How Food Affects Cancer

Eating for cancer prevention depends on knowing which foods can damage body cells and which foods can protect cells from damage.

I’ve heard people say that they believe cancer is unavoidable It’s true that we inherit a tendency to develop certain cancers, but scientists estimate that only about 5 percent of all cancers have a genetic origin. On the other hand, about 35 percent of cancers are related to nutritional factors. (To fill in the numbers, about 30 percent of cancers are thought to be related to tobacco use, and the remaining 30 percent are attributed to all remaining factors, including bacterial and viral infections, pollution, radiation, and occupational hazards.) Some foods can damage body cells, setting them up for precancerous changes, while other foods protect cells from damage. Cancer prevention depends on knowing the difference.

Foods to Avoid or Limit

Processed and Red Meats
A growing body of evidence links high intake of processed meats (such as bacon, salami, and bologna) and red meat in general (beef, pork, and lamb) to an increased risk of colon and rectal cancer, and possibly other cancers as well. The reasons are still being investigated, but many experts believe the high concentration of heme iron present in red meat plays a role. Heme iron is a type of highly absorbable iron found only in animal proteins. (Vegetables, legumes, fortified cereals, and other plant foods contain only nonheme iron, which doesn’t appear to carry the same risk.) Heme iron may damage the cells that line the colon, making them more susceptible to cancerous growth. Processed meats are often made from red meat and most contain chemical preservatives, such as nitrites and nitrates, which have been identified as possible cancer-causing agents. What’s more, the processes of curing, smoking, or salting meat creates additional compounds with cancer-causing potential.

I advise avoiding or dramatically limiting your intake of processed meats, including pepperoni, salami, pastrami, hot dogs, bologna, ham, bacon, beef and pork sausages, and bratwurst. If you’re a red-meat lover, enjoy fresh, unprocessed beef, lamb, or pork (preferably lean cuts) no more than twice a week. In other words, go ahead and savor a good burger or steak once in a while, but don’t make ground beef, pork chops, steaks, and beef roasts mealtime staples. Looking on the bright side, cutting more red meat out of your diet means you’ll be more inclined to fill your plate with healthful, waistline-friendly vegetarian proteins like lentils, starchy beans, and whole soy foods.

Salty Foods
Salt is thought to increase the risk of stomach and esophageal cancers by damaging the lining of the throat and stomach. Too much damage can cause changes in DNA and increased cell growth. Also, salt allows H. pylori bacteria to thrive, which can increase the risk of stomach cancer. If you enjoy salty and pickled foods, eat them only in moderation. Limit your intake of salt itself, sauerkraut, pickles, all pickled vegetables and fish, salt-cured fish and meats, and of course all those salty processed meats listed above.

Meats Cooked at High Temperatures
Cooking meats at high temperatures produces chemicals called heterocyclic amines (HCAs), which have been linked to many cancers, including those of the colon, pancreas, bladder, prostate, and breast. The most HCAs are found in proteins (beef, pork, poultry, and fish) that have been fried, broiled, grilled, or barbecued — all cooking methods that typically use high temperatures. Roasting and baking produce fewer HCAs, and poaching, stewing, and boiling meat produce the least. There aren’t any specific guidelines about the amount of HCAs that can be considered “safe” or “dangerous.” I recommend limiting your intake of meat cooked at high heat, but there’s no reason for paranoia. If you love a good grilled steak, feel free to indulge once in a while. Just be sure to trim away excess fat before grilling and cut off charred or burned parts before eating the meat. This goes for chicken, turkey, and seafood too. To further reduce your risk of consuming harmful HCAs, marinate your meat before tossing it on the grill. Marinating meat in a flavorful liquid with plenty of herbs and spices has been shown to dramatically cut back on HCA formation, perhaps because the antioxidants in seasonings block the creation of HCAs. Also, small pieces of chicken, fish, and lean beef cook faster and spend less time on the grill, therefore producing fewer HCAs; so try cooking kebabs instead of large breasts and steaks whenever you can. In general, definitely consider cutting back if you eat beef or other grilled meats more than three times per week.

