New research published earlier this month in JAMA Internal Medicine (3 June 2013) has found that vegetarian diets are associated with lower all-cause mortality.
A total of 96,469 Seventh-day Adventist men and women were recruited between 2002 and 2007, from which an analytic sample of 73,308 participants remained after exclusions. Study participants filled out a diet and lifestyle questionnaire at the start of the study, then every two years after that, filled out hospital history forms and listed any hospitalizations and diagnoses of cancers, stroke, heart attack and diabetes during the previous two years.
According to the researchers,
“Research data showed a progressive weight increase from a total vegetarian diet toward a non-vegetarian diet. Additionally, levels of cholesterol, diabetes, high blood pressure, and the metabolic syndrome all had the same trend – the closer you are to being a vegetarian, the lower the health risk in these areas. In the case of type 2 diabetes, prevalence in vegans and lacto-ovo vegetarians was half that of non-vegetarians, even after controlling for socioeconomic and lifestyle factors.”
Compared to non-vegetarians, the vegetarians watched less television, slept more hours per night, consumed more fruits and vegetables, consumed less saturated fat, and typically ate foods with a low glycaemic index, such as beans, legumes and nuts.
The study has attracted some media interest, with headlines in the UK Daily Mail, for example, asking if vegetarianism is the secret to a longer life.
This type of research is nothing new. Almost 20 years ago the Oxford Vegetarian Study (Thorogood et al., 1994) found a significant reduction in mortality from cancer and overall mortality in non-meat eaters. There was also a lower rate of ischaemic heart disease among vegetarians. In this study though, it was difficult to disentangle which features of the vegetarian diet were responsible for the protective effect, and the authors concluded their data did not provide justification for encouraging omnivores to change to a vegetarian diet as there were several attributes of the vegetarian diet, apart from not eating meat, which might reduce risk
An editorial entitled Should we all be vegetarians?, by Dr Robert B Baron from the University of California, accompanies this latest study. Dr Baron points out that like all observational studies, this one provides associations and not cause and effect evidence.
As with many of these studies, the avoidance or limitation of meat may simply be a marker for a healthier diet and lifestyle. And, as Dr Baron comments, “although the authors use state-of-the-art approaches to adjust for potential confounders, one can never be sure that there are not other factors influencing the association between vegetarian diets and mortality”
Commenting to HeartWire, Dr Robert H Eckel from the University of Colorado agrees. “We need to put this study into perspective. Is a vegetarian diet heart healthy? Probably yes. Should people convert to a vegetarian diet based on this study? Absolutely not. I think they need to look at their overall diet and make sure it is consistent with what we know about diet and heart disease.”
I’d agree. I think the key is to have a healthy balanced diet and an active lifestyle, whether or not you eat meat. For those who do eat meat it’s important to stick to the appropriate portion sizes, and to have very lean cuts. For those who choose to follow a vegetarian or vegan eating pattern the most important consideration is to ensure the diet is balanced and, in particular, that the important nutrients that meat would have provided, such as iron, are provided by alternative foods, such as nuts, seeds, lentils, cooked dried beans and tofu.
To reduce risk of cardiovascular disease and cancer, include plenty of wholegrains, fruits and vegetables in the daily diet. It’s also important to consume foods that are low in total fat, saturated fats and trans fats. If meat is eaten it should be very lean. Poultry should be eaten without skin, and dairy products should be low-fat. In addition, a regular intake of fish (once or twice a week) will boost intakes of omega-3 fatty acids, and will help lower the risk heart disease, along with other dietary and lifestyle strategies.