1. Is it possible to get enough protein on a vegetarian diet?
Absolutely, it’s actually difficult to become protein deficient unless you quit eating all together. Just about all unrefined foods contain significant amounts of protein. Potatoes are 11% protein, oranges 8%, beans 26%, and tofu 34%. In fact, people have been known to grow at astounding rates (doubling their body size in only six months) on a diet of only 5% protein. These people are infants and they do it during the first 6 months of life, fueled by breast milk, which contains just 5% protein.
2. How much protein do I need, anyway?
The Recommended Dietary Allowance (R.D.A.) for protein is 0.8 grams a day per kilogram of bodyweight. (Divide your weight in pounds by 2.2 to get kilograms.) Athletes may require more protein, but the amount is small (1.0 to 1.5 grams per kilogram of bodyweight), an amount easily obtainable from a vegetarian diet.
Excess protein consumption can cause a variety of problems including bone mineral loss, kidney damage, and dehydration. Your body can only use so much protein, the excess is either broken down through oxidization, placing an enormous strain on the kidneys, or it is stored as body fat. Neither option is particularly desirable.
3. What’s the difference between complete and incomplete proteins?
Animal protein contains all nine of the essential amino acids, so it has been referred to as a "complete" protein. The nine essential amino acids can also be found in plant proteins, however no single plant source contains all nine of them. Therefore, plant protein has been referred to as "incomplete."
It was once widely believed that vegetarians had to carefully combine plant protein sources in each meal in order to obtain all nine essential amino acids. However, scientific studies have shown that the human body can store essential amino acids and combine them as necessary. So, while combining beans and rice, or peanut butter and bread produces a complete protein, it’s not necessary to consciously do this at every meal. If you eat a varied diet and adequate calories, combining proteins is not an issue.