Anticancer Diet Basics
In this post, integrative radiation oncologist Brian Lawenda M.D. and I provide a brief overview of the seven nutritional factors we consider to be the most important in helping to prevent and overcome cancer*.
1. Increase the amount of cancer-fighting phytonutrients in your diet
Phytonutrients (Greek for “plant nutrients”) are naturally occurring compounds that are found mainly in plant foods such as vegetables, fruits, legumes, nuts, herbs, spices or mushrooms.
Many of these compounds have similar cancer-fighting effects as the drugs used by oncologists to treat cancer, and act on various stages of cancer’s development. They are thought to halt the development and spread of cancer cells, notably by promoting cancer cells to self-destruct (apoptosis) or by blocking the growth of new blood vessels to feed growing tumors (angiogenesis).
Eating a wide variety of foods containing these compounds is likely to be more protective than eating a large amount of just one type. For instance, although broccoli contains several compounds with have anti-cancer actions, eating it every day of the year isn’t likely to offer as much protection as, say, eating broccoli one day, peppers the next, tomatoes and onions the day after that, etc.
Different plant foods also reinforce each other’s effects; for instance, the antioxidant lycopene in tomato skins is absorbed better when the tomatoes have been cooked with olive oil and garlic than when eaten on their own. This is called “nutrient synergy” and is an important concept to remember when preparing meals. (I discuss nutrient synergy in more detail in my book, Zest for Life: The Mediterranean Anti-Cancer Diet.)
If you are having trouble eating large quantities of fruits and vegetables in your daily diet, one way to increase the amount of their important nutrients is by using a juicer. This will enable you to “eat” many more fruits and vegetables than you could if you ate them in their whole form. However, whenever possible, do eat fruits and vegetables in their whole form as they are even more nutritious than their juice; only use a juicer to top up your anticancer phytonutrients, but not to proivide the bulk of these.
I recommend juicers that “masticate” or crush rather than grind and expel the juice. Masticating juicers extract significantly more of the anti-cancer nutrients than the other types of juicers (i.e. centrifugal and pulp ejection juicers) which simply shred and expel many of the important parts of the fruits and vegetables into a waste container.
Carbohydrates are a key macronutrient, for the body converts them into glucose, which is used to fuel our muscles and organs, including – most importantly – our brain. However, some types of carbohydrate are more beneficial than others, and some are downright unhealthy.
All vegetables and fruits, nuts, seeds, legumes and whole grains contain a significant proportion of carbohydrates. When they are whole and unprocessed, they also contain a wide range of important nutrients and plant chemicals that keep us healthy and can help to protect us from cancer. We should eat these daily.
Refined carbohydrates are another matter. They largely consist of starch that is devoid of nutrients – “empty calories” in other words – and this can increase our cancer risks in various ways:
- For one, the absence of cancer-protective plant chemicals means that our body has fewer resources to defend itself against rogue cells that may grow into tumors.
- In addition. sugar and refined starches contribute to weight gain, and as scientists have found, body fatness is a key cause of several cancers.
- Moreover, eating sugar and refined carbohydrates triggers the production of hormones that may promote cancer. When we eat sugar or refined flour our blood-sugar (glucose) level rises. To stabilize this, our pancreas produces a hormone called insulin. This also acts as a growth factor for tumor cell proliferation and is accompanied by the release of another hormone, insulin-like growth factor-1 (IGF-1), that is thought to further stimulate cell growth and inhibit spontaneous cancer cell death (apoptosis).
So, it’s important to distinguish between “bad” carbohydrates (refined and nutrient depleted, they push blood-glucose levels sharply higher and trigger IGF-1 production) and “good” carbohydrates (they are nutrient-dense and high in fiber, and don’t boost blood-glucose levels as sharply).
As a general rule of thumb, sugar, sweetened foods and drinks and any foods made from white flour (cakes, cookies, candies, white bread, crackers, French fries, etc.) should be avoided.
On the other hand, healthy carbohydrates are found in:
- Non-starchy vegetables and fruits (particularly the non-tropical fruits: apples, pears, oranges, grapefruits, peaches, plums, apricots, berries, etc.)
- Legumes (beans, chickpeas, lentils, whole and split dried peas, etc.)
- Nuts, seeds and whole grains (brown rice, buckwheat, wild rice, quinoa, barley, whole-wheat pasta, whole-grain bread, etc.)
3. Be careful about the types of fat you eat; avoid “bad” fats, favor “good” fats
- Increase the risk of developing cancer (especially more aggressive cancers) and cancer progression
- Suppress the immune system and increase inflammation in the body
- Increase the risk of dying from numerous cancers (i.e. breast, prostate, colorectal, lung).