Good Foods to Choose

Cancer is a disease of opportunity: If a rogue cell has a chance to mutate, it may become cancerous. Along with avoiding mutation triggers, cancer prevention depends on protecting our health and putting up roadblocks to stop precancerous cells from turning bad and running amok. Our best hope is to eat a wide variety of nutrient-dense plant foods, including vegetables, fruits, starchy beans, lentils, and whole grains. Please note that although scientists typically focus on certain nutrients in relation to particular types of cancer, there are probably many beneficial interactions among the compounds in these healthy foods — and they may help prevent cancer in many areas of the body, not just the ones that are mentioned here. So, the strongest cancer-prevention plan is to eat a good mix of healthy plant foods, without focusing too strongly on any one nutrient.

Antioxidant Vitamins and Minerals (Vitamin C, Vitamin E, and Beta-carotene)
Antioxidants are your body’s version of a computer’s antivirus software. Antioxidants circulate through your cells, repairing DNA that has been damaged by harmful, reactive oxygen molecules called free radicals in much the same way that an antivirus program combs a hard drive seeking out and restoring infected files. Left unchecked, damaged DNA may impair normal cell reproduction and growth and set in motion processes that can eventually result in cancer. For this reason, a diet that emphasizes antioxidant-rich foods like vegetables, fruits, and whole grains may be one of your best defenses against cancer. Note that the key word here is foods. Nearly two decades of disappointing research trials have taught us that you’re far better off getting your antioxidants in their natural states, not in the isolated, purified forms found in supplements. Researchers have repeatedly tested high-dose antioxidant supplements to see if they reduce cancer rates, and time and time again, supplements have shown no benefit. (Sometimes they even have adverse health effects.) Some scientists believe that antioxidants work synergistically with other nutrients and compounds in foods, which may explain why stripping them out and plunking them into bottles doesn’t seem to offer any cancer protection. The moral of the story: When it comes to fighting cancer, load up on antioxidants from healthy, delicious foods only.

Vitamin C: Vitamin C is an antioxidant that helps to prevent the formation of cancer-causing nitrogen compounds. Diets high in vitamin C have been linked to a reduced risk of cancers of the stomach, colon, esophagus, bladder, breast, and cervix. Again, these results have been found for vitamin C–rich foods, rather than supplements, which seem less reliable.
BEST FOODS FOR VITAMIN C: Guava, bell peppers (all colors), oranges and orange juice, grapefruit and grapefruit juice, strawberries, pineapple, kohlrabi, papayas, lemons and lemon juice, broccoli, kale, brussels sprouts, kidney beans, kiwi, cantaloupe, cauliflower, cabbage (all varieties), mangoes, white potatoes, mustard greens, tomatoes, sugar snap peas, snow peas, clementines, rutabagas, turnip greens, raspberries, blackberries, watermelon, tangerines, okra, lychees, summer squash, persimmons

Vitamin E: Some research shows that eating a vitamin E–rich diet reduces the risk of stomach, colon, lung, liver, and other cancers, but, as with other antioxidants, vitamin E supplements have largely struck out. I recommend adding vitamin E–rich foods to your diet; they are safe and will help keep you and your cells healthy.
BEST FOODS FOR VITAMIN E: Almonds and almond butter, sunflower seeds and sunflower butter, wheat germ, hazelnuts, spinach, dandelion greens, Swiss chard, pine nuts, peanuts and peanut butter, turnip greens, beet greens, broccoli, canola oil, red bell pepper, collard greens, avocados, olive oil, mangoes

Beta-carotene: Beta-carotene is a powerful antioxidant. Studies have shown that people who eat a diet high in beta-carotene — found primarily in orange and leafy green vegetables — have a reduced risk of cancer, particularly of the lung, colon, and stomach. (These results are for beta-carotene from food sources only. In one study, beta-carotene supplements actually increased the risk of lung cancer in smokers.) Among premenopausal women, one study found that eating a lot of vegetables that include beta-carotene, folate, vitamin C, and fiber reduced the risk of breast cancer by about half.
BEST FOODS FOR BETA-CAROTENE: Sweet potatoes, carrots, kale, butternut squash, turnip greens, pumpkin, mustard greens, cantaloupe, red bell pepper, apricots, Chinese cabbage, spinach, lettuces (especially darker lettuces), collard greens, Swiss chard, watercress, grapefruit (pink, red), watermelon, cherries, mangoes, tomatoes, guava, asparagus, red cabbage

