Q. Following the lead of our 12-year-old daughter, my wife has become a vegetarian. She says she's willing to continue serving meat and chicken, but I sense that she'd rather not. What can you tell me about the safety of a vegetarian diet?

A. Most people who choose vegetarian diets are motivated by their personal philosophies, ethical beliefs, or religious convictions. But health certainly is a factor, and if a vegetarian eating plan is constructed properly, it can be an asset to health.

Many people who eschew animal foods think of themselves as vegetarians. But some of these folks simply avoid red meat, while others eliminate all animal products, and many are in between. Here is a glossary of various vegetarian menus:

Vegan. Eats no meat, fish, poultry, eggs, dairy products, or honey.

Lacto vegetarian. Eats no meat, fish, poultry, or eggs but does eat dairy products.

Ovo vegetarian. Eats no meat, fish, poultry, or dairy products but does eat eggs.

Lacto-ovo vegetarian. Eats no meat, fish, or poultry but does eat dairy products and eggs.

Pescetarian (also called pesco vegetarian). Eats no meat or poultry but does eat fish.

Pollo vegetarian. Eats no meat or fish but does eat poultry.

Semi- (or partial) vegetarian. Avoids meat but eats fish and poultry.

Macrobiotic diet. Relies on eating brown rice and other whole grains, supplemented with vegetables, beans or bean products such as tofu, kelp and other sea vegetables, and typically a small amount of fish and a limited quantity of certain fruits. Avoids dairy products and processed or refined foods.

Vegetarians come in many stripes. Some avoid all animal products, others allow eggs and dairy products, while some also accept fish.

Without eating any animal products, strict vegetarians may lack certain nutrients. Vitamin B12, for example, is naturally present only in animal foods — but since it's added to fortified grains and cereals, vegetarians who consume these products can get enough. Iron is another potential problem, at least for menstruating women. Popeye was right in extolling spinach as a source of iron, but he was a step behind today's nutritionists, who know that the body is much less efficient at absorbing iron from vegetable sources than from red meat. Fortunately, inexpensive B12 and iron supplements are available over the counter for people who need them.

Animal protein provides the protein building blocks that best meet the needs of the human animal. But even strict vegetarians can get the proper mix of amino acids and proteins if they eat a variety of protein-rich plants, such as beans.

One of the best things about a vegetarian diet is that it's likely to be low in nutrients that contribute to disease. The list includes cholesterol, saturated fat, and sodium. At the same time, fruits and vegetables provide healthful amounts of vitamins and potassium, while nuts and olive oil offer "good" omega-3 polyunsaturates and monounsaturated fats. Fish are particularly desirable for their omega-3s and proteins.

A 2006 study confirms the benefits of vegetarian eating. Scientists compared 35 healthy vegetarians with 35 equally healthy nonvegetarians. None of the volunteers used medications and none were smokers or drinkers. On average, the vegetarians were leaner, had lower blood pressure, and had better cholesterol and blood sugar levels. The vegetarians also had better cardiac function and vascular reactivity. To make vegetarian diets healthful, meal plans should include non- or low-fat dairy products, whole grains, and olive oil and other healthy fats.

Your daughter's vegetarianism may have been motivated by feelings for animals, your wife's by an interest in health and nutrition. If you need additional reasons, consider family solidarity and peace.

— Harvey B. Simon, M.D.

Editor, Harvard Men's Health Watch

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