TUESDAY, Dec. 27 (HealthDay News) -- Vegan diets are considered by some to be extreme, a strict way of eating that exists on the radical fringes of vegetarianism.

But today, a growing number of people are giving vegan diets a second look, and nutritionists now believe that a well-thought-out vegan eating plan could be the most healthy way to live for most people.

"Properly planned vegan diets are healthy, nutritionally adequate and may provide health benefits in the prevention and treatment of many diseases," said Vandana Sheth, a registered dietitian and nutrition educator in Rancho Palos Verdes, Calif., and a spokeswoman for the American Dietetic Association.

Vegan diets are plant-based and exclude all animal products, even items like milk, cheese and eggs that are allowed in some forms of vegetarian diets.

Veganism drew added attention in 2011 from a pair of U.S. notables. Former President Bill Clinton -- long famous for McDonald's runs and barbeque lunches -- announced in August that he had converted to a vegan diet. And domestic doyenne Martha Stewart dedicated an hour-long episode of her TV show in March to the vegan lifestyle.

Research has found that people who follow a vegetarian or vegan lifestyle enjoy a number of health benefits, Sheth said. These include:

• Lower cholesterol levels.
• Lower blood pressure.
• A healthier body mass index.
• Decreased risk for heart disease.
• Decreased risk for cancer.
• Better control and prevention of diabetes.

"They don't have to worry about cholesterol because cholesterol is only found in animal products," Sheth said. "And as you would expect, vegan diets are much higher in fiber."

Sheth added that research has found vegan diets to be appropriate for people at all stages of the life cycle -- even people at crucial stages, such as growing children, pregnant or lactating women, and highly active athletes.

One of the long-standing criticisms of a vegan diet has been that people will miss out on many essential nutrients that are in rich supply in animal products. Nutritionists say that is no longer a serious concern, although people in a vegan lifestyle do need to pay careful attention to their supply of certain nutrients.

Interestingly, protein is not one of the nutrients that vegans need to worry about, even though plants are not the best sources because their proteins do not break down into the full range of amino acids that the human body requires for healthy functioning.

"It's true that most plant foods don't contain all the essential amino acids needed by our bodies, while animal proteins do," said Andrea Giancoli, a registered dietitian in Los Angeles and a spokeswoman for the American Dietetic Association. "But a grain plus a bean makes a complete protein. As long as you're getting a variety of those, you are fine -- and they don't need to be consumed at the same time."

Sheth and Giancoli also noted that certain vegan "super foods" like soy products and quinoa have been found to contain proteins that break down all the essential amino acids.

"It is absolutely possible to get enough protein from beans, lentils, tofu, soy products and other plant sources like seeds and nuts," Sheth said. "As long as you're getting a varied amount throughout the day, your body can mix it up and get what it needs."

Nutrients that vegans do have to keep careful track of in their diets, according to Sheth and Giancoli, include vitamin B12, a key nutrient in cell metabolism, nerve function and blood production, and calcium, which is needed for healthy bones. Animal products are rich in vitamin B12, and dairy products contain loads of calcium.

However, vegans can get B12 and calcium from fortified cereals and fortified dairy substitutes such as soy or rice milk. "You need to be a smart consumer and read labels to make sure you're buying products that are fortified," Giancoli said. Dark green leafy vegetables like broccoli, collard greens or kale also are good sources of calcium.

Vegans also have to make sure they get enough iron, which is essential in the creation of hemoglobin, the protein in red blood cells that delivers oxygen to cells and tissues throughout the body. Again, animal products are much more rich in iron, although plant foods such as dried beans, dark green leafy vegetables and fortified dairy substitutes are good sources.

"Keep in mind that our bodies are able to absorb more iron from food if the meal is also rich in vitamin C," Sheth said. "If you're having spinach, you might have tomatoes or a citrus dressing with it to increase absorption."

Omega-3 fatty acids probably represent the greatest nutritional challenge for vegans, the two nutritionists said. Thought to be critical for cognitive function and healthy cardiovascular function, omega-3s appear in large amounts only in fatty fish such as salmon -- a dietary no-no for vegans.

Some plant sources -- flaxseeds, soybeans, pumpkin seeds and walnuts, for example -- contain a type of omega-3 fatty acid, but it's not the same type found in fish and has not been proven to have the same level of health benefits, Giancoli said.

"There's some concern that vegans may be missing out," she said.

Finally, vegans need to keep in mind that it's just as easy for them to indulge in an unhealthy diet as it is for omnivores, Sheth said.

She recommends that her vegan clients follow the federal government's "My Plate" guidelines for eating, the same as everyone else should. "You're basically just replacing the protein source," Sheth said. "Otherwise, it's the same meal."

More information

The U.S. Department of Agriculture has more on vegetarian eating.