Unhealthy fats include trans fats (found in partially and fully hydrogenated fats and frying oil) and fats high in omega-6 fatty acids (such safflower, sunflower, corn, soy or cottonseed oil). Both trans fats and omega-6 fatty acids are thought to promote inflammation in the body, which can fuel the growth and spread of cancer cells. They can also block the body’s utilization of healthy fats, such as omega-3-rich fish oils.
Animals fed with omega-6-rich grains such as soy and corn generally produce eggs, milk and meat that are also rich in these fats; for this reason, avoid factory-farmed animal foods and seek out, wherever possible, meat, milk and eggs from grass-fed and free-ranging animals.
Saturated fats are a grey area; for a long time they were thought to promote cancer by fuelling inflammation and causing weight gain (two major cancer risk factors); however, recent investigations have cast doubt on this hypothesis, and more research is needed to obtain a clearer picture. (For more information about the link between saturated fats and cancer, read Fats 101.)
Healthier fats include:
- Monounsaturated fats, such as those found in olive oil, avocados, nuts, seeds and canola oil, and
- Polyunsaturated fats, especially those rich in omega-3 fatty acids, found in fatty, cold-water fish (such as sardines, salmon, mackerel, anchovies, herring); eggs, milk and meat from farm animals fed omega-3 rich feed or from wild animals; flaxseeds, walnuts, walnut oil, canola oil, and green leafy vegetables.
To ensure an adequate intake of omega-3 fatty acids, aim to eat oily fish two to three times a week. These fish are high in protein and omega-3 fatty acids: cod, sablefish, salmon, mackerel, sardines, and anchovies. Smaller fish (i.e. sardines, mackerel, and anchovies) & wild salmon have less mercury and PCBs (a toxin) than bigger fish like tuna, swordfish and shark, which should generally be avoided. Consider taking omega-3 supplements if you do not eat fish regularly
The consumption of processed and red meat is associated with an increased risk of colorectal cancer. Several factors may contribute to this:
- Corn and soy-fed animals (unless the package says otherwise, they were most likely fed corn or soy) are higher in pro-inflammatory omega 6-fatty acids and saturated fats.
- Many commercially-raised, non-organic, animals are subjected to growth hormones to produce larger and faster growing animals. These growth hormones may stimulate cancer cells as well.
- Processed meat (e.g. bacon, bologna, hot dogs, ham, deli meats) contains added nitrates which are converted into potentially cancer-causing nitrosamines in the gut.
- Cooking red meat at high temperatures can produce other cancer-causing compounds, so rather than flash-frying or barbecuing, gentle braising or stewing are safer cooking methods.
The American Institute for Cancer Research recommends limiting cooked red meat consumption to 18 oz (equivalent to 24 oz raw meat) a week, and avoiding processed meats altogether.
5. Limit the amount of dairy products in your diet
Dairy is a controversial topic in the cancer context: critics claim that growth factors, hormones, saturated fats and pesticide residues in milk increase cancer risks, whereas defenders argue that in particular calcium and vitamin D in cows’ milk may have a protective effect.
According to the AICR, milk probably decreases the risk of colon cancer and possibly that of bladder cancer, but diets high in calcium from milk and dairy products increase the risk of prostate cancer.
Milk is not indispensible to human health; indeed, many populations do not consume milk at all because their bodies cannot produce the enzyme needed to digest it, and they are nonetheless healthy! Calcium — for which many people drink milk — can be obtained from many other sources: small fish eaten with their bones (e.g. whole canned sardines), meat (when rendered on the bone in stews and broths), green leafy vegetables, nuts and legumes.
When consuming dairy, why not take our cues from the Mediterraneans? Here, dairy is usually eaten in small portions – almost as a condiment rather than a major food group. Milk by the glass is rarely consumed, and the most popular dairy products include fermented curds and cheeses made from goats’, ewes’ and occasionally cows’ milk (e.g. kefir, yogurt, halloumi and feta cheese).
When you do eat dairy products, seek out the highest quality possible, made with milk from pastured organic cows. Moreover, try replacing dairy with non-dairy options such as almond, hazelnut or soy “milk” and yogurt, which can easily be used to replace cow’s milk in most recipes (though make sure they are not heavily sweetened).
The ethanol in alcoholic drinks contributes to several common cancers, including those of the breast, mouth and throat and esophagus; some research also links it to liver and bowel cancer. The risk of some alcohol-related cancers is even greater in smokers.
