Guest contributor: Professor Richard Béliveau, Ambassador for Colorectal Cancer Canada.
Our view of cancer has changed a lot in the last few years. Once thought to be a devastating disease that appeared overnight, we now know that cancer is a chronic illness and that in most cases, it takes several decades to reach a clinical stage.
We are all carriers of immature tumours and therefore at high risk of developing cancer, but advances in research have clearly shown that the progression of micro-tumours into mature cancers is strongly influenced by our lifestyle and in particular, our eating habits.
Thanks to rigorous analyses conducted by cancer organizations such as the World Cancer Research Fund, the American Cancer Society, and the Canadian Cancer Society, we can identify 10 key lifestyle elements that increase cancer risk. Consequently, we can adopt certain behaviours to counteract this risk, behaviours which could significantly decrease the incidence of cancer in our societies.
One crucial but generally well-known aspect is of course to reduce exposure to carcinogens such as cigarette smoke, alcohol, and ultraviolet rays.
Tobacco alone is responsible for a third of all cancers because of the radical increase in the risk of lung cancer and a dozen or so other types of cancer in smokers, while alcohol and UV rays are well-characterized inducing agents of cancer of the digestive system and skin cancer respectively.
A lesser known fact is how much diet, excess weight, and physical inactivity also factor into cancer risk. Lack of plant-based foods, overconsumption of foods high in sugar and fat, an excess of red meats, cured meats, and even very salty foods have all been associated with heightened cancer risk.
This diet represents the worst possible combination for staying healthy but the best for promoting cancer growth.
Without exception, every country that adopts a Western-style diet faces an alarming increase in obesity, diabetes, and several forms of cancer.
On the one hand, the excess calories lead to weight gain, and many studies have clearly shown that excess weight and obesity have been associated with an increased risk of several forms of cancer.
On the other hand, the low consumption of plant products deprives the body of thousands of anti-inflammatory and cancer-fighting molecules that could hinder the progression of cancerous cells and reduce the incidence of several types of cancer.
All in all, it is estimated that lifestyle elements linked to food and weight are responsible for approximately one third of all cancers, a percentage equal to the number caused by tobacco, still the most significant carcinogen described to date.
Eating the right foods
Plant foods are a fundamental component of any diet that aims to fight cancer, but several scientific studies suggest that the types of fruits and vegetables chosen could play a role as important as the quantity consumed, because certain foods are special sources of cancer-fighting molecules.
It is not therefore merely a question of ingesting the minimum five servings of fruit and vegetables recommended by public health agencies; it is especially necessary to prioritize those most capable of preventing cancer development.
Let’s seize this opportunity to shift the probabilities in our favour by taking advantage of this arsenal of cancer-fighting compounds existing naturally in certain everyday foods.
Nearly two thirds of the cases of cancer currently affecting the population could be prevented simply by modifying our lifestyles, a positive impact no treatment can possibly match, given the complexity of clinically diagnosed cancer.
On this page, you will find 15 types of foods that help prevent cancer.
GARLIC AND ITS COUSINS KEEP CANCER AT A DISTANCE
- Phytochemical compounds: Allicin, diallyl sulfide, diallyl trisulfide
- Main types of cancer: Esophageal, stomach, colon
Garlic is perhaps the oldest example of a plant used as much for its nutritional properties as for its positive impact on health.
Regarded by the Egyptians and Greeks as a food that grants strength and endurance (the first Olympians were fed on garlic before competitions, making it the first performance-enhancing substance in history!), garlic was also an essential ingredient in the traditional medicine of the first civilizations, used from earliest antiquity as a remedy for a wide variety of conditions, from infections to problems with circulation, breathing, and digestion.
Several population-based studies indicate that people who regularly consume vegetables from the garlic family (garlic, onion, shallots, chives, leeks) have a lower risk of developing certain types of cancer, in particular those of the digestive system (stomach, esophagus, colon). A protective effect against cancers of the prostate, pancreas, and breast were also reported.
Garlic and its close relatives are therefore vital vegetables in the prevention of cancer; for this purpose, it is important to eat them as regularly as possible. The World Health Organization recommends adults eat 2 to 5 g of fresh garlic daily (about one clove).
BERRIES: SMALL FRUIT, BIG ENEMY OF CANCER
- Phytochemical compounds: Anthocyanins (delphinidin), ellagic acid
- Main types of cancer: Breast, colon
Strawberries, blueberries, and raspberries are exceptional sources of cancer-fighting phytochemical compounds.
Because of certain properties, berries are able to interfere with several of the processes involved in the growth and invasive potential of cancer cells.
