The role of diet in prostate cancer

Optimal Dietary Intake of Riboflavin Associated with Lower Risk of Cervical Cancer in Korea: Korean National Health and Nutrition Examination Survey 2010-2021

BACKGROUND

This study aimed to evaluate the association between the dietary intake of vitamin B complex (thiamine, riboflavin, and niacin) and cervical cancer in Korea.

METHODS

The data from the Korean National Health and Nutrition Examination Survey (KNHANES) from 2010 to 2021 were analyzed, which included 28,306 participants who were categorized into non-cervical cancer and cervical cancer groups. The following dietary intake threshold levels of thiamine, riboflavin, and niacin were identified based on the recommended daily allowances (RDAs): thiamine, 1.1 mg/day; riboflavin, 1.2 mg/day; and niacin, 14 mg/day.

RESULTS

Among 28,306 participants, 27,976 were in the non-cervical cancer group and 330 were in the cervical cancer group. Riboflavin intakes of more than 1.2 mg/day but less than 2.4 mg/day were associated with a significantly reduced risk of cervical cancer, whereas intakes of above 2.4 mg/day were not associated with cervical cancer. Thiamine and niacin intakes were not significantly related to the risk of cervical cancer.

CONCLUSIONS

The results of this study suggest that an intake of riboflavin of 1.2-2.4 mg/day may contribute to a lower risk of cervical cancer.

Dietary vitamin D intake and the bladder cancer risk: A pooled analysis of prospective cohort studies

BACKGROUND & AIMS

Diet may play an essential role in the aetiology of bladder cancer (BC). Vitamin D is involved in various biological functions which have the potential to prevent BC development. Besides, vitamin D also influences the uptake of calcium and phosphorus, thereby possibly indirectly influencing the risk of BC. The aim of the present study was to investigate the relation between vitamin D intake and BC risk.

METHODS

Individual dietary data were pooled from ten cohort studies. Food item intake was converted to daily intakes of vitamin D, calcium and phosphorus. Pooled multivariate hazard ratios (HRs), with corresponding 95% confidence intervals (CIs) were obtained using Cox-regression models. Analyses were adjusted for gender, age and smoking status (Model 1), and additionally for the food groups fruit, vegetables and meat (Model 2). Dose-response relationships (Model 1) were examined using a nonparametric test for trend.

RESULTS

In total, 1994 cases and 518,002 non-cases were included in the analyses. The present study showed no significant associations between individual nutrient intake and BC risk. A significant decreased BC risk was observed for high vitamin D intake with moderate calcium and low phosphorus intake (Model 2: HR_{high vitD, mod Ca, low P}: 0.77, 95% CI: 0.59-1.00). No significant dose-response analyses were observed.

CONCLUSION

The present study showed a decreased BC risk for high dietary vitamin D intake in combination with low calcium intake and moderate phosphorus intake. The study highlights the importance of examining the effect of a nutrient in combination with complementary nutrients for risk assessment. Future research should focus on nutrients in a wider context and in nutritional patterns.

Dietary B group vitamin intake and the bladder cancer risk: a pooled analysis of prospective cohort studies

PURPOSE

Diet may play an essential role in the aetiology of bladder cancer (BC). The B group complex vitamins involve diverse biological functions that could be influential in cancer prevention. The aim of the present study was to investigate the association between various components of the B group vitamin complex and BC risk.

METHODS

Dietary data were pooled from four cohort studies. Food item intake was converted to daily intakes of B group vitamins and pooled multivariate hazard ratios (HRs), with corresponding 95% confidence intervals (CIs), were obtained using Cox-regression models. Dose-response relationships were examined using a nonparametric test for trend.

RESULTS

In total, 2915 BC cases and 530,012 non-cases were included in the analyses. The present study showed an increased BC risk for moderate intake of vitamin B1 (HRB1: 1.13, 95% CI: 1.00-1.20). In men, moderate intake of the vitamins B1, B2, energy-related vitamins and high intake of vitamin B1 were associated with an increased BC risk (HR (95% CI): 1.13 (1.02-1.26), 1.14 (1.02-1.26), 1.13 (1.02-1.26; 1.13 (1.02-1.26), respectively). In women, high intake of all vitamins and vitamin combinations, except for the entire complex, showed an inverse association (HR (95% CI): 0.80 (0.67-0.97), 0.83 (0.70-1.00); 0.77 (0.63-0.93), 0.73 (0.61-0.88), 0.82 (0.68-0.99), 0.79 (0.66-0.95), 0.80 (0.66-0.96), 0.74 (0.62-0.89), 0.76 (0.63-0.92), respectively). Dose-response analyses showed an increased BC risk for higher intake of vitamin B1 and B12.

