So, what does the literature have to say about the vegan diet and lung cancer? When I first started researching the relationship between plant-based diets and health, I initially thought that smoking was the only real environmental factor in the development of lung cancer. While smoking is the primary etiological factor in the development of lung cancer, dietary practices do seem to play a role.
So, are vegetarian/vegan diets associated with a decreased risk of developing lung cancer? Yes, it appears so. According to Joan Sabate of Vegetarian Nutrition Volume III, “Overall, the protective association with vegetarianism seems most pronounced for colon, stomach, and lung cancer.”1
Anyway, hat is less clear is whether or not this association is due to diet or non-diet-related factors—i.e. a reduced proclivity to smoke among vegetarian populations—or both. Make no mistake about it: the regular smoking of tobacco is the primary factor when it comes to one’s risk of lung cancer. Heavy smoking increases the risk of lung cancer about 40-fold and accounts for over 80% of lung cancer incidence in Western countries.2
However, as you will see in the coming paragraphs, there are many ways in which a healthy, whole food vegan diet may potentially help mitigate the risk of developing lung cancer—whether you smoke two packs a day or never touched a cigarette.
So, how widespread is lung cancer worldwide?
Firstly, according to the World Health Organization (WHO), globally, cancer is the second leading cause of mortality, accounting for almost one in six deaths. In 2012 alone, there were 14 million new cancer cases diagnosed worldwide. It’s predicted that this number will increase by 70% over the next twenty years.3
Of this number, lung cancer is among the most commonly occurring cancers worldwide (aside from nonmelanoma skin cancers).4,3
Anyway, let’s get down to it: why is it thought that a healthy whole food vegan diet helps prevent lung cancer?
1) Some Epidemiological Evidence Suggests Better Lung Cancer Outcomes Among Plant-Based Eaters
Going way back to the 1950s, researchers Wynder and Lemon compared the cancer rates of SDA hospital patients to non-SDA patient cancer rates.5
According to the abstract, “Epidermoid cancer of the lung, previously shown to be related to smoking, was 10 times less common among Seventh-day Adventists than among the general population, even among those Seventh-day Adventists living in the Los Angeles area where all are exposed to smog.”
You might say, well SDAs are a temperant bunch. They’re known for a whole host of healthy habits. And you’d be right.
These researchers went on to say, “Similarly, cancers of the mouth, larynx, and esophagus, previously shown to be related not only to smoking but also to heavy drinking, were at least 10 times less common among Seventh-day Adventist men than among men of the general population.”5
So, from there a series of US-based SDA studies were conducted from the late 1950s to mid-1960s in which researchers took measures to control for other healthy lifestyle and SES factors characteristic of SDA population—smoking habits, educational attainment, social class, etc.
For example, one study compared SDA medical professionals with non-SDA health professionals.6
Well, when compared to non-SDA physicians (sharing many lifestyle and SES factors such as social class and education), the association of the vegetarian diet with reduced cancer risk wasn’t nearly as pronounced as when SDA populations are compared to the general public.
However, a follow-up of this population was completed in 1976 and SDA outcomes were compared to the US white population—they compared SMRs which I’ll touch on below.
SMRs for most cancer sites were reduced (a good thing), and significantly so for lung cancer.7
So, what’s this SMR business? In epidemiology statistics, there’s something called standardized mortality ratio (SMR) which is the ratio between the number of deaths you observe in a study population and the number of deaths you’d have expected based on certain information (age- and sex-specific rates in a standard population, etc.).
Keep in mind that the lower the SMR, the better. We’ll be needing this concept to make sense of some of the studies to come.
The Oxford Vegetarian Study was a prospective study which involved roughly 6000 vegetarians and 5000 nonvegetarians.8
The SMR for all subjects was 0.62. However, for meat-eaters, the SMR was 0.80 while for vegetarians the SMR was only 0.50. Cancer-specific SMRs were performed revealing a slightly lower SMR for lung cancer when the vegetarians were compared with meat eaters.9
From 1966 to 1981, a cohort study was performed involving over 122,000 Japanese men in which participants were divided into two groups: one group having “SDA-like” lifestyle behaviors (never smoked, didn’t drink alcohol or eat meat) and the other group having a normal/non-temperance lifestyle.10
Upon comparing age-adjusted relative risks of death from cancer in the two groups, researchers found that the “SDA-like” group experienced lower risk for most cancer sites—especially those related to smoking—i.e. cancers of the lungs, mouth, pharynx, and esophagus.