Vitamin D
Experts consider the United States to be in the middle of a vitamin D–deficiency epidemic. We just don’t get enough. In previous generations, vitamin D deficiency wasn’t a problem because people spent ample time in the great outdoors and took in large amounts of the primary source: sunlight. Our skin makes all the vitamin D we need when exposed to sunlight. But the world has changed. We now spend less time outside, and the protective ozone layer has eroded, so sunlight today contains more cancer-causing ultraviolet radiation than it did a few decades ago. Fortunately, most of us use sunscreen regularly to protect our skin, but unfortunately, sunscreen keeps our skin from using sunlight to produce vitamin D. In some studies, low vitamin D levels have been linked to several cancers, including colon and breast. Scientists theorize that vitamin D may help block the development of blood vessels that feed growing tumors and help stop the proliferation of cancerous and precancerous cells. To cover your bases, I recommend eating plenty of vitamin D–rich foods and choosing vitamin D–fortified dairy products. Because few foods provide vitamin D, you should consider a daily multivitamin or separate supplement that provides 800 to 1,000 IUs of vitamin D3 (cholecalciferol, the most potent form).
BEST FOODS FOR VITAMIN D: Wild salmon (fresh, canned), mackerel (not king), sardines, herring, milk (fat-free, 1% low-fat), soy milk, fortified yogurt (fat-free, low-fat), egg yolks, UV-treated mushrooms

Omega-3 Fatty Acids
There is no consensus about the role of omega-3 fatty acids in cancer prevention. However, some research has shown that eating plenty of omega-3s in the form of fatty fish may reduce the incidence and progression of colon, breast, and prostate cancers. Researchers at Columbia University studied more than 21,000 men and found that those who ate the most fish had a 37-percent reduced risk of colorectal cancer. It is believed that omega-3 fatty acids may help prevent cancer by inhibiting cancer-cell proliferation and disrupting steps that are critical to tumor growth. Omega-3 fatty acids also help reduce inflammation, which means that they are likely to help reduce the possibility of cellular mutations. But even if omega-3s don’t directly reduce the risk of cancer, they certainly help keep our bodies strong and healthy. Plus, fish and shellfish are terrific main-course replacements for red meat, which may increase the risk of certain cancers. For all these reasons, I highly recommend adding omega-3-rich foods to your diet. (My Best Foods list that follows includes only the fatty fish that have been shown to be low in mercury, PCBs, and dioxins.)
BEST FOODS FOR OMEGA-3 FATTY ACIDS: Wild salmon (fresh, canned), herring, mackerel (not king), sardines, anchovies, trout (wild, rainbow), Pacific oysters, chia seeds, ground flaxseed, walnuts, butternuts (white walnuts), seaweed, walnut oil, canola oil, soybeans (edamame)

There’s more to good nutrition than vitamins and minerals. All plant foods — grains, fruits, and vegetables — contain small amounts of phytonutrients: naturally occurring chemical compounds that are just as important as vitamins and minerals are for maintaining health. There are thousands of known phytonutrients, many of which have demonstrated the potential to protect us against cancer. Cruciferous vegetables, for example, contain phytonutrients known as glucosinolates, which help inhibit the metabolism of some carcinogens, may stop the proliferation of cancer cells, and cause the body to produce detoxification enzymes. Onions, garlic, and other members of the Allium family of vegetables are rich in sulfur compounds, such as allicin, which appear to have antitumor properties. Lycopene, an antioxidant found in concentrated amounts in cooked tomato products, may offer protection against prostate, lung, and stomach cancers.

Then there are the flavonoids, such as anthocyanins and quercetin, found in plant foods such as berries, onions, apples, and purple grapes. These powerful antioxidants seem to help reduce the type of inflammation associated with cancer progression. Ellagic acid is the latest phytonutrient to enter the scene, although it’s been quietly hanging out in berries, nuts, and pomegranates for millennia. In laboratory and animal studies, ellagic acid has been shown to inhibit cancer-cell growth and deactivate cancer-causing compounds.

