Cancer, Vegetarianism, and Diet
(Last updated October 29, 2008.)
There has not been enough data on vegans to determine their cancer rates.
The tables below show the results of cancer mortality and incidence rates from all studies that have looked at vegetarians. Unless otherwise noted, the rates are given for mortality, not incidence. Statistically significant findings are in red type. As you can see, most studies have not shown a difference between vegetarians and meat-eaters regarding cancer.
If you are not familiar with them, click here for a quick explanation of Disease Rate Statistics.
General Cancer
| Study | Years | Rate vs Non-veg | Significance | Adjustments | Notes |
| Heidelberg Vegetarian (1) | 1978-1989 | 1.59 | .87, 2.94 | gender, duration of diet, BMI (smoking did not effect results) | Non-vegetarians ate meat "occasionally." |
| Health Food Shoppers (2) | 1973-1997 | 1.05 | .96, 1.15 | age, gender, smoking, excluded first 5 years of follow-up | |
| Oxford Vegetarian (2) | 1980-2000 | 1.06 | .85, 1.34 | age, gender, smoking, excluding first 5 years of follow -up | |
| EPIC-Oxford (3) | 1993-2002 | 1.11 | .82, 1.51 | age, gender, smoking | |
No study has found a difference in mortality between vegetarians and meat-eaters for all cancers combined.
Colorectal Cancer
| Study | Years | Rate vs Non-veg | Significance | Adjustments | Notes |
| Adventist Health (4) | 1976-1982 | 0.53 | .35, .81 | age, gender | Incidence. 6 years of follow up. |
| Meta-Analysis (5) | 1999 | 0.99 | .77, 1.27 | age, gender, smoking status, and study | |
| Health Food Shoppers (2) | 1973-1997 | 0.85 | .52, 1.39 | age, gender, smoking, excluded first 5 years of follow-up | |
| Oxford Vegetarian (2) | 1980-2000 | 1.42 | .76, 2.67 | age, gender, smoking, excluding first 5 years of follow -up | |
| Oxford Vegetarian (6) | 1980-1999 | 0.85 | .55, 1.32 | age, sex, alcohol, smoking | Incidence |
The Adventist Health Study was the only one to find a significant effect. One note of caution about that study is that it lasted only 6 years.
Prostate Cancer
| Study | Years | Rate vs Non-veg | Significance | Adjustments | Notes |
| Adventist Health (4) | 1976-1982 | 0.65 | .44, .95 | age, gender | Incidence. 6 years of follow up. |
| Meta-Analysis (5) | 1999 | 0.91 | .60, 1.39 | age, gender, smoking status, and study | |
| Health Food Shoppers (2) | 1973-1997 | 1.29 | .62, 2,68 | age, gender, smoking, excluded first 5 years of follow-up | |
| Oxford Vegetarian (2) | 1980-2000 | 0.66 | .27, 1.59 | age, gender, smoking, excluding first 5 years of follow -up | |
The results for prostate cancer are similar to colorectal; only the Adventist Health Study showed a statistically significant difference.
Breast Cancer
| Study | Years | Rate vs Non-veg | Significance | Adjustments | Notes |
| India (7) | 1980-1984 | 1.25 | .48, 1.67 | age, region | Incidence. Case control. |
| Adventist Health (4) | 1976-1982 | 0.8 | .56, 1.15 | age | Incidence. 6 years of follow up. |
| Meta-Analysis (5) | 1999 | 0.95 | .55, 1.63 | age, smoking status, and study | |
| Health Food Shoppers (2) | 1973-1997 | 1.62 | 1.01, 2.60 | age, smoking, excluded first 5 years of follow-up | |
| Oxford Vegetarian (2) | 1980-2000 | 1.23 | .66, 2.31 | age, smoking, excluding first 5 years of follow -up | |
| South Asian-Born Women Living in UK (8) | 1995-1999 | 0.77 | .50, 1.19 | age, smoking, excluding first 5 years of follow -up | Incidence. Case control. |
Unfortunately, the one (barely) significant finding for breast cancer was that vegetarians had more in the Health Food Shoppers study. However, the study did not adjust for having children which is protective against breast cancer and tends to be lower in vegetarian women.
