What Does Eating Plants Do For Cancer? Part Four

Lifestyle Choices for Cancer Prevention

As is probably becoming obvious from Part One, Two and Three of this discussion about cancer and diet, probably the single most important tweak you can make in your diet in order to prevent cancer is to stop eating meat. There are also other positive dietary changes that can discourage cancer. This is the first of two blog articles on this subject and I hope that they can provide you with some helpful steps you can take in your own eating habits to make your body more inhospitable to cancer.


The number of ways that eating meat encourages cancer is astounding. Read Part Two and Three of this article series for a discussion outlining the negative effects of eating meat. Avoiding meat should not be a worrisome thing. The only nutrients that meats supply are protein, fat, some minerals and a few vitamins. All of these nutrients and a multitude more are easily obtained in the much more healthy packages of plants.


Research on milk is discovering that this white liquid is much more than just a farm product to be consumed as food. What makes milk the perfect food for babies is also what makes milk dangerous for ingestion later on in life. In reality milk is a signalling system that uses certain amino acids as endocrine messengers to prepare a child’s body systems for a long and healthy future. First and foremost milk promotes growth but it also formats body processes specifically for life as a human being, processes such as those that will be used for fat, glucose and protein metabolism and instructions for the development and maturation of the immune system. In addition milk activates mTORC1, a complicated system that encourages growth, creates and supports body fat cells and inhibits tumour suppressing proteins and programmed cell death (1). Unfortunately there is accumulating evidence that mTORC1 signaling is associated with the development of diseases of civilization such as cancer (especially prostate cancer) as well as hypertension, obesity, type-2 diabetes, Alzheimer’s disease and acne (2,3,4,5,6,7,8,9,10,11,12,13). A myriad of studies unequivocally link the ingestion of milk with breast cancer (14), with prostate cancer (15,16,17,18) and with ovarian cancer (19). Recent studies have also uncovered a link between a bovine leukemia virus found in milk and the development of breast cancer (20).

The main concern for people considering removing dairy from their diet is how they will get enough calcium. Milk is not the only source of calcium from food nor is it even the best source. Epidemiological studies show that the countries whose residents drink the most milk also have the highest rates of osteoporosis and bone fractures (54). Eating a variety of vegetables, starches and fruit provides more than sufficient calcium to meet our needs (53). Our bodies are able to adjust to a relatively low calcium intake by becoming more efficient at absorbing and conserving calcium just as the body adjusts to high calcium intakes by increasing the excretion of calcium (52). Green leafy plants are calcium rich and their calcium is actually more bioavailable than that of milk. Only about 30% of the calcium contained in milk is absorbable by the body. One cup of bok choy, 1 ½ cups of kale or 2 cups of broccoli all contain less total calcium than an 8 ounce glass of milk, however they will supply the same amount of absorbable calcium due to their higher absorption rate of 50 to 60% (50,53). Beans and other legumes are also good sources of calcium.


Reviews of studies on many cancer types reveal that body fatness has a significant effect on cancer progression and death from cancer (21). Conglomerations of fat cells appear as a threat to the body and cause an inflammatory response which can stimulate both development of cancer and its growth. (For more information see “What Does Eating Plants Do For Cancer? Part Two”.) (22,23)


There is substantial evidence that exercise is linked to lower cancer rates (24). A meta-analysis of 52 epidemiological studies shows that the most physically active people have a 24% lower risk of colon cancer than those who are the least active (25). In a 2013 meta-analysis, physically active women had a 12% lower risk of breast cancer than more inactive women (26). Endometrial cancer shows a similar relationship. A 2015 meta-analysis found a 20% lower risk of endometrial cancer with high physical activity (27). Lower rates of cancers of the esophagus, liver, stomach, kidney, head and neck, rectum and bladder are also linked to higher physical activity (28). Simply being sedentary increases cancer risk along with risks of cardiovascular disease, type 2 diabetes, and premature death (29,30).

