Diet and prostatic cancer: a case-control study in northern Italy

Whole Grains, Refined Grains, and Cancer Risk: A Systematic Review of Meta-Analyses of Observational Studies

PubMed, Web of Science, and the Cochrane Database of Systematic Reviews were searched for meta-analyses that provided risk estimates (±95% confidence intervals) for associations between intakes of whole and refined grains and risk of total and site-specific cancer. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines were followed. Only meta-analyses that included whole grains and refined grains as separate food groups, and not as part of dietary patterns, were included. A total of 17 publications were identified that met inclusion criteria. Within these, results from a total of 54 distinct meta-analyses were reported for whole grains and 5 meta-analyses for refined grains. For total cancer mortality, 7 meta-analyses of cohort studies indicated that whole grain intake was associated with 6% to 12% lower risk in comparison of highest vs. lowest intake groups, and 3% to 20% lower risk for doses ranging from 15 to 90 g/day. For site-specific cancers, meta-analyses indicated that whole grain intake was consistently associated with lower risks of colorectal, colon, gastric, pancreatic, and esophageal cancers. Limited data were available for refined grains, with only 4 publications providing risk estimates, and only 1 of the meta-analyses included more than 3 studies. High intake of refined grains was associated with increased risk of colon and gastric cancer. By contrast, in the only dose-response meta-analysis, each 90 g/day consumption of refined grains was associated with a 6% lower risk of total cancer. In addition to the limited number of published meta-analyses on refined grains, results were also weakened due to the fact that refined grains were frequently defined to include both staple grain foods and indulgent grain foods, and the majority of studies included in the meta-analyses provided no specific definition of refined grains. Overall, meta-analyses of cohort and case-control studies consistently demonstrate that whole grain intake is associated with lower risk of total and site-specific cancer, and support current dietary recommendations to increase whole grain consumption. By contrast, the relationship between refined grain intake and cancer risk is inconclusive.

Terfezia boudieri: A Desert Truffle With Anticancer and Immunomodulatory Activities

Desert truffles have high nutritional value and grow wild in the Mediterranean basin and Western Asia. Although, many studies were performed to evaluate truffles nutritious values and phytochemical composition, studies are limited to evaluate their anticancer and/ or immunomodulatory effects. Our study was conducted to evaluate the anticancer and immunomodulatory effects of Terfezia boudieri (desert truffle). Different solvent extracts were prepared from the truffle and MTT assay was used to measure their anticancer activity against cancer cell lines (T47D, MCF-7, MDA-MB231, HCT-116, and Hela). Total phenolic content in each extract was determined by using Folin-Ciocalteu reagent and qualitative phytochemical screening was performed using standard methods. The degree of apoptosis induction (using caspase 3 assay) and vascular endothelial growth factor expression were detected using standard kits. Also, ELISA was used to measure levels of IFN-γ, IL-2, IL-4, and IL-10 secreted by splenocytes after treatment with the extracts. The effect of the extracts on splenocytes proliferation was measured using MTT assay. Macrophage function was evaluated using nitro blue tetrazolium assay and pinocytosis function was evaluated using neutral red method. Terpenoids, phytosterols, and carbohydrates were present in all the solvent extracts, while tannins, alkaloids and flavonoids were detected only in aqueous/methanol and aqueous extracts. The highest total phenolic content was observed in aqueous and aqueous methanol extracts. The growth of cancer cell lines was inhibited by T. boudieri extracts in a dose dependent manner. N-hexane extract was the most potent against most cell lines. Aqueous/methanol extract showed high apoptosis induction and angiogenesis suppression effects. An increase in TH1 cytokines (IFN-γ, IL-2) level and a decrease in TH2 cytokine (IL-4) level were evident after lymphocytes stimulation by aqueous/methanol, n-hexane and ethyl acetate extracts of T. boudieri. Ethyl acetate extract of T. boudieri were the most potent extracts to stimulate lymphocytes proliferation while all other extracts showed moderate stimulation. Aqueous/methanol extract was the most active extract to stimulate phagocytosis. Ethyl acetate extract was the most active extract to stimulate pinocytosis. The use of T. boudieri provides variable health benefits. N-hexane, ethyl acetate, and aqueous/methanol extracts exhibited anticancer activities and are potent stimulators of innate and acquired immunity. Further testing is needed to identify the biologically active compounds and detect them quantitatively using GC-MS analysis.

Tobacco, Alcohol, Diet and Risk of prostate Cancer

A hospital-based case-control study of the association between tobacco smoking, alcohol drinking and several relevant dietary items and prostate cancer was carried out in the National Cancer Institute of Uruguay between January 1988 and December 1994. The sample included 156 patients with histologically proven prostatic cancer and 302 controls with a variety of neoplastic and non-neoplastic diseases. The results showed increased risks of prostate cancer associated with beer drinking, meat, milk and fruit consumption, after adjusting for major confounders. The possible role of N-nitroso compounds from beer in prostatic carcinogenesis is discussed.

Fish-Derived Omega-3 Fatty Acids and Prostate Cancer: A Systematic Review

BACKGROUND

The use of natural health products in prostate cancer (PrCa) is high despite a lack of evidence with respect to safety and efficacy. Fish-derived omega-3 fatty acids possess anti-inflammatory effects and preclinical data suggest a protective effect on PrCa incidence and progression; however, human studies have yielded conflicting results.

METHODS

A search of OVID MEDLINE, Pre-MEDLINE, Embase, and the Allied and Complementary Medicine Database (AMED) was completed for human interventional or observational data assessing the safety and efficacy of fish-derived omega-3 fatty acids in the incidence and progression of PrCa.

RESULTS

Of 1776 citations screened, 54 publications reporting on 44 studies were included for review and analysis: 4 reports of 3 randomized controlled trials, 1 nonrandomized clinical trial, 20 reports of 14 cohort studies, 26 reports of 23 case-control studies, and 3 case-cohort studies. The interventional studies using fish oil supplements in patients with PrCa showed no impact on prostate-specific antigen levels; however, 2 studies showed a decrease in inflammatory or other cancer markers. A small number of mild adverse events were reported and interactions with other interventions were not assessed. Cohort and case-control studies assessing the relationship between dietary fish intake and the risk of PrCa were equivocal. Cohort studies assessing the risk of PrCa mortality suggested an association between higher intake of fish and decreased risk of prostate cancer-related death.

CONCLUSIONS

Current evidence is insufficient to suggest a relationship between fish-derived omega-3 fatty acid and risk of PrCa. An association between higher omega-3 intake and decreased PrCa mortality may be present but more research is needed. More intervention trials or observational studies with precisely measured exposure are needed to assess the impact of fish oil supplements and dietary fish-derived omega-3 fatty acid intake on safety, PrCa incidence, treatment, and progression.

Association between dietary inflammatory index and prostate cancer among Italian men

Previous studies have shown that various dietary components may be implicated in the aetiology of prostate cancer, although the results remain equivocal. The possible relationship of inflammation derived from dietary exposures with prostate cancer risk has not been investigated. We examined the ability of a newly developed dietary inflammatory index (DII) to predict prostate cancer risk in a case-control study conducted in Italy between 1991 and 2002. A total of 1294 patients aged < 75 years with incident, histologically confirmed carcinoma of the prostate served as cases. A total of 1451 subjects aged < 75 years who were admitted to the same hospitals as cases for a wide spectrum of acute, non-neoplastic conditions served as controls. The DII was computed based on dietary intake assessed using a previously validated seventy-eight-item FFQ. Logistic regression models were used to estimate multivariable OR adjusted for age, study centre, years of education, social class, BMI, smoking status, family history of prostate cancer and total energy intake. Men with higher DII scores had a higher risk of prostate cancer when analysed using the DII as both continuous (OR 1.06, 95% CI 1.00, 1.13) and categorical, i.e., compared with men in the lowest quartile of the DII, men in the third and fourth quartiles were at elevated risk (OR(Quartile 3 v. 1) 1.32, 95% CI 1.03, 1.69 and OR(Quartile 4 v. 1) 1.33, 95% CI 1.01, 1.76; P trend= 0.04). These data suggest that a pro-inflammatory diet, as indicated by the increasing DII score, is a risk factor of prostate cancer in Italian men.

