Side Effects of Becoming Vegetarian

Vegetarians tend to have lower cholesterol levels than non-vegetarians, as well as a lower risk of heart disease and Type II diabetes. ArtKolo/Shutterstock

There are several medical studies linking vegetarian diets to lower incidences of certain types of cancers, heart disease, Type II diabetes and other chronic diseases. Many news headlines say vegetarians live longer than meat eaters.

Thinking about going veggie? Before permanently clearing out the steak knives from your kitchen, consider some of the following possible side effects of becoming vegetarian:

1. Low cholesterol levels: Virtually every medical study on vegetarian populations, including the prominent Oxford Vegetarian Study of 5,000 vegetarian subjects, have concluded that vegetarians have lower cholesterol levels than non-vegetarians. Most in the mainstream medical community, including the American Heart Association, recommend keeping total cholesterol levels under 200.

However, another study by the Honolulu Heart Program — which focused on the cholesterol levels more than 3,500 Japanese-American men aged 71-93 years, not necessary what eating trends produced those cholesterol levels — concluded that “Only the group with low cholesterol concentration ... had a significant association with mortality.” The Heart Program study, according to at least one medical doctor, demonstrates that having continuously, extremely low levels of cholesterol may lead to an early death.

2. Increased risk of colorectal cancer: One would assume that heavy meat eaters would have a higher risk of developing colorectal cancer but a review published in the American Journal of Clinical Nutrition of the aforementioned Oxford study reveals, "Within the study, the incidence of all cancers combined was lower among vegetarians than among meat eaters, but the incidence of colorectal cancer was higher in vegetarians than in meat eaters."

Vegetarians demonstrated a 39 percent higher incidence of colorectal cancer, which is confounding, given that eating red meat leads to higher colorectal cancer rates. The study’s researchers, although not unequivocal in being able to explain the findings, theorize that the vegetarian participants were perhaps not eating sufficient amounts of fruits and vegetables.

3. Lower bone mineral density: While it’s possible for vegetarians to consume adequate amounts of protein, calcium, iron and vitamin D (if supplementing properly or getting enough sunlight) to ensure proper muscle and bone development, one study concluded that vegetarians had approximately 5 percent lower bone-mineral density (BMD) than non-vegetarians. The results of the study, the authors conclude, suggest that vegetarian diets — especially vegan diets — are associated with lower BMD. But don’t despair if you’re a vegetarian or thinking about becoming one. The authors claim that the “magnitude of the association is clinically insignificant.”

4. Lower levels of vitamin B12: A study in the Journal of Agricultural and Food Chemistry says that omnivores have a significantly higher cluster of cardiovascular risk factors than vegetarians. But one potential risk of becoming a vegetarian seems to be the preponderance of lower vitamin B12 in the blood. B12 helps with metabolism, converting food into stable energy, utilizing iron, producing healthy red blood cells, and a host of other benefits.

The risk of low B12 levels, according to the study’s authors, can result in arteriosclerosis. Several vegetarian-friendly foods such as cereals are fortified with vitamin B12. If you’re a lacto-ovo vegetarian and eat dairy and eggs, you are likely consuming adequate amounts of B12. Yeast extracts are a good choice for vegetarians abstaining from dairy and eggs.

Walnuts are a great source of omega-3 fatty acids for vegetarians. Pauline Mak/flickr

5. Insufficient levels of omega-3 fatty acids: A paper published in the European Journal of Clinical Nutrition claims that vegetarians have lower levels of long-chain omega-3 fatty acids, particularly EPA and DHA. Sufficient levels of long-chain omega-3s are beneficial for cardiovascular health, say the study’s authors, who also concluded that DHA supplementation at a dose of about 2 grams per day eventually decreased plasma cholesterol.

Katie Minor, a senior instructor of nutrition at the University of Idaho, tells, "Nuts and flaxseed can supply enough sources of essential fatty acids. I haven’t seen evidence that vegetarians are lacking in essential fatty acids. They seem to be adequate."

Based on the conclusions of numerous medical studies, eating a vegetarian diet offers numerous health benefits. However, the same advice can be offered for vegetarians as for omnivores: exercise regularly, eat plenty of fresh vegetables and fruit every day and avoid processed foods.

One last morsel for thought: if you’re concerned at all about side effects of becoming vegetarian, Minor says to consider being a "flexitarian."

"Flexitarians are people who are vegetarian most of the time, but once in a while will consume an animal protein," she says. "The more restrictive you are with your diet, the more you’ll have to closely monitor what you’re consuming and the more likely your need will be to supplement. Work with a registered dietitian to make sure you’re not at risk for dietary deficiencies."