CONCLUSION

Our findings highlight the importance of future research on the food sources of B group vitamins in the context of the overall and sex-stratified diet.

The role of dietary fat throughout the prostate cancer trajectory

Prostate cancer is the second most common cancer diagnosed world-wide; however, patients demonstrate exceptionally high survival rates. Many lifestyle factors, including obesity and diet, are considered risk factors for advanced prostate cancer. Dietary fat is a fundamental contributor to obesity and may be specifically important for prostate cancer patients. Prostate cancer treatment can result in changes in body composition, affecting quality of life for survivors by increasing the risk of co-morbidities, like cardiovascular disease and diabetes. We aim to examine dietary fat throughout the prostate cancer treatment trajectory, including risk, cancer development and survivorship. Focusing on one specific nutrient throughout the prostate cancer trajectory provides a unique perspective of dietary fat in prostate cancer and the mechanisms that may exacerbate prostate cancer risk, progression and recurrence. Through this approach, we noted that high intake of dietary fat, especially, high intake of animal and saturated fats, may be associated with increased prostate cancer risk. In contrast, a low-fat diet, specifically low in saturated fat, may be beneficial for prostate cancer survivors by reducing tumor angiogenesis and cancer recurrence. The insulin-like growth factor (IGF)/Akt signaling pathway appears to be the key pathway moderating dietary fat intake and prostate cancer development and progression.

Linking vitamin B1 with cancer cell metabolism

The resurgence of interest in cancer metabolism has linked alterations in the regulation and exploitation of metabolic pathways with an anabolic phenotype that increases biomass production for the replication of new daughter cells. To support the increase in the metabolic rate of cancer cells, a coordinated increase in the supply of nutrients, such as glucose and micronutrients functioning as enzyme cofactors is required. The majority of co-enzymes are water-soluble vitamins such as niacin, folic acid, pantothenic acid, pyridoxine, biotin, riboflavin and thiamine (Vitamin B1). Continuous dietary intake of these micronutrients is essential for maintaining normal health. How cancer cells adaptively regulate cellular homeostasis of cofactors and how they can regulate expression and function of metabolic enzymes in cancer is underappreciated. Exploitation of cofactor-dependent metabolic pathways with the advent of anti-folates highlights the potential vulnerabilities and importance of vitamins in cancer biology. Vitamin supplementation products are easily accessible and patients often perceive them as safe and beneficial without full knowledge of their effects. Thus, understanding the significance of enzyme cofactors in cancer cell metabolism will provide for important dietary strategies and new molecular targets to reduce disease progression. Recent studies have demonstrated the significance of thiamine-dependent enzymes in cancer cell metabolism. Therefore, this review discusses the current knowledge in the alterations in thiamine availability, homeostasis, and exploitation of thiamine-dependent pathways by cancer cells.

A Prospective Study of Polyunsaturated Fatty Acid Levels in Blood and Prostate Cancer Risk

BACKGROUND

Animal models suggest that n-3 fatty acids inhibit prostate cancer proliferation, whereas n-6 fatty acids promote it, but epidemiologic studies do not uniformly support these findings.

METHODS

A nested case-control study was conducted among 14,916 apparently healthy men who provided blood samples in 1982. Blood fatty acid levels were determined for 476 men diagnosed with prostate cancer during a 13-year follow-up and their matched controls. Conditional logistic regression was used to estimate the relative risks (RR) and 95% confidence intervals (95% CI) of total, non-aggressive (stage A/B and Gleason < 7) and aggressive (stage C/D, Gleason >or= 7, subsequent distant metastasis or death) prostate cancer associated with blood levels of specific fatty acids expressed as percentages of total fatty acids.