Dietary carrot consumption and the risk of prostate cancer

PURPOSE

Previous studies regarding the association between carrot intake and prostate cancer risk have reported inconsistent results. We conducted a meta-analysis to summarize evidence on this association and to quantify the potential dose-response relationship.

METHOD

A systematic literature search of papers published in August 2013 was conducted using PubMed, EMBASE, Scopus, Web of Science, the Cochrane register, and the Chinese National Knowledge Infrastructure databases, and the references of the retrieved articles were screened. The summary risk estimates with 95% confidence intervals (CIs) for the highest versus the lowest intake of carrots were calculated. A dose-response meta-analysis was also conducted for the studies reporting categorical risk estimates for a series of exposure levels.

RESULTS

We found a significantly decreased risk of prostate cancer associated with the intake of carrots (odds ratio 0.82, 95% CI 0.70-0.97). In addition, the dose-response meta-analysis indicated that for each serving per week, or 10 g per day increment of carrot intake, the risk estimate of prostate cancer was 0.95 (0.90-0.99) or 0.96 (0.94-0.99). There was no evidence of significant publication bias based on Begg's funnel plot (P = 1.000) or Egger's test (P = 0.804).

CONCLUSION

Carrot intake might be inversely associated with prostate cancer risk. Because of the limited number of cohort studies and substantial heterogeneity observed between studies in this meta-analysis, further well-designed prospective studies are warranted to confirm the findings from our study.

Coffee and risk of prostate cancer incidence and mortality in the Cancer of the Prostate in Sweden Study

PURPOSE

Coffee intake has recently been associated with significantly lower risk of lethal and advanced prostate cancer in a US population.

METHODS

We studied the association between coffee and prostate cancer risk in the population-based case-control study Cancer of the Prostate in Sweden. Dietary data were available for 1,499 cases and 1,112 controls. We calculated odds ratios (ORs) for the risk of prostate cancer in high versus low categories of coffee intake using logistic regression. We studied overall prostate cancer risk as well as risk of fatal, advanced, localized, high-grade, grade 7, and low-grade disease.

RESULTS

Mean coffee intake was 3.1 cups per day among both cases and controls. Coffee intake was not associated with overall prostate cancer risk. Risk of fatal prostate cancer was inversely, but not statistically significantly, associated with coffee intake, with an odds ratio of 0.64 [95 % confidence interval (CI) 0.34-1.19, p value for linear trend = 0.81] for men consuming greater than 5 cups per day compared to men drinking less than 1 cup per day. The highest intake of coffee was associated non-significantly with lower risk of advanced disease (OR = 0.73, 95 % CI 0.41-1.30, p trend = 0.98) and associated significantly with lower risk of high-grade cancer (Gleason 8-10; OR = 0.50, 95 % CI 0.26-0.98, p trend = 0.13). Risk of localized, grade 7, and low-grade cancers was not associated with coffee intake.

CONCLUSIONS

This study provides some support of an inverse association between coffee and lethal and high-grade prostate cancer.

Food groups and risk of prostate cancer: a case-control study in Uruguay

OBJECTIVE

The role of foods and beverages has been studied in detail in order to establish probable risk factors for prostate cancer.

METHODS

Data were derived from 326 cases with incident and microscopically confirmed adenocarcinomas of the prostate and 652 controls. Odds ratios and 95 % confidence intervals of prostate cancer were estimated by unconditional multiple logistic regression.

RESULTS

We identified the following food items as risk factors: lamb meat, salted meat, whole milk, total eggs, and maté consumption. The highest OR was associated with total eggs (OR, 2.43; 95 % CI, 1.70-3.48), followed by salted meat (OR, 2.65; 95 % CI, 1.36-3.76), maté consumption (OR, 1.96; 95 % CI, 1.17-3.31), and whole milk (OR, 2.01; 95 % CI, 1.26-2.51).

CONCLUSIONS

The final model, fitted by stepwise forward method, included total eggs, salted meat, whole milk, and maté consumption, whereas fruits were protective.

Milk and dairy consumption among men with prostate cancer and risk of metastases and prostate cancer death

BACKGROUND

Whether milk and dairy intake after a prostate cancer diagnosis is associated with a poorer prognosis is unknown. We investigated postdiagnostic milk and dairy intake in relation to risk of lethal prostate cancer (metastases and prostate cancer death) among participants in the Health Professionals Follow-Up Study.

METHODS

The cohort consisted of 3,918 men diagnosed with apparently localized prostate cancer between 1986 and 2006, and followed to 2008. Data on milk and dairy intake were available from repeated questionnaires. We used Cox proportional hazards models to calculate HRs and 95% CIs of the association between postdiagnostic milk and dairy intake and prostate cancer outcomes.

RESULTS

We ascertained 229 prostate cancer deaths and an additional 69 metastases during follow-up. In multivariate analysis, total milk and dairy intakes after diagnosis were not associated with a greater risk of lethal prostate cancer. Men with the highest versus lowest intake of whole milk were at an increased risk of progression (HR = 2.15, 95% CI: 1.28-3.60; P(trend) < 0.01). Men in the highest versus lowest quintile of low-fat dairy intake were at a decreased risk of progression (HR = 0.62; 95% CI: 0.40-0.95; P(trend) = 0.07).

CONCLUSIONS

With the exception of whole milk, our results suggest that milk and dairy intake after a prostate cancer diagnosis is not associated with an increased risk of lethal prostate cancer.

IMPACT

This is the first larger prospective study investigating the relation between postdiagnostic milk and dairy intake and risk of lethal prostate cancer.

Update on the relationship of fish intake with prostate, breast, and colorectal cancers

A systematic review of prospective cohort and case-control studies investigating relationships between the intake of fish and incidence of prostate, breast, or colorectal cancers was conducted. A total of 106 studies fulfilled the requirements stated in the "Search strategy and selection criteria." Among 273 estimates of association reported by these studies, 53 indicated decreased risk while 12 indicated increased risk associated with fish intake. The hypothesis linking fish consumption and low cancer incidence appears to be supported by little epidemiological data. However, there are several factors that may mask potential protective associations with fish intake. The type and the amount of fish eaten, the cooking method, the stage of the cancer and, amongst women, menopausal status may all be important factors that relate to whether fish is protective or not. Future epidemiologic studies with a clearer assessment of these factors are needed to know more about the effects of fish consumption on cancer risk. Therefore, until there are better measures of dietary exposure or biomarkers to correlate self-report, no conclusion can be drawn regarding the recommendation for increasing fish consumption in general to reduce the risk of developing the most common cancers in Western societies.

Impact of consumption of vegetable, fruit, grain, and high glycemic index foods on aggressive prostate cancer risk

Prostate cancer is a common but complex disease, and distinguishing modifiable risk factors such as diet for more aggressive disease is extremely important. Previous work has detected intriguing associations between vegetable, fruit, and grains and more aggressive prostate cancer, although these remain somewhat unclear. Here we further investigate such potential relationships with a case-control study of 982 men (470 more aggressive prostate cancer cases and 512 control subjects). Comparing the highest to lowest quartiles of intake, we found that increasing intakes of leafy vegetables were inversely associated with risk of aggressive prostate cancer [adjusted odds ratio (OR) = 0.66, 95% CI: 0.46, 0.96; P trend = 0.02], as was higher consumption of high carotenoid vegetables (OR = 0.71, 95% CI: 0.48, 1.04; P trend = 0.04). Conversely, increased consumption of high glycemic index foods were positively associated with risk of aggressive disease (OR = 1.64, 95% CI: 1.05, 2.57; P trend = 0.02). These results were driven by a number of specific foods within the food groups. Our findings support the hypothesis that diets high in vegetables and low in high glycemic index foods decrease risk of aggressive prostate cancer.