On the one hand, polyphenols such as delphinidin (blueberry) or ellagic acid (raspberry and strawberry) inhibit the activity of proteins necessary for the formation of a network of blood vessels near tumours (angiogenesis), depriving them of their supply of oxygen and nutritive molecules.
On the other hand, recent studies show that consuming only one serving of blueberries per week is associated with a 31% reduction in the risk of hormone-independent breast cancer in post-menopausal women.
Blueberries could also have a positive indirect impact on cancer risk by specifically blocking the transformation of preadipocytes into mature adipocytes, which reduces fat accumulation and prevents the development of obesity, an important risk factor in several types of cancer.
In the same vein, an analysis of the dietary habits of more than 200,000 Americans revealed that those who consume two servings per week of foods rich in anthocyanins, particularly blueberries, have a 25% lower risk of developing type 2 diabetes and are therefore less susceptible to the heightened risk of cancer associated with chronic hyperglycemia.
Because berry season is relatively short, the fruit is often preserved for later use.
Freezing berries whole is considered the best method to preserve both the integrity of the fruit and its phytochemical content. Jams are also a suitable method, as an analysis of the polyphenols contained in strawberries preserved in this way showed no significant loss after 5 months at 25°C.
However, cooking berries for a long time and subsequently storing them, in the form of pies, for example, seems more problematic, as these things are associated with a significant reduction in anthocyanin content.
CAROTENOIDS PUT COLOUR IN PREVENTION
- Phytochemical compounds: Lycopene, beta-carotene, lutein, fucoxanthin
- Main types of cancer: Prostate, lung, breast
Carotenoids are natural pigments responsible for colours ranging from yellow-orange to purple-red in a large number of fruits and vegetables.
Though over 600 distinct carotenoids exist, beta-carotene (carrots), lutein (spinach) as well as lycopene (tomatoes) on their own represent nearly 80% of carotenoids, and these molecules have been the most studied to date.
The lycopene in tomatoes is the carotenoid whose cancer-fighting action is the best established. Regular consumption of tomato-based products is associated with an approximately 25% epidemiological reduction in the risk of prostate cancer, and this protection can even reach 53% for advanced forms of the disease. This cancer-fighting effect of lycopene has been observed primarily in men 65 years and older who do not have a family history of prostate cancer.
That being said, other dietary carotenoids should not be overlooked, as high levels of alpha and beta-carotene as well as lutein are associated with a significant reduction in the risk of breast and lung cancer.
This cancer-fighting action is not limited to soil-grown fruits and vegetables. Laboratory studies show that the fucoxanthin in seaweed could be among the carotenoids with the strongest cancer-fighting capabilities, an effect that could contribute to the exceptional longevity of the inhabitants of Okinawa, who eat these foods daily.
It is essential to eat whole fruits and vegetables to harness the benefits of carotenoids.
OLIVE OIL, THE SOUL OF THE MEDITERRANEAN DIET
- Phytochemical compounds: Oleic acid, oleocanthal, hydroxytyrosol, taxifolin
- Main types of cancer: Breast, colon
The diet of the people living around the Mediterranean Sea has numerous health benefits, including the prevention of cardiovascular disease and several types of cancer.
It’s not surprising however, since it’s an exemplary diet, rich in fruits and vegetables, rich in monounsaturated fats and polyunsaturated omega-3s, a diet in which the complex sugars from fibre and grains are the main source of carbohydrates, and in which protein comes mostly from fish and legumes instead of red meat.
Population-based studies show that people who follow a Mediterranean-style diet have an approximately 15% lower risk of being affected by cancer.
Olive oil seems to play the largest role in this protective effect. A recent randomized clinical trial demonstrated that women who follow a Mediterranean diet rich in olive oil had a 40% lower chance of developing breast cancer.
Because randomized trials are considered to be the ultimate point of reference in clinical research (subjects are randomly distributed, which minimizes statistical distortion), the drastic reduction in breast cancer risk observed after adherence to a Mediterranean diet therefore represents some of the strongest evidence to date of the pivotal role played by diet in preventing cancer.
It is important to favour virgin or extra virgin oils, both for their superior taste and their effect on health. These oils contain polyphenols present in the olives at the start of the process. It is easy to tell if they are present: one of these polyphenols, oleocanthal, causes a tickling or prickling sensation in the throat, which is caused by its specific interaction with the receptors present only in the pharynx. So the more it prickles, the better the anti-inflammatory action of the olive oil!
