Some people follow a largely vegetarian diet because they can't afford to eat meat. Becoming a vegetarian has become more appealing and accessible, thanks to the year-round availability of fresh produce, more vegetarian dining options, and the growing culinary influence of cultures with largely plant-based diets.

Approximately six to eight million adults in the United States eat no meat, fish, or poultry, according to a Harris Interactive poll commissioned by the Vegetarian Resource Group, a nonprofit organization that disseminates information about vegetarianism. Several million more have eliminated red meat but still eat chicken or fish.

About two million have become vegans, forgoing not only animal flesh but also animal-based products such as milk, cheese, eggs, and gelatin. Traditionally, research into vegetarianism focused mainly on potential nutritional deficiencies, but in recent years, the pendulum has swung the other way, and studies are confirming the health benefits of meat-free eating.

Nowadays, plant-based eating is recognized as not only nutritionally sufficient but also as a way to reduce the risk for many chronic illnesses. According to the American Dietetic Association, "appropriately planned vegetarian diets, including total vegetarian or vegan diets, are healthful, nutritionally adequate, and may provide health benefits in the prevention and treatment of certain diseases."

"Appropriately planned" is the operative term. Unless you follow recommended guidelines on nutrition, fat consumption, and weight control, becoming a vegetarian won't necessarily be good for you.

A diet of soda, cheese pizza, and candy, after all, is technically "vegetarian." For health, it's important to make sure that you eat a wide variety of fruits, vegetables, and whole grains.

It's also vital to replace saturated and trans fats with good fats, such as those found in nuts, olive oil, and canola oil. And always keep in mind that if you eat too many calories, even from nutritious, low-fat, plant-based foods, you'll gain weight.

So it's also important to practice portion control, read food labels, and engage in regular physical activity. You can get many of the health benefits of being vegetarian without going all the way.

For example, a Mediterranean eating pattern — known to be associated with longer life and reduced risk of several chronic illnesses — features an emphasis on plant foods with a sparing use of meat.

Even if you don't want to become a complete vegetarian, you can steer your diet in that direction with a few simple substitutions, such as plant-based sources of protein — beans or tofu, for example — or fish instead of meat a couple of times a week.

Only you can decide whether a vegetarian diet is right for you. Strictly speaking, vegetarians are people who don't eat meat, poultry, or seafood. But people with many different dietary patterns call themselves vegetarians, including the following:

Vegans (total vegetarians): Do not eat meat, poultry, fish, or any products derived from animals, including eggs, dairy products, and gelatin.

Lacto-ovo vegetarians: Do not eat meat, poultry, or fish, but do eat eggs and dairy products.

Lacto vegetarians: Eat no meat, poultry, fish, or eggs, but do consume dairy products.

Ovo vegetarians: Eat no meat, poultry, fish, or dairy products, but do eat eggs.

Partial vegetarians: Avoid meat but may eat fish (pesco-vegetarian, pescatarian) or poultry (pollo-vegetarian).

Harvard Health Publishing