Coffee consumption and prostate cancer risk and progression in the Health Professionals Follow-up Study

BACKGROUND

Coffee contains many biologically active compounds, including caffeine and phenolic acids, that have potent antioxidant activity and can affect glucose metabolism and sex hormone levels. Because of these biological activities, coffee may be associated with a reduced risk of prostate cancer.

METHODS

We conducted a prospective analysis of 47,911 men in the Health Professionals Follow-up Study who reported intake of regular and decaffeinated coffee in 1986 and every 4 years thereafter. From 1986 to 2006, 5035 patients with prostate cancer were identified, including 642 patients with lethal prostate cancers, defined as fatal or metastatic. We used Cox proportional hazards models to assess the association between coffee and prostate cancer, adjusting for potential confounding by smoking, obesity, and other variables. All P values were from two-sided tests.

RESULTS

The average intake of coffee in 1986 was 1.9 cups per day. Men who consumed six or more cups per day had a lower adjusted relative risk for overall prostate cancer compared with nondrinkers (RR = 0.82, 95% confidence interval [CI] = 0.68 to 0.98, P(trend) = .10). The association was stronger for lethal prostate cancer (consumers of more than six cups of coffee per day: RR = 0.40, 95% CI = 0.22 to 0.75, P(trend) = .03). Coffee consumption was not associated with the risk of nonadvanced or low-grade cancers and was only weakly inversely associated with high-grade cancer. The inverse association with lethal cancer was similar for regular and decaffeinated coffee (each one cup per day increment: RR = 0.94, 95% CI = 0.88 to 1.01, P = .08 for regular coffee and RR = 0.91, 95% CI = 0.83 to 1.00, P = .05 for decaffeinated coffee). The age-adjusted incidence rates for men who had the highest (≥6 cups per day) and lowest (no coffee) coffee consumption were 425 and 519 total prostate cancers, respectively, per 100 000 person-years and 34 and 79 lethal prostate cancers, respectively, per 100 000 person-years.

CONCLUSIONS

We observed a strong inverse association between coffee consumption and risk of lethal prostate cancer. The association appears to be related to non-caffeine components of coffee.

Serum retinol and risk of prostate cancer

Greater exposure to retinol (vitamin A) may prevent prostate cancer, although under some conditions it could promote cell growth and de-differentiation. The authors prospectively examined prostate cancer risk and serum retinol levels, measured by using high-performance liquid chromatography, at baseline (n = 29,104) and after 3 years (n = 22,843) in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study cohort. Cox proportional hazards models were used to estimate the relative risk of total (n = 2,041) and aggressive (n = 461) prostate cancer by quintiles of baseline and 3-year serum retinol concentrations and by change in serum retinol levels from baseline to 3 years. Men with higher retinol concentrations at baseline were more likely to develop prostate cancer (quintile 5 vs. quintile 1 hazard ratio = 1.19, 95% confidence interval: 1.03, 1.36; P(trend) = 0.009). The results were similar for aggressive disease. Joint categorization based on baseline and 3-year retinol levels showed that men who were in the highest quintile at both time points had the greatest increased risk (baseline/3-year quintile 5/quintile 5 vs. quintile 1/quintile 1 hazard ratio = 1.31, 95% confidence interval: 1.08, 1.59). In this largest study to date of vitamin A status and subsequent risk of prostate cancer, higher serum retinol was associated with elevated risk, with sustained high exposure conferring the greatest risk. Future studies may clarify the underlying biologic mechanisms of the retinol-prostate cancer association.

Fish consumption and prostate cancer risk: a review and meta-analysis

BACKGROUND

Prostate cancer incidence varies 60-fold globally, which suggests the roles of lifestyle and dietary factors in its cause. To our knowledge, a comprehensive assessment of the association between fish consumption and prostate cancer incidence and mortality has not been reported.

OBJECTIVE

We conducted a meta-analysis of fish intake and prostate cancer by focusing on the incidence of prostate cancer and prostate cancer-specific mortality and included subgroup analyses based on race, fish type, method of fish preparation, and high-grade and high-stage cancer.

DESIGN

We searched MEDLINE and EMBASE databases (May 2009) for case-control and cohort studies that assessed fish intake and prostate cancer risk. Two authors independently assessed eligibility and extracted data.

RESULTS

There was no association between fish consumption and a significant reduction in prostate cancer incidence [12 case-control studies (n = 5777 cases and 9805 control subjects), odds ratio (OR): 0.85; 95% CI: 0.72, 1.00; and 12 cohort studies (n = 445,820), relative risk (RR): 1.01; 95% CI: 0.90, 1.14]. It was not possible to perform a meta-analysis for high-grade disease (one case-control study, OR: 1.44; 95% CI: 0.58, 3.03), locally advanced disease (one cohort study, RR: 0.80; 95% CI: 0.61, 1.13), or metastatic disease (one cohort study, RR: 0.56; 95% CI: 0.37, 0.86). There was an association between fish consumption and a significant 63% reduction in prostate cancer-specific mortality [4 cohort studies (n = 49,661), RR: 0.37; 95% CI: 0.18, 0.74].

CONCLUSION

Our analyses provide no strong evidence of a protective association of fish consumption with prostate cancer incidence but showed a significant 63% reduction in prostate cancer-specific mortality.

Diet and prostate cancer risk with specific focus on dairy products and dietary calcium: a case-control study

BACKGROUND

Despite the prevalence of prostate cancer worldwide, only a few risk factors have been well-established. The role of diet, especially of dairy products, in the etiology of prostate cancer is still controversial.

METHODS

This study assessed the association of dietary components, particularly dairy products and dietary calcium, on prostate cancer risk in a case-control study of 197 cases and an equal number of individually matched controls recruited in Montreal, Canada. A semi-quantitative food frequency questionnaire was administered in which the usual consumption frequency and amounts consumed of more than 200 food items were recorded.

RESULTS

We found a twofold increased risk of prostate cancer associated with an increased intake of dairy products {Odds Ratio (OR) = 2.19; 95% Confidence Intervals (CI) 1.22-3.94}. A significant trend of decreasing prostate cancer risk with higher intake was found for legumes, nuts, finfish/shellfish and for alpha-tocopherol after adjustment for calcium intake. Milk was the only dairy product significantly associated with prostate cancer risk, with OR = 2.27; 95% CI (1.25-4.09) for the highest versus lowest quartiles of consumption. Calcium, the main micronutrient contained in dairy products, showed only a borderline association with prostate cancer risk (P = 0.09), with slightly higher risk for higher calcium intake. In conclusion, this study supports the hypothesis that dairy products, especially milk, are involved in the etiology of prostate cancer. However, the mechanisms by which the various nutrients in dairy products and total diet may interact to influence this risk remain unknown.