Lung Cancer
| Study | Years | Rate vs Non-veg | Significance | Adjustments | Notes |
| Adventist Health (4) | 1976-1982 | 0.86 | .42, 1.79 | age, gender, smoking | Incidence. 6 years of follow up. |
| Meta-Analysis (5) | 1999 | 0.84 | .59, 1.18 | age, gender, smoking status, and study | |
| Health Food Shoppers (2) | 1973-1997 | 1.19 | .70, 2.02 | age, gender, smoking, excluding first 5 years of follow -up | |
| Oxford Vegetarian (2) | 1980-2000 | 1.27 | .60, 2.68 | age, gender, smoking, excluding first 5 years of follow -up | |
No significant findings.
Uterus Cancer
| Study | Years | Rate vs Non-veg | Significance | Adjustments | Notes |
| Adventist Health (4) | 1976-1982 | 0.85 | .58, 1.23 | age, gender | Incidence. 6 years of follow up. |
No significant findings.
Stomach Cancer
| Study | Years | Rate vs Non-veg | Significance | Adjustments | Notes |
| Meta-Analysis (5) | 1999 | 1.02 | .64, 1.62 | age, smoking status, and study | |
No significant findings.
Pancreas Cancer
| Study | Years | Rate vs Non-veg | Significance | Adjustments | Notes |
| Adventist Health (10) | 1976-1982 | Incidence. 6 years of follow up. | |||
| non-vegetarian = 1.0 | 0.46 | .06, 1.39 | age, sex, smoking, other foods | ||
| meat > daily vs. veg | 2.18 | 1.04, 4.58 | age, gender | ||
Vegetarians had about half the rate of pancreas cancer compared to people who ate meat more than daily. In comparison to all meat-eaters, the rates were not different.
Brain Cancer
| Study | Years | Rate vs Veg | Significance | Adjustments | Notes |
| Adventist Health (11) | 1976-1982 | age, gender | Incidence. 6 years of follow up. | ||
| Glioma Cancer | |||||
| meat < than daily | 1.56 | .52, 5.63 | |||
| meat > daily | 1.75 | .34, 8.54 | |||
| Meningioma Cancer | |||||
| meat < than daily | 0.36 | .09, 1.46 | |||
| meat > daily | 0 | P < .05 | |||
Among people who ate meat more than daily, there were no cases of meningioma cancer and this finding was statistically significant.
Oral Cancer
| Study | Years | Rate vs Non-veg | Significance | Adjustments | Notes |
| India (9) | 1980-1984 | 0.55 | .40, .74 | age, region | Incidence. Case control. |
Vegetarians had significantly lower rates of oral cancer in this study of Indian vegetarians.
There is no data on North American vegetarians who are not also Seventh-day Adventists.
Because the Meta-Analysis included participants in the Health Food Shoppers, Adventist Health, Heidelberg Vegetarian, and Oxford Vegetarian studies; and the EPIC-Oxford study includes many of the same people as were in the Oxford Vegetarian study, many of these results are not on completely different populations, and so there is not as much evidence as the above tables might seem to imply.
Diet and Lifestyle Components and Cancer
In 2004, Diet, Nutrition and the Prevention of Cancer was published in the journal, Public Health Nutrition. Two of the authors, Timothy Key and Naomi Allen, have been involved in many of the above studies. Walter Willett of the Harvard School of Public Health also co-authored this paper which reviews what is currently known about diet and cancer. They summarize their findings based on levels of evidence:
Convincing Evidence
- Physical activity lowers the risk of colon cancer.
- Being overweight increases the risk of esophagus, colorectum, endometrium, and kidney cancer. It also increases the risk of breast cancer in postmenopausal women.
- Alcohol increases the risk of oral cavity, pharynx, larynx, esophagus, liver, and breast cancer.
