No association between egg intake and prostate cancer risk: a meta-analysis

Eggs - a scoping review for Nordic Nutrition Recommendations 2023

Cardiovascular diseases (CVD), type 2 diabetes (T2D), and cancer are a significant public health burden in the Nordic and Baltic countries. High intake of eggs, mainly due to its high cholesterol content, has been suggested to have adverse health effects. The purpose of this scoping review is to describe the evidence related to the impact of egg intake on health. A literature search identified 38 systematic reviews and meta-analyses on egg consumption in relation to health outcomes published between 2011 and 30 April 2022. Overall, current evidence from systematic reviews of randomized clinical trials indicates that higher egg intake may increase serum total cholesterol concentration and the ratio of low-density lipoprotein to high-density lipoprotein cholesterol, but with substantial heterogeneity in the response. However, recent evidence from observational studies does not provide strong support for a detrimental role of moderate egg consumption (up to one egg/day) on the risk of CVD, especially in the European studies. The overall evidence from observational studies indicates that egg consumption is not associated with increased risk of mortality or T2D in European study populations. There is also little support for a role of egg consumption in cancer development, although a weak association with higher risk of certain cancers has been found in some studies, mainly case-control studies. Again, no associations with cancer risk have been observed in European studies. Systematic reviews and meta-analyses of egg consumption in relation to other health-related outcomes are scarce. There are also limited data available on the associations between the consumption of more than one egg/day and risk of diseases. Based on the available evidence, one egg/day is unlikely to adversely affect overall disease risk.

The Health Benefits of Egg Protein

Once the general public accepts that dietary cholesterol is not a concern for cardiovascular disease risk, foods that have been labeled as high-cholesterol sources, including eggs, may be appreciated for their various other dietary components. One of the nutrients in eggs that deserves further discussion is egg protein. Egg protein has been recognized to be highly digestible and an excellent source of essential amino acids, with the highest attainable protein digestibility-corrected amino acid score. Egg protein has been shown to decrease malnutrition in underdeveloped countries, possibly increase height in children, and protect against kwashiorkor. Egg protein has been demonstrated to be important to skeletal muscle health and protective against sarcopenia. Egg protein also can decrease appetite, resulting in a reduction in the caloric intake from the next meal and weight reduction. Other protective effects of egg protein addressed in this review include protection against infection as well as hypotensive and anti-cancer effects.

Effect of Plant- and Animal-Based Foods on Prostate Cancer Risk

CONTEXT

Many studies have explored whether plant and animal-based food consumption is associated with prostate cancer (PCa) risk, but there is much discordance.

OBJECTIVE

To perform an updated review of the literature that further investigates the association of plant- and animal-based food consumption with PCa risk.

METHODS

This review was conducted by using 3 databases and produced a total of 550 references. The search was limited to a publication date range of 2006 to February 2017, English language, and humans. After case reports, comments, letters, editorials, and duplicate references were removed, 297 citations remained for review. Articles that did not investigate the association of dietary patterns or a major component of diet with PCa were excluded.

RESULTS

Of the 297 references found, 47 were eligible for inclusion in this review. The authors identified 2 very large cohort studies (≥100,000 participants), 6 large cohort studies (≥40,000 participants), 11 medium cohort studies (≥10,000 participants), 10 small cohort studies (<10,000 participants), 13 case-control studies, 4 meta-analyses, and 1 population study investigating diet and PCa risk. Most studies showed that plant-based foods are associated with either decreased or unchanged risk of PCa, whereas animal-based foods, particularly dairy products, are associated with either increased or unchanged risk of PCa.

CONCLUSION

This review of the literature suggests that consumption of higher amounts of plant-based foods may be associated with decreased PCa risk, and consumption of higher amounts of dairy products may be associated with increased PCa risk.

Egg consumption and human health: an umbrella review of observational studies

Egg consumption has been an area of controversy regarding its impact on human health largely due to the content in cholesterol and its potential role in cardio-metabolic outcomes. This study aimed to summarise the level of evidence of egg consumption on various health outcomes. A systematic search for meta-analyses was performed: study design, dose-response relationship, heterogeneity and agreement of results over time, and identification of potential confounding factors were considered to assess the level of evidence. Results from this umbrella review showed a substantial no association between egg consumption and a number of health outcomes, including cancer, cardiovascular and metabolic disorders. In contrast, evidence of possible beneficial effects toward stroke risk has been found. In conclusions, egg may be part of a healthy diet; however, additional studies exploring confounding factors are needed to ascertain the potential detrimental effects.

Egg Consumption in Relation to Glioma: A Case-Control Study

BACKGROUND AND AIMS

Data on the link between egg consumption and brain tumors are limited. The objective of this study was to investigate the association between egg consumption and odds of glioma in Iranian adults.

METHODS

In this hospital-based case-control study, 128 newly-diagnosed cases of glioma and 256 age- and sex-matched controls were enrolled from hospitals. Patients with pathologically confirmed glioma (without any other cancers) were considered eligible. We collected data on dietary intakes, including egg consumption, using a 126-item validated FFQ. Egg consumption was computed from all foods containing this food as their ingredients. Participants were categorized into tertiles of egg consumption. Conditional logistic regression was used to examine the association between egg consumption and glioma.