RESULTS

Whole blood levels of all long-chain n-3 fatty acids examined and of linoleic acid were inversely related to overall prostate cancer risk (RR(Q5vs.Q1), 0.59; 95% CI, 0.38-0.93; P(trend) = 0.01 for total long-chain n-3 fatty acids and RR(Q5vs.Q1), 0.62; 95% CI, 0.41-0.95; P(trend) = 0.03 for linoleic). Blood levels of gamma-linolenic and dihomo-gamma-linolenic acids, fatty acids resulting from the metabolism of linoleic acid, were directly associated with prostate cancer (RR, 1.41; 95% CI, 0.94-2.12; P(trend) = 0.05 for gamma-linolenic and RR, 1.54; 95% CI, 1.03-2.30; P(trend) = 0.02 for dihomo-gamma-linolenic acid). Levels of arachidonic and alpha-linolenic acids were unrelated to prostate cancer.

CONCLUSIONS

Higher blood levels of long-chain n-3 fatty acids, mainly found in marine foods, and of linoleic acid, mainly found in non-hydrogenated vegetable oils, are associated with a reduced risk of prostate cancer. The direct associations of linoleic acid metabolites with prostate cancer risk deserve further investigation.

Spatial analysis of prostate cancer incidence and race in Virginia, 1990-1999

BACKGROUND

Racial disparities exist in prostate cancer incidence. An important contributor to these disparities may be socioeconomic status.

METHODS

Virginia Cancer Registry data, 1990-1999 (37,373 cases) were geocoded to the Census tract and county level. The annualized, age-adjusted incidence rates for African Americans and whites were calculated, and crude and smoothed maps of these rates were produced. Statistical tests for clustering of cases were conducted. Prostate cancer incidence was statistically modeled as a function of area-based measures of poverty, median household income, education, rural status, ratio of physicians to population in each county, percentage of men in each county obtaining prostate cancer screening with the prostate-specific antigen (PSA) test, and percent of households headed by females.

RESULTS

Prostate cancer incidence was elevated in the eastern and central portions of the state. Statistical tests for clustering were highly significant (Tango's test, p<0.008; spatial scan statistic, p<0.001). Poverty and lower education were associated with a decreased incidence among whites but not African Americans. Median household income and urban status were positively associated with incidence for both populations. Among whites, increased percent of female heads of households and ratio of physicians per population were associated with increased incidence. Associations between predictor variables and prostate cancer incidence were seen only in the census tract level analyses.

CONCLUSIONS

Overall, the findings support the argument that area measures of poverty and education do not explain the increased incidence of prostate cancer among African Americans. Other factors, such as dietary practices, may help explain racial disparities in prostate cancer incidence. Because of the large differences between tract and county level results, the time and expense of obtaining data geocoded to the tract level seems worthwhile.

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.

Dietary Fat and Prostate Cancer

PURPOSE

Data from histopathological and migratory studies suggest that 1 or more late stage environmental promoters are involved in the development of clinical carcinoma of the prostate. Laboratory investigations and variously designed epidemiological studies in man have suggested that dietary fat may be one of these candidate tumor promoters but other studies have questioned this association. The biologically plausible associations that have been hypothesized include total energy consumption, altered androgen metabolism, oxidative stress, specific fatty acid consumption and pesticide intake. We provide a critical appraisal of the existing evidence for an association between dietary fat consumption and prostate cancer, and review the biologically plausible relationships.

MATERIALS AND METHODS

All 33 published case-control and cohort studies that examined the relationship between prostate cancer and dietary fat or specific fatty food types were critically appraised. Eight studies suggested a statistically significant association, and many studies noted significant associations for specific types of fatty foods (eg milk or meat) and prostate cancer.

RESULTS

In light of the inherent biases in the methodology of studying dietary fat intake and carcinoma of the prostate, we conclude that the evidence is consistent.

CONCLUSIONS

Corroborative studies in humans are required to better define this relationship. Prospective studies of dietary intervention should be encouraged.

