What Does Eating Plants Do For Cancer? Part One

The thought of being diagnosed with cancer is terrifying. We all have members of our families and friends that have dealt with or are dealing with this dreaded disease. Some people beat it and go on to live a long life but others, sadly, pass on much too early. Research into the causes of cancer is gradually amassing more and more information about this killer and medical practice is gaining ground on the treatment side. But how about preventing cancer in the first place? Did you know that research is discovering the mechanisms of cancer growth and ways to prevent it from flourishing?

Cancer is a very complicated disease and manifests itself in numerous ways so let’s start very simply by looking at the effect that human blood has on cancer cells in a petri dish. Back in 2005 Dr. Dean Ornish led a randomized, controlled study on 93 men with early, biopsy proven prostate cancer who had chosen not to undergo any conventional treatment. The men were randomly assigned to either an experimental group that was advised to make comprehensive lifestyle changes (they were taught to eat a plant-based diet and increase their exercise) or to a control group given standard care and then they were followed for a year. Human blood cells are an important part of the immune system and are able to attack and kill cancer cells with some success. When the blood of the subjects in the control group of this study, the group that was eating a standard Western diet, was dripped onto prostate cancer cells in a petri dish their blood was hostile enough to decrease prostate cancer cell growth by 9%. However, the blood of the participants in the experimental group, the group that was eating a plant-based diet and exercising regularly, inhibited cancer growth by 70%, an effect nearly eight times stronger than that of the control group. After a year, PSA (prostate-specific antigen – a marker for prostate cancer) had DECREASED by 4% in the experimental group but INCREASED by 6% in the control group. Decreases in PSA and in cancer cell growth occurred according to the degree that the participant followed the lifestyle changes. (1) Another study showed similar results on breast cancer cells with significant improvements in cancer cell-killing strength after only two weeks of lifestyle changes (2).

Moving out of petri dishes and on to actual people, the huge EPIC Study looking at diet and cancer found a 28% lower incidence of all cancers combined in vegetarians (3). Another study completed in 2014 and published in the journal Cell Metabolism showed that middle-aged men and women eating high protein diets, especially those high in animal protein, had a 75% increase in overall mortality and a four-fold greater risk in dying from cancer (4). This is a mortality risk comparable to that of smoking cigarettes.

The American Institute of Cancer Research (AICR) lists Ten Recommendations for Cancer Prevention (5,10). These recommendations are based on a report called “Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective”, a report not tied to any governmental or industry initiatives (10). The purpose of this report was to “review all the relevant research using the most meticulous methods in order to generate a comprehensive series of recommendations of food, nutrition, and physical activity designed to reduce the risk of cancer and suitable for all societies.” An expert panel reviewed close to one thousand papers on diet and cancer and stated that “None of our recommendations are based on ‘could be’ conclusions. All are based on judgements that evidence is definite or probable.” Here are the Ten Recommendations for Cancer Prevention;

1 Be as lean as possible without becoming underweight.
2 Be physically active for at least 30 minutes every day. Limit sedentary behavior.
3 Avoid sugary drinks. Limit consumption of energy-dense foods.
4 Eat more of a variety of vegetables, fruits, whole grains and legumes such as beans.
5 Limit consumption of red meats (such as beef, pork and lamb) and avoid processed meats.
6 If consumed at all, limit alcoholic drinks to 2 for men and 1 for women a day.
7 Limit consumption of salty foods and foods processed with salt (sodium).
8 Don’t rely on supplements to protect against cancer.

The Expert Report also makes two recommendations for specific groups:

9 NEW MOTHERS: Breastfeed babies exclusively for up to 6 months before adding other liquids or foods.
10 CANCER SURVIVORS: After treatment, follow the recommendations for cancer prevention.
ALERT And always remember — do not smoke or chew tobacco.