From 1976 to 1982, cancer incidence was examined in a cohort of about 34,000 non-Hispanic white SDA members.11,12 For most major cancers—including lung cancer—the SDAs experienced low cancer risk.
SDA Studies Conducted Outside the U.S.
That’s just in the US. Worldwide there are about 3 million SDAs, compared to the 600,000 or so in the US.
In the Netherlands, SDA mortality was examined in 4000 members over about a ten year period—from 1968 to 1977.
In this study, researchers found lung cancer (among other cancers) to be significantly lower than expected—an SMR of 0.45 was found for lung cancer.13
In Norway, just over 7000 SDAs were followed over a period of 25 years—from 1961 to 1986—in which the members were monitored for cancer. Researchers found lung cancer incidence to be significantly decreased in SDAs under the age of 75 as compared to the general Norwegian population.14
In 1983, the cancer morbidity of male Copenhagen SDA members from 1943 to 1977 was reported on. Results were also presented for members of non-SDA temperance societies—societies that refrained from many indulgences but didn’t characteristically restrict meat intake.
The SIR (like SMR but for cancer incidence) was significantly lower amongst SDA members for all cancers including lung cancer. In this review, cancer incidence among the other temperance societies showed very little difference from the general population.15
2) Vegans Don’t Consume Meat
From 1976 to 1982, several food groups were examined in relation to cancer, including cancer of the lungs.
Meat and poultry intakes have been evaluated in regard to lung cancer risk, with the relative risks being somewhat elevated.16
The 2016 Continuous Update Project (CUP) report found some (albeit limited) evidence for a connection between processed meat intake and an increased risk of lung cancer.17
This finding was confirmed by a meta-analysis of 5 cohort studies and 13 case-control studies, which found a 34% increased risk of lung cancer to be associated with the highest consumption of meat.18
In the 5 cohort studies, a 20% elevated risk of lung cancer was observed. High intakes of red meat were found to be associated with elevated risks of lung cancer—by 30% and 23% for men and women, respectively.
3) Vegan Diets Emphasize Fruits and Veggies
As mentioned above, between 1976 and 1982, there were several food groups that were examined in relation to cancer of the lungs.
While there was some relationship between meat intake and lung cancer, much more significant, associations were found between intakes of plant foods and reduced lung cancer risk. Specifically, there was a protective association found between green salad and fruit intake and lung cancer risk.
Even after controlling for smoking history, lung cancer risk was still decreased by 74% in those who frequently consumed fruit.16
Below, I present a few examples rapid style:
- Data from an SDA incidence study provided some evidence for a connection between meat consumption and increased cancer risk in general, but the evidence was much stronger for an association between reduced cancer risk and increased intakes of fruits, vegetables, soy foods, nuts, and legumes. And these protective associations were observed for lung cancer specifically.1
- We’ve talked before about the World Cancer Research Fund International/American Institute for Cancer Research (WCRF/AICR)—wow, that’s a mouthful. Well, the WCRF/AICR issued a report in 2017 where they rated the evidence as strong for a protective role of certain plant foods in decreasing the incidence of lung cancers as well as cancers of the mouth, larynx, and pharynx.19
- According to researchers, Marine van
Berleere(Chru Lille University Medical Center), and Luc Dauchet (Lille University), fruits and/or vegetable intake is associated with a decrease in the risk of cancer at certain sites including lung cancer.20
- A recent review by Steinmetz and Potter, looked at 22 animal studies and 206 human epidemiologic studies wherein the authors concluded that fruits and vegetables were effective in preventing several forms of cancer including lung cancer.21 Twenty of the studies reviewed were cohort studies (the best kind) of which all found a protective effect of fruit and vegetable consumption against lung cancer development. Another 174 of the studies reviewed were case-control studies each of which found “convincing” evidence for a protective effect conferred by fruits and vegetables against lung cancer. Specifically, a 50% decreased risk of cancer was seen with fruit and veggie intakes classified as high. Raw vegetable consumption appeared to confer the most protection.
