Dietary patterns and risk of prostate cancer: a factor analysis study in a sample of Iranian men

Introduction

Prostate cancer is one of the most common cancers in males worldwide,^1,2 and the second leading cause of cancer mortality in men in the United States after lung cancer.³ Studies on the epidemiology of prostate cancer in Iran are rare.^4,5 Prostate cancer is reported as the third most common cancer in men and the sixth most common cancer in Iran.⁴ Incidence of prostate cancer in Iranian men is higher than other countries in Asia.⁶

Clearly identified risk factors for prostate cancer include age, ethnicity, and family history, but the role of other risk factors such as diet, alcohol consumption, exposure to ultraviolet radiation, chronic inflammation, and occupational exposure are less fully investigated.⁷ Diet, for example, can play an important role in incidence of prostate cancer.⁸

Associations between diet and disease risk can be explored in relation to individual nutrients and food consumption and also dietary patterns^9,10 defined by national or regional eating habits. Prostate cancer incidence has been associated with calcium, green tea, lycopene, pectin, pomegranate, selenium, soy, vitamin D and vitamin E,^1,11,12 however, this approach to assess nutrients individually has limitations because people eat diets consisting of a variety of foods with complex compounds of nutrients, therefore, interactions and complex inter-relationships between nutrients, cannot be properly recognized.^9,13 Since the relationship between diet and disease is very complicated, it is suggested that dietary pattern analysis, instead of analyzing a particular nutrient, can be provides more detailed information on the relationship between diet and the risk of disease.^9,14

A limited number of studies have examined the relationship between dietary patterns and risk of prostate cancer.¹³ While some of them report a positive association between the Western dietary pattern and risk of prostate cancer,^15-18 other studies show no association.^13,19,20 On the other hand, some studies show a protective effect of Healthy and Mediterranean dietary patterns on prostate cancer^3,13,15 but most studies do not find any association between them.^17-20 And also, information about the role of dietary patterns in developing prostate cancer is limited in Iranian men.

The purpose of the present study is to explore the relationship between dietary patterns and prostate cancer risk among Iranian men.

Materials and Methods

Results

Using factor analysis, 2 major dietary patterns were identified: an “unhealthy” dietary pattern characterized by higher consumption of hydrogenated fats, refined grains, butters, red meats, process meats, organ meats, sweets, desserts, soft drinks, salt, high-fat dairy, snacks, tea and coffee; and a “healthy” dietary pattern characterized by higher consumption of legumes, fish, low-fat dairy, fruits and fruit juices, vegetables, poultry, nuts and eggs. The factor-loading matrixes for these dietary patterns are shown in Table 2. Factor loading represents the correlation coefficient between a food group with each pattern. Larger values indicate stronger correlations, and positive or negative sign indicates direct or inverse relationships between that group and the pattern. These 2 major dietary patterns explained 21.4% of the total variance in dietary intakes.

Characteristics of participants in relation to prostate cancer are presented in Table 3. Statistically significant differences between cases and controls were observed for calorie intake (P = 0.02), physical activity (P < 0.001), drinking alcohol (P = 0.002) and smoking (P = 0.019).

OR and CIs for risk of prostate cancer by tertiles of food pattern scores are shown in Table 4. After adjusting for the potential confounding effects of alcohol consumption (yes or no), smoking (yes, no), total energy intake, physical activity level and educational level, the healthy dietary pattern was associated with a decreased risk of prostate cancer (highest versus lowest tertile OR: 0.24; 95% CI: 0.07-0.81; trend P = 0.025). The unhealthy dietary pattern was associated with an increased risk of prostate cancer (highest versus lowest tertile OR: 3.4; 95% CI: 1.09-10.32; trend P = 0.037).

Discussion

Cancer is a major health problem for Iran and rates are increasing.⁴ Unfortunately, unlike developed countries, Iranian treatment and management of cancer is challenging. The majority of Iranian patients with cancer are faced with an unpleasant and tragic end; cancer takes both their lives and their money. The best strategy, therefore, is to focus on the prevention of disease. Food plays an important role in the prevention (and progression) of a variety of diseases, including cancer.

