What are the risks of following a vegetarian diet?

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Carmen Patrick Mohan, MD
Internal Medicine
On the whole, vegetarian diets are associated with improved cardiovascular health. Vegetarians tend to have favorable body weights, decreased risk for diabetes mellitus, lower all-cause mortality, and in some instances, lower risk of cancer. However, vegetarian diets are thought to confer only a modest benefit in preventing cardiovascular disease. 

Some experts believe the benefits of a vegetarian diet could be further leveraged by mitigating against the two main risks of vegetarian diets -- vitamin B12 deficiency and low levels of omega 3 fatty acids. B12 deficiency is more typical of vegan-vegetarians who do not consume animal-products such as animal milk, eggs, or cheese.

Vegetarians, by definition, do not eat fish which are the richest dietary source of omega 3 fatty acids and key to optimal heart health.  In order to further reduce their risk of cardiovascular disease, vegetarians should talk to their doctors about possibly needing vitamin B12 supplements and considering omega 3 fatty acid supplementation. 

It should be noted some research suggests that vegetarian diets, especially vegan diets, are associated with lower bone mineral density (BMD), but this does not appear to cause problems with bone fractures if calcium intake is sufficient. Also, iron deficiency appears to be rare in vegetarians, but pregnant or nursing women should take care to discuss diet with their health care providers.
Donna Feldman
Nutrition & Dietetics
Vegetarian diets can be extremely healthy:
  • lots of vegetables, whole grains and legumes
  • low fat
  • high fiber
  • healthy vegetable oils
With all those benefits, how could a vegetarian diet be risky? It all depends on balance.

Some people think being vegetarian just means not eating meat. They eat a highly processed diet, full of snack foods, soft drinks and convenience foods. It’s entirely possible to be a vegetarian and never touch a vegetable. Leaving pepperoni off a pizza may technically be vegetarian, but it isn’t necessarily healthy. Swapping soy burgers for beef burgers is technically vegetarian, but it isn’t necessarily healthier if you eat soy burgers, French fries and soda pop for lunch everyday.
 
Another risk for vegetarians is lack of certain nutrients found primarily in animal foods, especially meat. Protein is usually the first thing vegetarians think about. Our highest quality sources for protein are animal foods: meats, poultry, fish, eggs, milk, yogurt and cheese. While plant foods have some protein, it’s not as high quality or as concentrated. For example, 2 TB of peanut butter has almost as much protein as 1 oz of cooked chicken breast meat. The peanut butter is almost 200 calories, while the chicken is around 50. And the quality of that peanut butter protein isn’t quite as good for human needs.
 
Iron is another nutrient of concern. We get lots of iron from meat, especially red meats like beef, pork, bison and lamb. Dairy foods, which vegetarians can eat, are not good iron sources; eggs are a fair source. So cutting out meat means getting more iron from plant sources. Leafy green vegetables and whole grains have significant iron, but if you’re a vegetarian who doesn’t eat vegetables or whole grains, your iron sources will be more limited. 

One possible benefit of a vegetarian diet is the emphasis on healthy fats from vegetable oils. But if your vegetarian diet is heavy on cheese, sour cream and cream cheese you could end up eating a high saturated fat diet. That’s easy to do if you depend on pizza, burritos, bagels and soy burgers every day.
Joel H. Fuhrman, MD
Family Medicine
Although whole food vegetarian and flexitarian diets that include the occasional or minimal use of animal products may markedly reduce the risk for coronary heart disease, diabetes, and many common cancers, the real Achilles heel of no-animal-fat and low-animal-fat diets is this increased risk of hemorrhagic stroke at an older age. This is because animal products and processed foods contribute to plaque formation called atherosclerosis.

Atherosclerosis promotes blood clots that cause heart attacks and embolic strokes. However, this process may also thicken, and therefore protect, the small, fragile blood vessels in the brain from rupturing due to the stress from chronic high blood pressure. When a diet is high in fatty animal products and processed foods, the thickened blood vessel walls caused by the unhealthful, heart-attack-promoting diet actually protect against the occurrence of this more uncommon cause of strokes. In medical studies, higher cholesterol levels are associated with increased risk of other strokes, but lower risk of hemorrhagic strokes.
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Vegetarian Diets

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onal meats or fish as in the Macrobiotic diet with it's Zen beliefs, or the Indian Ayurvedic diet, which finds milk and dairy central to good health along with plants. Anyone considering a vegetarian diet should learn about the food values of different vegetables, and consider getting advice on whether or not to supplement the diet with vitamins and minerals, particularly if you have special nutritional needs like growing children or pregnant or lactating women.
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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.