Human prostate cancer risk factors

Prostate cancer has the highest prevalence of any nonskin cancer in the human body, with similar likelihood of neoplastic foci found within the prostates of men around the world regardless of diet, occupation, lifestyle, or other factors. Essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. This review is a contemporary and comprehensive, literature-based analysis of the putative risk factors for human prostate cancer, and the results were presented at a multidisciplinary consensus conference held in Crystal City, Virginia, in the fall of 2002. The objectives were to evaluate known environmental factors and mechanisms of prostatic carcinogenesis and to identify existing data gaps and future research needs. The review is divided into four sections, including 1) epidemiology (endogenous factors [family history, hormones, race, aging and oxidative stress] and exogenous factors [diet, environmental agents, occupation and other factors, including lifestyle factors]); 2) animal and cell culture models for prediction of human risk (rodent models, transgenic models, mouse reconstitution models, severe combined immunodeficiency syndrome mouse models, canine models, xenograft models, and cell culture models); 3) biomarkers in prostate cancer, most of which have been tested only as predictive factors for patient outcome after treatment rather than as risk factors; and 4) genotoxic and nongenotoxic mechanisms of carcinogenesis. The authors conclude that most of the data regarding risk relies, of necessity, on epidemiologic studies, but animal and cell culture models offer promise in confirming some important findings. The current understanding of biomarkers of disease and risk factors is limited. An understanding of the risk factors for prostate cancer has practical importance for public health research and policy, genetic and nutritional education and chemoprevention, and prevention strategies.

Energy imbalance and prostate cancer

In this review, the emerging evidence that excessive energy intake relative to energy expenditure increases the risk of prostate cancer is discussed. The adverse effects of energy imbalance can be inferred from an experimental study demonstrating reduced prostate tumor growth, lower circulating concentrations of insulin-like growth factor-I and decreased expression of vascular endothelial growth factor with energy restriction in transplantable tumor models. The effects of energy restriction on factors mediating greater proliferation relative to apoptosis and angiogenesis suggest that energy imbalance may act late in the carcinogenic pathway. Energy intake also has been evaluated in relation to prostate cancer risk in 23 analytic epidemiologic studies. Among studies reporting effect estimates, 8 of 14 case-control studies support a direct association [top versus bottom quantile, OR(summary) = 1.3; 95% confidence interval (CI), 1.1-1.4], but none of four cohort studies do (RR(summary) = 1.0; 95% CI, 0.8-1.2). The four case-control studies that evaluated advanced disease suggest a higher risk with higher energy intake (OR(summary) = 1.6; 95% CI, 1.2-2.0). However, none of these studies considered the balance of energy intake with body size and physical activity, the major determinants of variability in energy demand. Numerous research questions remain to be addressed, including, Which biological pathways are adversely affected by energy imbalance? Does energy imbalance act early or late in prostate carcinogenesis? What is the optimal energy balance for minimizing risk of clinically important prostate cancer? Evidence is beginning to show that energy intake in excess of expenditure may affect prostate carcinogenesis and, in particular, risk of advanced disease.

Dietary fat and carcinogenesis

Epidemiologic investigations have suggested a relationship between dietary fat intake and various types of cancer incidences. Furthermore, epidemiologic studies as well as studies with animal models have demonstrated that not only the amount but also the type of fat consumed is important. At present, the mechanism by which dietary fat modulates carcinogenesis has not been elucidated. The effects of dietary fat on the development of tumours have been summarized in the present review with emphasis on colorectal, pancreas, breast and prostate cancer. It is concluded that influence on synthesis of prostaglandins and leukotrienes may be the universal mechanism by which dietary fats modulate carcinogenesis.

Nutrition and prostate cancer

Scientific evidence suggests that differences in the diet may, in large part, account for the variability of prostate cancer rates around the world. Epidemiologic studies and animal experiments have yielded compelling results to warrant clinical intervention studies on nutrition from scientists who work on the prevention and treatment of prostate cancer. This article reviews the most recent evidence as to possible mechanisms of action of various dietary constituents, and explores evidence of various nutritional strategies for the prevention of prostate cancer progression.

Diet, micronutrients, and the prostate gland

Diseases of the prostate gland, particularly adenocarcinoma and benign prostatic hyperplasia (BPH), are age-related. Prostate cancer is the most commonly occurring tumor in U.S. men. Differences in the incidence of this disease among ethnic populations are not due solely to genetic differences. Many efforts have been devoted to studying associations between nutrition and prostate cancer. The strongest association appears to be related to total fat intake and increased risk of this malignancy. Evidence also exists to suggest a role for certain micronutrients, such as zinc, selenium, vitamin E, lycopene, phytoestrogens, and phytosterols, although the role of nutrition and micronutrients in protection against prostate cancer is less convincing. Further research is necessary.

Smoking, plasma vitamins C, E, retinol, and carotene, and fatal prostate cancer: seventeen-year follow-up of the prospective basel study

BACKGROUND

Prostate cancer has one of the highest incidence rates of all cancers. Vitamin intake and tobacco use may have an impact on incidence and mortality, but epidemiologic evidence is scarce and inconsistent.