TAKE SPECIAL NOTE OF RECOMMENDATION 10 – The same diet that can prevent cancer from forming in the first place can also prolong life after a cancer diagnosis. And an added bonus; the same diet is also good for the cardiovascular system and the respiratory system.

This report spawned a plethora of studies testing the link between these recommendations and the risk of cancer. The results of one study show that women who meet at least five out of six of these recommendations (having normal body weight, being physically active, eating mostly foods of plant origin, avoiding energy-dense foods and red and processed meats and limiting alcoholic drinks) have a reduced breast cancer risk of 60% compared to women who meet none of the recommendations (8). Other studies show that, as more of the AICR recommendations are adhered to, there follows an association with significantly less incidence of many other cancers as well – endometrial, colorectal, lung, kidney, stomach, oral, liver, bladder and esophageal (6,7) as well as lower mortality in older female survivors of breast cancer and cancer in general (9). A follow up of the Health Professionals Study looking at almost 48,000 men found significantly increased risk of colon cancer specifically linked to animal protein consumption. This increased risk was independent of fruit and vegetable consumption and also independent of saturated fat, total fat, and animal fat intake meaning that animal protein in particular was the link to cancer development (11). A study performed in Hawaii followed 190,000 residents for seven years and found that those who consumed the most red meat and processed meat were 50% more likely to develop pancreatic cancer than those who ate the least (12). Another study involving half a million men and women between the ages of 50 and 71 found that both red meat and processed meat consumption was significantly associated with cancers of the colon and lung and that red meat intake was associated with elevated risk of cancers of the esophagus and liver (13). Other studies show similar results with lower consumption of animal-based foods and decreased risks for rectal cancer (14,15,16), renal cell (kidney) cancer (17,18,19,20), and bladder cancer (21,22).

Eating a completely plant-based diet means the complete avoidance of animal-based food sources. Multiple long-term studies from around the world have noted the correlation between animal foods and increased risk of many different types of cancers.

In Part Two and Three of this series on Cancer, we’ll delve into specific factors that can increase cancer incidence and others that protect against cancer.


1 Ornish, D., Weidner, G., Fair, W.R., Marlin, R. et al. Intensive lifestyle changes may affect the progression of prostate cancer. J Urol. 2005 Sep; 174(3):1065-1069.

2 Barnard, R.J., Gonzalez, J.H., Liva, M.E., Ngo, T.H. Effects of a low-fat, high-fiber diet and exercise program on breast cancer risk factors in vivo and tumor cell growth and apoptosis in vitro. Nutr Cancer. 2006; 55(1):28-34.

3 Key, T.J., Appleby, P.N., Spencer, E.A., Travis, R.C., Roddam, A.W., Allen, N.E. Cancer incidence in vegetarians: results from the European Prospective Investigation into Cancer and Nutrition (EPIC-Oxford). Am J Clin Nutr. 2009 May; 89(5): 1620S-1626S.

4 Levine, M.E., Suarez, J.A., Brandhorst, S., Balasubramanian, P., Cheng, C-W. et al. Low Protein Intake Is Associated with a Major Reduction in IGF-1, Cancer, and Overall Mortality in the 65 and Younger but Not Older Population Cell Metabolism March 2014; 19(3), p407–417.

5 http://www.aicr.org/can-prevent/what-you-can-do/10-recommendations.html?referrer=https://www.google.ca/

6 Romaguera, D., Vergnaud, A.C., Peeters, P.H., van Gils, C.H., Chan, D.E. el al. Is concordance with World Cancer Research Fund/American Institute for Cancer Research guidelines for cancer prevention related to subsequent risk of cancer? Results from the EPIC study. Am J Clin Nutr. 2012 Jul; 96(1):150-163.

7 Vergnaud, A.C., Romaguera, D., Peeters, P.H., Chan, C.H. et al. Adherence to the World Cancer Research Fund/American Institute for Cancer Research guidelines and risk of death in Europe: results from the European Prospective Investigation into Nutrition and Cancer cohort study. Am J Clin Nutr. 2013 May; 97(5):1107-20.