Different fruits and vegetables contain various combinations of phytonutrients, so to ensure that you are getting as many different protective compounds as possible, I recommend eating nine servings of vegetables and fruits per day. Go for variety, rather than focusing on just one or two of your favorites.

BEST CRUCIFEROUS VEGETABLES:Broccoli, broccoli rabe, brussels sprouts, cabbage, cauliflower, collard greens, daikon, kale, kohlrabi, mustard greens, rutabagas, turnips, bok choy, arugula, horseradish, radishes, Swiss chard, wasabi (Japanese horseradish), watercress and cress

BEST ALLIUM VEGETABLES:Onions, garlic, shallots, leeks, scallions, chives, ramps

BEST FOODS FOR LYCOPENE:Tomatoes (and all tomato-based products including tomato sauce, paste, soup, and juice), watermelon, guava, pink grapefruit, red bell peppers

BEST FOODS FOR QUERCETIN:Onions, kale, leeks, cherry tomatoes, broccoli, blueberries, black currants, elderberries, lingonberries, cocoa powder (unsweetened), apricots, apples with skin, grapes (red, purple, black), tomatoes, tea, green beans, lettuces, hot chili peppers, celery, chives, red cabbage, lemons, grapefruit

BEST FOODS FOR ANTHOCYANINS:Blackberries, black currants, blueberries, eggplant, elderberries, raspberries, cherries, boysenberries, grapes (red, black, purple), strawberries, plums, cranberries, rhubarb, red onions, red apples, peaches, cabbage (red, purple), red beets, blood oranges

BEST FOODS FOR ELLAGIC ACID:Raspberries, blackberries, strawberries, walnuts, pecans, cranberries, pomegranates, grapes (red, black, purple)

Tea contains compounds called catechins, which are thought to be able to stop the growth of cancer cells and help prevent cellular mutations that contribute to cancer development. In Japan, where tea is the preferred beverage, green-tea consumption has been shown to reduce the risk of stomach cancer among women. In China, green-tea drinkers were found to have a reduced risk of developing rectal and pancreatic cancers compared with non-tea drinkers. Regular tea drinkers have also been shown to be at lower risk for colon, breast, ovarian, prostate, and lung cancers. After analyzing tea’s chemical components, scientists have discovered that black tea, oolong tea, green tea, and white tea all seem to have value as cancer preventive agents, and each variety seems to protect against different types of mutagens.

Herbs and Spices
Herbs and spices have been used as folk medicines for thousands of years. These days, scientists are busy trying to determine which claims for cancer prevention are true and which are myths. A few of the most promising herbs and spices are turmeric, rosemary, and ginger.

Turmeric is the yellow-colored spice found in curry powder. Curcumin, the active ingredient in turmeric, functions as both an anti-inflammatory and an antioxidant, and it may help prevent cancer by interfering with aspects of cellular signaling. In laboratory animals, curcumin has been shown to help prevent cancer of the breast, colon, stomach, liver, and lung.

Rosemary is a wonderful, fragrant herb that is easy to grow and quite versatile when it comes to cooking. I use it in meat dishes, roasted vegetables, and savory baked goods. Rosemary contains the antioxidant compounds caffeic acid and rosmarinic acid. Laboratory studies have shown that rosmarinic acid can protect against cell damage and prevent DNA fragmentation.

Gingerroot has a pungent, spicy flavor that works well in both savory and sweet dishes. This one root contains more than 50 antioxidant and anti-inflammatory compounds, and some of these phytonutrients have been shown to suppress the growth of cancer cells and tumors in laboratory studies. Ginger isn’t a miracle food, but it’s certainly an incredibly healthy addition to a cancer-fighting diet. Try grating fresh gingerroot into stir-fries or hearty stews, steeping a few slices of gingerroot in hot water to make a delicious tea, or adding fresh or ground gingerroot to recipes for healthy muffins or fruit crisps.
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