Nutrition plays an important role in every part of our health, from disease to weight issues to life expectancy. So why are so many of us ignorant about what makes up a good diet? Dr. Oz talks to Dr. Joel Fuhrman, author of Eat to Live, about what we should be eating.

As a former Olympic skater, Dr. Fuhrman says he's had a lifelong interest in nutrition—both for improved stamina and a healthy immune system. Today, he says he helps everyone from athletes to everyday people eat better, live better and overcome diseases. He says his theory of eating is basic: Eat foods that are naturally high in nutrients and low in calories. "We've shifted so far away from a diet that would have been naturally adapted to our species," Dr. Fuhrman says. "You can't live on processed foods and factory-made foods and expect to have normal health."

Dr. Fuhrman recommends adding the following foods to your diet:

• Nuts and seeds: Dr. Fuhrman says you should eat these in their whole form rather than in oils—when oil is extracted, some beneficial effects are lost.
• Vegetable protein: Animal proteins don't provide the vitamins and nutrients we need, Dr. Fuhrman says. Beans and various greens increase the micronutrient density in our diet, as well as prevent diseases.
• Green vegetables: Most green vegetables derive 35 to 50 percent of their calories from protein, Dr. Fuhrman says. There are even studies that show that certain greens are related to lower rates of diseases worldwide.

With healthcare costs skyrocketing, Dr. Fuhrman says there is a movement toward fighting diseases with natural elements. "Let's not just give more money to drug companies to make a pill to cure cancer," he says. "Let's see if we can prevent it by cleaning up the environment and by eating healthier."