Dairy products, dietary calcium and vitamin D intake as risk factors for prostate cancer: a meta-analysis of 26,769 cases from 45 observational studies

In this study, we examined the available evidence and sources of heterogeneity for studies of dairy products, calcium, and vitamin D intake and the risk of prostate cancer. We pooled data from 45 observational studies using a general variance-based, meta-analytic method employing CIs. Summary relative risks (RRs) were calculated for specific dairy products such as milk and dairy micronutrients. Sensitivity analyses were performed to test the robustness of these summary measures of effect. Cohort studies showed no evidence of an association between dairy [RR = 1.06; 95% confidence interval (CI) = 0.92-1.22] or milk intake (RR = 1.06; 95% CI = 0.91-1.23) and risk of prostate cancer. This was supported by pooled results of case-control analyses (RR = 1.14; 95% CI = 1.00-1.29), although studies using milk as the exposure of interest were heterogeneous and could not be combined. Calcium data from cohort studies were heterogeneous. Case-control analyses using calcium as the exposure of interest demonstrated no association with increased risk of prostate cancer (RR = 1.04; 95% CI = 0.90-1.15). Dietary intake of vitamin D also was not related to prostate cancer risk (RR = 1.16; 95% CI = 0.98-1.38). The data from observational studies do not support an association between dairy product use and an increased risk of prostate cancer.

Mass screening-based case-control study of diet and prostate cancer in Changchun, China

AIM

To investigate possible correlation factors for prostate cancer by a population-based case-control study in China.

METHODS

We carried out a mass screening of prostate cancer in Changchun, China, using a prostate-specific antigen assisted by Japan International Cooperation Agency. From June 1998 to December 2000, 3 940 men over 50 years old were screened. Of these, 29 men were diagnosed with prostate cancer. We selected 28 cases and matched them with controls of low prostate-specific antigen value (< 4.1 ng/mL) by 1:10 according to age and place of employment. A case-control study of diet and prostate cancer was then carried out.

RESULTS

After adjustment for education, body mass index (BMI), smoking, alcohol consumption, marriage and diet, intake of soybean product was discovered to be inversely related to prostate cancer. Men who consumed soybean product more than twice per week on different days had a multivariate odds ratio (OR) of 0.38 (95% confidence interval [CI], 0.13-1.12). In addition, men who consumed soybean products more than once per day had a multivariate OR of 0.29 (95% CI, 0.11-0.79) compared with men who consumed soybean products less than once per week. The P for trend was 0.02, which showed significant difference. There was no significant difference in P trend for any dairy food. Even when we matched the cases and controls by other criteria, we found that soybean food was the only preventive factor associated with prostate cancer.

CONCLUSION

Our study suggests that consumption of soybeans, one of the most popular foods in Asia, would decrease the risk of prostate cancer.

Correlations of dietary patterns with prostate health

Both genetic and environmental influences may be involved in etiology of prostate health and prostate cancer. These include ethnic origin, family history, smoking, and diet. Adiposity and excess energy intake are potentially distinct risk factors and positive associations with prostate cancer risk for both were observed among case-control and cohort studies. Some epidemiological studies support an association between dietary fat, particularly saturated or animal fats, and prostate cancer risk. Of these, several suggest reduced risk with low-fat diets high in n-3 fatty acids and increased risk with high-fat diets rich in n-6 fatty acids. Others suggested association with higher meat intake, possibly due to heterocyclic amines and polycyclic aromatic hydrocarbons, produced during grilling or frying. Positive association of prostate cancer risk with dairy intake could involve alpha-methylacyl-CoA racemase activity (required for beta-oxidation of phytanic acid present in dairy products and red meat) or the suppression of vitamin D activity by calcium. Inverse associations were observed with dietary intake of plant foods. These include cereals, soy products, and fruit and vegetable sources of carotenoids. Numerous plant constituents may act synergistically in the prevention and inhibition of prostate disorders. These diet-risk associations may lead to future individualized diet recommendations based upon genetic polymorphisms.

Family history of urogenital cancers in patients with bladder, renal cell and prostate cancers

Family history of urogenital cancers has been associated with an increased risk of cancer at the same sites. To evaluate the risks of bladder, prostate and renal cell neoplasms for family history of urogenital cancers in first-degree relatives, we analysed data from a case-control study conducted in northern Italy between 1985 and 1992 and including a total of 1,356 incident, histologically confirmed cancer cases: 727 bladder, 348 renal cell and 281 prostate cancer cases. Controls were 1,067 patients admitted to the same network of hospitals for acute, nonneoplastic conditions. Unconditional logistic regression was used to estimate odds ratios (ORs) of urogenital cancers, adjusting for age, sex, study centre, education, body mass index, smoking habit, alcohol consumption and number of brothers and, where appropriate, sisters. ORs of urogenital cancers for subjects with at least 1 first-degree relative with cancer at the same site were 6.1 [95% confidence interval (CI), 2.3-16.6] for bladder, 2.0 (95% CI: 0.6-6.2) for renal cell and 2.0 (95% CI: 0.9-4.1) for prostate cancer.

Serum lycopene, other carotenoids, and prostate cancer risk: a nested case-control study in the prostate, lung, colorectal, and ovarian cancer screening trial

BACKGROUND

Reports from several studies have suggested that carotenoids, and in particular lycopene, could be prostate cancer-preventive agents. This has stimulated extensive laboratory and clinical research, as well as much commercial and public enthusiasm. However, the epidemiologic evidence remains inconclusive.

MATERIALS AND METHODS

We investigated the association between prediagnostic serum carotenoids (lycopene, alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein, and zeaxanthin) and risk of prostate cancer in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, a multicenter study designed to examine methods of early detection and risk factors for cancer. The study included 692 incident prostate cancer cases, diagnosed 1 to 8 years after study entry, including 270 aggressive cases, with regional or distant stage (n = 90) or Gleason score >or=7 (n = 235), and 844 randomly selected, matched controls. As study participants were selected from those who were assigned to annual standardized screening for prostate cancer, results are unlikely to be biased by differential screening, a circumstance that is difficult to attain under non-trial conditions.

RESULTS

No association was observed between serum lycopene and total prostate cancer [odds ratios (OR), 1.14; 95% confidence intervals (95% CI), 0.82-1.58 for highest versus lowest quintile; P for trend, 0.28] or aggressive prostate cancer (OR, 0.99; 95% CI, 0.62-1.57 for highest versus lowest quintile; P for trend, 0.433). beta-Carotene was associated with an increased risk of aggressive prostate cancer (OR, 1.67; 95% CI, 1.03-2.72 for highest versus lowest quintile; P for trend, 0.13); in particular, regional or distant stage disease (OR, 3.16; 95% CI, 1.37-7.31 for highest versus lowest quintile; P for trend, 0.02); other carotenoids were not associated with risk.

CONCLUSION

In this large prospective study, high serum beta-carotene concentrations were associated with increased risk for aggressive, clinically relevant prostate cancer. Lycopene and other carotenoids were unrelated to prostate cancer. Consistent with other recent publications, these results suggest that lycopene or tomato-based regimens will not be effective for prostate cancer prevention.

A prospective study of dietary calcium, dairy products and prostate cancer risk (Finland)

High dietary intakes of calcium and dairy products have been hypothesized to enhance prostate cancer risk, but available prospective data regarding these associations are inconsistent. We examined dietary intakes of calcium and dairy products in relation to risk of prostate cancer in the Alpha-Tocopherol, Beta-Carotene (ATBC) Cancer Prevention Study, a cohort of 29,133 male smokers aged 50-69 years at study entry. Dietary intake was assessed at baseline using a validated 276-item food use questionnaire. Cox proportional hazards regression was used to adjust for known or suspected risk factors for prostate cancer. During 17 years of follow-up, we ascertained 1,267 incident cases of prostate cancer. High versus low intake of dietary calcium was associated with a marked increase in prostate cancer risk. The multivariate relative risk (RR) of prostate cancer for > or =2,000 mg/day compared to <1,000 mg/day of calcium intake was 1.63 (95% confidence interval (CI), 1.27-2.10; p trend < 0.0001). Total dairy intake was also positively associated with risk of prostate cancer. The multivariate RR of prostate cancer comparing extreme quintiles of intake was 1.26 (95% CI, 1.04-1.51; p trend = 0.03). However, no association with total dairy intake remained after we adjusted for calcium (p trend = 0.17). Findings were similar by stage and grade of prostate cancer. The results from this large prospective study suggest that intake of calcium or some related component contained in dairy foods is associated with increased prostate cancer risk.