Therefore the AICR recommends that if alcohol is consumed at all, it should be limited to two drinks a day for men and one for women. The AICR defines “one drink” as half a pint/250ml of normal strength beer or cider; a small (1oz/25ml) measure of spirits, or one small (4fl oz/125ml) glass of wine.
7. Avoid Cancer-Causing Chemicals
Some foods may contain cancer causing substances, and although these are usually present in trace amounts only, it’s best to reduce your exposure to them wherever possible.
As mentioned above, some carcinogens are found in meat cooked at high temperatures (e.g. barbecued or flame-grilled). Marinating meat with spices and herbs can reduce the formation of these compounds, as does slowly cooking meat at low temperatures. Meats preserved with nitrites, smoked meat and fish may also contain carcinogenic compounds and are best avoided.
Organic food should also feature in a comprehensive anticancer diet. For one, organic produce contains more phenols – natural plant chemicals – and a more favorable omega-6-to-3 ratio of essential fatty acids, than non-organically grown produce. Moreover, organic produce contains fewer pesticide residues. And even though most conventional pesticide residues are deemed “safe,” in people whose bodies’ detoxification capacity is impaired by cancer and its treatments, even “safe” levels of pesticides may be too much.
Meanwhile, the meat, milk and eggs from organically reared animals also contain more beneficial nutrients, with the added plus that these animals are not routinely treated with hormones and antibiotics that can leave residues in the animal products. Buy organic, pasture-fed animal products wherever possible; the higher price can be offset by eating smaller portions, which is healthier anyway (see section 4, above).
It’s not an “all-or-nothing” choice; if you can’t afford to go 100% organic, pick those foods that you eat frequently and/or that may be particularly prone to carrying pesticide residues and replace these with organics.
The Environmental Working Group publishes a Shopper’s Guide featuring the 12 foods that are highest in pesticide residues (the “Dirty Dozen” features apples (worst), celery, sweet bell peppers, peaches, strawberries, imported nectarines, grapes, spinach, lettuce and cucumbers) and those that are least-contaminated (the “Clean Fifteen” include mushrooms (best), watermelon, grapefruit, sweet potatoes, cantaloupe, kiwi, eggplant, mangoes, asparagus, sweet peas, cabbage, avocado, pineapples, sweet corn and onions). Print out this list and bring it shopping with you; when buying produce that’s high on the “Dirty Dozen” list, make sure it’s organic; when choosing from the least-contaminated foods, conventionally-grown items are fine.
Another diet-related risk factor emanates from so-called aflatoxins, toxic substances produced by moulds or fungi and found on cereal grains, legumes, seeds and nuts (especially peanuts) stored in warm, damp conditions. According to the AICR, exposure levels are low in Europe and Australia, higher in the U.S. and high in many low-income countries – especially tropical regions with a warm, damp climate, poor storage facilities and incomplete aflatoxin monitoring.
To reduce potential aflatoxin exposure, buy grains and nuts (particularly corn or peanuts) from reputable sources, store them in a dry, cool place (ideally the refrigerator or freezer) and do not keep them for more than a few months before eating.
Another potentially problematic compound is bisphenol-A (BPA). It is used to make plastic containers and the linings that coat the insides of food and drink cans and is thought to act as a “xenoestrogen” – a substance that acts like estrogen and thereby may stimulate hormone receptors on cell membranes. Moreover, even at weak concentrations BPA has been shown to block the effects of several commonly used chemotherapy agents on breast cancer cells.
Experts disagree at which concentrations BPA may be dangerous, but until more is known about safe levels, we’re best-off minimizing our exposure to BPA. This can be done by:
- Buying fresh, unpackaged foods and preparing meals from scratch
- Buying or storing food in glass or stainless steel, rather than plastic containers
- Feeding babies with glass, rather than plastic bottles
- Drinking water from glass or stainless steel bottles rather than plastic;using ceramic, glass or metal bowls to prepare food (esp. if you use a microwave oven.)
- Instead of a plastic water kettle, use an old-fashioned enamel or stainless steel stove-top kettle
Take it one day at a time
If all this seems like rather a tall order, don’t worry — you don’t have to turn your diet around overnight. The most sustainable improvements are usually achieved by gradual, not drastic, changes. Get help from your partner, family, friends or a nutrition coach to plan how you will improve your diet to bolster your body’s defences against cancer. And know that with every portion of broccoli you eat, every beer you decline and every half-hour walk, you are doing something positive for your health.
This post was co-authored by radiation oncologist Brian Lawenda M.D. and first published on Integrative Oncology Essentials.