- Aflatoxin is a mold that contaminates some foods, especially in underdeveloped countries; it increases liver cancer in areas rampant with the hepatitis virus.
- Chinese-style salted fish increases risk of nasopharynx cancer.
Probable Evidence
- Case studies have shown that fruits and vegetables lower the risk of oral cavity, esophagus, stomach, and colorectum cancer. Prospective studies have not shown a strong effect for colorectal cancer, indicating that the protective effect is probably modest. The other cancers have yet to be evaluated through prospective studies.
- Physical activity lowers risk of breast cancer.
- Salt preserved foods and salt increase the risk for stomach cancer. This may be only for people with H. pylori infection (a cause of ulcers), but this relation hasn't been thoroughly examined.
- Preserved meat and red meat increase the risk of colorectal cancer.
- Very hot (temperature) drinks and foods increase risk of oral cavity, pharynx, and esophagus cancer.
Insufficient Evidence
- There is insufficient evidence to conclude that fiber, soy, fish, omega-3 fatty acids, carotenoids, vitamins B2, B6, folate, B12, C, D, E, calcium, zinc, selenium, non-nutrient plant constituents (phytochemicals such as allium compounds in garlic, flavonoids, isoflavones, and lignans) lowers the risk of cancer.
- There is insufficient evidence that animal fats, heterocyclic amines, polycyclic aromatic hydrocarbons, and nitrosamines increase the risk of cancer.
The authors conclude:
"Since the 1981 Doll and Peto review on diet and cancer mortality (12), about one third of cancers have generally been thought to be related to dietary factors. More recent evidence suggests that this number may be too high, but a revised quantitative estimate is beyond the scope of this review. Among the diet-related factors, overweight/obesity convincingly increases the risks of several common cancers. After tobacco, overweight/obesity appears to be the most important avoidable cause of cancer in populations with Western patterns of cancer incidence. Among non-smoking individuals in these populations, avoidance of overweight is the most important strategy for cancer prevention."
Footnotes
1. Chang-Claude J, Frentzel-Beyme R. Dietary and lifestyle determinants of mortality among German vegetarians. Int J Epidemiol. 1993 Apr;22(2):228-36.
2. Appleby PN, Key TJ, Thorogood M, Burr ML, Mann J. Mortality in British vegetarians. Public Health Nutr. 2002 Feb;5(1):29-36.
3. Key TJ, Appleby PN, Davey GK, Allen NE, Spencer EA, Travis RC. Mortality in British vegetarians: review and preliminary results from EPIC-Oxford. Am J Clin Nutr. 2003 Sep;78(3 Suppl):533S-538S.
4. Fraser GE. Associations between diet and cancer, ischemic heart disease, and all-cause mortality in non-Hispanic white California Seventh-day Adventists. Am J Clin Nutr. 1999 Sep;70(3 Suppl):532S-538S.
5. Key TJ, Fraser GE, Thorogood M, Appleby PN, Beral V, Reeves G, Burr ML, Chang- Claude J, Frentzel-Beyme R, Kuzma JW, Mann J, McPherson K. Mortality in vegetarians and nonvegetarians: detailed findings from a collaborative analysis of 5 prospective studies. Am J Clin Nutr. 1999 Sep;70(3 Suppl):516S-524S.
6. Sanjoaquin MA, Appleby PN, Thorogood M, Mann JI, Key TJ. Nutrition, lifestyle and colorectal cancer incidence: a prospective investigation of 10998 vegetarians and nonvegetarians in the United Kingdom. Br J Cancer. 2004 Jan 12;90(1):118-21.
7. Rao DN, Ganesh B, Desai PB. Role of reproductive factors in breast cancer in a low -risk area: a case-control study. Br J Cancer. 1994 Jul;70(1):129-32.
8. Dos Santos Silva I, Mangtani P, McCormack V, Bhakta D, Sevak L, McMichael AJ. Lifelong vegetarianism and risk of breast cancer: a population-based case-control study among South Asian migrant women living in England. Int J Cancer. 2002 May 10;99(2):238-44.