Consumption of different types of meat and the risk of renal cancer: meta-analysis of case-control studies

BACKGROUND

Kidney cancers account for almost 2% of all cancers worldwide, with 150,000 new cases and 78,000 deaths from the disease occurring annually. An increase in the incidence of kidney neoplasm in western countries was noticed in the past few years. Between 1988 and 1992, the incidence of renal cancer per 100,000 person-year among males in USA, Norway, and France was 34.1, 9.00, and 16.10, respectively. Among females in the same countries, it was 5.70, 5.00, and 7.30, respectively. Although several individual case-control studies examined the association of meat intake and renal cancer risk, the results were inconsistent because of the insufficient statistical power of the individual studies. Therefore, the following meta-analysis was designed to help in clarifying the association.

METHODS

Electronic search of MEDLINE, OVID, and PUBMED databases which have articles published between (1966 and 2006) was conducted to select studies for this meta-analysis.

STATISTICAL ANALYSIS

Fixed and random-effects meta-analytical techniques were used to estimate the overall association between meat consumption and kidney cancer.

RESULTS

Thirteen case-control studies were found. This meta-analysis supported a positive relationship between meat consumption and risk of renal cancer. Summary results indicated that there was from 20% to 22% higher risk of renal cancer among those in the highest relative to the lowest category of poultry and processed meat consumption. Consumption of all meat and red meat was associated with 27% and 30% higher risk, respectively. The increased risks were statistically significant.

CONCLUSIONS

Increased consumption of all meat, red meat, poultry, and processed meat is associated with an increase risk of kidney cancer. Reduction of meat consumption is an important approach to decreasing the incidence of kidney cancer in the general population.

Highly elevated PSA and dietary PhIP intake in a prospective clinic-based study among African Americans

African-American men die from prostate cancer (PC) nearly twice as often as white US men and consume about twice as much of the predominant US dietary heterocyclic amine, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a genotoxic rat-prostate carcinogen found primarily in well-cooked chicken and beef. To investigate the hypothesis that PhIP exposure increases PC risk, an ongoing prospective clinic-based study compared PC screening outcomes with survey-based estimates of dietary PhIP intake among 40-70-year-old African-American men with no prior PC in Oakland, CA. They completed food-frequency and meat-cooking/consumption questionnaires and had a prostate-specific antigen (PSA) test and digital-rectal exam. Results for 392 men indicated a 17 (+/-17) ng/kg day mean (+/-1 s.d.) daily intake of PhIP, about twice that of white US men of similar age. PhIP intake was attributable mostly to chicken (61%) and positively associated (R(2)=0.32, P<0.0001) with saturated fat intake. An odds ratio (95% confidence interval) of 31 (3.1-690) for highly elevated PSA > or =20 ng/ml was observed in the highest 15% vs lowest 50% of estimated daily PhIP intake (> or =30 vs < or =10 ng/kg day) among men 50+ years old (P=0.0002 for trend) and remained significant after adjustment for self-reported family history of (brother or father) PC, saturated fat intake and total energy intake. PSA measures were higher in African-American men with positive family history (P=0.007 all men, P<0.0001 highest PSA quartile). These preliminary results are consistent with a positive association between PhIP intake and highly elevated PSA, supporting the hypothesis that dietary intervention may help reduce PC risk.

Fruit and vegetables in cancer prevention

Our aim was to review the epidemiological literature on possible cancer-preventive effects of the consumption of fruits and vegetables in humans, to quantify the effect of high versus low consumption of fruits and vegetables, and to give an overall assessment of the existing evidence. We based our work on an expert meeting conducted by the International Agency for Research on Cancer in 2003. A qualitative reading and evaluation of relevant articles on the cancer-preventive effect of the consumption of fruits and vegetables was made followed by the calculation of the mean relative risk and range for cohort and case-control studies separately. The possible population-preventable fraction for modifying diet in relation to fruit and vegetable consumption was calculated as well as an overall statement about the degree of evidence for the cancer-preventive effect of fruit and vegetable consumption for each cancer site. There is limited evidence for a cancer-preventive effect of the consumption of fruits and vegetables for cancer of the mouth and pharynx, esophagus, stomach, colon-rectum, larynx, lung, ovary (vegetables only), bladder (fruit only), and kidney. There is inadequate evidence for a cancer-preventive effect of the consumption of fruits and vegetables for all other sites. Applying this range of risk difference to the range of prevalence of low intake, the preventable fraction for low fruit and vegetable intake would fall into the range of 5-12%. It is important to recognize that this is only a crude range of estimates and that the proportion of cancers that might be preventable by increasing fruit and vegetable intake may vary beyond this range for specific cancer sites and across different regions of the world.

International comparisons of prostate cancer mortality rates with dietary practices and sunlight levels

Prostate cancer mortality rates vary widely across the world. The purpose of this study is to identify environmental factors associated with prostate cancer mortality risk. Prostate cancer mortality rates in 71 countries were compared to per capita food intake rates using age-adjusted cancer rates (year 2000) from the International Agency for Research on Cancer, and food consumption data (1990-1992) provided by the Food and Agricultural Organization of the United Nations. Simple regression models were applied to prostate cancer mortality rates and consumption rates for 38 foods (or food categories), and sunlight levels (latitude from the equator and ultraviolet indexes). The analysis found a correlation between increased prostate cancer mortality rates and the consumption of total animal calories, total animal fat calories, meat, animal fat, milk, sugar, alcoholic beverages, and stimulants. The consumption of cereal grains and rice, in particular, correlated strongly with decreasing prostate cancer mortality. The analysis found that increased sunlight levels and consumption of oilseeds, soybeans, and onions also correlate with decreased prostate cancer mortality risk. Stepwise multiple regression analysis was used to build a regression model with minimum colinearity between the variables. Cereals, total animal fat calories, sugar, and onions are the foods that resulted in a model with the best fit. Cereals, ultraviolet index, sugar, and onions were the variables found to provide the best fit in a model when ambient sunlight exposure was included as a factor.

Human sensitivity to PhIP: a novel marker for prostate cancer risk

2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) has been implicated in the development of colon, prostate and mammary gland tumors in rats. In this study, we developed a modified in vitro mutagen sensitivity assay, with activated PhIP (N-OH-PhIP) as the challenge mutagen and chromosome aberrations as the endpoint, and applied it in a pilot prostate cancer case-control study of 81 cases and 84 age and ethnicity-matched controls. Our results showed significantly higher baseline breaks among the cases, mean+/-S.E.=1.86+/-0.23 versus 0.96+/-0.14 in controls; P=0.006. Individuals with high baseline breaks (dichotomized at the control median) had a 36% increased risk for PC (OR=1.36; 95% CI=1.08-1.72). In stratified analysis, high baseline breaks was associated in younger participants (< or = 60 years) with an OR of 1.71 (1.14-2.57) and in those with a positive family history of PC, an OR of 1.43 (0.97-2.11). PhIP treatment induced significantly higher breaks in cases, mean+/-S.E.=5.07+/-0.39 versus 3.83+/-0.24 in controls; P=0.05. Higher PhIP-induced breaks was associated with an overall 17% increased risk for PC (OR=1.17; 95% CI=1.03-1.33), a significantly increased risks (OR=1.19; 95% CI=1.00-1.41) among younger participants, non-smokers (OR=1.39, 1.03-1.88) and 1.20 (1.00-1.45) among those with no family history of PC. Results from this pilot study demonstrate differential sensitivity to PhIP among subgroups and therefore, this assay have potential as a susceptibility marker for prostate cancer risk.

