A Review of Recent Scientific Papers Related to Vegetarianism
News from the Sixth International Congress on Vegetarian Nutrition
This past February, I was privileged to attend the 6th International Congress on Vegetarian Nutrition at Loma Linda University. The three-day congress featured the most current scientific information related to vegetarian nutrition. More than 900 researchers, experts, and advocates of plant-based diets representing over 30 countries attended this congress. I"ll be including more information from the congress in upcoming issues of Vegetarian Journal and on VRG"s blog. Here is a sample of some of the findings that were presented:
- In a large study of Seventh-day Adventists, vegans, lacto-ovo vegetarians, and fish-eaters had a lower risk of thyroid disease than meat eaters.
- Vegetarian diets, especially vegan diets, have markedly lower carbon footprints and result in less greenhouse gas production than do non-vegetarian diets.
- Vegans in the Adventist Health Study had the lowest risk of metabolic syndrome, the name for a group of risk factors that raises risk for heart disease, diabetes, and stroke.
- Female vegetarian students at Loma Linda University did not have a higher risk of eating disorders than did non-vegetarian students.
- A vitamin B12-fortified toothpaste used daily for 5 weeks improved vitamin B12 status in vegans and vegetarians.
- A plant-based diet to combat diabetes was found to be acceptable by Navajo Nation participants.
- Fewer calories appear to be available from nuts than calorie charts indicate. There are several possible explanations for this; one may be that nuts are often incompletely chewed and therefore are not completely digested.
- India"s obesity epidemic exceeds that of the U.S.; many factors were identified that have led to the high obesity rates, including rapid urbanization and a move away from traditional, faith-based vegetarian diets.
How do Health and Ethical Vegetarians Differ?
There are many reasons for choosing to be vegetarian. Some people are primarily motivated by their own health; some are vegetarian for the animals; some cite environmental concerns as their main motivation. These different motivations may affect how long people continue to follow vegetarian diets, how much they know about nutrition, and the magnitude of their conviction that vegetarianism is an important part of their life. Researchers surveyed 292 vegetarians. Those who said that their primary motivation for following a vegetarian diet was for health or weight loss were categorized as "health vegetarians." Those whose primary motivation was animal rights, ethics, the environment, world hunger, or spiritual or religious beliefs were categorized as "ethical vegetarians."
In this study, vegans and vegetarians were grouped together as "vegetarians." Some differences were seen between health vegetarians and ethical vegetarians. Ethical vegetarians scored higher on measures of conviction and were more likely to believe that vegetarianism is right for everyone and that vegetarianism is an important part of their personality. The groups were similar in their belief that vegetarianism is right for them as individuals. Nutrition knowledge, both of general and of vegetarian nutrition, was similar between the two groups. Study subjects who originally became vegetarian for ethical reasons had been vegetarian for significantly longer than subjects who became vegetarian for health related reasons. In contrast, The Vegetarian Resource Group found no difference in the rate of staying vegetarian for at least three years and being primarily motivated by health reasons versus being motivated by ethical reasons (http://www.vrg.org/research/retention_survey_2009.php).
1 Hoffman SR, Stallings SF, Bessinger RC, Brooks GT. 2013. Differences between health and ethical vegetarians. Strength of conviction, nutrition knowledge, dietary restriction, and duration of adherence. Appetite [Epub ahead of print]
Lower Heart Disease Risk
A recent large study from the UK examined close to 45,000 men and women; about a third were vegetarian. Subjects" diets were tracked for an average of 12 years. Some subjects also had their blood pressure and blood cholesterol measured. Over the follow-up period, there were 169 deaths from heart disease, and over 1000 hospitalizations related to heart disease (heart attack, angina, or other problems). Vegetarians had a 32% lower risk of having heart disease than those who eat meat or fish. This lower risk may be due in part to the lower blood pressure, lower BMI, and lower blood cholesterol concentrations seen in the vegetarians. This study, along with others with similar results, supports the importance of a vegetarian diet in reducing the risk of being hospitalized for or dying from heart disease.
1 Crowe FL, Appleby PN, Travis RC, Key TJ. 2013. Risk of hospitalization or death from ischemic heart disease among British vegetarians and nonvegetarians: results from the EPIC-Oxford cohort study. Am J Clin Nutr 97(3):597-603.
Vegetarians and Vitamin B12
Two recent reports have provided evidence that vegetarians need to be more aware of vitamin B12. The first report was based on identifying published studies from the last 22 years that measured vitamin B12 status in vegetarians. A total of 12 accurate studies of adults from different countries were found. Depending on who was studied and what measurements were used, from 11% to 90% of vegetarians, including vegans, lacto vegetarians and lacto-ovo vegetarians, were identified as B12 deficient1. These results suggest that not all vegetarians are aware of the importance of fortified foods or B12 supplements to ensure adequate B12 consumption.
The second report looked at homocysteine levels in vegetarian and non-vegetarian blood. Vitamin B12 is involved in the metabolism of homocysteine. When someone lacks enough vitamin B12 for homocysteine to be properly metabolized, blood homocysteine levels are high, which means they are associated with an increased risk of heart disease. The researchers who did this study compiled data on homocysteine levels from many studies and found that vegans had the highest homocysteine levels, followed by lacto-ovo and lacto vegetarians. Non-vegetarians had the lowest homocysteine levels. Blood vitamin B12 was just the opposite — vegans were lowest, then lacto and lacto-ovo vegetarians, then non-vegetarians2. Most people in these studies were not using vitamin B12 supplements or eating fortified foods. The one study where vegans and nonvegetarians had similar levels of homocysteine and vitamin B12 was one where many vegans did use supplements and fortified foods.
1 Pawlak R, Parrott SJ, Raj S, Cullum-Dugan D, Lucus D. 2013. How prevalent is vitamin B(12) deficiency among vegetarians? Nutr Rev 71(2):110-17.
2 Obersby D, Chappell DC, Dunnett A, Tsiami AA. 2013. Plasma total homocysteine status of vegetarians compared with omnivores: a systematic review and meta-analysis. Br J Nutr 109(5):785-94.
Eating Vegetables Reduces the Risk of ER- Breast Cancer
Breast cancer is the second leading cause of cancer deaths in U.S. women. About one out of eight women will be diagnosed. To decrease the occurrence of breast cancer, it is important to identify changeable risk factors. Estrogen receptor negative (ER-) breast cancer accounts for 15-20% of breast cancers and is more common in African American and Asian women. This type of breast cancer has few known risk factors that can be modified and has a lower 5-year survival rate than estrogen receptor positive (ER+) breast cancer. A recent study provided insight into one possible means of reducing risk of this kind of breast cancer: eating vegetables. The study included close to 100,000 women who were followed for many years. Overall, women who developed any form of breast cancer or who developed ER+ breast cancer did not seem to differ from women who did not develop breast cancer in terms of their dietary intakes of fruits and vegetables. Women who ate the most vegetables and fruits had a lower risk of ER- breast cancer when compared to women who ate the lowest amount of these foods. Vegetable consumption appeared to be more important than fruit in reducing risk of this cancer. Women who ate close to a pound of vegetables per day had about a 15% lower risk of developing ER- breast cancer compared to women eating less than 7 ounces of vegetables daily. Women cannot predict if they will get breast cancer, or what type, but eating more vegetables seems like a simple thing to do to reduce the risk of ER- breast cancer.
1 Jung S, Spiegelman D, Baglietto L, et al. 2013. Fruit and vegetable intake and risk of breast cancer by hormone receptor status. J Natl Cancer Inst 105(3):219-36.