By Paula Amato MD
Originally published on Advocate.com July 09 2012 3:00 AM ET
Is a vegetarian diet a healthier choice? The short answer: It depends, largely because not all vegetarian diets are created equal. There are many different reasons people may choose to be vegetarians, including health, the environment, and religion. And that reason will influence a person’s food choices. Because vegetarianism includes a wide spectrum of dietary practices, it makes it difficult to find clear relationships between diet and health outcomes. Vegetarians who live on french fries and pasta are likely not healthier than a person who eats fish, eggs, or unprocessed lean meat along with lots of veggies.
A vegetarian diet is one that does not include meat. Concern about the nutritional adequacy of vegetarian diets centers around intakes of vitamin B12, iron, zinc, calcium, iodine, vitamin D, and omega-3 fatty acids, which are found more readily in meat, eggs, and fish. However, when a vegetarian diet is appropriately planned and includes foods fortified with those same minerals and vitamins, it can be nutritionally adequate and may lower the risk of chronic diseases compared to a typical Western diet, composed of lots of red and processed meats, dairy products, eggs, high-fat foods, refined grains, and sugary desserts and drinks.
There is convincing evidence that a vegetarian diet is associated with a lower risk of heart disease, lower LDL cholesterol levels, and lower rates of hypertension and type 2 diabetes. Vegetarians also tend to have a lower prevalence of obesity, lower overall rates of cancer, and greater life expectancy.
Unfortunately, little evidence exists that the absence of meat, rather than other attributes of the vegetarian diets, accounts for these health benefits. Vegetarian diets allow for a large variety of different intakes from all other food groups. For example, there is little information that indicates disease risk reduction from a vegetarian diet exceeds that achievable by increasing vegetable and fruit consumption in a diet that also includes meat.
Meat consumption has been associated with increased risk of colon cancer, although not all data are consistent. More recently, a study in the United Kingdom found that consuming a vegetarian diet and a high intake of dietary fiber (over 25 grams a day) were both associated with a lower risk of diverticular disease, a common bowel disorder. Since a majority of people in the Unites States fail to meet the recommended average intake of dietary fiber, this may have much to do with the growing rate of diverticular disease. At the same time, rising obesity rates will lead to substantial increases in heart disease, diabetes, and possibly cancer.
Vegetarian, plant-based diets are associated with longevity and a lower risk of chronic disease and are acceptable dietary practices in terms of health outcomes, but right now there is insufficient evidence that they confer greater benefit than, for example, a Mediterranean diet (which emphasizes whole grains, fish and seafood, olive oil, legumes, and fruits and veggies).
Bottom line: We need more research on the association between the spectrum of types of vegetarian diets and risk of chronic disease before we can make dietary recommendations to the general public. In addition to considering nutritional quality, researchers should also consider economics, and the environment. A compelling argument for the unique benefits of a vegetarian diet may be most appropriately made on ecological grounds. But until all the evidence becomes available, it seems most prudent to consume a mostly plant-based diet.
Paula Amato, MD, is a reproductive endocrinologist at Oregon Health & Science University in Portland and a member of the board of the Gay and Lesbian Medical Association.