Supplemental and dietary vitamin E, beta-carotene, and vitamin C intakes and prostate cancer risk

BACKGROUND

Vitamin E, beta-carotene, and vitamin C are micronutrient antioxidants that protect cells from oxidative damage involved in prostate carcinogenesis. In separate trials, supplemental vitamin E was associated with a decreased risk of prostate cancer among smokers and supplemental beta-carotene was associated with a decreased risk of prostate cancer among men with low baseline plasma beta-carotene levels.

METHODS

We evaluated the association between intake of these micronutrient antioxidants from foods and supplements and the risk of prostate cancer among men in the screening arm of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. At baseline, trial participants completed a 137-item food frequency questionnaire that included detailed questions on 12 individual supplements. Cox proportional hazards models were used to estimate relative risks (RRs) and 95% confidence intervals (CIs). All statistical tests were two-sided.

RESULTS

We identified 1338 cases of prostate cancer among 29 361 men during up to 8 years of follow-up. Overall, there was no association between prostate cancer risk and dietary or supplemental intake of vitamin E, beta-carotene, or vitamin C. However, among current and recent (i.e., within the previous 10 years) smokers, decreasing risks of advanced prostate cancer (i.e., Gleason score > or = 7 or stage III or IV) were associated with increasing dose (RR for > 400 IU/day versus none = 0.29, 95% CI = 0.12 to 0.68; Ptrend = .01) and duration (RR for > or = 10 years of use versus none = 0.30, 95% CI = 0.09 to 0.96; Ptrend = .01) of supplemental vitamin E use. Supplemental beta-carotene intake at a dose level of at least 2000 microg/day was associated with decreased prostate cancer risk in men with low (below the median of 4129 microg/day) dietary beta-carotene intake (RR = 0.52, 95% CI = 0.33 to 0.81). Among smokers, the age-adjusted rate of advanced prostate cancer was 492 per 100,000 person-years in those who did not take supplemental vitamin E, 153 per 100,000 person-years in those who took more than 400 IU/day of supplemental vitamin E, and 157 per 100,000 person-years in those who took supplemental vitamin E for 10 or more years. Among men with low dietary beta-carotene intake, the age-adjusted rate of prostate cancer was 1122 per 100,000 person-years in those who did not take supplemental beta-carotene, and 623 per 100,000 person-years in those who took at least 2000 microg/day of supplemental beta-carotene.

CONCLUSIONS

Our results do not provide strong support for population-wide implementation of high-dose antioxidant supplementation for the prevention of prostate cancer. However, vitamin E supplementation in male smokers and beta-carotene supplementation in men with low dietary beta-carotene intakes were associated with reduced risk of this disease.

A Prospective Study of Calcium Intake and Incident and Fatal Prostate Cancer

Prostate cancer is the most common incident cancer and the second leading cause of cancer mortality in U.S. males. Higher milk intake has been relatively consistently associated with an increased risk of prostate cancer, especially advanced prostate cancer. Some data suggest that high intake of calcium might account for this association, but this relationship remains controversial. We hypothesized that high calcium intake, possibly by lowering 1,25(OH)2 vitamin D levels, is associated with poorer differentiation in prostate cancer and thereby with fatal prostate cancer. We examined calcium intake in relation to prostate cancer risk using data from the Health Professionals Follow-up Study, a prospective cohort study of 47,750 male health professionals with no history of cancer other than nonmelanoma skin cancer at baseline. We assessed total, dietary, and supplementary calcium intake in 1986, 1990, 1994, and 1998, using a validated food frequency questionnaire. We calculated the multivariable relative risk (RR) and 95% confidence intervals (95% CI) using Cox proportional hazards regression. Over 16 years of follow-up, we identified 3,544 total cases of prostate cancer, 523 advanced (extraprostatic) cases, and 312 fatal cases. Higher calcium intake was not appreciably associated with total or nonadvanced prostate cancer but was associated with a higher risk of advanced and fatal prostate cancer [for fatal prostate cancer, compared with men whose long-term calcium intake was 500-749 mg/d (excluding supplement use of <5 years); those with intakes of 1,500-1,999 mg/d had a RR, 1.87; 95% CI, 1.17-3.01; and those with > or = 2,000 mg/d had a RR, 2.43; 95% CI, 1.32-4.48; P(trend) = 0.003]. Dietary calcium and supplementary calcium were independently associated with an increased risk. For high-grade prostate cancer (Gleason > or = 7), an association was observed for high versus low calcium intake (RR, 1.89; 95% CI, 1.32-2.71; P(trend) = 0.005), but a nonsignificant, inverse association was observed for organ-confined, low-grade prostate cancer (RR, 0.79; 95% CI, 0.50-1.25; P(trend) = 0.09). In a sample of this cohort, higher calcium intake was associated with lower circulating 1,25(OH)2 vitamin D levels. Our findings suggest that calcium intakes exceeding 1,500 mg/d may be associated with a decrease in differentiation in prostate cancer and ultimately with a higher risk of advanced and fatal prostate cancer but not with well-differentiated, organ-confined cancers.

Role of diet in prostate cancer development and progression

Increasing evidence supports the important role of nutrition in cancer prevention, including prevention of prostate cancer. In this review, we summarize data for some of the most consistently observed dietary associations for prostate cancer incidence, briefly consider possible postdiagnostic effects of nutrition on prostate cancer progression/survival, discuss new but limited data on diet-gene interactions, and comment on current areas of controversy for future research focus. Potential protective dietary elements include tomatoes/lycopene, other carotenoids, cruciferous vegetables, vitamin E, selenium, fish/marine omega-3 fatty acids, soy, isoflavones and polyphenols; whereas milk, dairy, calcium, zinc at high doses, saturated fat, grilled meats, and heterocyclic amines may increase risk. It is important to note that randomized clinical trial data exist only for vitamin E, calcium, beta-carotene, and selenium (all of which suggest inverse or no association). Several genes, such as MnSOD, XRCC1, and GST, may modify the association of specific nutrients and foods with prostate cancer risk; and further research is warranted to confirm these initial observed relationships. Until further clinical trial data are available on specific supplements and prostate cancer prevention, it would be prudent to emphasize a diet consisting of a wide variety of plant-based foods and fish; this is similar to what is recommended (and what is more well established) for the primary prevention of heart disease.

Comparisons of prostate cancer mortality rates with dietary practices in the United States

From 1930 to 1992, prostate cancer mortality rates in the United States doubled and then declined somewhat until 2000. The objective of this study is to determine whether variations in prostate cancer mortality rates correlate with dietary changes that occurred over that period. Simple linear regression models were applied to age-adjusted prostate cancer mortality rates and per-capita consumption rates for 18 foods from 1930 to 2000. Correlation coefficients were calculated while comparing food consumption rates to prostate cancer mortality rates for the same year. Correlation coefficients were then recalculated when the prostate cancer mortality rates were compared with food consumption rates that occurred: 1 yr; 2 yr; 3 yr; and continuing in progression for 21 yr before the occurrence of the prostate cancer mortality. The largest positive correlation coefficients were associated with the consumption of: total meat (red meat, poultry and fish) (R = 0.83, T between 0 and 1); added fats and oils (R = 0.83, T = 21); ice cream (R = 0.83, T = 20); margarine (R = 0.81, T = 4); salad/cooking oil (R = 0.82, T between 3 and 4) and; vegetable shortening (R = 0.81, T between 1 and 2) where R is the correlation coefficient and T is the time in years between consumption and mortality. In conclusion, this study found strong positive correlations between prostate cancer mortality and the consumption of: total meat; added fats and oils, ice cream, salad/cooking oils, margarine, and vegetable shortening. The connection between total meat consumption and prostate cancer risk is consistent with previous studies in the literature. The link between salad/cooking oil consumption and prostate cancer risk may be consistent with past studies which suggest that mu-linolenic acid (a component of salad/cooking oils) is a suspected risk factor for prostate cancer.