Exercise has a very positive effect on the body including the lowering of hormone levels (insulin and estrogen) and growth factors, helping to prevent obesity, reducing inflammation, improving the function of the immune system and encouraging faster movement of food through the digestive system. Taking all this into consideration can provide a compelling reason to be more active.


Oils isolated from plant sources are susceptible to oxidation, especially after long periods of storage in a kitchen. Oxidation results in the formation of chemically reactive oxygen, an inflammatory molecule that promotes aging, cardiovascular disease and cancer. Experiments show that isolated plant oils actually promote more cancer than saturated fats (20). Note that this only refers to oils removed from plants; plant oils that are a part of a whole plant promote health not cancer. Your best solution is to avoid isolated oils altogether. If you do feel the need to use oil once in a while, buy small amounts and store them in a cold, dry place.


The human gastrointestinal tract is the home of trillions of bacteria that play an enormous role in health. This community is made up of thousands of species of micro-organisms, some healthy and some not so healthy. The healthy ones help with absorption and digestion of nutrients and the synthesis of some vitamins and amino acids as well as keeping unhealthy micro-organisms in check (56). The more diversity there is in your gut bacterial population, the healthier you will be. When more unhealthy species are thriving the risk of colon, gastric, esophageal, pancreatic, laryngeal, breast and gallbladder cancers increases (33).

Fiber eaten in the diet is not digested in the small intestine. It travels all the way to the end of the digestive system and, when the fiber reaches the large intestine, the healthy micro-organisms that live there break it down and release short-chain fatty acids such as butyrate. Butyrate has many beneficial actions including supporting the health of the lining of the intestine, reducing inflammation, repairing genes and increasing intestinal motility (the muscular action that moves food material along the intestine). It also plays a role in the prevention and inhibition of colorectal cancer (55,57). In 2011 a randomized controlled trial placed seventeen obese men on a high protein/moderate carbohydrate diet for 4 weeks then changed them to a high-protein/low carbohydrate diet for the next 4 weeks. The high-protein/low-carbohydrate diet increased the concentration of hazardous metabolites in the intestine and significantly decreased concentrations of cancer-protective metabolites, including butyrate, resulting in an increase in the risk of colon cancer (31). A 2013 study of people with colon cancer found that low fiber intake reduced butyrate formation and increased the risk of adenomas of the colon (32).

On the other side of the coin, a recent study illustrated that diets high in fiber from plant-based foods enhance the growth of healthy gut bacteria while diets high in fat and animal products lead to the overgrowth of unhealthy gut bacteria with accompanying increased inflammation and risks of diabetes and some cancers (58). Another study showed that people who eat a purely plant-based diet have the healthiest intestinal bacteria compared to omnivores and vegetarians (51).

The lesson from all this? Eat lots of fiber. In practical terms, this means eat lots of vegetables, fruits, whole grains, and legumes, all foods that feed the healthy bacteria that produce short-chain fatty acids. Don’t worry about eating too much fiber. Most people in the Western world eat about 15 to 20 gm of fiber daily. Aim for twice this much or more. Traditional societies who are famous for living long, healthy lives consume 3 to 4 times more fiber than this.

The following are excellent sources of gut friendly fiber;
Legumes such as beans, lentils
Whole grains such as whole wheat, oats, wheat bran, corn
Greens such as kale, spinach, asparagus
Onions, garlic, leeks
Cruciferous vegetables such as kale, cabbage, cauliflower
Jerusalem artichokes
Fruits such as bananas, blueberries


The human immune system is a battalion of specific organs and cells that defend against threats to our health. Plants are known to have immune boosting properties derived from the phytonutrients that are an integral part of their structure. Phytonutrients are found only in miniscule amounts in animal foods; they are synthesized within plants. In fact plants on average contain over 64 times the average number of phytonutrients found in animal-based foods (34).