8 Hastert, T.A., Beresford, S.A., Patterson, R.E., Kristal, A.R., White, E. Adherence to WCRF/AICR cancer prevention recommendations and risk of postmenopausal breast cancer. Cancer Epidemiol Biomarkers Prev. 2013 Sep; 22(9):1498-1508.

9 Inoue-Choi, M., Robien, K., Lazovich, D. Adherence to the WCRF/AICR guidelines for cancer prevention is associated with lower mortality among older female cancer survivors. Cancer Epidemiol Biomarkers Prev. 2013 May; 22(5):792-802.

10 World Cancer Research Fund / American Institute for Cancer Research. Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective. Washington DC: AICR, 2007; ISBN: 978-0-9722522-2-5

11 Giovannucci, E., Rimm, E.B., Stampfer, M.J., Colditz, G.A., Ascherio, A., Willett, W.C. Intake of fat, meat, and fiber in relation to risk of colon cancer in men. Cancer Res. 1994 May 1; 54(9):2390-7.

12 Nöthlings, L. R. W., Murphy, S.P., Hankin, J. H., Henderson, B.E., Kolonel, L.N. Meat and Fat Intake as Risk Factors for Pancreatic Cancer: The Multiethnic Cohort Study . Oct 5, 2005; Journal of the National Cancer Institute 97(19): 1458–1465.

13 Cross, A.J., Leitzmann, M.F., Gail, M.H. et al. A prospective study of red and processed meat intake in relation to cancer risk. PLoS Med. 2007 Dec; 4(12):e325.

14 English, D.R.,MacInnis, R.J., Hodge,A., Hopper,A.M. et al. Red meat, chicken and fish consumption and risk of colorectal cancer. 2004. Cancer Epidemiol Biomarkers Prev, 13(9); 1509 – 1514.

15 Gonzalez, C.A. Nutrition and Cancer: The current epidemiological evidence. Br J Nutr. 2006; 96(1 Suppl): S42-S45.

16 Bingham, S.A., Day, N.E., Luben, R., Ferrari, P., et al. Dietary fiber in food and protection against colorectal cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC): An observational study. Lancet 2003; 361(9368): 1496 – 1501.

17 Lee, J.E., Giovannucci, E., Smith-Warner, S.A. et al. Intakes of fruits, vegetables, vitamins A, C and E, and carotenoids and risk of renal cell cancer. Cancer Epidemiol Biomarkers Prev 2006; 15(12):1445-1452.

18 Faramawi, M.F., Johnson, E., Fry, M.W. et al. Consumption of different types of meat and the risk of renal cancer: Meta-analysis of case-control studies. Cancer Causes Control 2007; 18(2): 125-133.

19 Daniel, C.R., Cross, A.J., Graubard, B.I., Park, Y. et al. Large prospective investigation of meat intake, related mutagens, and risk of renal cell carcinoma. Am J Clin Nutr 2012; 95(1): 155-162.

20 Daniel, C.R., Park, Y., Chow, W.H., Graubard, B.I. et al. Intake of fiber and fiber-rich plant foods is associated with a lower risk of renal cell carcinoma in a large US cohort. Am J Clin Nutr 2013; 97(5): 1036 – 1043.

21 Michaud, D.S., Spiegelman, D., Clinton, S.K. Rimm, E.B., Willett, W.C, Giovannucci, E.L. Fruit and vegetable intake and incidence of bladder cancer in a male prospective cohort. J Natl Cancer Inst 1999; 91(7): 605-613.

22 Allen, N.E., Appleby, P.N., Key, T.J., Bueno-de-Mesquita, H.B., Ros, M.M., Kiemeney, L.A., Tjønneland, A. et al. Macronutrient intake and risk of urothelial cell carcinoma in the European prospective investigation into cancer and nutrition. Int J Cancer. 2013 Feb 1; 132(3): 635-644

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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