The relationship between intakes of specific nutrients and many cancers has been widely studied. According to fact that the diets include a variety of foods with complex combinations of nutrients interactions and complex inter-relationships between nutrients, cannot be properly recognized.^9,14 Therefore, it is suggested that dietary pattern analysis, instead of analyzing a particular nutrient, can provide more detailed information on the relationship between diet and the risk of disease.^9,14Attention to food groups rather than singular nutrients is more likely to reflect the usual dietary intake, and represent features of the total diet, including all nutrient interactions.¹⁴ And also, the determination of dietary patterns and their relationship to disease can give us the clearer and applicable approach to deal with the disease.

Factor analysis is one of the most reliable methods to identify dietary patterns.²⁶ In this study, by using factor analysis, 2 major dietary patterns were identified. The first pattern was termed an “unhealthy”, characterized by diets high in red and organ meat, saturated fats, high-fat dairy products, refined grains, sweets and desserts, salt, and soft drinks, and low in whole grains and unsaturated fat. The second pattern was termed “healthy”: diets were typically higher in legumes, fish, low-fat dairy products, fruits, vegetables and eggs. The unhealthy pattern can be described as energy dense, and the healthy pattern as nutrient dense. There was an inverse relation between the healthy pattern and risk of prostate cancer; the unhealthy pattern, in contrast, was associated with increased risk of prostate cancer.

The present findings are consistent with a number of other studies. In a study in Tehran of 50 men and 100 controls, 2 dietary patterns were identified: “Western diet” (including higher levels of consumption of sweets, desserts, total meat, tea and coffee, French fries, salt, soft drinks, red meat or processed meat) and “healthy diet” (including higher levels of consumption of legumes, fish, dairy products, fruits and fruit juices, vegetables, boiled potatoes, cereals and eggs). The study showed that the western dietary pattern was associated with a significantly increased risk of prostate cancer (OR = 4.0, 95% CI = 1.5-11.0); the healthy dietary pattern was associated with a decreased risk of prostate cancer (OR = 0.4, 95% CI = 0.2-1.0).¹⁵In a case-control study of diet and prostate cancer in Australia, three dietary patterns were identified: vegetarian, western and health-conscious. The western diet (with higher consumption levels of red and processed meat, fried fish, chips, hamburgers, white bread and whole milk was associated with higher risk of prostate cancer (1.82, 95% CI = 1.15-2.87, trend P = 0.02).¹⁶

Not all studies have shown this association. Muller and colleagues, for example, identified four dietary patterns among people with prostate cancer. These were (a) Mediterranean (high intake of meats, vegetables, and fruits, and low intake of cakes and sweet biscuits); (b) Vegetable (high intake of vegetables); (c) Meat & Potatoes (high intake of meats and potato); and (d) Fruit & Salad (high intake of salad greens and fruit). They did not, however, find any association between these patterns and risk of prostate cancer.²⁰ Extensive overlap of dietary patterns with each other may be one of the reasons that no associations between dietary patterns and prostate cancer were observed. In another study, 2 dietary patterns, “prudent” (which includes high intake of fruits, vegetables, whole grains, fish and poultry) and “western” (which contained a lot of red and processed meat, refined grains and high fat dairy products) were identified.²⁷ The “western” dietary pattern was associated with an increased risk of prostate cancer, but this did not reach statistical significance, due possibly limitations in their study.

