HealthDay News — Eating a vegetarian diet reduces the risk for death from any cause, but particularly cardiovascular mortality in men, results from a large prospective study indicate.
The adjusted hazard ratio for all-cause mortality among vegetarians, including vegans and semi-vetegarians who ate just fish or meat no more than once a week, was 0.88 (95% CI: 0.80-0.97), Michael J. Orlich, MD, and colleagues from Loma Linda University in California reported in JAMA Internal Medicine.
Among men who ate a vegetarian diets, cardiovascular mortality was significantly lower (HR 0.71, 95% CI 0.57-0.90), as well as death from ischemic heart disease (HR 0.71, 95% CI 0.51-1), compared with nonvegetarians, the researchers added.
Although previous studies have shown an association between vegetarian diet and risk reduction for several chronic diseases, including hypertension, metabolic syndrome, diabetes and ischemic heart disease, mortality studies have had conflicting results.
To better understand this aspect, Orlich and colleagues conducted a prospective study involving 73,308 participants in the Adventist Health Study 2 to examine the correlation between vegetarian dietary patterns and all-cause and cause-specific mortality.
Diet was assessed using a quantitative food frequency questionnaire. Participants were classified into five dietary patterns:
- Vegan – those who avoided eggs, dairy, fish and meat (7.6%)
- Lacto-ovo-vegetarian – those who ate eggs and dairy but avoided fish and meat (28.9%)
- Pesco-vegetarian – those who at fish but not meat (9.8%)
- Semi-vegetarian – those who ate fish or meat no more than once weekly (5.5%)
- Nonvegetarian (48.2%)
Mean patient age was 58 years, and about two-thirds were women. Participants who adhered to vegetarian diets ranged in age from 19 to 39 years. During a mean follow-up of 5.79 years, there were 2,570 deaths or 6.05 deaths per 1,000 person-years.
Compared with non-vegetarians, the adjusted hazard ratios for all-cause mortality were 0.85 for vegans, 0.91 for lacto-ovo-vegetarians, 0.81 for pesco-vegetarians, and 0.92 for semi-vegetarians, the researchers found.
By sex, reductions in all-cause mortality risk associated with vegetarian diet were significant for men (HR 0.82; 95% CI: 0.72-0.94), but not women (HR 0.93; 95% CI: 0.82-1.05), the researchers found.
For both sexes combined, there were no significant reductions in mortality due to cardiovascular disease or ischemic heart disease. However there was a significant decrease in death from “other” causes (HR 0.85; 95% CI: 0.73-0.99).
Unlike men, women vegetarians had no significant reductions in CVD- or ischemic heart disease-related mortality.
Overall, all types of vegetarian diets were significantly correlated with reduced renal mortality (HR 0.48, 95% CI 0.28-0.82), and endocrine mortality (HR 0.61, 95% CI 0.40-0.92) for both men and women. However, the correlations were larger and more often significant for men than women. There were no clear reductions in deaths from cancer.
“The evidence that vegetarian diets, or similar diets with reduced meat consumption, may be associated with a lower risk of death should be considered carefully by individuals as they make dietary choices and by those offering dietary guidance,” the researchers wrote.
They called for more studies to assess sex-specific mechanisms to explain mortality differences among male and female vegetarians.
In an accompanying commentary, Robert B. Baron, MD, of the University of California San Francisco, noted the choice to follow a vegetarian diet is not just based on health benefits, but may be motivated by ethical, religious and environmental reasons.
“First and foremost, dietary advice needs to be given to patients based on their own dietary history and preferences, their motivation to change their diet and clinical circumstances,” he wrote.
Although nutritionists disagree on the elements that make up an “ideal diet,” Baron noted, “virtually all agree that diets should limit added sugars and sugary drinks, refined grains and large amounts of saturated and trans fats.”
Study limitations include short follow-up and the potential for nondietary confounding factors.