METHODS

Plasma vitamins C, E, retinol, and carotene were measured in 1971-1973 in 2,974 men working in Basel, Switzerland. In 1990, the vital status of all participants was assessed.

RESULTS

Two hundred and ninety men had died from cancer, including 30 with prostate cancer. On average, prostate cancer cases were 15 years older and smoked slightly more frequently than survivors. The mean values of plasma carotene, and of vitamin C, were nonsignificantly lower in prostate cancer cases than in survivors. After calculation of relative risk using the Cox model with exclusion of mortality during the first 2 years of follow-up, low vitamin E levels in smokers were related to an increased risk for prostate cancer. Relative risks of low vitamin C and carotene levels were about 1. A slightly but nonsignificantly increased risk was observed for low levels of retinol.

CONCLUSIONS

Given the profound implication if the risk of prostatic cancer could be reduced, the relationship with vitamin E and smoking requires further study.

Diet, nutrition, and prostate cancer

Cancer of the prostate gland is one of the most common malignancies in affluent nations, in part due to the application of new screening and diagnostic tools. The development of life-threatening prostate cancer is the culmination of a complex series of initiation and promotional events over a period of decades and under the influence of many interacting genetic and environmental factors. A rapidly accumulating scientific literature provides compelling evidence for the hypothesis that diet and nutrition are important factors modifying risk of prostate cancer. Additional resources devoted to interactive research efforts by laboratory scientists and epidemiologists will provide further enlightenment and continued refinement of our assessment of risks and benefits for specific nutrients and dietary patterns. These studies provide hope that evidence-based dietary interventions will significantly impact the risk of prostate cancer and enhance the efficacy of therapeutic interventions.

Dietary fat consumption and health

Dietary Guidelines have emerged over the past 30 years recommending that Americans limit their consumption of total fat and saturated fat as one way to reduce the risk of a range of chronic diseases. However, a low-fat diet is not a no-fat diet. Dietary fat clearly serves a number of essential functions. For example, maternal energy deficiency, possible exacerbated by very low-fat intakes (< 15% of energy), is one key determinant in the etiology of low birth weight. The debate continues over recommendations for limiting total fat and saturated fatty acid intake in children. Recent evidence indicates that diets with adequate energy providing less than 30% of energy from fat are sufficient to promote normal growth and normal sexual maturation. More attention needs to be devoted to the effect of dietary fat reduction on the nutrient density of children's diets. The association between dietary fat and CHD has been extensively studied. Diets high in saturated fatty acids and trans fatty acids increase LDL cholesterol levels, and in turn, the risk of heart disease. The relationship between high-carbohydrate/low-fat diets and CHD is more ambiguous because high-carbohydrate diets induce dyslipidemia in certain individuals. Obesity among adults and children is now of epidemic proportions in the United States. High-fat diets leading to excessive energy intakes are strongly linked to the increasing obesity in the United States. However, the prevalence of obesity has increased during the same time period that dietary fat intake (both in absolute terms and as a percentage of total dietary energy) has decreased. These trends suggest that a concomitant decrease in total dietary energy and modifications of other lifestyle factors, such as physical activity, also need to be emphasized. Obesity is also an independent risk factor for the development of diabetes. The current availability of fat-modified foods offers the potential for dietary fat reduction and treatment of the comorbidities associated with diabetes. However, to date, few studies have documented the effectiveness of fat-modified foods as part of a weight loss regimen or in reduction in CHD risks among individuals with diabetes mellitus. The association between total dietary fat and cancer is still under debate. While there is some evidence demonstrating associations between dietary fat intake and cancers of the breast, prostate, and colon, there are serious methodologic issues, including the difficulty in differentiating the effects of dietary fat independent of total energy intake. Reported total fat and saturated fatty acid intakes as a percentage of total energy have been declining over the past 30 years in the United States. Despite this encouraging trend, the majority of individuals--regardless of age--do not report consuming a diet that meets the levels of fat and saturated fatty acids recommended by the Dietary Guidelines for Americans. On a relative basis, saturated fat intake has gone down less than has total fat intake. Individuals of all ages who report consuming a diet with < or = 30% of energy from fat consistently have lower energy intakes. Given the increasing rates of obesity in the United States at an earlier and earlier age, dietary fat reduction may be an effective part of an overall strategy to balance energy consumption with energy needs. In each of the age/gender groups reporting consumption of < or = 30% of energy from fat and less than 10% of energy from saturated fatty acids, fat-modified foods play a more important role in their diets than for people who are consuming higher levels of fat and saturated fat. The data are clear than fat-modified foods make a more significant contribution to diets of consumers with low-fat intakes. While one cannot argue cause and effect from the results presented, the patterns of fat-modified foods/low-fat intakes are consistent. The focus on overall diet quality is often lost in the national obsession with lowering fat inta

