Egg consumption and cancer risk

Many people like eggs. It is an indispensable part of their diet. In Singapore, for example, every person, on average, ate 323 eggs in 2015. Amount to almost one egg per day per person in this small country [1].

Eggs – a favourite of many.

Not surprisingly, since egg is a good source of inexpensive, high-quality protein and many vitamins and minerals, especially choline, vitamins B12, B2, B5, D, as well as phosphorus [2].  Many nutritionists and dieticians also promote the replacement of red meat and processed meat with eggs as part of a healthier diet to lower the risk of health conditions, such as the metabolic syndrome [3]. With many of the nutrients being highly bioavailable, egg is also considered as an important food source for the elderly, pregnant women, children, those who are recovering from illnesses, and athletes [4]. Similarly, many vegetarians also include egg in their diet to ensure sufficient intake of essential nutrients, especially vitamin D and B12.

Many vegetarians also include egg in their diet to ensure sufficient intake of essential nutrients, especially vitamin D and B12

Does eating egg has any health risk?

Egg is a major source of dietary cholesterol

Yes, it does. It is well known that egg yolk contains a lot of cholesterol and high egg consumption has been associated with the risk of cardiovascular diseases including heart attack and stroke [5]. Even though recent research evidence has indicated that consuming cholesterols from the diet has little impact on the blood cholesterol level, it is still advisable to limit the intake of high cholesterol food according to the latest recommendation by the American Heart Association [2].

Another health risk of egg consumption is cancer. Something few people are aware of. Let’s look at a few types of cancer that has been linked to egg consumption.

Colon cancer

Diagram showing T stages of bowel cancer CRUK 276

Study: egg consumption is linked to colon or bowel cancer.


A systematic review of 15 case-control and cohort studies published in 1994 found that egg consumption is associated with an increased risk of colon cancer, especially among women. The risk of colon cancer can be 7-8 times higher among those who consumed more eggs, compared to those who rarely consumed eggs [6]. Such findings are supported by another study, which analysed data of egg consumption in 34 countries collected by the World Health Organization and Food and Agriculture Organization. It was found that egg consumption was associated with an increased risk of mortality from colon and rectal cancers at the population level [7].

Breast cancer

Study: women who ate more than 5 eggs/week had a significantly higher risk of breast cancer

Egg consumption was associated with increased breast cancer risk. This was concluded by a meta-analysis of 13 studies conducted worldwide with a total sample size of over 700,000. Asian and European population, post-menopausal women, and those who consumed more than 2 eggs a week are found to have increased breast cancer risk correlated with egg consumption [8]. Another study by Harvard School of Public Health that investigated the link between egg consumption and sex hormone-related cancers also discovered that women who ate more than 5 eggs/week had a significantly higher risk of breast cancer compared to those who did not eat any egg at all [9].

Ovarian cancer

Diagram showing stage 1 ovarian cancer CRUK 193

Study: egg consumption is linked to ovarian cancer risk.


The same study from Harvard School of Public Health also found similarly increased in ovarian cancer risk by consuming more than 5 eggs per week [9]. A similar conclusion has also been reached by another independent study published in the Journal of Clinical Nutrition by a group of Chinese researchers. The conclusion was based on a meta-analysis of a total of 12 studies with 629,453 subjects and 3728 ovarian cancer cases [10].

Prostate cancer

Prostate Cancer

Study: consumption of eggs may increase risk of developing a more lethal-form of prostate cancer


Another sex hormone-related cancer that was investigated in the study conducted by the Harvard School of Public Health was prostate cancer. The study found no evidence of increased risk between consumption of egg and the total incidents of prostate cancer. In contrast, a 47% increase in risk of prostate cancer fatality was found to be associated consuming more than 5 eggs a week [9]. In another publication also reported that men who consumed 2.5 or more eggs per week had an 81% increased risk of lethal prostate cancer compared to men who consumed less than 0.5 eggs per week. Hence, men could develop prostate cancer, regardless of whether they eat eggs or not. Consumption of eggs, however, may increase risk of developing a more lethal-form of prostate cancer [10].

Bladder cancer

Bladder Cancer (27785800576)

Study: bladder cancer is also linked to consumption of eggs.


The risk of bladder cancer and egg intake was meta-analysed in a study that included 4 cohort and 9 case-controlled studies [11]. The study found an overall increased risk of egg consumption with bladder cancer. However, the risk differed significantly by geographic region, with population in Japan showing a reduced risk, while increased risk was observed in Uruguayans, no association was found in Western countries. Hence, association of risk of bladder cancer with egg consumption may be affected by other dietary factors [11].

Why egg consumption may cause cancer?