GREEN TEA TO SOOTHE THE SOUL…AND THE BODY
- Phytochemical compounds: Epigallocatechin gallate
- Main types of cancer: Colon, stomach
Of all the plants that make up the human diet, Camellia sinensis leaves include the highest proportion of cancer-fighting molecules.
A single cup of green tea can contain up to nearly 200 mg of polyphenols (flavonols, phenolic acids, catechins), notably epigallocatechin gallate (EGCG), the molecule primarily responsible for green tea’s health benefits.
More than 11,000 scientific studies have shown that EGCG is a versatile molecule capable of interfering in the multitude of processes used by cancer cells to grow and invade the organs.
The importance of these numerous biological activities is well illustrated by the marked decrease in the risk of several forms of cancer, particularly colon cancer, associated with the regular consumption of green tea.
Japanese green teas, which are richer in catechins, are the best source of EGCG, especially when the leaves are infused for eight to ten minutes to extract the maximum amount of molecules present.
Avoid drinking the tea when it is too hot, as high temperatures seem to counteract the reduction in stomach cancer risk observed in those who regularly consume this beverage.
A HANDFUL OF NUTS A DAY KEEPS THE DOCTOR AWAY
- Phytochemical compounds: Linolenic acid, phenolic compounds
- Main types of cancer: Breast, colon, prostate
Nuts and seeds are exceptional foods that have been marginalized far too long because of a phobia against all things fat.
However, they are probably one of the classes of foods with the greatest health benefits! In fact, several observations indicate that simply consuming 3 servings of nuts per week can reduce the risk of premature death by around 30%, due to a significant reduction in the risk of heart disease, type 2 diabetes, respiratory diseases, and cancer. In the latter case, a protective effect against colon and prostate cancers was suggested and could be linked to nuts’ elevated content of anti-inflammatory omega-3, fibre, and phenolic compounds. Recently, regular consumption of nuts (twice a week) has been associated with a significant reduction in the risk of pancreatic cancer, possibly by preventing type 2 diabetes, which is an important risk factor for this form of cancer.
From a botanical point of view, nuts, hazelnuts, chestnuts, and pecans are the only true representatives of this family, but in practice, the term “nuts” includes almonds, cashews, Brazil nuts, pistachios, and peanuts. All of these make phenomenal snacks whose health benefits often go unnoticed, sometimes even in the case of foods that have always been part of our everyday lives. For example, a study suggests that girls who regularly eat peanut butter have a 40% lower chance of developing benign proliferative breast disease, lesions that significantly increase future cancer risk.
SEEDS AND GRAINS
- Phytochemical compounds: Linoleic acid, lignans (secoisolariciresinol, matairesinol)
- Main types of cancer: Breast, colon.
Like nuts, flaxseeds are an exceptional source of anti-inflammatory short-chain omega-3 fatty acids, and it’s likely that regular consumption reduces chronic inflammation and creates conditions that are unfavourable for cancer cell growth.
In this context, it is interesting to note that for patients with prostate cancer, the growth of their cancer slows significantly following daily consumption of 30 g of ground flaxseeds for one month.
Flaxseeds, as well as whole grains, also contain phenomenal amounts of lignans, a class of phytoestrogens distinct from the isoflavones found in soy.
Studies show that consumption of flaxseeds or bread made with these seeds is associated with an approximately 20% reduction in the risk of breast cancer, which is in keeping with the protective effect observed in lignans originating in other plant foods. This decreased risk could be linked to reduced inflammation, as the presence of large quantities of urinary lignans is accompanied by a decrease in several inflammatory markers.
Adding flaxseeds to yogurt, breakfast cereal, or even when baking a cake is an easy and inexpensive way to enjoy their benefits. Another good approach is to eat products made with whole grains (bread, cereal, pasta) because in addition to containing significant quantities of lignans, they are also important sources of fibre and so can play an important role in the prevention of colorectal cancer.
RED WINE, A DIVINE BEVERAGE
- Phytochemical compounds: resveratrol
- Main type of cancer: colon
Red wine is a complex beverage containing thousands of phytochemical compounds, of which one, resveratrol, is among the few molecules of nutritional origin able to have a simultaneous effect on several essential stages of cancer growth, in particular that of the colon.
To enjoy red wine’s benefits, however, the key is still moderation because, in large amounts, alcohol is extremely harmful to cells and increases considerably the risk of several types of cancer, including that of the mouth, liver, and breast.
SOY, A CANCER-FIGHTING LEGUME
- Phytochemical compounds: Genistein
- Main type of cancer: Breast
Soybeans are a rich source of isoflavones, a class of phytoestrogens that interfere with the growth of certain hormone-dependent cancers, in particular those of the breast and prostate.