9. Rao DN, Ganesh B, Rao RS, Desai PB. Risk assessment of tobacco, alcohol and diet in oral cancer--a case-control study. Int J Cancer. 1994 Aug 15;58(4):469-73.
10. Mills PK, Beeson WL, Abbey DE, Fraser GE, Phillips RL. Dietary habits and past medical history as related to fatal pancreas cancer risk among Adventists. Cancer. 1988 Jun 15;61(12):2578-85.
11. Mills PK, Preston-Martin S, Annegers JF, Beeson WL, Phillips RL, Fraser GE. Risk factors for tumors of the brain and cranial meninges in Seventh-Day Adventists. Neuroepidemiology. 1989;8(5):266-75.
12. Doll R, Peto R. The causes of cancer: quantitative estimates of avoidable risks of cancer in the United States today. Journal of the National Cancer Institute 1981;66:1191-308.
Other Papers Reviewed in Preparing this Report
American Dietetic Association; Dietitians of Canada. Position of the American Dietetic Association and Dietitians of Canada: Vegetarian diets. J Am Diet Assoc. 2003 Jun;103(6):748-65.
Chang CC, Yu MW, Lu CF, Yang CS, Chen CJ. A nested case-control study on association between hepatitis C virus antibodies and primary liver cancer in a cohort of 9,775 men in Taiwan. J Med Virol. 1994 Jul;43(3):276-80.
Frentzel-Beyme R, Claude J, Eilber U. Mortality among German vegetarians: first results after five years of follow -up. Nutr Cancer. 1988;11(2):117-26.
Key TJ, Schatzkin A, Willett WC, Allen NE, Spencer EA, Travis RC. Diet, nutrition and the prevention of cancer. Public Health Nutr. 2004 Feb;7(1A):187-200.
Key TJ, Fraser GE, Thorogood M, Appleby PN, Beral V, Reeves G, Burr ML, Chang- Claude J, Frentzel-Beyme R, Kuzma JW, Mann J, McPherson K. Mortality in vegetarians and non-vegetarians: a collaborative analysis of 8300 deaths among 76,000 men and women in five prospective studies. Public Health Nutr. 1998 Mar;1(1):33-41.
Key TJ, Thorogood M, Appleby PN, Burr ML. Dietary habits and mortality in 11,000 vegetarians and health conscious people: results of a 17 year follow up. BMJ. 1996 Sep 28;313(7060):775-9.
Kinlen LJ, Hermon C, Smith PG. A proportionate study of cancer mortality among members of a vegetarian society. Br J Cancer. 1983 Sep;48(3):355-61.
Kinlen LJ. Meat and fat consumption and cancer mortality: A study of strict religious orders in Britain. Lancet. 1982 Apr 24;1(8278):946-9.
Mills PK, Beeson WL, Phillips RL, Fraser GE. Cohort study of diet, lifestyle, and prostate cancer in Adventist men. Cancer. 1989 Aug 1;64(3):598-604.
Mills PK, Beeson WL, Phillips RL, Fraser GE. Dietary habits and breast cancer incidence among Seventh-day Adventists. Cancer. 1989 Aug 1;64(3):582-90.
Phillips RL. Role of life-style and dietary habits in risk of cancer among seventh-day adventists. Cancer Res. 1975 Nov;35(11 Pt. 2):3513-22.
Singh PN, Fraser GE. Dietary risk factors for colon cancer in a low -risk population. Am J Epidemiol. 1998 Oct 15;148(8):761-74.
Snowdon DA. Animal product consumption and mortality because of all causes combined, coronary heart disease, stroke, diabetes, and cancer in Seventh-day Adventists. Am J Clin Nutr. 1988 Sep;48(3 Suppl):739-48.
Taylor EF, Burley VJ, Greenwood DC, Cade JE. Meat
consumption and risk of breast cancer in the UK Women's Cohort
Study. Br J Cancer. 2007 Apr 10;96(7):1139-46. Erratum in: Br J Cancer. 2007 Jun 4;96(11):1780.
"Vegetarian" / "no meat" categories did not exclude fish.