• SeattleCancerNutrition

What You Need To Know About Vegan Diets and Cancer

With so many diets claiming to cure or treat cancer, and so many headlines offering confusing and even contradictory information about cancer nutrition, it’s understandable that you may have some questions about whether a vegan diet is best for your cancer journey. Research shows that well-planned vegetarian and vegan diets are highly effective for cancer prevention and risk reduction. I have years of experience working in cancer treatment and specializing in plant-based nutrition, so I have a lot to say about vegan diets and cancer. There are lots of considerations here, so I’m going to break down what you need to know about vegan diets and cancer.

Vegan diets may provide benefits in cancer treatment and prevention makes sense in a number of ways. They’re generally whole-foods based, cutting out processed foods (if you do it correctly) and studies show that plant-based dietary patterns have MORE beneficial nutrients like vitamins and minerals than even omnivorous diets. have known cancer-fighting nutrients like fiber, antioxidants, and phytochemicals that support the immune system, reduce inflammation, and slow cancer growth.

I’m no stranger to the criticisms, myths, and misconceptions about vegan nutrition, so I can speak to them all and I’m excited to break it down for you here today. Of course there are some considerations to removing all animal foods from the diet, especially if that’s a main staple of how you’re currently eating. Vegan diets aren’t more nutritious by default; any dietary pattern needs to be balanced to meet your needs. To see those anti-cancer benefits, your diet should consist of mostly plants and minimal amounts of refined and processed foods. Remember, foods like chips, french fries and even cookies and candy are often vegan, too!

As a board certified specialist in cancer nutrition who specializes in plant-based eating, I can tell you that it’s possible to plan a satisfying and nutritionally-adequate vegan diet that meets all of your needs -- even during treatment. Planning is key, and that’s what nutrition experts like me are here to help with. So let’s dive in and explore vegan diets and cancer!

What You Need To Know About Vegan Diets and Cancer

There’s a reason cancer organizations recommend filling most of your plate with plants. The research is clear about the benefits of eating a diet that minimizes red and processed meats and loads up on fruits, vegetables, whole grains, and beans.

Many studies have shown that plant-based vegetarian and vegan diets lower the risk of cancer overall, including breast, prostate and gastrointestinal cancer. A 2013 study found that vegan diets in particular offered the lowest risk for cancer overall and those specific to women, like breast and gynecological cancers. A 2015 study found that men who followed a vegan diet had a 35% lower risk of prostate cancer than men who followed a non-vegan and non-vegetarian diet.

We know why we see these benefits. Plant foods are the best sources of antioxidants, fiber and phytochemicals -- nutrients that fight cancer in different ways, like slowing cancer progression and helping with blood sugar management.They’re typically low in saturated fat and high in fiber.

It’s important to clarify that these benefits show up when people eat mostly fruits, vegetables, whole grains, beans, and healthy fats, and less refined grains, saturated fats, and sugar-sweetened beverages. Many processed foods are technically vegan but don’t offer a whole lot of benefits for cancer. In other words, the quality of your vegan diet matters a lot. A whole food vegan diet is what offers the best protection against cancer.

Nutritional Concerns on Plant-Based Diets

It’s a myth that vegan diets are nutritionally inadequate because they exclude all animal foods (that includes dairy and honey, since it’s made from bees). While it’s true that animal foods are a better source of some nutrients - namely B12 - research shows that a well-planned vegan diet can meet (nearly) all of your needs.

Vitamin B12 is one of those nutrients that may be lacking in a vegan diet because it’s found mostly in animal foods. I always make sure my clients are getting a reliable source of Vitamin B12 from fortified foods or supplements. The good news is that many foods are Vitamin B12-fortified (meaning the nutrient is added to the food), including breakfast cereals, some non-dairy milks, vegan spreads, nutritional yeast, and meat alternatives. A food label will tell you how much, if any, Vitamin B12 has been added. If you want to learn more about this topic, you can check out this magazine article I was quoted in.

Other nutrients of potential concern on a vegan diet include vitamin D, calcium, iron, zinc, iodine, and omega-3 fats. Below I’ve listed where you can find each of these nutrients in a vegan diet:

  • Iron: Beans, lentils, chickpeas, nuts and seeds, tofu, kale, dried fruit, quinoa, and iron-fortified foods like breakfast cereals. Eat these foods with a source of Vitamin C, like a squeeze of lemon juice, which will help your body absorb the iron from plants.