- Another study by Key et al., showed a protective effect of daily fresh fruit consumption in the prevention of lung cancer, as well as ischemic heart disease.22
- As I’ve written about in several other articles, the effect of fruits and veggies on cancer cells depends on the specific plants. Fruits and veggies can vary quite dramatically in both the magnitude of
effectthey have in preventing cancer as well as the specific sites of cancer they seem to influence. For example, according to some studies, green, leafy vegetables and carrots provide the most protection against cancer of the lungs, whereas the cruciferous vegetables tend to be effective in preventing colorectal and thyroid cancers.23-25
- When I think of soy foods and their prowess in preventing certain cancers, I tend to think of cancers with a primarily hormonal etiology such as breast and prostate cancers. However, it’s been suggested that the consumption of soybeans may partly account for the low incidence of a wide range of cancers seen in Japanese men and women. Chinese populations who consume soybeans and soy food products in high amounts have only half the rate of lung cancer compared with Chinese populations who rarely consume soy products.26
4) Plant-Based Diets Confer Protection to Current Smokers
Increased fruit and vegetable consumption was strongly associated with lower lung cancer risk in a 2015 WCRF/AICR-CUP meta-analysis.27,28
In this meta-analysis by Viera, et al. the following decreases in lung cancer risk were seen:
- For 100 grams/day of fruits and vegetables: 4% risk reduction
- For 100 grams/day of fruits: 8% risk reduction
- For 100 grams/day of vegetables: 6% risk reduction
Interestingly, when stratified by smoking status, for the most part, these associations proved to be more significant in smokers compared to former and never smokers.
This is thought to be potentially due to fruits and vegetables playing a role in counteracting the oxidative stress and carcinogenic effects of the tobacco—oxidative damage to DNA is one of the main tobacco-related pathways leading to carcinogenesis.29
Two other meta-analyses published in 2015 also explore the implications of fruit and veggie consumption on lung cancer outcomes and came to similar findings.30,31
5) Legumes and the Hispanic Paradox
According to health statistics and epidemiological studies, Hispanics live, on average, longer than both non-Hispanic whites and African Americans. Why is this a paradox? Because Hispanic populations have more cardiovascular disease (CVD) risk factors.32
Despite having more CVD risk factors, Hispanics have lower rates of coronary events, CVD, and mortality compared to other races. This goes for both males and females, and even persists after adjusting for sex, age, and CVD comorbidities.33
Additionally, mortality rates from both lung cancer and chronic obstructive pulmonary disease (COPD) happen to be the lowest among Hispanics.34,35
Not only do Hispanic subjects have lower rates of lung cancer, but they also have higher rates of survival from lung cancer, as well as colon and breast cancers.36,35
What’s this have to do with beans?
Well, several hypotheses have been put forward in hopes of explaining this phenomenon.
- Healthy migrant hypothesis
- Genetic hypothesis
- Salmon bias hypothesis
- Psychosocial explanations—some contribute it to the high level of family support and strong social network among Hispanics
- Nutritional risk factors
Naturally, some of these hypotheses have more support than others. According to Drummond, evidence is lacking for many of these hypothesis.38
Nutritional variables have sparked the interest of many researchers as dietary practices encompass cultural factors shared by the majority of Hispanics, specifically, their high intake of beans.39
Just how many legumes do Hispanics consume compared to other populations? Well, in the US, Hispanics account for 33% of all bean consumption, despite representing only 11% of the U.S. population.40
Compared to white subjects (a medium risk group for lung cancer), Hispanics consume up to five times more beans per capita—which comes to approximately 14.24 kg (~31.4 lb) versus 2.51 kg (about 5.5 lb) per year, for Hispanics and white, respectively.41
The Legume-Lung Cancer Connection
There’s a good bit of evidence that high legume intakes have anti-inflammatory effects likely due to the high fiber content of the beans.42,43
There’s also strong evidence in support of the hypothesis that high intakes of beans and bean products may, in part, explain the lower rates of mortality from lung cancer and COPD seen in Hispanics compared with other populations.39
According to Young and Hopkins, “Legumes are very high in fiber and have recently been shown to attenuate systemic inflammation significantly, which has previously been linked to susceptibility to COPD and lung cancer in large prospective studies.”39
Inositol hexaphosphate (phytate) has demonstrated extraordinary anticancer effects in a wide range of study designs (in vitro, in diet, etc.) for several cancers, including lung cancer.44
Among its many superpowers, phytate is capable of:45
- Reducing inflammation
- Enhancing immunity
- Inducing the destruction of tumor cells
- Reducing cell proliferation.
