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  • Three large scale human studies have confirmed a decreased risk of lung cancer with increase consumption of apples, due to their quercetin (polyphenol) content

  • One study from Hawaii showed a 40-50% decreased risk of lung cancer in people with the highest intake of flavonoids from apples and onions.

  • Further studies on apple polyphenols and lung cancer will be reported here. If you would like to be notified when more research is published, sign up for the AP Science alerts.

Dietary catechins and epithelial cancer incidence: the Zutphen elderly study, Int J Cancer. 2001
Intake of Flavonoids and Lung Cancer, Journal of the National Cancer Institute
Flavonoid intake and risk of chronic diseases, American Journal of Clinical Nutrition 2002
Apple phytochemicals and their health benefits, Nutr J. 2004

Int J Cancer. 2001 Apr 15;92(2):298-302.

Dietary catechins and epithelial cancer incidence: the Zutphen elderly study.

Arts IC, Hollman PC, Bueno De Mesquita HB, Feskens EJ, Kromhout D.

National Institute of Public Health and the Environment (RIVM), Department of Chronic Diseases Epidemiology, PO Box 1, NL-3720 BA Bilthoven, The Netherlands.

The flavonoids, a group of more than 4,000 polyphenolic antioxidants, are potential cancer preventive components of fruits and vegetables. Catechins, one of the 6 major groups of flavonoids, are present in high concentrations in tea as well. Our objective was to evaluate the association between intake of catechins and incidence of epithelial cancers with data from the Zutphen Elderly Study, a prospective cohort study among 728 men aged 65-84 years in 1985. The average catechin intake at baseline was 72 mg/day (range, 0-355 mg/day). After 10 years of follow-up, 96 incident epithelial cancers were recorded, including 42 cases of lung cancer. After multivariate adjustment, catechin intake was not associated with epithelial cancer (risk ratio [RR] from lowest to highest tertile: 1.00, 0.75, 0.94; p for trend: 0.82), or lung cancer (RR from lowest to highest tertile: 1.00, 0.72, 0.92; p for trend: 0.80). Catechins not from tea were borderline significantly inversely associated with lung cancer incidence (RR and 95% confidence interval [CI] for a 7.5-mg increase in intake: 0.66, 0.42-1.05), whereas catechins from tea were not. Catechins from apple, the major source of non-tea catechins, were also related to lung cancer incidence (RR and 95% CI for a 7.5-mg catechin increase: 0.67, 0.38-1.17). Because tea, the major catechin source in this population, was not associated with cancer risk, it seems unlikely that catechins are responsible for the observed inverse trend between non-tea catechins and lung cancer incidence. However, differences in bioavailability of the various catechins may play a role; effects on individual cancer sites cannot be excluded and merit further investigation. Copyright 2001 Wiley-Liss, Inc.

PMID: 11291060 [PubMed - indexed for MEDLINE]

Journal of the National Cancer Institute, Vol. 92, No. 2, 154-160, January 19, 2000
© 2000 Oxford University Press

Intake of Flavonoids and Lung Cancer

Loïc Le Marchand, Suzanne P. Murphy, Jean H. Hankin, Lynne R. Wilkens, Laurence N. Kolonel

Affiliation of authors: Etiology Program, Cancer Research Center of Hawaii, University of Hawaii, Honolulu.

Correspondence to: Loïc Le Marchand, M.D., Ph.D., Etiology Program, Cancer Research Center of Hawaii, University of Hawaii, 1236 Lauhala St., Suite 407, Honolulu, HI 96813 (e-mail:

BACKGROUND: To investigate the possible relationship between intake of flavonoids—powerful dietary antioxidants that may also inhibit P450 enzymes—and lung cancer risk, we conducted a population-based, case-control study in Hawaii. METHODS: An in-person interview assessed smoking history and usual intake of 242 food items for 582 patients with incident lung cancer and 582 age-, sex-, and ethnicity-matched control subjects. Subjects who donated a blood sample were genotyped for the P450 enzyme variant allele CYP1A1*2 by use of a polymerase chain reaction-based method. Logistic regression analysis was used to compute odds ratios (ORs) and 95% confidence intervals (CIs). All P values are two-sided. RESULTS: After adjusting for smoking and intakes of saturated fat and ß-carotene, we found statistically significant inverse associations between lung cancer risk and the main food sources of the flavonoids quercetin (onions and apples) and naringin (white grapefruit). The lung cancer OR for the highest compared with the lowest quartile of intake was 0.5 (95% CI = 0.3-0.9) for onions (P for trend = .001) and 0.6 (95% CI = 0.4-1.0) for apples (P for trend = .03). The OR for the highest compared with the lowest tertile of intake for white grapefruit was 0.5 (95% CI = 0.2-0.9) (P for trend = .02). No association was found for important food sources of other flavonoids. Using published food-composition data for flavonoids, we found an inverse association between intake of quercetin and risk of lung cancer (P for trend = .07) that appears consistent with associations for its food sources. The effect of onions was particularly strong against squamous cell carcinoma (a cell type specifically associated with CYP1A1*2 in our study) and was modified by the CYP1A1 genotype, suggesting that CYP1A1 may play a role in this association. CONCLUSION: If replicated, particularly in prospective studies, these findings would suggest that foods rich in certain flavonoids may protect against certain forms of lung cancer and that decreased bioactivation of carcinogens by inhibition of CYP1A1 should be explored as underlying mechanisms.