  • Calcium: Kale, broccoli, cabbage, bok choy, turnip greens, beans, chickpeas, oranges, figs, tahini, some non-dairy milks, and tofu (when prepared with calcium - check the label to confirm)

  • Vitamin D: Vitamin D is not found in many foods, even animal foods. Sunlight is the best source. If you’re not getting regular sun exposure, you can get this vitamin from supplements or fortified foods like plant milks, fruit juice, and breakfast cereal. You can also get it from mushrooms that were exposed to ultraviolet light, which a food label will confirm. If you want to learn more about getting enough vitamin D in the winter, check out this article I wrote.

  • Zinc: Soy products, beans like chickpea and kidney, peas, whole grains, seeds, nuts, and fortified foods

  • Omega-3 fats: Flaxseed (whole or oil), chia seeds, walnuts, canola oil, soybean oil, edamame, beans like kidney and navy, hemp seeds, and algae-based supplements

It’s not inevitable that vegan diets will fall short on any of these nutrients. In many cases, careful planning will help you get there. Even though I encourage my clients to get these nutrients from foods as much as possible, there’s nothing wrong with taking supplements if you’re struggling to meet your needs with food alone.

Vegan Sources of Protein

I get a lot of questions about protein in the vegan diet. It’s a topic that requires a lot of myth busting because most people think of meat when they think of protein. Plant foods contain some amount of protein, and research shows that vegan diets typically meet or exceed recommendations. On top of being very doable, it’s also really beneficial to consume mostly plant proteins for cancer prevention and treatment. That’s because they contain less saturated fat and more fiber, healthy unsaturated fats, vitamins, minerals, and phytochemicals.

Your protein needs will be higher if you’re on a vegan diet and recovering from surgery, chemotherapy, and radiation. Getting enough protein is absolutely essential to support your healthy cells, so please make sure to talk to your care team or a registered dietitian to make sure you’re meeting your needs. The last thing I want is for your body to lack the nutrients and energy it needs to get through treatment. As long as you eat enough calories, eat a variety of foods, and include legumes (foods like beans and soy) in your diet, you’ll be able to meet those needs. Legumes are important because your body relies on their nutrients to build protein, so make sure to eat them on a daily basis.

You might be surprised to learn just how many plant foods contain protein. The best sources include:

  • Legumes, which include all types of bean (chickpeas, pinto, navy, black, kidney, soybeans, etc), lentils, peas, and peanuts

  • Soyfoods like soymilk, tofu, tempeh, and edamame

  • Whole grains like quinoa, brown rice, tortillas, oats, cereal, bulgur, whole-wheat bread and pasta

  • Nuts and nut butters like peanuts, pistachios and almonds

  • Seeds like pumpkin and sunflower

A lot of people ask me if they have to combine plant proteins like beans and rice to make a “complete” protein. The answer is no. As long as you consume a variety of these foods over the course of a day, your body will have the nutrients it needs to build protein.

If you’re looking for cooking inspiration, I have a lot of recipes that feature vegan proteins:

Additional Considerations for the Cancer Population

One reason vegan diets are so helpful in reducing cancer risk is because they’re really high in fiber from so many fruits, vegetables, whole grains and legumes. But there are times when getting a lot of fiber isn’t so helpful. If you’re recovering from surgery on your gastrointestinal tract, or experiencing diarrhea related to medications or treatment itself, fiber can irritate the gastrointestinal tract and make symptoms worse. In these situations, a low-fiber diet may be best, depending on what your care team prescribes.

Getting enough calories on a vegan diet is another important consideration. You naturally may consume less calories if you’re eating mostly plant foods, and this can be a problem if you’re losing weight during treatment and need to bump calories. However, vegan diets aren’t designed for weight loss and they CAN absolutely be as high in calories as any other diet - or even more! Make sure to include calorie-rich foods like nuts and nut butters, avocado, vegetable oils, beans, whole grains like brown rice and quinoa, dried fruit, and starchy vegetables.

Following a vegan diet during treatment can be challenging and may require some support from a registered dietitian who specializes in cancer and plant-based diets. If you’re struggling to maintain your weight and meet your nutrient needs, registered dietitians like me are uniquely positioned to address these challenges and help you develop an individualized nutrition plan.

The Bottom Line

Vegan diets are packed with cancer-fighting plant foods and nutrients, which is why research supports their use for cancer risk reduction and treatment. Planning will be really important to make sure you’re meeting all of your nutritional needs while excluding animal foods. Cancer-specific challenges that may come up when following a vegan diet will warrant the support of a registered dietitian like me who can help you plan a diet that is adequate in calories, protein, and other nutrients. If you have questions or comments about vegan nutrition in general or during treatment, please drop them below and we can continue the conversation.

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