Dr. Day is a cardiologist/electrophysiologist at the Intermountain Medical Center Heart Institute in Salt Lake City, Utah. He graduated from Johns Hopkins Medical School and completed his residency and fellowships in cardiology and electrophysiology at Stanford University. He is the former president of the Heart Rhythm Society and currently serves as the president of the Utah chapter of the American College of Cardiology.
How to Prevent Cancer: The Anti-Cancer Diet
As hard to believe and sad as this may sound, today it’s estimated that 1 in 2 men and 1 in 3 women in the US will get cancer at some point in their lives (1).
While genes do play a role in cancer development, the good news is that it has been estimated that 90-95% of cases are caused by lifestyle and environmental factors. This means you do have a lot of control over whether or not you develop cancer at one point in your life. Some researchers now feel that by following a healthy lifestyle, roughly 75-80% of cancer cases would be prevented (2).
Cancer Can Strike Anyone
I have personally always feared cancer, feeling powerless against this enemy. I am blessed that cancer does not run in my family, but I know that certainly does not make me immune. I want to believe that if we do everything right we will be protected from all health tragedies, but deep down I know that is not the case.
My dear colleague and friend just recently began chemotherapy for metastatic lung cancer; he has never smoked a day in his life, has no family history of cancer, has been running marathons his entire life, and eats a healthy diet. It just does not seem fair, someone who has always lived a healthy life developing stage 4 lung cancer at a young age.
What causes cancer?
According to studies, 25–30% of cancer cases are due to tobacco use, 30–35% are linked to a poor diet, and 15–20% are due to infections. The remaining percentage are due to environmental factors including alcohol, radiation, stress, lack of physical activity, environmental pollutants, etc. (2)
What can I eat to prevent cancer?
I am often asked this question so I want to summarize what I’ve learned after reviewing many medical studies on the “anti-cancer” diet topic. First and foremost, focus on eating a diet that is filled with protective fruits and vegetables and low in inflammation causing foods and preparation methods.
This type of diet will help you to reach and maintain a healthy weight, which studies have shown us is a protectant against cancer development. Obesity increases the risk for developing cancer due to the on-going stress and inflammation it puts on the body, therefore a diet that is very high in nutrients, but overall low in calories, is the best kind for protecting against cancer (3).
Here is how to go about adopting an anti-cancer diet:
1. Make fruits and vegetables the star of your meals-
According to numerous credible studies, all fruits and vegetables seem protective against cancer. This is because fruits and vegetables contain vital antioxidants and phytochemicals.
Antioxidants fight something called “free radicals” within the body. Free radicals are really a by-product of living a normal life; they are produced by our everyday actions like walking and eating, however when they become outnumbered due to their counterpart antioxidants being too low within the body, they can cause all kinds of harm.
Some studies have shown that more than 25,000 different phytochemicals are in fruits and vegetables. Phytochemicals are the plant chemicals that nourish us and help to keep us healthy and free of cancer (4).
Fruits and vegetables have been shown to help protect us against almost all forms of cancer. Interestingly, certain studies show that fruits and vegetables are especially helpful in preventing breast cancer in women who are not physically active (5). While eating a diet high in fruits and vegetables is not an excuse NOT to exercise, it is interesting that a healthy diet high in phytochemicals and antioxidants from fruits and vegetables could be protective against cancer even for people who are unable to exercise regularly, perhaps when they are healing from an injury or another physical condition.
This is just one more reason why an anti-cancer diet is so important. A wide variety of fruits seem to be best for optimal cancer protection. For example, the rockstar of fruits, blueberries, have been shown to help prevent breast cancer (6). In addition, all types of citrus fruits, oranges, grapefruit, lemon and lime juice for example, are also correlated with a decreased risk of developing breast cancer (7).
A wide variety of vegetables can help to prevent cancer, including all leafy greens like spinach and kale, mushrooms, onions, tomatoes, broccoli, cauliflower, and many more. In fact, there are basically zero vegetables that do not contribute at least something towards preventing cancer (8).