6) Vegan Diets Emphasize Higher Intakes of Carotenoid-Containing Plant Foods
Interest in potential anti-cancer properties of carotenoids came about decades ago when epidemiological evidence regularly demonstrated diets rich in fruits and veggies to be associated with reduced cancer risk.
This data, combined with evidence from animal models led researchers to assume that carotenoids—a nutrient ubiquitous to fruits and vegetables—was the sole component of plant foods accounting for the anti-cancer effects seen.46
This seemed to be further confirmed by studies that showed higher blood beta-carotene concentrations to be associated with decreased cancer risk, especially stomach and lung cancers.47
As you might imagine, they hadn’t quite connected all the dots yet. When researchers put beta-carotene supplements to the test as a chemo-preventive agent they were surprised to find that isolated beta-carotene (from pills) seemed to put the experimental group at higher relative risk for developing lung cancer compared to control.
It seems high-doses of isolated beta-carotene has the opposite effect (when it comes to cancer prevention) than the same amount when acquired from whole food sources.48
What’s the takeaway here? Well, beta-carotene may play a role in preventing lung cancer. Of course, it doesn’t do it alone, as it’s only one of a large number of carotenoids found in fruits and vegetables, which in themselves are only one class of many phytochemicals. So, you can’t go wrong by including an ample amount of beta-carotene-containing plant foods.
Fruits and veggies contain a wide range of bioactive, structurally diverse phytochemicals (phytosterols, polyphenols, lectins, etc.) whose characteristics likely help prevent diseases such as lung cancer.49
The lesson is that it’s the consumption of ample amounts of fruit and vegetables that lower the risk of lung other cancers. The chemopreventive effect of a whole food, plant-based diet should be the focus—not trying to hack the benefits of whole plant food by taking a single component.
Anyway, hopefully, you were as pleasantly surprised as I was to find that plant-based diets are, in fact, associated with reduced lung cancer risk. So, keep scarfing them down… and, of course, don’t smoke.
- Joan Sabaté-Rosemary Ratzin-Turner. Vegetarian Nutrition (Page 78). Crc Press – 2001
- Marine van Berleere, Luc Dauchet, François Mariotti. Vegetarian and Plant-based Diets in Health and Disease Prevention (Page 350). Elsevier Academic Press – 2017.
- World Health Organization. 2017. Cancer—Fact sheet. Available at http://www.who.int/media centre/factsheets/fs297/en/
- WCRF/AICR (World Cancer Research Fund International/American Institute for Cancer Research). 2012. Continuous Update Project report: Diet, nutrition, physical activity and pancreatic cancer. Available at wcrf.org/cupreports.
- Wynder, E. and Lemon, F. Cancer, coronary artery disease, and smoking—a preliminary report on differences in incidence between Seventh-Day Adventists and others. California Medicine, 89:267-272, 1958.
- Phillips, R.L. Role of lifestyle and dietary habits in risk of cancer among Seventh- Day Adventists. Cancer Res., 35:3513-3522, 1975.
- Phillips, R.L., Garfinkel, L., Kuzma, J.W., Beeson, W.L., Lotz, T., and Brin, B. Mortality among California Seventh-Day Adventists for Selected Cancer Sites. J. Natl. Cancer Inst., 65:1097-1107, 1980.
- Thorogood, M., Mann, J., Appleby, P., and McPherson, P. Risk of death from cancer and ischemic heart disease in meat- and non-meat-eaters. BMJ, 308:1667- 71, 1994.
- Key, T.J., Fraser, G.E., and Thorogood, M., et al., Mortality in vegetarians and non-vegetarians: detailed findings from a collaborative analysis of 5 prospective studies. Am. J. Clin. Nutr., 70 (suppl):516S-24S, 1999.
- Hirayama, T. Mortality in Japanese with life-styles similar to Seventh-Day Adventists. Strategy for risk reduction by life-style modification. Natl. Cancer Inst. Monogr., 69:143-153, 1985.
