LOMA LINDA, California — In a large observational study of generally middle-aged American Seventh-day Adventists, the vegetarians in the group--ranging from vegans to those who ate meat once a week--were 12% less likely to die within six years than their meat-eating peers [1]. Men who ate a vegetarian diet were significantly less likely to die from ischemic heart disease or CVD. Does this mean everyone should forgo eating meat? Not so fast, experts caution, pointing to study limitations. But it does add support for following a "heart-healthy" diet.
The Adventist Health Study 2 was published online June 3, 2013 in JAMA Internal Medicine.
According to lead author Dr Michael J Orlich (Loma Linda University, CA), "This research gives more support to the idea that certain vegetarian dietary patterns may be associated with reduced mortality and increased longevity" and can be used to guide food choices.
However, in an accompanying editorial [2], Dr Robert B Baron (University of California, San Francisco) points out since it was an observational study, cause-and-effect conclusions cannot be drawn from it, and it was based on a one-time questionnaire. He urges clinicians counseling patients to be less focused on a vegetarian vs nonvegetarian diet and rather to look to the broader goal of improving the diet.
Asked to comment, Dr Robert H Eckel (University of Colorado Anschutz Medical Campus, Aurora) concurs. "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," he told heartwire .
Cut Out Meat and Live Longer?
Previous studies found that eating nuts, fruit, salads, fiber, and polyunsaturated fats or following a "healthy" or vegetarian or Mediterranean diet was linked with longer life, whereas eating red or processed meat upped mortality, the authors report. The first Adventist Health Study of about 30 000 Seventh-day Adventists living in California in the 1970s found a link between vegetarianism and lower all-cause mortality. But the European Prospective Investigation into Cancer and Nutrition-Oxford (EPIC-Oxford) cohort study did not find this association.
To investigate this, the researchers examined data from 73 308 Seventh-day Adventist men and women over age 25 who were living in the US from 2002 to 2007. The study participants had a mean age of around 57 years, and about 66% were women.
Based on their replies to questions about their consumption of 200 foods over the past year, the participants were classed into the following dietary patterns:
Vegan: Ate eggs, dairy products, fish, and meat less than once a month (n=5548; 7.6%).
Lacto-ovo–vegetarian: Ate eggs and dairy products once a month or more; ate fish and meat less often (n=21 177; 28.9%).
Pescovegetarian: Ate fish once a month or more; ate meat less often (n=7194; 9.8%).
Semivegetarians: Ate meat once a month or more; ate fish or meat no more than once a week (n=4031; 5.5%).
Nonvegetarians: Ate fish or meat more than once a week (35 359; 48.2%).
Over a follow-up of a mean of 5.79 years, 2570 participants died.
Compared with nonvegetarians, the hazard ratio (HR) for all-cause mortality for all vegetarians combined was significant: 0.88 (95% CI 0.80–0.97). The HR for all-cause mortality ranged from 0.81 to 0.92 in the different vegetarian types and was significant only for lacto-ovo-vegetarians and pescovegetarians.
Some vegetarian diets were significantly associated with lower mortality from CVD, ischemic heart disease, renal disease, and endocrine disease (diabetes), but not from cancer. The associations were larger and more likely to be significant in men than in women.
In men, following any type of vegetarian diet was associated with a significant lower risk of dying from CVD or ischemic heart disease, but in women, this type of diet was linked with a nonsignificant lower risk of these outcomes. Men who were vegetarians had a nonsignificant lower risk dying from stroke, but among women, this type of diet appeared to increase the odds of dying from stroke.
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