Growth factor involvement in progression of prostate cancer

Understanding how the regulation of growth factor pathways alters during prostate cancer (PC) progression may enable researchers to develop targeted therapeutic strategies for advanced disease. PC progression involves the shifting of cells from androgen-dependent growth to an androgen-independent state, sometimes with the loss or mutation of the androgen receptors in PC cells. Both autocrine and paracrine pathways are up-regulated in androgen-independent tumors and may replace androgens as primary growth stimulatory factors in cancer progression. Our discussion focuses on growth factor families that maintain homeostasis between epithelial and stromal cells in the normal prostate and that undergo changes as PC progresses, often making stromal cells redundant. These growth factors include fibroblast growth factor, insulin-like growth factors, epidermal growth factor, transforming growth factor α, retinoic acid, vitamin D3, and the transforming growth factor β families. We review their role in normal prostate development and in cancer progression, using evidence from clinical specimens and models of PC cell growth.

Dietary energy and nutrients in relation to preclinical prostate cancer

Previous studies of diet and prostate cancer have focused on advanced disease and have suggested a positive association with saturated fat intake. We report a study assessing the relationship between diet and preclinical prostate cancer. A total of 215 men with preclinical prostate cancer and 593 controls with no evidence of cancer participated in a case-control study conducted in Quebec City between October 1990 and May 1993. The study population comprised two groups: men treated surgically for benign prostatic hypertrophy and participants in a prostate cancer screening program. Trained nutritionists interviewed the participants on their usual diet using a diet history questionnaire. Odds ratios for prostate cancer associated with quartiles of dietary intake and P values for trend were estimated by logistic regression while controlling for age, education, group, and family history of prostate cancer. A positive association was observed between total energy intake and preclinical prostate cancer (p = 0.004). The odds ratios for prostate cancer increased with each quartile of energy intake: 1.00, 1.77, 1.90, and 2.67. After adjustment for energy, nutrients were not associated with prostate cancer. This study provides some evidence that total energy intake is related to preclinical prostate cancer and suggests that diet could be involved earlier than thought in the occurrence of prostate cancer.

Cancer of the prostate: a nutritional disease?

In summary, epidemiologic and laboratory evidence increasingly demonstrate that nutritional factors, especially reduced fat intake, soy proteins, vitamin E derivatives, and selenium, may have a protective effect against prostate cancer. The experimental observation that low-fat diets and soy protein extracts may influence the progression of established tumors, rather than inhibiting etiologic factors, is particularly intriguing because it may serve to help explain the paradox whereby the incidence of clinical prostate cancer shows wide geographic variation, yet the evidence persists that the incidence of microfocal tumors is essentially the same worldwide. These observations, plus the likelihood that nutrition trials are likely to have little in the way of toxicity that would preclude their completion, argue that such trials should be performed. It is estimated that 30% to 50% of human malignancies may be related to dietary factors, and although the feasibility of trials involving low-fat diets has been proved in ongoing trials for colon and breast cancer, no similar study exists for prostate malignancy. Critics of epidemiologic research argue that data derived from case-control studies are subject to recall bias and are thus artifactual. Indeed, many researchers now believe that the breast cancer-dietary fat hypothesis has been discredited. The major difference between the prostate cancer and breast cancer literature is the remarkable consistency of the cohort studies. In these studies, exposure is determined prospectively and is therefore free from recall bias. In this sense they more closely resemble a clinical trial. The majority of cohort studies involving dietary fat and breast cancer have been negative. We believe that these data justify large-scale trials in the area of prevention of prostate cancer. One such proposed study already submitted for National Institutes of Health funding from a consortium of centers is the Prostate Interventional Nutrition Study (PINS), modeled after the Women's Interventional Nutrition Study, which investigates the effect of low-fat diets in women receiving therapy for node-positive breast cancer. The PINS study will be limited to men who have detectable serum PSA levels but no other clinical evidence of disease after radical prostatectomy. All subjects will receive nutritional guidance, with randomization between a control arm receiving the currently recommended 30% fat diet and an interventional arm in which a 15% fat diet is supplemented with soy protein, vitamin E, and selenium. The end points for evaluation will be compared with progression based on changes in PSA and the time of onset of clinical, as opposed to biochemical, disease. Single-institution trials involving groups thought to be at high risk of developing clinical cancer--including men with persistently elevated PSA levels, two negative prostate biopsies, high-grade prostatic intraepithelial neoplasia on biopsy, and a strong family history of prostate cancer--are being initiated at MSKCC and other institutions.

