It's no surprise, then, that athletes often raise the question, "Does a vegetarian diet improve performance?"

When trying to measure the effects of nutrition on performance, there is no clear answer. The reason is this: One's performance is affected by several factors — genetic endowment, training and nutrition.

Some nutritional deficiencies will impair performance, while some nutrients may delay fatigue and improve performance. How important nutrition is to performance will depend upon a host of other factors including gender, age, body weight, eating and lifestyle patterns, environment, type of training, and the activity itself.

There are world-class vegetarian athletes whose success is attributed to vegetarianism; however, there are far more numerous world-class athletes who are not vegetarian.

All types of vegetarians except the vegan (who excludes all animal products, including milk, cheese, eggs, butter and honey) can readily obtain a balanced diet of nutrients and calories without the complicated "food combining" myth that is so widespread.

The more restrictive the diet, the more challenging it is to consume a balanced meal. If not planned appropriately, several concerns arise.

Particularly in the athlete's case, consuming adequate calories can be troublesome for those who expend 1,000 calories or more each day through activity. A plant-based diet often contains fewer calories than an animal-based diet, so consuming higher caloric items such as nuts, beans, corn, green peas, potatoes, sweet potatoes, avocados, raisins, other dried fruits and whole wheat bread can circumvent any insufficient caloric intake.

Although protein may often appear to be lacking in a vegetarian diet, it usually isn't. Provided sufficient calories are consumed, protein needs are likely being met. Plant proteins are not digested as well as animal proteins because the fiber in plant foods binds with them. Thus, vegetarians consuming no animal products (vegans) require approximately 10% more protein than those who do include animal products in their diets.

Americans consume, on average, about 100 grams of protein daily. For a 70 kg person (154 lbs.), this is 1.4 grams of protein per kilogram of body weight.

This average consumption is for the nonathlete; an athlete's caloric intake is usually greater than a nonathlete, which means more protein is necessary. Most athletes who are eating sufficient calories have little difficulty meeting the recommended amount of protein.

The two most common plant foods that can offer the quality of protein equivalent to that of animal protein are grains and legumes. And although it had been previously thought that you had to consume these "complementary" proteins within the same meal in order to obtain the high biological value of protein, that is no longer believed to be the case.

Provided you consume these foods during the same day, you will have obtained sufficient amino acids to constitute those of animal proteins. Such grains as wheat, corn, rice and oats combined with legumes such as soybeans, peanuts, navy beans, kidney beans, lima beans, black-eyed peas and chickpeas (also called garbanzo beans) provide all the amino acids animal products provide.

Of special note, soybeans contain all the essential amino acids and are equivalent to animal proteins in quality. Compared to other legumes, they are higher in protein, as well. Soybeans are 38% protein by weight, while other legumes range from 20-30% in protein. Other constituents in the soybean include 18% oil, 15% carbohydrate, and 15% dietary fiber.

Remember, if you are a lacto-ovo vegetarian (vegetarians who exclude meat from their diets but do include dairy products and eggs), you will be obtaining complete protein through the milk, eggs, yogurt and cheese you consume.

Another element vegans should keep in mind is the B12 deficiency they may experience. Animal products are the sole foods that contain B12; however, numerous B12-fortified products are now widely available, such as fortified soymilk and breakfast cereals.

Also, because animal products are rich sources of iron, calcium and zinc, deficiencies in these minerals could result from a vegetarian diet. Research has shown, however, that by carefully balancing the intake of grains, legumes, and vegetables, deficiencies may be avoided.

Ultimately, whether a vegetarian diet is adopted to enhance performance, lower risk for disease, or even for ethical reasons, it appears that a properly planned vegetarian diet certainly won't hinder performance.

It may not increase your race PR or your endurance, but isn't that what training is for?

Good Luck!