Phytonutrients include a huge group of compounds including;
Flavonoids (including anthocyanidins in berries and other fruit, flavones in parsley, lettuce, apples and oranges, and flavonols in onions, almonds, sweet potatoes and garbanzo beans)
Plant sterols
Dietary fiber
Vitamins C and E
Dithiolthiones, glucosinolates and indoles
Protease inhibitors
Allium compounds

Phytonutrients Isolated from their plant source have not been shown to have much beneficial effect. It is the complex mixtures of interacting natural chemicals within a whole plant and their multifaceted defence strategy that produces the powerful health-protective effects (35).
Antioxidants exert their anti-cancer effects by destroying free radicals, those damaging molecules that cause inflammation and damage cells throughout the body. Just a quick look through the scientific literature yields many studies showing the beneficial link between phytonutrients and cancer. Phytonutrients have been shown to interfere with the activities of cancer stem cells, the root of most cancers (36). Consuming dietary antioxidants from a variety of plant foods is associated with a reduced risk for gastric cancer (37). Antioxidants from fruits and vegetables protect against non-Hodgkin lymphoma (38). In a 2012 study, powdered strawberries showed marked improvement in cancerous lesions of the esophagus (39). Consuming lycopene by eating tomato products helps prevent prostate, lung and stomach cancer and may also reduce the risk of cancers of the pancreas, colon and rectum, esophagus, oral cavity, breast, and cervix (40,60). Genistein, present in soy-based foods, acts as chemotherapy for a range of cancers include breast, prostate, lung and colorectal cancer (41). The phytonutrient 6-shogaol, found in ginger, targets breast cancer stem cells, the self-renewing cells that are the original cause of breast cancer malignancy. It has cancer-destroying effects at concentrations that are non-toxic to normal cells (42). Polyphenols in apple peels have strong tumour suppressant, anti-angiogenic and anti-metastatic properties in breast and prostate cancer. Tumour cells can turn off the tumour suppressor protein, maspin; apple peels turn it back on (43,44). Cranberries have an extremely high phenol content and inhibit growth and spread of prostate and other cancers (45,46).

Most plants that we use as food are health promoting but some are especially endowed with health protecting properties. These plants work by activation and suppression of specialized immune cells along with free radical scavenging activities and anti-inflammatory effects (47,48). Some plants with extra immune boosting properties include;
Garlic (Allium sativum)
Green tea (Camellia sinensis)
Ginger (Zingiber officinale)
Black cumin (Nigella sativa)
Turmeric (Curcuma longa)
Licorice (Glycyrrhiza glabra)
Purple coneflower (Echinacea)
St. John’s wort (Hypericum perforatum)

Phytonutrients that have been found to interfere with cancer stem cells include (36);
Green tea
Curcumin (found in turmeric)
Resveratrol (grapes, peanuts)
Lycopene (tomatoes, watermelon, pink grapefruit)
Luteolin (peppers, green vegetables)
Genistein (soy, red clover, coffee)
Piperine (black pepper)
Beta-carotene (orange vegetables)
Sulforaphane (cruciferous vegetables such as broccoli, kale)
These phytonutrients can be as effective against cancer as conventional chemotherapy without severe side effects such as suppression of the immune system and toxicity to many organs (36).

It is supremely easy to acquire copious amounts of phytonutrients. Adding to the health benefits of the above plants are many other fruits and vegetables which are also extremely high in antioxidants and have inhibitory effects on the growth and spread of cancer (49). These include (59);
Prunes and plums
Pink grapefruit
Red grapes
Brussels sprouts
Red bell peppers
Sweet potatoes

So dig into all the fruits and vegetables you can fit on your plate. All you need to do is enjoy their brilliant colours and delectable taste.


More on this topic in “What Does Eating Plants Do For Cancer? Part Five” …..coming soon.



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Promoting a healthy adventurous lifestyle powered by plants and the strength of scientific evidence.

My name is Debra Harley (BScPhm) and I welcome you to my retirement project, this website. Over the course of a life many lessons are learned, altering deeply-rooted ideas and creating new passions.

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