one or a few states -- producing results that may indicate a nation-wide trend.
Third, the unique lifestyle of the subjects (Seventh-day Adventists), with a widevariety of dietary habits; also a very low percentage of alcohol consumption or cigarette smoking, which reduces the possibility of confounding by these non-dietary factors.
Overall, the study found that:
- There was an association between vegetarianism, as a single category (and this was clearest in the vegan diet), and all cancers, indicating mild but convincing protection for overall cancer risk;
- Vegetarians had less gastrointestinal cancer (i.e., colon cancer, pancreatic cancer, liver cancer, stomach cancer, etc), especially among lacto-ovo-vegetarians;
- Vegan women experienced fewer female-specific cancers;
- Pesco vegetarians (fish eaters) seemed to have protection for cancers of therespiratory and urinary system.
"This study suggests that vegetarian diets may decrease the incidence of all cancers combined and these preliminary results particularly show a decreased risk of female-specific cancers (vegans) when compared with non-vegetarians, and gastrointestinal cancers (lacto-ovo-vegetarians)," concludes Gary Fraser, MD, PhD, principal investigator of AHS-2.
Adventist Health Study-2 (AHS-2) is one of the largest and most exciting health studies of its kind and will have national importance and international significance. It is a cohort study of over 96,000 Seventh-day Adventists in the U.S. and Canada who enrolled between 2002 and 2007. Adventists, due in part to their unique dietary habits, have a lower risk than other Americans of heart disease, several cancers, and probably high blood pressure, arthritis, and diabetes. This, along with their wide variety of dietary habits, provides a special opportunity for careful research to answer a host of scientific questions about how diet (and other health habits) may change the risk of suffering from many chronic diseases.
Two previous studies on Adventist health involving 24,000 and 34,000 Californian Adventists have been directed from Loma Linda University over the last 40 years. These have been among the first to raise scientific awareness of the close relationship between diet and health. This groundbreaking work has brought visibility and accolades to the lifestyle recommended by Seventh-day Adventists from both the scientific and lay communities. AHS-2 is conducted by researchers at Loma Linda University School of Public Health. For more information, visit www.adventisthealthstudy.com.