2. Consume cruciferous vegetables regularly-
Data are especially strong for the cancer-preventative properties of all cruciferous vegetables. Cruciferous vegetables include broccoli, cauliflower, brussel sprouts, kale, bok choy, and various types of cabbage.
While fruits and veggies in general are very potent anti-cancer agents, cruciferous vegetables seem to be some of the strongest, thanks to their potent sulfur-containing phytochemicals. The compounds found in cruciferous vegetables can knock out cancer carcinogens before they even start turning ordinary harmless cells into cancerous ones. It’s best to ideally consume some sort of cruciferous vegetables everyday if you can, but if not, aim to have them as often as possible.
Try buying the organic varieties of fruits and vegetables whenever you have access to them, so that you limit pesticide exposure. And consume the freshest cruciferous vegetables that you can, since they begin losing nutrients quickly after being harvested. One great option is to buy frozen vegetables, since these are often picked at their peak of freshness and come in organic varieties that can still be bought at good prices. For much more information on cruciferous vegetables, you can refer to my article here.
3. Consume the right kinds of carbohydrates-
Studies have shown that sugary processed foods (also called simple carbs) increase the risk of breast cancer. The types of sweets to avoid include: soda, sweetened juices and sports drinks, cookies, cake, flavored yogurts, ice cream, candy, sweetened cereals, and so on (9).
In studies, women who ate diets high in sugar and simple carbohydrates were at a 35% increased risk of breast cancer, especially if they were also overweight. While simple sugars are a risk factor for cancer, 100% real, whole grains can be a protector. Whole grains including barley, sorghum, millet, rye, and oats contain important antioxidants, vitamins, minerals, and fiber- so these are a good addition to any diet, as long as they are not refined and stripped of their beneficial nutrients (10).
4. Consider eating a plant-based diet more often-
Studies show that a plant-based diet is often one of the best ways to prevent cancer. Contrary to popular belief in the U.S., animal products are not the only source of protein-legumes, nuts, seeds, 100% whole grains, and even many vegetables contain plenty of protein too, in addition to many other nutrients like fiber and trace minerals (11).
I personally eat legumes, nuts, and seeds daily as a great source of plant-based protein and fiber. The American Heart Association recommends eating both legumes and nuts on most days of the week because they are good for the heart and for cancer prevention.
5. Make sure to eat a high amount of dietary fiber-
The average American eats roughly 15 grams of fiber daily, while the daily recommended amount according to nutrition experts is around 30 grams daily. If you aren’t eating a diet high in fruits and vegetables already, and you aren’t normally a “plant-based” eater who consumes legumes, nuts, and seeds then chances are you’re not getting enough dietary fiber.
In studies, fiber is correlated with preventing colon cancer because a high fiber diet results in a faster gut transit time for your food (12). Fiber helps to pull toxins, waste, and heavy metals out of your gut, leaving you with a healthier gut flora. It’s an excellent way to prevent constipation and it also helps to make you feel fuller, so you are less likely to snack on junk foods throughout the day and can stick to a healthy diet.
If you don’t know how much fiber you eat each day, there are many excellent apps now that can help you to track this. Personally, I track my nutrient intake via the app “Lose It” and “Health” on my iPhone. I average 68 grams of fiber daily!
6. Include nuts and seeds in your diet often-
Nuts have been shown to help prevent cancer according to studies. Due to their high amount of antioxidants and trace minerals. Nuts, like all essential healthy fats, also help to make you feel satisfied after eating so you can go longer without snacking and minimize overeating.
Focus on consuming nuts and seeds like almonds, chia seeds, flax seeds, and walnuts to get plenty of healthy plant-based fats and omega-3 fatty acids which are protective against cancer (13). Minimize saturated fats from animal products and refined, hydrogenated oils that are used in many store-bought packaged foods.