RESULTS

After adjustment for age, sex and energy intake, individuals in the middle tertile of egg consumption were 58% (OR 0.42; 95% CI 0.24, 0.73) less likely to have glioma compared with those in the lowest tertile. Further adjustment for other potential confounders strengthened the association; such that participants with the greatest consumption of egg intake were 62% (0.38; 0.18, 0.76) less likely to have glioma compared with those with the lowest consumption. Additional controlling for dietary intakes did not change the association significantly (0.39; 0.18, 0.85).

CONCLUSION

We found an inverse association between egg consumption at the amount of almost 2 eggs/week and odds of glioma. Further studies are required to examine this association.

Association between Dietary Inflammatory Index and Prostate Cancer in Shiraz Province of Iran

Background: Dietary components like food items and nutrients have been implicated to play a role in modulating inflammation and the development of prostate cancer. Studies examining this association have not been extensively explored in Middle Eastern Countries. Material and Methods: We examined the association between the dietary inflammatory index (DIITM) and prostate cancer in the Shiraz province of Iran. A total of 60 incident cases and 60 controls attending the same hospital as the cases were recruited. The energy adjusted DII (E-DIITM) was computed based on dietary intake assessed using a validated food frequency questionnaire (FFQ). Logistic regression was used to estimate odds ratios. Results: Men with higher E-DII (>0.96) were at higher risk of prostate cancer (OR = 2.55; 95% CI =1.04–6.23) compared to men with E-DII ≤0.96. Conclusion: These data suggest a pro-inflammatory diet, as indicated by increasing DII score, may be a risk factor for prostate cancer in Iranian men.

Prostate cancer progression and mortality: a review of diet and lifestyle factors

PURPOSE

To review and summarize evidence on the role of diet and lifestyle factors and prostate cancer progression, with a specific focus on habits after diagnosis and the risk of subsequent disease recurrence, progression, or death.

METHODS

Given the well-documented heterogeneity of prostate cancer and the long survivorship of the majority of diagnoses, our goal was to summarize and describe modifiable risk factors for clinically relevant prostate cancer. We focused where possible on epidemiologic studies of post-diagnostic habits and prostate cancer progression, defined as recurrence (e.g., PSA risk, secondary treatment), metastasis, or death. Where data were limited, we also describe evidence on risk factors and indicators of prostate cancer aggressiveness at diagnosis.

RESULTS

A variety of dietary and lifestyle factors appear to affect prostate cancer progression. Several generally widely recommended lifestyle factors such as not smoking, maintaining a healthy body weight, and regular vigorous physical exercise also appear to affect prostate cancer progression. Several dietary factors, such as tomato sauce/lycopene, cruciferous vegetables, healthy sources of vegetable fats, and coffee, may also have a role in reducing risk of prostate cancer progression.

CONCLUSION

Diet and lifestyle factors, in particular exercise and smoking cessation, may reduce the risk of prostate cancer progression and death. These promising findings warrant further investigation, as their overall impact might be large.

Mediterranean Diet and cancer risk: an open issue

The traditional Mediterranean Diet of the early 1960s meets the characteristics of an anticancer diet defined by the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AIRC). A diet rich of whole grains, pulses, vegetables and fruits, limited in high-calorie foods (foods high in sugar or fat), red meat and foods high in salt, without sugary drinks and processed meat is recommended by the WCRF/AIRC experts to reduce the risk of cancer. The aim of this review was to examine whether Mediterranean Diet is protective or not against cancer risk. Three meta-analyses of cohort studies reported that a high adherence to the Mediterranean Diet significantly reduces the risk of cancer incidence and/or mortality. Nevertheless, the Mediterranean dietary pattern defined in the studies' part of the meta-analyses has qualitative and/or quantitative differences compared to the Mediterranean Diet of the early 1960s. Therefore, the protective role of the Mediterranean Diet against cancer has not definitely been established. In epidemiological studies, a universal definition of the Mediterranean Diet, possibly the traditional Mediterranean Diet of the early 1960s, could be useful to understand the role of this dietary pattern in cancer prevention.

Egg intake and cancers of the breast, ovary and prostate: a dose–response meta-analysis of prospective observational studies