For breast cancer, currently available data indicates that it is consumption during childhood and adolescence that is most closely associated with decreased risk, which could explain, at least in part, the huge difference in the incidence of this type of cancer between Asian and Western populations.
In the past several years, certain questions have been raised concerning soy consumption by women with breast cancer, but a large number of clear and unequivocal studies show that soy is completely safe and could even be associated with a significant decrease in risk of relapse.
The isoflavones in soy are present in significant quantities in the beans themselves (edamame), tofu, and even miso, and these foods are all simple, fast, and economical ways to benefit from the cancer-fighting properties of these molecules.
Processed foods made with soy protein concentrates, on the other hand, are essentially devoid of isoflavones and play no role in cancer prevention.
THE MAGIC OF MUSHROOMS
- Phytochemical compounds: Polysaccharides (i.e. lentinan)
- Main type of cancer: Breast
Apart from their culinary properties, mushrooms have always been an important component of numerous countries’ traditional medicines, particularly in Asia.
When it comes to cancer prevention, epidemiological studies found encouraging results when they examined the relationship between mushroom consumption and reduced risk of developing cancer.
For example, an analysis of several studies conducted on the impact mushrooms have on breast cancer showed that daily consumption of 10 g of mushrooms is associated with a decreased risk of approximately 20%. It would appear that this protective effect could be associated with heightened activity in the immune system caused by the active compounds in mushrooms, which increase the chances of controlling new tumours and preventing them from reaching a mature stage.
CRUCIFEROUS VEGETABLES TO CROSS OUT CANCER
- Phytochemical compounds: Sulforaphane, PEITC, I3C
- Main types of cancer: Lung, bladder, prostate
Cruciferous vegetables are a plant family that possesses the trait of producing flowers with four petals arranged in a Greek cross.
The different forms of cabbage, broccoli, cauliflower, radish, and turnip are the main types of cruciferous vegetables consumed, but watercress, arugula, and rapini are also part of this family and provide an opportunity to enjoy the benefits of cruciferous vegetables while also adding a touch of variety to one’s culinary experience.
The important of these vegetables in cancer prevention stems from the fact that they are the only food plants to contain significant amounts of glucosinolates, a class of inert compounds that are, however, transformed into powerful cancer-fighting molecules (isothiocyanates et indoles) when the plant cells are broken by chewing:
Detoxification of carcinogens
Interruption of the spread of cancer cells
Death of cancer cells
Regular consumption of cruciferous vegetables is associated with a significant reduction in the risk of several forms of cancer. This protective effect is particularly well documented for lung cancer (even in smokers), bladder cancer, and prostate cancer, but recent studies suggest that the vegetables could also reduce the risk of colon, stomach, and breast cancers.
To reap the most benefit from cruciferous vegetables’ cancer-fighting properties, steam or sauté them to maximize their isothiocyanate content.
As an exception to the general rule, frozen vegetables from this family should be avoided because blanching at high temperatures, which is required to preserve the vegetables, inactivates myrosinase.
However, recent work indicates that adding a radish extract to these vegetables can compensate for the loss of this enzyme, and these products could prove to be of interest in the near future.
CHOCOLATE, FOOD OF THE GODS
- Phytochemical compounds: proanthocyanidins
- Main type of cancer: Colon
The interest in dark chocolate’s beneficial effects stems from its abundance of phytochemical compounds: a single square of dark chocolate contains twice as many polyphenols as a glass of red wine and as many as a cup of green tea that is infused for a long time. Dark chocolate’s positive effect is particularly well documented when it comes to cardiovascular diseases, with regular consumption of 5 to 10 g of 70% chocolate being associated with a significant decrease (50%) in mortality linked to these diseases. It’s also interesting to note that these cardiovascular effects also translate into better blood circulation to the brain, which could contribute to the significant improvement in memory and cognitive functions observed after chocolate consumption.
Related to cancer, it was observed that eating 45 g of dark chocolate containing 860 mg of polyphenols was associated with a marked decrease in DNA damage in blood cells caused by oxidative stress, which reduces the risk of mutations that can initiate cancer. These results are consistent with several preclinical studies which have shown that the polyphenols in cocoa paste provide robust anticancer and antiangiogenic activity and are capable of slowing the development of several types of cancer in laboratory animals, notably that of the colon. In the latter instance, this protective effect could be linked to a reduction in inflammation, as the majority of the polyphenols in cacao reach the colon, where intestinal bacteria transform them into phenolic acids and short-chain fatty acids with anti-inflammatory properties. Similarly to fruits and vegetables, including dark chocolate in our dietary habits could have important benefits for intestinal function and, consequently, for the prevention of colorectal cancer.
