One of the first questions asked when someone finds out I eat a whole foods, plant-based diet is, "If you don't eat meat, how do you get enough protein in your diet to stay healthy and strong?" The answer: a diet rich in a variety of vegetables, fruits, whole grains, nuts, legumes, and seeds adequately provides all the protein you need.
In the modern American diet, protein is pretty much synonymous with meat. Plants do, however, contain ample protein of their own. For example, 100 calories of broccoli (about 10 ounces of food) contains 11.2 grams of protein while 100 calories of sirloin (about 1 ounce of food) contains 5.4 grams.1 As you can see, not only do you get to eat more food without blowing your calories for the day but you also get more and better protein.
In addition to getting to eat more and fill fuller, plants contain a slue of other beneficial nutrients such as antioxidants and phytochemicals which have wonderful cancer prevention properties. Phytochemicals are plant-derived chemicals which occur naturally in plants. Phytochemicals work as cancer inhibitors and support immune system health. Antioxidants function as "scavengers of toxins"2 and thus have the ability to help fight off cancer causing toxins in the body. Antioxidants can be colorless but they're what give many of our plants their beautiful hues. Cartenoids are one form of antioxidants. You may have heard of a couple of cartenoids such as beta-carotene (gives carrots and pumpkins their red-orange coloring) or lycopene (gives tomatoes their rich red color) because they have been popularized for their anti-cancer activity. The most important thing to remember though is that these are just a few of the thousands of compounds that, when consumed as whole foods, work synergistically with our bodies to create optimal health. You can get all the protein you need along with an array of health promoting benefits when you eat a diet rich in whole, plant-based foods.
1 Caloric example taken from: Fuhrman, Joel M.D. Eat to Live. New York, Little, Brown and Company, 2003, p59-60