7. Limit the amount of red and processed meats you consume-
There are significant data linking red and processed meats with cancer. For example, bladder cancer has been shown to increase as more red and processed meats are included in the diet (14). According to studies, red meat also increases the risk for lung, prostate, and breast cancers too (15), (16), (17).
Until recently we have not known why red meat is consistently linked to an increase risk of cancer. In a recent study published in Proceedings of the National Academy of Sciences, Dr. Ajit Varki identified the possible link between red meat and cancer. This link is from a sugar molecule, Neu5Gc, which is found in red meat but not in poultry or fish. While Neu5Gc is found in other animals, this molecule is foreign to humans and appears to trigger an immune reaction which may then lead to cancer.
Perhaps this risk could be avoided with wild or organic red meats but there are not much data as of now that tell us whether or not this is the case. So in the meantime, regularly consume plant sources of protein like beans, real whole grains, nuts, and seeds, and consume less low-quality meat products.
When you do include meat in your diet, treat it like it is a condiment- added to your meal to add a bit of extra flavor- but not the main dish. I learned this from when I lived in Asia in the 1980s; I was surprised to see that meat was just used to flavor the dishes rather than being the star of the main course, as it is in the U.S.
It is important to remember that meat is not the only source of protein. We should eat 1 gram of protein per 1 kilogram of body weight. Very active people may need a higher amount, but there are many non-meat protein options such as legumes, nuts, and seeds.
Fish and organic, cage-free poultry are better options for cancer prevention according to studies (18). The American Heart Association recommends fish twice weekly. This could be the best cancer preventing source of animal protein there is, especially if it is a wild oily fish. My personal favorite is Wild Alaskan Salmon; you can read more about how I include salmon and other fish in my diet here.
8. Prepare your food in the healthiest ways possible-
Some cooking methods preserve more nutrients in your food and release less toxins than others. When cooking meat, be careful not to burn it or cook it at very high temperatures at this can release toxins and carcinogens into the food (19). The safest way to cook meat is to boil or steam it, but try to minimize using a BBQ. Also choose fresh cuts of meat rather than smoked, cured, or preserved meats
Another toxic group of foods to avoid is oxidized oils, meaning oils that turn rancid or lose their health benefits when they are cooked at high temperatures. Oils to avoid cooking at high heat- meaning frying, BBQing, or even roasting with them- include soybean oil, safflower oil, canola ice, corn oil, sunflower oil, and other vegetable oils. Even olive oil, which normally healthy, does not have a “high smoke point” and cannot withstand very high heat cooking. Try using coconut oil for high heat cooking instead, since it has a higher smoke point before turning rancid.
When cooking, try using cancer-preventative fresh herbs and spices to naturally flavor fresh food yourself, rather than buying pre-flavored packaged foods which likely contain artificial ingredients, sodium, sugar and preservatives. Try using curry, ginger, garlic, thyme, oregano, and basil which all have antioxidant abilities and other anti-cancer benefits (20).
The Big Picture
Cancer often starts developing many, many years before it ever manifests. While potentially cancerous cells are formed inside of our bodies all the time, fortunately our immune system normally takes care of killing these dangerous cells.
In the end we are all mortal and something will fail us at some point in our lives.
The key is to live as healthy as we can to avoid any unnecessary suffering. However, when tragedy does unfortunately strike, we need to find meaning in our health challenges. I am praying that my friend quickly recovers from his struggles with lung cancer. And I also hope that you can use the information in this article to begin eating a powerful anti-cancer diet that will help protect you and your family from disease as much as possible.
If you have a history of cancer or want to learn more, you will want to be sure to speak with your doctor about what diet is right for you and can best help to protect you against cancer.
What changes have you made in your diet to help protect you from cancer?
Disclaimer Policy: This website is intended to give general information and does not provide medical advice. This website does not create a doctor-patient relationship between you and Dr. John Day. If you have a medical problem, immediately contact your healthcare provider. Information on this website is not intended to diagnose or treat any condition. Dr. John Day is not responsible for any losses, damages or claims that may result from your medical decisions.