Nutrition and Cancer Prevention

A Plant-Based Diet and Variety Are Your Best Weapons

An Article By
Suzanne Dixon, MPH, MS, RD
Dietitian & Epidemiologist
University of Michigan Comprehensive Cancer Center

The amount of information that we receive about the role of nutrition in preventing cancer is overwhelming. We hear about research studies on the news. We see programs on TV. We read about it in the newspaper, magazines, and books. It’s on the internet. How can you sort through it all? Who’s right? Too much information at once, and you become overloaded. Then you say, "Forget it, I won’t even bother."

But giving up would be giving up the amazing power and control that you have over your risk of cancer. "What?" you say. "I can lower my risk of cancer just by what I eat?" YOU BET YOU CAN! That’s what’s so exciting about nutrition and cancer. Food is POWER and you control it.

Did you know that about 1/3 of all cancers are caused by poor diet? Another 1/3 of cancers are caused by tobacco (cigarettes, snuff, etc.). In 1999, about 1.5 million people were diagnosed with cancer. Think about that for a minute. That means that if everyone ate well and stopped using tobacco products, about 1 million of those cancers NEVER WOULD HAVE OCCURRED. That’s how much power YOU have over YOUR health. Amazing, isn’t it? Read on to learn what type of nutrition best prevents cancer.

The single, most important thing that you can do to reduce your risk of cancer, is to eat a plant-based diet. Plant-based diet? What does that mean?

Many hundreds of research studies tell us that if we focus our diet on eating a wide variety of fruits, vegetables, whole grains, and legumes (beans, lentils, chickpeas, etc.), we are doing the best thing possible to lower our risk of cancer.

Eating lots of fruits, vegetables, grains, and legumes is the dietary pattern that is most associated with prevention of cancer. Places in the world where the diet is mostly vegetarian have the lowest rates of cancer. Much lower than in the U.S.! This doesn’t mean you should never eat meat. Rather, you should try to increase these plant foods in your diet, and use meat less.

Foods from the plant kingdom have many other things in them besides vitamins and minerals. These other nutrients are called phytochemicals or phytonutrients. ‘Phyto’ means plant, so phytochemicals are ‘plant chemicals’. We could call them ‘Fight-O’ chemicals because they fight cancer so well. Phytochemicals lower the risk of cancer. It’s THAT SIMPLE.

Did you know that Beta-carotene is a phytochemical? Beta-carotene is a member of a family of plant chemicals known as carotenoids. Carotenoids give fruits and vegetables their bright colors. Beta-carotene is orange and gives carrots and sweet potatoes their bright orange color.

To date, over 600 carotenoids have been identified in nature! Beta-carotene just happens to be the most well known carotenoid. Much less is known about the other carotenoids (for example, alpha-carotene, lutein, lycopene, zeaxanthin, and many, many others).

Why Not Just Get Phytochemicals from Supplements? It’s So Much Easier.

People often ask, "Can’t I just take a beta-carotene or lycopene pill and get my phytochemicals that way?" The answer is "DEFINITELY NOT!" But why not?

If you get beta-carotene from a pill, what about the other hundreds of phytochemicals that are not in that pill? Scientists are just beginning to understand how phytochemicals fight cancer. They haven’t even discovered all that plants have to offer. New phytochemicals are being identified every day. We don’t know which phytochemicals, in what amounts best fight cancer.

But we do know something. You MUST get these things from plant foods, NOT supplements, to have them fight cancer. In fact, several studies show an INCREASED risk of cancer in people who took supplements of certain phytochemicals. But research does agree that people who get more of these phytochemicals from foods have lower risk of all cancers! One way phytochemicals help protect against cancer is by acting as antioxidants. Let’s see how antioxidants work in the body to fight cancer.

Every human being needs oxygen to live. The body needs a constant supply of oxygen to produce energy – energy that’s needed to power a beating heart, keep the lungs inhaling and exhaling, allow our muscles to work, and all the functions of day to day life. But oxygen can also cause damage in the body.

As our bodies use oxygen to produce energy, oxygen byproducts, called free radicals are formed. Another name for free radicals is oxidants. Free radicals (or oxidants) cause oxidation, a process that damages cells and can lead to cancer. But what does oxidation really mean?

Think of an old rusting bridge. This is oxidation. Oxidation causes the metal to rust. The rusted metal is weak. It can’t perform its function. This same exact process happens in your body. Well, you don’t actually rust, but your body parts and cells do get damaged and weak. They stop performing their functions. And this can lead to cancer.

So, here’s where antioxidants come in. Remember that we called these bad oxygen byproducts free radicals or oxidants? Antioxidants are ‘against’ oxidants. It’s right in the name! Antioxidants stop the bad effects of free radicals before they can damage your body and cells. They change free radicals into harmless waste that the body can eliminate. Research shows that antioxidants may even be able to ‘undo’ some of the damage that’s already been done.

Antioxidants from different foods work in different ways to battle free radicals. That’s why it’s so important to get your cancer-fighting antioxidants from all different foods. Studies show that people who eat a wider variety of foods also have lower risk of cancer.

A lot of phytochemicals, including beta-carotene, act as antioxidants to protect against cancer. Other phytochemicals that aren’t antioxidants protect against cancer through many other complex processes that researchers are just beginning to understand.

We already know that the best place to get these cancer fighting phytochemicals is from plant foods – fruits, vegetables, whole grains, and legumes. But, do you eat enough of the right kinds of plant foods? REMEMBER, a WIDE VARIETY of plant foods is the key to cancer prevention.

The last time you ate a piece of fruit, what was it? Chances are, it was an apple or a banana. It’s not that these foods aren’t good for you, they are! But, if you just stick to the foods you are familiar with, you won’t get the maximum cancer fighting power. When did you last eat a kiwifruit or dark red berries such as strawberries, blueberries, or dark cherries? How about mangos and guavas? Boysenberries? Blackberries?

Now think about vegetables. Not counting potatoes and corn, what vegetables do you regularly eat? Do you eat fresh spinach? Broccoli? What about greens, such as collard greens, mustard greens, kale and kohlrabi? Do you include asparagus and squash? If not, you should!

Remember, there are hundreds, possibly thousands of cancer fighting phytochemicals in plants. If you just stick to a familiar few types, you’ll miss out on all the other cancer fighting phytochemicals that are found in the foods you don’t eat on a regular basis.

And don’t forget about whole grains. Most bread doesn’t count. It’s from refined, white flour. You need to get whole grains, which include things like oatmeal and whole grain cereals. Why not start using some different whole grains, like barley, amaranth, rye, buckwheat, and others?

What if I Already Have Cancer?

If you’re undergoing treatment, don’t worry about these changes now. While in treatment, you must eat whatever you can, whenever you can and keep your weight up. Once you get through treatment and are feeling a little better, then you can increase the plant foods in your diet.

If you’ve already had cancer, it’s even MORE important that you begin to focus on eating more plant foods. If you’re not in treatment or are already done with your treatment, you should begin making these changes TODAY.

Scientists now know that not only do these foods help prevent cancer, they may actually help people who already have cancer. This is because they may help undo some of the damage that’s already been done to your body cells. The positive effects of phytochemicals and antioxidants occur at all stages of the cancer process.

How Do I Know if I’m Eating Enough of a Variety of Plant Foods?

Below is a list of fruits and vegetables. Take a pencil and put a check mark next to the ones you eat on a regular basis (at least a few times per month). You should have check marks by at least ½ (about 20 fruits & 20 vegetables – 40 total for both lists) of these foods. If not, start adding them to your diet today.