Who says eating healthy can’t be delicious?
THE PEACH, A CANCER-FIGHTING INDULGENCE
- Phytochemical compounds: chlorogenic acids
- Main type of cancer: Breast
Peaches, like their close botanical relatives from the Rosaceae family (prunes, pears, apples), contain significant amounts of chlorogenic and neochlorogenic acids, two polyphenols that contribute to the cancer-fighting properties of these foods.
For example, peach extracts containing chlorogenic and neochlorogenic acids are capable of specifically blocking the growth of breast cancer cells, while having no effect on normal, non-cancerous cells. In preclinical models, this inhibitory effect translates into a significant reduction in tumour growth and the formation of metastases, and this from amounts of polyphenols easily attainable by diet alone (two peaches). These observations are consistent with recent studies that show that regular consumption of peaches and nectarines is associated with a significant reduction (40%) in certain types of breast cancer. With the current knowledge available, there is no doubt that peaches and nectarines are an attractive addition to the diet of anyone interested in reducing their risk of breast cancer.
CITRUS FRUITS, CANCER-FIGHTING MOLECULES WITH ZEST
- Phytochemical compounds: Monoterpenes, flavanones
- Main type of cancer: Stomach
Best known for their high vitamin C content, citrus fruits also contain several phytochemical compounds (polyphenols and monoterpenes) that can help prevent cancer.
Laboratory studies suggest that these molecules are active against several types of cancer cells, and epidemiological findings indicate that regular consumption of citrus fruits is associated with a decreased risk of stomach and esophageal cancers.
Citrus fruits also indirectly affect cancer risk by regulating the enzyme systems involved in the elimination of foreign substances from the body.
Citrus fruits are often consumed in juice form, and it is important to keep in mind that these beverages are high in sugar, and the lack of fibre results in very rapid absorption of the glucose and fructose they contain.
Rediscovering the delight of eating an orange or a grapefruit whole is a good way, then, to benefit from these exceptional fruits, while avoiding sudden changes in blood sugar, which can lead to excess weight.
COFFEE, A CUP OF PREVENTION
- Phytochemical compounds: Caffeine, caffeic acid
- Main types of cancer: Liver, breast, colon, melanoma
More than a simple stimulant, coffee is, in fact, a very complex beverage containing a large range of phytochemical molecules that are biologically active in different ways.
An analysis of 60 population-based studies shows that regular coffee drinkers have an approximately 20% lower risk of developing cancer than non-coffee drinkers or those who drink it only rarely. This protective effect is particularly well documented in the case of liver cancer, with an approximately 40% reduction in the risk of developing this disease.
Another study also showed that women who drink coffee regularly have a 20% lower risk of developing breast cancer.
Coffee may also significantly reduce relapses in women who have fought hormone-dependent breast cancer and who were treated with tamoxifen, moderate coffee consumption being associated with a 50% reduction in relapses.
About the author: Richard Béliveau, Ph.D.
Richard Béliveau, Ph.D. in Biochemistry, is Scientific Director of the Chair in Prevention and Treatment of Cancer of the Université du Québec à Montréal.
He was Professor of Surgery and Physiology at Université de Montréal and held the Chair of Neurosurgery of the CHUM. He is an associate researcher at the Cancer Prevention Center in the Department of Oncology at McGill University and member of the Experimental Cancer Therapy Group at the Jewish General Hospital of Montreal. He is full Professor of Biochemistry at Université du Québec à Montréal and member of the Coalition Priorité Cancer au Québec. He is the founder of Angiochem and Katana Biopharma, two biotech companies that develop new drugs targeting brain disorders and various types of cancer.
He has published more than 250 articles in world-class scientific and medical journals. He also authored several best-selling books that have been translated into 28 languages across 37 countries, including “Foods that Fight Cancer”, “Cooking with Foods that Fight Cancer”, “Eating Well, Living Well”, “Death: the Scientific Facts”, “Samurai”, and “Preventing Cancer”. He wrote more than 550 medical research columns in the Journal de Montréal. He was awarded the Public’s Choice Prize at the Salon du Livre de Montréal, he was named Person of the Year by L’Actualité magazine and Personality of the Province of Quebec by Au Québec newspaper. He was also named Emeritus alumnus of the Collège de Trois-Rivières, Université du Québec and Université Laval. He is Professor Emeritus of Biochemistry.