Several possibilities have been suggested. High cholesterol content of eggs is a possible cause since cholesterol was found to assist in the proliferation of cancer cells [12]. Cholesterol serves as a precursor for the biosynthesis of sex hormones such as androgens and oestrogens that promote cell proliferation, thereby contributing to the progression of breast, prostate and ovarian cancers [9].

Egg yolk is high in cholesterol and choline.

Another potential culprit is choline, a water-soluble vitamin-like essential nutrient. It was found in prostate cancer cells that choline concentration is much higher than normal cells. Choline was implicated in the building of cell membrane structure and function of cancer cells and involved in a enzymatic mechanism that helps cancer cells to grow [13].

The feeding of egg-laying hens with growth and ovulation promoting hormones in commercial facilities is yet another potential culprit. It was found that commercial laying hens also spontaneously develop ovarian cancer at a high rate [14]. With hormones playing a major role in the progression of many cancers, including breast, prostate, ovarian, and colorectal cancer [15], the accumulation of dietary hormone intake has been suggested as a potential cancer promoting factor [16].

Is commercial egg laying hens the root cause of eggs’ cancer risk?

Nonetheless, none of these hypotheses have been thoroughly researched and validated. Hence, the knowledge of how egg consumption may cause cancer remains incomplete.

Conclusion

Current research has shown that egg consumption is linked to several types of cancer, including colon, breast, ovarian, prostate, and bladder. Even though the knowledge is still incomplete, the potential risk of over consumption of egg cannot be ignored. Hence, if egg cannot be avoided in your diet due to nutritional reason, it is wise to limit the number of egg consumption to only 2 or less per week. A switch to organic free-range chicken eggs may also be necessary to mitigate the risk.

 

References

[1]        Speech by Minister Lawrence Wong at AVA’s Food Industry Convention, Agri-Food Vet. Auth. Singapore. (2015). https://www.ava.gov.sg/docs/default-source/press-releases/min-wong-speech-at-ava-food-industry-convention.pdf (accessed November 27, 2017).

[2]        Z.S. Clayton, E. Fusco, M. Kern, Egg consumption and heart health: A review, Nutrition. 37 (2017) 79–85. doi:10.1016/j.nut.2016.12.014.

[3]        N. Becerra-Tomás, N. Babio, M.Á. Martínez-González, D. Corella, R. Estruch, E. Ros, M. Fitó, L. Serra-Majem, I. Salaverria, R.M. Lamuela-Raventós, J. Lapetra, E. Gómez-Gracia, M. Fiol, E. Toledo, J. V. Sorlí, M.R. Pedret-Llaberia, J. Salas-Salvadó, Replacing red meat and processed red meat for white meat, fish, legumes or eggs is associated with lower risk of incidence of metabolic syndrome, Clin. Nutr. 35 (2016) 1442–1449. doi:10.1016/j.clnu.2016.03.017.

[4]        J.M. Miranda, X. Anton, C. Redondo-Valbuena, P. Roca-Saavedra, J.A. Rodriguez, A. Lamas, C.M. Franco, A. Cepeda, Egg and egg-derived foods: effects on human health and use as functional foods., Nutrients. 7 (2015) 706–29. doi:10.3390/nu7010706.

[5]        J.D. Spence, D.J. Jenkins, J. Davignon, Dietary cholesterol and egg yolks: Not for patients at risk of vascular disease, Can. J. Cardiol. 26 (2010) e336–e339. doi:10.1016/S0828-282X(10)70456-6.

[6]        K.A. Steinmetz, J.D. Potter, Egg consumption and cancer of the colon and rectum., Eur. J. Cancer Prev. 3 (1994) 237–45. http://www.ncbi.nlm.nih.gov/pubmed/8061589 (accessed November 27, 2017).

[7]        J. Zhang, Z. Zhao, H.J. Berkel, Egg Consumption and Mortality From Colon and Rectal Cancers: An Ecological Study, Nutr. Cancer. 46 (2003) 158–165. doi:10.1207/S15327914NC4602_08.

[8]        R. Si, K. Qu, Z. Jiang, X. Yang, P. Gao, Egg consumption and breast cancer risk: a meta-analysis, Breast Cancer. 21 (2014) 251–261. doi:10.1007/s12282-014-0519-1.

[9]        N. Keum, D.H. Lee, N. Marchand, H. Oh, H. Liu, D. Aune, D.C. Greenwood, E.L. Giovannucci, Egg intake and cancers of the breast, ovary and prostate: a dose–response meta-analysis of prospective observational studies, Br. J. Nutr. 114 (2015) 1099–1107. doi:10.1017/S0007114515002135.