- Beeson, W.L., Mills, P.K., Phillips, R.L., Andress, M., and Fraser, G.E. Chronic disease among Seventh-Day Adventists, a low-risk group. Cancer, 64:57-81, 1989.
- Mills, P.K., Beeson, W.L., Phillips, W.L., and Fraser, G.E. Cancer incidence among California Seventh-Day Adventists, 1976-82. Am. J. Clin. Nutr., 59 (suppl):1136S-1142S, 1994.
- Berkel, J. and de Waard, F. Mortality pattern and life expectancy of Seventh- Day Adventists in the Netherlands. Int. J. Epidemiol., 12:455-59, 1983.
- Fonnebo, V. and Helseth, A. Cancer Incidence in Norwegian Seventh-Day Adventists 1961 to 1986. Cancer, 68:666-671, 1991.
- Jensen, O.M. Cancer risk among Danish male Seventh-Day Adventists and other temperance society members. J. Natl. Cancer Inst., 70:1011-14, 1983.
- Fraser, G.E., Beeson, W.L., and Phillips, R.L. Diet and lung cancer in California Seventh-Day Adventists. Am. J. Epidemiol., 133: 683-93, 1991.
- World Cancer Research Fund, American Institute for Cancer Research, 2016. Continuous Update Project. Findings & Reports. http://www.wcrf.org/int/research-we-fund/continuous-update-project-findingsreports.
- Yang, W.S., Wong, M.Y., Vogtmann, E., Tang, R.Q., Xie, L., Yang, Y.S., et al., December 1, 2012. Meat consumption and risk of lung cancer: evidence from observational studies. Ann. Oncol. 23 (12), 3163–3170.
- WCRF/AICR (World Cancer Research Fund International/American Institute for Cancer Research). 2017c. Continuous Update Project summary report. Available at http://www .wcrf.org/sites/default/files/CUP_Summary_Report_Sept17.pdf.
- Marine van Berleere, Luc Dauchet, François Mariotti. Vegetarian and Plant-based Diets in Health and Disease Prevention (Page 234). Elsevier Academic Press – 2017.
- Steinmetz, K. and Potter, J.D. Vegetables, fruit, and cancer prevention: A review. J. Am Dietetic Assoc., 96:1027-1039, 1996.
- Key, T.J.A., Thorogood, M., Appleby, P.N., and Burr, M.I. Dietary habits and mortality in 11,000 vegetarians and health conscious people: results of a 17- year follow up. BMJ, 313, 775, 1996.
- Food, Nutrition and the Prevention of Cancer: a Global Perspective, World Cancer Research Fund/American Institute for Cancer Research, Washington D.C., 1997.
- Dorant, E., van den Brandt, P.A., Goldbohm, R.A., and Sturmans, F. Consumption of onions and a reduced risk of stomach carcinoma. Gastroenterology, 110: 12, 1996.
- Steinmetz, K.A. and Potter, J.D. Vegetables, fruit, and cancer. II. Mechanisms. Cancer Causes Control, 2: 427, 1991.
- Messina, M.J., Persky, V., Setchell, K.D., and Barnes, S. Soy intake and cancer risk: a review of the in vitro and in vivo data. Nutr. Cancer., 21: 113, 1994.
- Vieira, A.R., Abar, L., Vingeliene, S., Chan, D.S.M., Aune, D., Navarro-Rosenblatt, D., Stevens, C., Greenwood, D., Norat, T., 2015a. Fruits, vegetables and lung cancer risk: a systematic review and meta-analysis. Ann. Oncol. http://dx.doi.org/10.1093/annonc/mdv381.
- Vieira, A.R., Vingeliene, S., Chan, D.S.M., Aune, D., Abar, L., Navarro Rosenblatt, D., Greenwood, D.C., Norat, T., 2015b. Fruits, vegetables, and bladder cancer risk: a systematic review and meta-analysis. Cancer Med. 4, 136–146. http://dx.doi.org/10.1002/cam4.327.
- Hecht, S.S., 1999. Tobacco smoke carcinogens and lung cancer. J. Natl. Cancer Inst. 91, 1194–1210. http:// dx.doi.org/10.1093/jnci/91.14.1194.