Taking into account race, culture and place, 2 dietary patterns associated with risk of prostate cancer have been identified: a healthy pattern that includes higher consumption levels of fruits and vegetables, legumes, whole grains, low-fat dairy, fish and poultry; and an unhealthy pattern that includes higher consumption levels of red and processed meat, refined grains, sweets, high-fat dairy and fried foods. Pathogenicity of the unhealthy diet patterns can be attributed to factors such as heterocyclic amines,^8,28oxidizing agents,^8,29 anabolic agents,^30-32 high-calorie,³³ high-fat^19,34 and lack of the antioxidants.³⁵

The main limitation of this study was the use of food frequency questionnaires for dietary assessment. Although we used a validated questionnaire, it can still over- or under-estimate consumption of specific foods. In factor analysis, the researcher can make subjective decisions that can impact on results and interpretation.^9,19 In this study, the 2 patterns were based on eigenvalues, scree plots, and interpretability to find significant patterns. Low sample size was another limitation of this study. And therefore, it was not possible to adjust the results for confounder effects of vitamins and mineral supplementation because information about this exposure was not collected at baseline. Because of the limitations of case-control studies, as well as limited studies conducted on the dietary pattern and the risk of prostate cancer in Iran, it is suggested that cohort studies be conducted in this regard.

An important issue in relation to cancer is assessment of exposure to toxins and various chemical compounds, or chemical pollution among the subjects. In Iran, use of pesticides and fertilizers, particularly nitrate fertilizers, are common.³⁶ Some pesticides are non-standard and potentially dangerous, with poor control over their use. These toxins, pesticides and fertilizers can easily enter the food chain.³⁷ Information on their levels of ingestion in Iran is sparse.

In conclusion, we found 2 major healthy and unhealthy dietary pattern which was associated with lower and higher risk of prostate cancer, respectively.

Ethical approval

Ethical approval was given by the Ethics Committee of the Deputy of Research and Technology of Kermanshah University of Medical Sciences (ethic number: KUMS.REC.1395.6).

Competing interests

The authors declare that they have no competing interests.

Authors’ contributions

AM contributed to the design of the study, data collection, analysis and interpretation of data and drafting of the manuscript. SMN contributed to the design of the study, analysis and interpretation of data, the management, appraised and revised of the manuscript. MR helped us in statistical analysis. MM helped us in data collection. MRM was involved in the design of the study. MN was involved in the conception of the study and assisted revision. All authors approved the final version of the manuscript for submission.

Acknowledgments

We thank the participants involved in our study. The author gratefully acknowledges the Research Council of Kermanshah University of Medical Sciences (grant number: 95021) for financial support. This work was performed in partial fulfillment of requirements for (master of sciences in nutrition, D) of (Amir Bagheri), in the faculty of Nutritional Science & Food Technology, Kermanshah University of Medical Sciences, Kermanshah, Iran.