Evidence suggests that egg intake may be implicated in the aetiology of sex hormone-related cancers. However, dose–response relationships between egg intake and such cancers are unclear. Thus, we conducted a dose–response meta-analysis to summarise the dose–response relationships between egg consumption and the risk of breast, prostate and gynaecological cancers. A literature search was performed using PubMed and Embase up to April 2015 to identify relevant prospective observational studies. Summary relative risk (RR) and 95 % CI were estimated using a random-effects model. For breast cancer, the linear dose–response meta-analysis found a non-significantly increased risk (RR for an increase of 5 eggs consumed/week: 1·05, 95 % CI 0·99, 1·11, n 16 023 cases). Evidence for non-linearity was not statistically significant (Pnon-linearity= 0·50, n 15 415 cases) but consuming ≥ 5 eggs/week was significantly associated with an increased risk of breast cancer compared with no egg consumption, with the summary RR being 1·04 (95 % CI 1·01, 1·07) for consuming 5 eggs/week and 1·09 (95 % CI 1·03, 1·15) for consuming about 9 eggs/week. For other cancers investigated, the summary RR for an increase of 5 eggs consumed/week was 1·09 (95 % CI 0·96, 1·24, n 2636 cases) for ovarian cancer; 1·47 (95 % CI 1·01, 2·14, n 609 cases) for fatal prostate cancer, with evidence of small-study effects (PEgger= 0·04). No evidence was found for an association with the risk of total prostate cancer. While our conclusion was tempered by the potential for publication bias and confounding, high egg intake may be associated with a modestly elevated risk of breast cancer, and a positive association between egg intake and ovarian and fatal prostate cancers cannot be ruled out.

Fruit and vegetable intake in relation to prostate cancer in Iranian men: a case-control study

BACKGROUND

Findings of epidemiologic studies on the relationship between fruit and vegetable consumption and prostate cancer (PCa) risk have been inconclusive. We therefore examined the association between intake of fruits and vegetables and PCa risk in Iran.

MATERIALS AND METHODS

In this hospital based, case-control study, a total of 50 patients with PCa and 100 controls underwent face-to-face interviews. Regression analysis was used to examine the relation between fruit and vegetable intake and PCa risk.

RESULTS

A protective independent effect was observed for the highest tertile of total fruit and vegetable (OR: 0.33, CI: 0.04-0.30, p value<0.001), total fruit (OR: 0.30, CI: 0.06-0.4, p value=0.03) and total vegetable (OR: 0.31, CI: 0.02-0.21, p value<0.001) consumption. Within the group of fruits, a significant inverse association was observed for apple and pomegranate (p trends were 0.01 and 0.016, respectively). In the vegetable group, a significant inverse association was observed for tomatoes (p trend<0.001) and cabbage (p trend=0.021).

CONCLUSIONS

The results of the present study suggested that fruits and vegetable intake might be negatively associated with PCa risk.

Egg consumption is associated with increased risk of ovarian cancer: Evidence from a meta-analysis of observational studies

BACKGROUND

The findings of epidemiologic studies on the association between egg consumption and ovarian cancer risk remain conflicting. The aim of this meta-analysis was to investigate whether an association exists between egg intake and ovarian cancer risk in epidemiologic studies.

METHODS

A literature search was carried out using PUBMED, EMBASE, and Cochrane Library Central database for all medical literature published in English-language journals up to August 2013. Before meta-analysis, between-study heterogeneity and publication bias were assessed using adequate statistical tests. Fixed-effect and random-effect models were used to estimate summary relative risks (RR) and the corresponding 95% confidence intervals (CIs). Subgroup analyses and sensitivity analysis were also performed.

RESULTS

A total of 12 eligible studies (six case-control studies and six cohort studies) were included, involving 629,453 subjects and 3728 ovarian cancer cases. We found that high egg intake (comparing the highest with the lowest category) was associated with a significant increased risk of ovarian cancer (RR = 1.21, 95% CI [1.06, 1.38]). When we examined whether the associations differed by study type, statistically significant effect of egg intake on ovarian cancer was observed among case-control studies (RR = 1.22, 95% CI [1.03, 1.43]), but not among cohort studies (RR = 1.20, 95% CI [0.97, 1.48]).

CONCLUSIONS

Our findings suggest that egg consumption may increase ovarian cancer risk. Additional studies, especially large prospective cohort studies, are warranted to confirm the findings.

Potential role of gastrointestinal microbiota composition in prostate cancer risk

Background

Among men in the U.S., prostate cancer is the most common cancer and the second leading cause of cancer death. Despite its prevalence, there are few established risk factors for prostate cancer. Some studies have found that intake of certain foods/nutrients may be associated with prostate cancer risk, but few have accounted for how intake and metabolic factors may interact to influence bioavailable nutrient levels and subsequent disease risk.

Presentation of the hypothesis

The composition of the gastrointestinal (GI) microbiome may influence metabolism of dietary compounds and nutrients (e.g., plant phenols, calcium, choline) that may be relevant to prostate cancer risk. We, therefore, propose the hypothesis that GI microbiota may have a markedly different composition among individuals with higher prostate cancer risk. These individuals could have microbial profiles that are conducive to intestinal inflammation and/or are less favorable for the metabolism and uptake of chemopreventive agents.

Testing the hypothesis

Because very little preliminary data exist on this potential association, a case–control study may provide valuable information on this topic. Such a study could evaluate whether the GI microbial profile is markedly different between three groups of individuals: healthy men, those with latent prostate cancer, and those with invasive prostate cancer. Any findings could then be validated in a larger study, designed to collect a series of specimens over time.

Implications of the hypothesis

Given the plethora of information emerging from the Human Microbiome Project, this is an opportune time to explore associations between the microbiome and complex human diseases. Identification of profiles that alter the host’s risk for disease may clarify inconsistencies in the literature on dietary factors and cancer risk, and could provide valuable targets for novel cancer prevention strategies.