American Journal of Clinical Nutrition, Vol. 76, No. 3, 560-568, September 2002

© 2002 American Society for Clinical Nutrition

Original Research Communication

Flavonoid intake and risk of chronic diseases1,2

Paul Knekt, Jorma Kumpulainen, Ritva Järvinen, Harri Rissanen, Markku Heliövaara, Antti Reunanen, Timo Hakulinen and Arpo Aromaa

Background: Flavonoids are effective antioxidants and may protect against several chronic diseases.

Objective: The association between flavonoid intake and risk of several chronic diseases was studied.

Design: The total dietary intakes of 10 054 men and women during the year preceding the baseline examination were determined with a dietary history method. Flavonoid intakes were estimated, mainly on the basis of the flavonoid concentrations in Finnish foods. The incident cases of the diseases considered were identified from different national public health registers.

Results: Persons with higher quercetin intakes had lower mortality from ischemic heart disease. The relative risk (RR) between the highest and lowest quartiles was 0.79 (95% CI: 0.63, 0.99: P for trend = 0.02). The incidence of cerebrovascular disease was lower at higher kaempferol (0.70; 0.56, 0.86; P = 0.003), naringenin (0.79; 0.64, 0.98; P = 0.06), and hesperetin (0.80; 0.64, 0.99; P = 0.008) intakes. Men with higher quercetin intakes had a lower lung cancer incidence (0.42; 0.25, 0.72; P = 0.001), and men with higher myricetin intakes had a lower prostate cancer risk (0.43; 0.22, 0.86; P = 0.002). Asthma incidence was lower at higher quercetin (0.76; 0.56, 1.01; P = 0.005), naringenin (0.69; 0.50, 0.94; P = 0.06), and hesperetin (0.64; 0.46, 0.88; P = 0.03) intakes. A trend toward a reduction in risk of type 2 diabetes was associated with higher quercetin (0.81; 0.64, 1.02; P = 0.07) and myricetin (0.79; 0.62, 1.00; P = 0.07) intakes.

Conclusion: The risk of some chronic diseases may be lower at higher dietary flavonoid intakes.

Key Words: Chronic disease • diet • flavonoids • flavonols • flavanones • flavones • prospective study • free radicals

[Reprint (PDF) Version of Full Study]


Nutr J. 2004 May 12;3(1):5.

Apple phytochemicals and their health benefits.

Boyer J, Liu RH.

Department of Food Science and Institute of Comparative and Environmental Toxicology, Cornell University, Ithaca, New York 14853-7201 USA.


Several studies have specifically linked apple consumption with a reduced risk for cancer, especially lung cancer. In the Nurses' Health Study and the Health Professionals' Follow-up Study, involving over 77,000 women and 47, 000 men, fruit and vegetable intake was associated with a 21% reduced risk in lung cancer risk in women, but this association was not seen in men. Very few of the individual fruits and vegetables examined had a significant effect on lung cancer risk in women, however apples were one of the individual fruits associated with a decreased risk in lung cancer. Women who consumed at least one serving per day of apples and pears had a reduced risk of lung cancer. Of the men involved, there was no association seen between any individual fruit or vegetable and lung cancer risk.

In a case control study in Hawaii, it was found that apple and onion intake was associated with a reduced risk of lung cancer in both males and females. Smoking history and food intake was assessed for 582 patients with lung cancer and 582 control subjects without lung cancer. There was a 40–50% decreased risk in lung cancer in participants with the highest intake of apples, onions, and white grapefruit when compared to those who consumed the lowest amount of these fruits. The decreased risk in lung cancer was seen in both men and women and in almost all ethnic groups. No associations were seen with red wine, black tea or green tea. Both onions and apples are high in flavonoids, especially quercetin and quercetin conjugates. Le Marchand et al.found an inverse association between lung cancer and quercetin intake although the trend was not statistically significant. Interestingly, the inverse association seen between apple and onion intake and lung cancer were stronger for squamous cell carcinomas than for adenocarcinomas.

In a Finnish study involving 10,000 men and women and a 24-year follow-up, a strong inverse association was seen between flavonoid intake and lung cancer development. In the sampled population, the mean flavonoid intake was 4.0 mg per day, and 95% of the total flavonoid intake was quercetin. Apples and onions together provided 64% of all flavonoid intake. The reduced risk of lung cancer associated with increased flavonoid consumption was especially strong in younger people and in nonsmokers. Apples were the only specific foods that were inversely related to lung cancer risk. Since apples were the main source of flavonoids in the Finnish population, it was concluded that the flavonoids from apples were most likely responsible for the decreased risk in lung cancer.

The relationship of dietary catechins and epithelial cancer was examined in 728 men (aged 65–84) as part of the Zutphen Elderly Study. Tea, a naturally high source of catechins, contributed 87% of the total catechin intake in this study, while apples contributed 8.0% of catechin consumption. It was found that total catechin and tea consumption did not have an effect on lung cancer, but apple consumption was associated with decreased epithelial lung cancer incidence. This supported the findings of the previous studies discussed, where apples were significantly inversely associated with lung cancer, and may suggest that catechins alone do not play have a effect against lung cancers. Other data from the Zutphen Elderly study showed an inverse association between fruit and vegetable flavonoids and total cancer incidence and tumors of the alimentary and respiratory tract. Again, tea flavonoids were not associated with a decrease in cancer risk.

[Reprint (PDF) Version of Full Study]

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