CONCLUSIONS

We have reviewed the evidence that nutritional factors play a role in the progression rate of prostate cancer and may help to explain the geographic variation in the incidence observed. However, without well-controlled prospective trials, the attractive hypothesis that nutrition plays a role in tumor progression remains simply an attractive hypothesis. To date, no definite proof of a preventive effect has been shown in a study that will withstand rigid scientific scrutiny. The opportunity exists, however, for the urologic community, working together with experts in the area of nutrition, not only to advance our understanding of prostate tumorigenesis, but to rebut those critics of modern medical technology who claim that we have ignored the total or holistic approach to healing. (ABSTRACT TRUNCATED)

Induction of apoptosis and altered nuclear/cytoplasmic distribution of the androgen receptor and prostate-specific antigen by 1alpha,25-dihydroxyvitamin D3 in androgen-responsive LNCaP cells

In addition to suppressing prostate cell growth, vitamin D also up-regulates the expression of androgen receptor (AR) and prostate-specific antigen (PSA). To study the mechanism involved in the control of these proteins, LNCaP cells were treated with 10 nM 1alpha,25-dihydroxyvitamin D3 and separated into cytosol and nuclear fractions. AR and PSA were analyzed by western blot analysis. A second approach involved incubating control and treated cells with [3H]R1881, fractionating the cells into the cytosolic and nuclear components, and quantifying the amount of radioactivity associated with the respective fractions. Alternatively, immunohistochemical assays were performed by staining cells with cognate antibodies for AR and PSA. Both biochemical and immunohistochemical analyses show proportionately greater increased presence of AR in the nucleus, accompanied by relatively reduced AR in the cytosol, following treatment of LNCaP cells with vitamin D3. Surprisingly, PSA was found to be present in the nuclear fraction in both control and treated cells. These results suggest that vitamin D3 promotes the translocation of AR from the cytosol to the nucleus. The presence of PSA in the nucleus of LNCaP cells raises the possibility of an autogenous mode of control of PSA gene expression.

Dietary fat and protein intake differ in modulation of prostate tumor growth, prolactin secretion and metabolism, and prostate gland prolactin binding capacity in rats

The combined effects of dietary fat and protein concentration on prostate tumor growth and endocrine homeostasis were evaluated in male rats. A 2 x 2 factorial experiment examined the effects of protein (5 and 20% of energy as casein) and fat (10 and 40% of energy as corn oil) on the growth of the Dunning R3327-H transplantable prostate adenocarcinoma in Copenhagen x Fisher F1 rats. Rats fed protein-restricted diets for 20 wk exhibited lower energy intakes, final body weights and tumor growth rates. Weanling male Sprague-Dawley rats fed protein-restricted diets for 4 wk had serum concentrations of prolactin, growth hormone and testosterone which were 68, 17 and 85% of controls, respectively. After 16 wk of feeding, there were no effects of dietary protein on serum hormone concentrations despite reduced energy intake and body weight. The metabolic clearance rate of serum prolactin was lower in rats fed the low protein diets for 4 or 16 wk; however, no differences were noted when adjusted for body weight. In vivo studies employing intravenously injected 125I-labeled prolactin revealed slight alterations in the metabolism of circulating prolactin monomer or binding to serum proteins in protein-restricted rats. The maximal binding capacity of prolactin receptors on the prostate membrane fraction was 42% lower in rats fed diets restricted in protein despite normal serum hormone concentrations at 16 wk. Dietary fat had no effect on tumor growth or prolactin homeostasis although a slightly greater serum testosterone was noted in rats fed high fat diets. In contrast, restriction of dietary protein caused significant changes in energy intake, serum hormone concentrations, prolactin metabolism, prostatic prolactin binding capacity and prostate tumor growth rates. These studies support the hypothesis that dietary protein and energy intake, particularly during periods of rapid growth and development, may alter prostate biology and modulate the risk of future prostate cancer progression.