The epidemiology of vitamin D and cancer incidence and mortality: a review (United States)

In vitro and animal studies indicate that vitamin D may have anti-cancer benefits, including against progression and metastasis, against a wide spectrum of cancers. Supporting an anti-cancer effect of vitamin D is the ability of many cells to convert 25(OH)D, the primary circulating form of vitamin D, into 1,25(OH)2D, the most active form of this vitamin. No epidemiologic studies have directly measured vitamin D concentrations or intakes on risk of total cancer incidence or mortality. However, higher rates of total cancer mortality in regions with less UV-B radiation, and among African-Americans and overweight and obese people, each associated with lower circulating vitamin D, are compatible with a benefit of vitamin D on mortality. In addition, poorer survival from cancer in individuals diagnosed in the months when vitamin D levels are lowest suggests a benefit of vitamin D against late stages of carcinogenesis. The only individual cancer sites that have been examined directly in relation to vitamin D status are colorectal, prostate and breast cancers. For breast cancer, some data are promising for a benefit from vitamin D but are far too sparse to support a conclusion. The evidence that higher 25(OH)D levels through increased sunlight exposure or dietary or supplement intake inhibit colorectal carcinogenesis is substantial. The biologic evidence for an anti-cancer role of 25(OH)D is also strong for prostate cancer, but the epidemiologic data have not been supportive. Although not entirely consistent, some studies suggest that higher circulating 1,25(OH)2D may be more important than 25(OH)D for protection against aggressive, poorly-differentiated prostate cancer. A possible explanation for these divergent results is that unlike colorectal tumors, prostate cancers lose the ability to hydroxylate 25(OH)D to 1,25(OH)2D, and thus may rely on the circulation as the main source of 1,25(OH)2D. The suppression of circulating 1,25(OH)2D levels by calcium intake could explain why higher calcium and milk intakes appear to increase risk of advanced prostate cancer. Given the potential benefits from vitamin D, further research should be a priority.

Glycemic index, glycemic load and risk of prostate cancer

Dietary carbohydrates have different glycemic and insulinemic potentials depending on type (glycemic index, GI) and amount (glycemic load, GL) of carbohydrate consumed or both. Insulin in turn has been implicated as a risk factor for several cancers, including that of the prostate. We assessed the relationship of GI and GL with prostate cancer risk in a multicenter case-control study. Cases and controls were recruited between 1991 and 2002 in the network of major teaching and general hospitals in 4 Italian areas. Cases were 1,204 men (age range 46-74 years) admitted for incident, histologically confirmed prostate cancer. Controls were 1,352 men (age range 46-74 years) admitted for acute, nonmalignant conditions unrelated to long-term modifications of diet. ORs of prostate cancer and the corresponding 95% CIs were derived using unconditional multiple logistic regression, including terms for age, study center, education, family history of prostate cancer, smoking, body mass index, physical activity, alcohol consumption, intake of energy, fiber and lycopenes. Compared to the lowest quintile of GI, the ORs were 1.23, 1.24, 1.47 and 1.57 for subsequent levels of GI. The corresponding values for GL were 0.91, 1.00, 1.20 and 1.41. No heterogeneity was found among strata of selected covariates. We found direct relations between dietary GI and GL and prostate cancer risk. Correcting for potential confounding factors did not substantially modify these associations.

Long-chain (n-3) fatty acid intake and risk of cancers of the breast and the prostate: recent epidemiological studies, biological mechanisms, and directions for future research

The association between dietary (n-3) fatty acids and hormone-responsive cancers continues to attract considerable attention in epidemiological, clinical, and experimental studies. We previously reviewed the epidemiological literature on the association between hormone-responsive cancers and the long-chain fatty acids eicosapentaenoic acid and docosahexaenoic acid. We concluded that the compelling evidence from ecological studies, animal models, and mechanistic experiments in vitro was not supported clearly by the available epidemiological data. To various degrees, epidemiological studies published more recently attempted to address some of the methodological limitations plaguing earlier studies by using validated questionnaires, examining specific fatty acids and their interrelationships, and adjusting estimates for a wider range of potentially confounding factors than in previous studies. In this review, our aim was to update the previous review with the results of recent epidemiological studies and to discuss possible biological mechanisms and directions for future research.

A two-generation reproduction study to assess the effects of cows' milk on reproductive development in male and female rats

OBJECTIVE

To examine whether the considerable quantities of increased female sex hormone levels found in modern milk as a result of modern dairy farming practices are safe for human consumption.

DESIGN

Males and females of the P generation were maintained on a diet containing milk for 10 weeks before mating. Exposure to milk was continued up to the end of weaning of the F2b offspring.

SETTING

Two-generation reproduction study.

ANIMAL(S)

Male and female Wistar Galas rats.

INTERVENTION(S)

P- and F1-generation rats were mated.

MAIN OUTCOME MEASURE(S)

Fertility, fecundity, and morphology and function of reproductive organs.

RESULT(S)

Although milk had growth-promoting effects in both parents and offspring, it caused no impairments in fertility, fecundity, or reproductive organ development in either generation. However, a whole litter from a dam of the P generation was born dead, three litters in total had a pup with skeletal abnormalities, and the AGD of F2a female pups was reduced. These events occurred only in the milk-treated rats. It is unknown whether these issues had any relevance to milk or only happened by chance.

CONCLUSION(S)

Further study is required to determine whether milk from pregnant cows is completely free from adverse effects on reproductive health.

A moderately low phosphate intake may provide health benefits analogous to those conferred by UV light - a further advantage of vegan diets

Although exposure to ultraviolet light is often viewed as pathogenic owing to its role in the genesis of skin cancer and skin aging, there is growing epidemiological evidence that such exposure may decrease risk for a number of more serious cancers, may have a favorable impact on blood pressure and vascular health, and may help to prevent certain autoimmune disorders - in addition to its well-known influence on bone density. Most likely, these health benefits are reflective of improved vitamin D status. Increased synthesis or intake of vitamin D can be expected to down-regulate parathyroid hormone (PTH), and to increase autocrine synthesis of its active metabolite calcitriol in certain tissues; these effects, in turn, may impact cancer risk, vascular health, immune regulation, and bone density through a variety of mechanisms. Presumably, a truly adequate supplemental intake of vitamin D - manyfold higher than the grossly inadequate current RDA - could replicate the benefits of optimal UV exposure, without however damaging the skin. Diets moderately low in bioavailable phosphate - like many vegan diets - might be expected to have a complementary impact on disease risks, inasmuch as serum phosphate suppresses renal calcitriol synthesis while up-regulating that of PTH. A proviso is that the impact of dietary phosphorus on bone health is more equivocal than that of vitamin D. Increased intakes of calcium, on the other hand, down-regulate the production of both PTH and calcitriol - the latter effect may explain why the impact of dietary calcium on cancer risk (excepting colon cancer), hypertension, and autoimmunity is not clearly positive. An overview suggests that a vegan diet supplemented with high-dose vitamin D should increase both systemic and autocrine calcitriol production while suppressing PTH secretion, and thus should represent a highly effective way to achieve the wide-ranging health protection conferred by optimal UV exposure.

Dietary intake of n-3 and n-6 fatty acids and the risk of prostate cancer

BACKGROUND

Laboratory studies have shown that n-3 fatty acids inhibit and n-6 fatty acids stimulate prostate tumor growth, but whether the dietary intake of these fatty acids affects prostate cancer risk in humans remains unclear.