[10]      S.-T. Zeng, L. Guo, S.-K. Liu, D.-H. Wang, J. Xi, P. Huang, D.-T. Liu, J.-F. Gao, J. Feng, L. Zhang, Egg consumption is associated with increased risk of ovarian cancer: Evidence from a meta-analysis of observational studies., Clin. Nutr. 34 (2015) 635–41. doi:10.1016/j.clnu.2014.07.009.

[11]      D. Fang, F. Tan, C. Wang, X. Zhu, L. Xie, Egg intake and bladder cancer risk: A meta-analysis, Exp. Ther. Med. 4 (2012) 906–912. https://www.spandidos-publications.com/etm/4/5/906 (accessed November 27, 2017).

[12]      O.F. Kuzu, M.A. Noory, G.P. Robertson, The Role of Cholesterol in Cancer., Cancer Res. 76 (2016) 2063–70. doi:10.1158/0008-5472.CAN-15-2613.

[13]      E.L. Richman, S.A. Kenfield, M.J. Stampfer, E.L. Giovannucci, S.H. Zeisel, W.C. Willett, J.M. Chan, Choline intake and risk of lethal prostate cancer: incidence and survival., Am. J. Clin. Nutr. 96 (2012) 855–63. doi:10.3945/ajcn.112.039784.

[14]      P.A. Johnson, C.S. Stephens, J.R. Giles, The domestic chicken: Causes and consequences of an egg a day, Poult. Sci. 94 (2015) 816–820. doi:10.3382/ps/peu083.

[15]      E.J. Folkerd, M. Dowsett, Influence of sex hormones on cancer progression., J. Clin. Oncol. 28 (2010) 4038–44. doi:10.1200/JCO.2009.27.4290.

[16]      Y. Handa, H. Fujita, Y. Watanabe, S. Honma, M. Kaneuchi, H. Minakami, R. Kishi, Does dietary estrogen intake from meat relate to the incidence of hormone-dependent cancers?, J. Clin. Oncol. 28 (2010) 1553–1553. doi:10.1200/jco.2010.28.15_suppl.1553.

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4 thoughts on “Egg consumption and cancer risk

  • ko ko win

    on

    Western so call researchers are irrational. Some say can eat and prevent cancer. Now some say cannot eat due to high incident of cancer. Cholesterol rich foods are no problem only trans fat rich foods are dangerous. Don’t want to listen . We will eat whatever we want to eat . Show me a person who live longer by following your controversy advices.

    • healthylivingsg

      on

      Thank you for your comment.

      I will say you are not the only one that feel that there are too many conflicting information from scientific research. However, many do not aware that scientific research is always an on-going process. It is the spirit of inquiry in science that continue to allow humankind to always explore the unknown and challenge the known. In the process, discoveries are made, old views are repelled, and knowledge is gained. Without such process, we may still be in the dark ages. Nonetheless, too much information, especially at this age of social media can be confusing and frustrating. Everyone needs to critically evaluate and assess the validity of the information received, and decides for himself/herself to accept, reject or KIV. Everyone has a choice. Therefore, even today, there are those who choose to believe the earth is flat, and dismiss the picture of the spherical earth as a great conspiracy theory. A personal choice.

      Coming to the second part of your comment that cholesterol is harmless. You may be absolutely right. Keeping within context of this article, it was clearly mentioned that all the possible causes that link egg consumption to cancer are mere hypotheses. Although there are some suggestive observations, none of them has been studied and validated yet. So the knowledge in this area is fairly limited.

      As for the third part, citing just one or two persons to demonstrate the validity of certain claim is considered anecdotal. It is better to refer to a population-based study. A study published in 2014 on the effect of different diet on the cohort of 96,000 American Adventists found that the 8% of vegans who also omit eggs and dairy, besides being vegetarians, are better compared to other vegetarian in term of vegan diets protection for obesity, hypertension, type-2 diabetes, and cardiovascular mortality. Nonetheless, there is no mention of cancer benefits of vegans compared to vegetarians in this study (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4073139/). In another study, vegan diets were found to show statistically significant protection for overall cancer incidence (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3565018/). So there is evidence from these studies supporting the health benefits of a plant-based diet devoid of eggs and dairy.

      Thank you for your comment. It gives me further opportunity to clarify and explain further on this topic.

  • Gosh… I have 2 eggs a day for breakfast. Can I find out what’s the next best alternative source of protein that I can go for?

    • healthylivingsg

      on

      The best replacement will be a variety of legumes, e.g. soy beans, chickpeas, green peas, mung beans, etc. Baked beans on toast, blended green smoothie with peas, or mung beans porridge are some breakfast ideas.

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