References

1. Torre LA, Siegel RL, Ward EM, Jemal A. Global cancer incidence and mortality rates and trends--an update. Cancer Epidemiol Biomarkers Prev 2016;25(1):16-27. doi: 10.1158/1055-9965.epi-15-0578. [Crossref]
2. Bashir MN. Epidemiology of prostate cancer. Asian Pac J Cancer Prev 2015;16(13):5137-41.
3. Yang M, Kenfield SA, Van Blarigan EL, Batista JL, Sesso HD, Ma J, et al. Dietary patterns after prostate cancer diagnosis in relation to disease-specific and total mortality. Cancer Prev Res (Phila) 2015;8(6):545-51. doi: 10.1158/1940-6207.capr-14-0442. [Crossref]
4. Pakzad R, Rafiemanesh H, Ghoncheh M, Sarmad A, Salehiniya H, Hosseini S, et al. Prostate cancer in Iran: trends in incidence and morphological and epidemiological characteristics. Asian Pac J Cancer Prev 2016;17(2):839-43.
5. Kolahdoozan S, Sadjadi A, Radmard AR, Khademi H. Five common cancers in Iran. Arch Iran Med 2010;13(2):143-6.
6. Akbari ME, Hosseini SJ, Rezaee A, Hosseini MM, Rezaee I, Sheikhvatan M. Incidence of genitourinary cancers in the Islamic Republic of Iran: a survey in 2005. Asian Pac J Cancer Prev 2008;9(4):549-52.
7. Heidenreich A, Bastian PJ, Bellmunt J, Bolla M, Joniau S, van der Kwast T, et al. EAU guidelines on prostate cancer. part 1: screening, diagnosis, and local treatment with curative intent-update 2013. Eur Urol 2014;65(1):124-37. doi: 10.1016/j.eururo.2013.09.046. [Crossref]
8. Mandair D, Rossi RE, Pericleous M, Whyand T, Caplin ME. Prostate cancer and the influence of dietary factors and supplements: a systematic review. Nutr Metab (Lond) 2014;11:30. doi: 10.1186/1743-7075-11-30. [Crossref]
9. Hu FB. Dietary pattern analysis: a new direction in nutritional epidemiology. Curr Opin Lipidol 2002;13(1):3-9.
10. Kant AK. Dietary patterns and health outcomes. J Am Diet Assoc 2004;104(4):615-35. doi: 10.1016/j.jada.2004.01.010. [Crossref]
11. Lin PH, Aronson W, Freedland SJ. Nutrition, dietary interventions and prostate cancer: the latest evidence. BMC Med 2015;13:3. doi: 10.1186/s12916-014-0234-y. [Crossref]
12. Masko EM, Allott EH, Freedland SJ. The relationship between nutrition and prostate cancer: is more always better? Eur Urol 2013;63(5):810-20. doi: 10.1016/j.eururo.2012.11.012. [Crossref]
13. Castello A, Boldo E, Amiano P, Castano-Vinyals G, Aragones N, Gomez-Acebo I, et al. Mediterranean dietary pattern is associated with low risk of aggressive prostate cancer: MCC-Spain Study. J Urol 2018;199(2):430-7. doi: 10.1016/j.juro.2017.08.087. [Crossref]
14. Barkoukis H. Importance of understanding food consumption patterns. J Am Diet Assoc 2007;107(2):234-6. doi: 10.1016/j.jada.2006.12.024. [Crossref]
15. Askari F, Parizi MK, Jessri M, Rashidkhani B. Dietary patterns in relation to prostate cancer in Iranian men: a case-control study. Asian Pac J Cancer Prev 2014;15(5):2159-63.
16. Ambrosini GL, Fritschi L, de Klerk NH, Mackerras D, Leavy J. Dietary patterns identified using factor analysis and prostate cancer risk: a case control study in Western Australia. Ann Epidemiol 2008;18(5):364-70. doi: 10.1016/j.annepidem.2007.11.010. [Crossref]
17. Rosato V, Edefonti V, Bravi F, Bosetti C, Bertuccio P, Talamini R, et al. Nutrient-based dietary patterns and prostate cancer risk: a case-control study from Italy. Cancer Causes Control 2014;25(4):525-32. doi: 10.1007/s10552-014-0356-8. [Crossref]
18. De Stefani E, Ronco AL, Deneo-Pellegrini H, Boffetta P, Aune D, Acosta G, et al. Dietary patterns and risk of advanced prostate cancer: a principal component analysis in Uruguay. Cancer Causes Control 2010;21(7):1009-16. doi: 10.1007/s10552-010-9527-4. [Crossref]
19. Jackson M, Tulloch-Reid M, Walker S, McFarlane-Anderson N, Bennett F, Francis D, et al. Dietary patterns as predictors of prostate cancer in Jamaican men. Nutr Cancer 2013;65(3):367-74. doi: 10.1080/01635581.2013.757631. [Crossref]
