You don't have to be a vegetarian, but eating a plant-based diet provides a health insurance policy against a range of cancers, including those of the mouth, pharynx, larynx, esophagus, stomach, colon, lung, and pancreas. Always fill two-thirds of your plate with veggies and whole grains, and devote just one-third to red meat, chicken, or fish.
Start by eating more dark leafy greens, such as spinach, kale, Swiss chard, bok choy, and romaine lettuce. Studies show that about half of all Americans eat no leafy greens, which leaves a huge hole in our diets, Dr. Willett says. We're missing out on cancer-fighting vitamins A, C, E, and B6, folate, and phytochemicals, which strengthen the immune system and protect cells and DNA from the oxidative damage that can lead to cancer.
Also increase your intake of vegetables like broccoli, cauliflower, cabbage, and Brussels sprouts, along with garlic, fruits, and whole grains, all of which contain a mix of nutrients and bioactive compounds such as beta-carotene, lycopene, quercetin, and vitamins that guard against cell damage. They're also low in calorie density, so you can eat more of them (and their cancer-fighting nutrients) without gaining weight.