OBJECTIVE

We prospectively evaluated the association between intakes of alpha-linolenic (ALA; 18:3n-3), eicosapentaenoic (EPA; 20:5n-3), docosahexaenoic (DHA; 22:6n-3), linoleic (LA; 18:2n-6), and arachidonic (AA; 20:4n-6) acids and prostate cancer risk.

DESIGN

A cohort of 47 866 US men aged 40-75 y with no cancer history in 1986 was followed for 14 y.

RESULTS

During follow-up, 2965 new cases of total prostate cancer were ascertained, 448 of which were advanced prostate cancer. ALA intake was unrelated to the risk of total prostate cancer. In contrast, the multivariate relative risks (RRs) of advanced prostate cancer from comparisons of extreme quintiles of ALA from nonanimal sources and ALA from meat and dairy sources were 2.02 (95% CI: 1.35, 3.03) and 1.53 (0.88, 2.66), respectively. EPA and DHA intakes were related to lower prostate cancer risk. The multivariate RRs of total and advanced prostate cancer from comparisons of extreme quintiles of the combination of EPA and DHA were 0.89 (0.77, 1.04) and 0.74 (0.49, 1.08), respectively. LA and AA intakes were unrelated to the risk of prostate cancer. The multivariate RR of advanced prostate cancer from a comparison of extreme quintiles of the ratio of LA to ALA was 0.62 (0.45, 0.86).

CONCLUSIONS

Increased dietary intakes of ALA may increase the risk of advanced prostate cancer. In contrast, EPA and DHA intakes may reduce the risk of total and advanced prostate cancer.

Leveling of prostate cancer mortality in Western Europe

BACKGROUND

Mortality from prostate cancer (CaP) has increased throughout Europe until the early 1990s. Trends in 24 European countries, the European Union (EU), six selected Central and Eastern European countries, and the Russian Federation have been updated to 1999.

METHODS

Cancer death certification data for CaP were abstracted from the World Health Organization database.

RESULTS

In the EU, the peak rate (15.7/100,000) was reached in 1993, followed by a leveling off and a decline to 14.1/100,000 in 1999. Age-standardized analysis for each subsequent age group of men aged 50 or over showed larger absolute falls in the elderly. CaP rates were lower in Central and Eastern European countries providing data, but showed a rise from 9.7/100,000 in 1980 to 11.3 in 1996, and leveled off thereafter. Rates were originally lower, but the rises larger in the Russian Federation (from 5.1/100,000 in 1980 to 8.1/100,000 in 1999). In the late 1990s, there was a threefold difference between the highest rates of 22/100,000 in Norway and those of 7.7 in Russia or 7.3 in Ukraine. Such a difference was, however, restricted to the elderly, since at age 35-64 the Russian rate (6.7/100,000) was the same as that of Norway, and only Greece and Italy had appreciably lower rates.

CONCLUSION

The pattern of trends in CaP rates observed across Europe is consistent with a favorable role of improved diagnosis, but mainly of advancements of therapy (including more widespread adoption of radical prostatectomy and androgen blockage) on CaP mortality in Western Europe.

Diabetes mellitus and risk of prostate cancer: a meta-analysis

AIMS/HYPOTHESIS

The association of diabetes mellitus with prostate cancer has been controversial. This study examines the strength of this association by conducting a detailed meta-analysis of the studies published in peer-reviewed literature on the subject.

METHODS

A comprehensive search for articles published up to 2003 was performed, reviews of each study were conducted and data were abstracted. Prior to meta-analysis, the studies were evaluated for publication bias and heterogeneity. Pooled relative risk (RR) was calculated using the random- and the fixed-effects models. Subgroup and sensitivity analyses were also performed.

RESULTS

We included 14 studies, published between 1971 and 2002, in the meta-analysis (five case-control studies, nine cohort studies). We found no evidence of publication bias ( p=0.89) or heterogeneity among the studies ( p=0.38). The association of diabetes with prostate cancer was statistically significant, both on the basis of a random-effects model (RR=0.91, 95% CI: 0.86 to 0.96), and on the basis of a fixed-effects model (RR=0.91, 95% CI: 0.88 to 0.94). When the analysis was stratified into subgroups according to study design, the association was inverse in both cohort and case-control studies, but only in the former was it statistically significant. The sensitivity analysis strengthened our confidence in the validity of this association.

CONCLUSIONS/INTERPRETATION

Our meta-analysis findings provide strong evidence that people with diabetes have a significant decrease in risk of developing prostate cancer. There is biological evidence to support this association.

Prostatitis as a risk factor for prostate cancer

BACKGROUND

The association of infection or inflammation of the prostate with prostate cancer has been suggested but not established. This study was undertaken to investigate this association.

METHODS

Cases were Olmsted County, Minnesota, residents with histologically proven prostate cancer diagnosed between January 1980 and December 1996. Cases (n = 409) were each matched to 2 control subjects (n = 803) on age at diagnosis of prostate cancer, residency in Olmsted County, and duration of the community medical record. The medical record of each subject was reviewed for a history of acute or chronic bacterial prostatitis or chronic pelvic pain syndrome (inflammatory type).

RESULTS

The relative odds of prostate cancer were elevated in men with history of any type of prostatitis (odds ratio [OR] = 1.7; 95% confidence interval [CI] = 1.1-2.6) or acute prostatitis (2.5; 1.3-4.7). The mean time from most recent episode of acute prostatitis to the diagnosis of prostate cancer was 12.2 years. After exclusion of men with acute prostatitis 2 years before the index date, the relationship was somewhat reduced (1.9; 0.9-3.8). Chronic bacterial prostatitis was more weakly associated with prostate cancer (1.6; 0.8-3.1), whereas chronic pelvic pain syndrome was not associated at all (0.9; 0.4-1.8).

CONCLUSIONS

Infection in the form of acute or chronic bacterial prostatitis may be associated with prostate cancer. However, our data do not provide compelling evidence to support this. As a result of the limitations of current methods of assessing chronic prostatitis, biochemical or tissue markers of infection or inflammation of the prostate may help clarify their role in the pathogenesis of prostate cancer.

A case-control study of diet and prostate cancer in Japan: possible protective effect of traditional Japanese diet

The age-adjusted incidence of prostate cancer is low in Japan, and it has been suggested that the traditional Japanese diet, which includes many soy products, plays a preventive role against prostate cancer. We performed a case-control study on dietary factors and prostate cancer in order to assess the hypothesis that the traditional Japanese diet reduces the risk of prostate cancer. Four geographical areas (Ibaraki, Fukuoka, Nara, and Hokkaido) of Japan were selected for the survey. Average daily intake of food from 5 years before the diagnosis was measured by means of a semi-quantitative food frequency questionnaire. We studied 140 cases and 140 individually age ( +/- 5 years)-matched hospital controls for analysis. Estimates of age-adjusted odds ratios (ORs) and linear trends were calculated by conditional logistic regression models with adjustment for cigarette smoking and total energy intake as confounding factors. Consumption of fish, all soybean products, tofu (bean curds), and natto (fermented soybeans) was associated with decreased risk. ORs of the fourth vs. first quartile and 95% confidence intervals (95%CIs) were 0.45 (0.20-1.02) for fish, 0.53 (0.24-1.14) for all soybean products, 0.47 (0.20-1.08) for tofu, and 0.25 (0.05-1.24) for natto. Consumption of fish and natto showed significantly decreasing linear trends for risk (P < 0.05). Consumption of meat was significantly associated with increased risk (the OR of the second vs. first quartile was 2.19, 95%CI 1.00-4.81). Consumption of milk, fruits, all vegetables, green-yellow vegetables, and tomatoes showed no association. Our results provide support to the hypothesis that the traditional Japanese diet, which is rich in soybean products and fish, might be protective against prostate cancer.