20. Muller DC, Severi G, Baglietto L, Krishnan K, English DR, Hopper JL, et al. Dietary patterns and prostate cancer risk. Cancer Epidemiol Biomarkers Prev 2009;18(11):3126-9. doi: 10.1158/1055-9965.epi-09-0780. [Crossref]
21. Esfahani FH, Asghari G, Mirmiran P, Azizi F. Reproducibility and relative validity of food group intake in a food frequency questionnaire developed for the Tehran Lipid and Glucose Study. J Epidemiol 2010;20(2):150-8.
22. Ghaffarpour M, Houshiar-Rad A, Kianfar H. The manual for household measures, cooking yields factors and edible portion of foods. Tehran: Nashre Olume Keshavarzy; 1999. [Persian].
23. Azar M, Sarkisian E. Food composition table of Iran: National Nutrition and Food Research Institute. Tehran: Shahid Beheshti University Press; 1980. [Persian].
24. Baghiani Moghaddam MH, Bakhtari Aghdam F, Asghari Jafarabadi M, Allahverdipour H, Dabagh Nikookheslat S, Safarpour S. The Iranian Version of International Physical Activity Questionnaire (IPAQ) in Iran: content and construct validity, factor structure, internal consistency and stability. World Appl Sci J 2012;18(8):1073-80. doi: 10.5829/idosi.wasj.2012.18.08.754. [Crossref]
25. Kim JO, Mueller CW. Factor analysis: Statistical methods and practical issues. Beverly Hills, CA: Sage Publications, Inc; 1978.
26. Esmaillzadeh A, Kimiagar M, Mehrabi Y, Azadbakht L, Hu FB, Willett WC. Dietary patterns, insulin resistance, and prevalence of the metabolic syndrome in women. Am J Clin Nutr 2007;85(3):910-8.
27. Wu K, Hu FB, Willett WC, Giovannucci E. Dietary patterns and risk of prostate cancer in U.S. men. Cancer Epidemiol Biomarkers Prev 2006;15(1):167-71. doi: 10.1158/1055-9965.epi-05-0100. [Crossref]
28. Zheng W, Lee SA. Well-done meat intake, heterocyclic amine exposure, and cancer risk. Nutr Cancer 2009;61(4):437-46. doi: 10.1080/01635580802710741. [Crossref]
29. Tappel A. Heme of consumed red meat can act as a catalyst of oxidative damage and could initiate colon, breast and prostate cancers, heart disease and other diseases. Med Hypotheses 2007;68(3):562-4. doi: 10.1016/j.mehy.2006.08.025. [Crossref]
30. Ma J, Giovannucci E, Pollak M, Chan JM, Gaziano JM, Willett W, et al. Milk intake, circulating levels of insulin-like growth factor-I, and risk of colorectal cancer in men. J Natl Cancer Inst 2001;93(17):1330-6.
31. Qin LQ, He K, Xu JY. Milk consumption and circulating insulin-like growth factor-I level: a systematic literature review. Int J Food Sci Nutr 2009;60(Suppl 7):330-40. doi: 10.1080/09637480903150114. [Crossref]
32. Cohen P, Peehl DM, Rosenfeld RG. The IGF axis in the prostate. Horm Metab Res 1994;26(2):81-4. doi: 10.1055/s-2007-1000777. [Crossref]
33. Kopeina GS, Senichkin VV, Zhivotovsky B. Caloric restriction - A promising anti-cancer approach: From molecular mechanisms to clinical trials. Biochim Biophys Acta 2017;1867(1):29-41. doi: 10.1016/j.bbcan.2016.11.002. [Crossref]
34. Ross RK, Henderson BE. Do diet and androgens alter prostate cancer risk via a common etiologic pathway? J Natl Cancer Inst 1994;86(4):252-4. doi: 10.1093/jnci/86.4.252. [Crossref]
35. Fabiani R, Minelli L, Bertarelli G, Bacci S. A Western dietary pattern increases prostate cancer risk: a systematic review and meta-analysis. Nutrients 2016;8(10):626. doi: 10.3390/nu8100626. [Crossref]
36. Mostafalou S, Karami-Mohajeri S, Abdollahi M. Environmental and population studies concerning exposure to pesticides in iran: a comprehensive review. Iran Red Crescent Med J 2013;15(12):e13896. doi: 10.5812/ircmj.13896. [Crossref]
37. Behrooz RD, Esmaili-Sari A, Bahramifar N, Ghasempouri SM. Organochlorine pesticide and polychlorinated biphenyl residues in human milk from the Southern Coast of Caspian Sea, Iran. Chemosphere 2009;74(7):931-7. doi: 10.1016/j.chemosphere.2008.10.014. [Crossref]