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An Introduction to Plant Based Diets

Hillary Wright, MS, RD
Senior Nutritionist

Dana Farber Cancer Institute

At first pass it may sound like vegetarianism, which itself can mean a few different things. The strictest form is a vegan diet, which only includes foods from plant sources, like fruits, vegetables, whole grains, soy foods, legumes, nuts and seeds. Many self-identified vegetarians are actually “lacto-ovo” vegetarians, meaning they eat plant foods, eggs, and dairy products, like milk, yogurt and cheese, but no animal flesh. There are also those who mainly consider themselves vegetarians but also eat seafood, some occasionally poultry, or maybe just avoid red meat. Despite the differences, what all have in common is a focus on getting most of their nutrients from plants. Two of the most recognized plant-based diets are the Mediterranean Diet and The DASH Diet (Dietary Approaches to Stop Hypertension). Both suggest significant increases in fruits and vegetables (targets are higher than those consumed by the average American), favor whole grains, and include plant proteins like nuts, seeds and legumes. Both suggest limitations on animal protein, with the Mediterranean Diet recommending seafood over poultry, and that red meat be consumed “sparingly.” Another less familiar but highly regarded plant-based diet in the nutrition science world is the OmniHeart diet. Backed by the National Institutes of Health, the OmniHeart Diet provides three different options for a heart-healthy plant-based diet that emphasize more carbohydrates, proteins or unsaturated fats, depending on one’s preferences. Like Mediterranean and DASH, all three OmniHeart patterns include a big push for more fruits and vegetables, and inclusion of plant proteins from nuts, seeds and legumes. It’s also worth noting that all these plant based plans allow dairy in moderation — all encouraging low or reduced-fat versions — and suggest limiting added sugars and refined carbohydrates.

Are Plant-based Diets Good for Cancer Survivors?

For cancer prevention and survivorship, cancer research and education organizations worldwide also advocate plant-based eating. The American Institute for Cancer Research (AICR), their European affiliate the World Cancer Research Fund, and the American Cancer Society all push for more plant foods (see links below for more details). All acknowledge that healthful forms of animal foods, like seafood, low fat dairy, eggs, poultry and lean meat (no more than 12 18 ounces per week) can be worked into a balanced, healthful eating plan.

What Makes Plant-based Diets So Healthy?

Aside from being low in calories and rich in fiber, vitamins, and minerals, plant foods are loaded with thousands of compounds called phytonutrients (“phyto” means plant in Greek) which act as natural antioxidants, anti-inflammatories and detoxifiers. These compounds mix and match in countless combinations within plants to provide these benefits. Examples of phytonutrients are the orange/red carotenoids in carrots and tomatoes, polyphenols in berries, tea and dark chocolate, and phytoestrogens in soybeans. Many of these compounds give plants their pigment, so varying up the colors of your fruits and vegetables, and eating a variety of whole grains, nuts, seeds and legumes, naturally varies these phytonutrients.

Making it Happen

Despite minor differences in the plant-based patterns mentioned above, they have a lot in common:

  • Aim to cover ½ your plate with vegetables, including a variety of colors to maximize phytonutrients
  • Include whole fruits with meals and snacks, with a goal of 2 servings or more per day
  • Choose whole grains, like brown rice, quinoa, oats, barley, millet and whole grain pasta, breads, cereals and crackers (look for the word “whole” in the first ingredient) over refined, “white flour” options whenever possible
  • Swap out animal proteins for plant proteins, like legumes, hummus, soy foods, and quinoa, starting with a goal of one “vegetarian” dinner per week and working up from there.
  • Find ways to incorporate nuts, nut butters and seeds into your snacks, salads, and meals at any opportunity
  • Choose plant-based fats, like olive, canola, avocado, and peanut oil over animal fats like butter and the fats found in red meat.

Eating more plant-based also means eating fewer foods from animal sources, which may require down-shifting your intake of meat, poultry, eggs, milk, yogurt and cheese to make room for more fruits, vegetables, whole grains, nuts, seeds and legumes. Of all the animal-based foods, seafood carries the most disease fighting benefits so is also a healthful alternative to meat.

  1. DASH Diet – Mediterranean Diet –
  2. OmniHeart Diet –
  3. American Institute for Cancer Research/World Cancer Research Fund –
  4. American Cancer Society –