- Wang, M., Qin, S., Zhang, T., Song, X., Zhang, S., 2015a. The effect of fruit and vegetable intake on the development of lung cancer: a meta-analysis of 32 publications and 20 414 cases. Eur. J. Clin. Nutr. 69, 1184–1192. http://dx.doi.org/10.1038/ejcn.2015.64.
- Wang, Y., Li, F., Wang, Z., Qiu, T., Shen, Y., Wang, M., 2015b. Fruit and vegetable consumption and risk of lung cancer: a dose-response meta-analysis of prospective cohort studies. Lung Cancer 88, 124–130. http://dx.doi.org/10.1016/j.lungcan.2015.02.015.
- Medina-Inojosa J, Jean N, Cortes-Bergoderi M, Lopez-Jimenez F. 2014. The Hispanic paradox in cardiovascular disease and total mortality. Prog Cardiovasc Dis 57 (3):286–92.
- Willey JZ, Rodriguez CJ, Moon YP, Paik MC, Di Tullio MR, Homma S, Sacco RL, Elkind MSV. 2012. Coronary death and myocardial infarction among Hispanics in the Northern Manhattan Study: Exploring the Hispanic paradox. Ann Epidemiol 22 (5):303–9.
- Centers for Disease Control and Prevention. 2014. Chronic obstructive pulmonary disease. Atlanta, GA: Centers for Disease and Prevention. https://www.cdc.gov/copd/data.html (accessed May 31, 2017).
- American Cancer Society. 2017. Cancer facts and statistics 2017. https://www.cancer.org /research/cancer-facts-statistics.html (accessed May 31, 2017).
- Howe HL, Wu X, Ries LAG, Cokkinides V, Ahmed F, Jemal A, Miller B, Williams M, Ward E, Wingo PA. 2006. Annual report to the nation on the status of cancer, 1975–2003, featuring cancer among US Hispanic/Latino populations. Cancer 107 (8):1711–42.
- Franzini L, Ribble JC, Keddie AM. 2001. Understanding the Hispanic paradox. Ethn Dis 11:496–518.
- Drummond MB. 2011. The Hispanic paradox unraveled? Am J Respir Crit Care Med 184 (11):1222–3. doi: http://10.1164/rccm.201109-1684ED.
- Young RP, Hopkins RJ. 2014. A review of the Hispanic paradox: Time to spill the beans? Eur Respir Rev 23 (134):439–49.
- Lucier G, Lin B-H, Allshouse J, Kantor LS. 2000. Factors affecting dry bean consumption in the United States. agmrc.org/media/cms/DryBeanConEF5442C497B.pdf.
- Mitchell DC, Lawrence FR, Hartman TJ, Curran JM. 2009. Consumption of dry beans, peas, and lentils could improve diet quality in the US population. J Am Diet Assoc 109 (5):909–13.
- Ma Y, Griffith JA, Chasan-Taber L, Olendzki BC, Jackson E, Stanek EJ, Li W, Pagoto SL, Hafner AR, Ockene IS. 2006. Association between dietary fiber and serum C-reactive protein. Am J Clin Nutr 83 (4):760–6.
- Ma Y, Hébert JR, Li W, Bertone-Johnson ER, Olendzki B, Pagoto SL, Tinker L, Rosal MC, Ockene IS, Ockene JK. 2008. Association between dietary fiber and markers of systemic inflammation in the Women’s Health Initiative Observational Study. Nutrition 24 (10):941–9
- Vucenik I, Shamsuddin AM. 2003. Cancer inhibition by inositol hexaphosphate (IP6) and inositol: From laboratory to clinic. J Nutr 133 (11):3778S–84S.
- Vucenik I, Shamsuddin AM. 2006. Protection against cancer by dietary IP6 and inositol. Nutr Cancer 55 (2):109–25.
- Krinsky, N. I. Carotenoids and cancer in animal models. J. Nutr., 119, 123, 1989.
- Flagg, E. W., Coates, R. J., and Greenberg, R. S. Epidemiologic studies of antioxidants and cancer in humans. J. Am. Coll. Nutr., 14, 419, 1995.
- Pryor, W. A., Stahl, W., and Rock, C. L. Beta carotene: from biochemistry to clinical trials. Nutr. Rev., 58, 39, 2000.
- WCRF/AICR, 2007. World Cancer Research Fund/American Institute for Cancer Research. Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective. AICR, Washington, DC.