Diet, nutrition and prostate cancer

Although much has been written, little is known about the causes of prostate cancer. Variations between populations in the incidence of invasive cancers, together with changes in the incidence of invasive cancers in migrants, have pointed to environmental (lifestyle) factors that might be amenable to intervention. Conversely, there is a lack of international variation in the prevalence of microscopic tumours, so the essential question is: what causes only some of the common microscopic tumours to become aggressive? Dietary factors hold the most promise in this regard and have been the subject of recent reviews. The strongest and most consistent effects are positive associations with animal products such as red meats, eggs and dairy foods, and possibly by implication, fat. Evidence of a protective effect of fruit and vegetables is weak and inconsistent, as is the relationship with vitamin A and carotenoids, such as beta-carotene. There are some interesting leads. Lycopene, the carotenoid found in tomatoes, has been reported to be protective; alpha-tocopherol supplementation has shown a protective effect in one intervention study; and vitamin D has been shown to be protective in a prospective study. Interest is also growing in phytoestrogens and the extent to which dietary manipulation with these and other phytochemicals might influence prostate cancer by modifying male sex hormone levels or actions. There is limited evidence of associations with obesity. It is not known whether these are related to a particular dietary pattern or to possible physiological effects on the male's hormonal milieu. Associations with lean body mass are likely to be related to the action of androgens during growth and development. Dietary and nutritional effects on prostate cancer do not appear to be strong, but they may be subtle and attenuated by measurement error. To explore these aspects further will require large prospective studies that include improved (repeated) dietary measurements and also blood sampling, so that genetic polymorphisms can be adequately investigated. Such studies are underway.

Prostate cancer and smoking: a review of case-control and cohort studies

BACKGROUND

The purpose of this study was to undertake a systematic analysis of the relation between smoking and prostate cancer.

METHODS

All published case-control and cohort studies including relevant data on this topic were collected. The magnitude of potential sources of divergent results among case-control studies was estimated comparing current, former, and ever to never smokers, stratified by type of controls (hospital vs. population) and by race. Cohort studies were discussed individually.

RESULTS

Neither a clinically nor a statistically significant association between smoking and prostate cancer seems likely, but it cannot be ruled out entirely. The association between other purported risk factors and prostate cancer is not likely to be confounded by the incomplete measurement and control for smoking habits because smoking and prostate cancer are not related.

CONCLUSIONS

For a valid assessment of other risk factors in prostate cancer patients the collection of complete smoking information is therefore less critical than in patients with other diseases. For a definitive assessment of the effect of smoking on prostate cancer incidence and mortality however, future studies need to focus on the collection of information on lifetime smoking habits, including tar exposure.

Nutritional factors and prostate cancer: a case-control study of French Canadians in Montreal, Canada

The relationship between the risk of prostate cancer and dietary intake of energy, fat, vitamin A, and other nutrients was investigated in a case-control study conducted in Montreal (Quebec), Canada. French Canadians aged 35 to 84 years with a recent, histologically confirmed diagnosis of adenocarcinoma of the prostate were identified through the admission offices of five major francophone teaching-hospitals in Montreal from 1989 to 1993. Population-based controls matched for age (+/- five years), language, and place of residence were selected by a modified random-digit dialing method. The study included 232 cases and 231 controls. Information on dietary intake was collected by means of a quantitative dietary history. No association was evident between energy intake and the risk of prostate cancer. In contrast, there was some evidence of an inverse association with intake of total fat, animal fat, monounsaturated fat, and particularly saturated fat (odds ratio = 0.69, 95 percent confidence interval = 0.40-1.18, P = 0.05), while a nonsignificant positive association was found with polyunsaturated fat. In addition, high intake of retinol and vegetable protein (highest cf lowest quartile) was associated with reduced risk, but was not statistically significant. No associations were established between intake of other nutrients and risk. These patterns persisted after adjustment for a number of potential confounding factors.

How is individual risk for prostate cancer assessed?

A man's risk of developing prostate cancer is influenced by both genetic and nongenetic factors. Genetic factors are particularly important at younger ages, and the attributable risk of strong genetic factors could be as high as 43% among men less than 55 years of age; however, only about 9% of all cases may be directly attributable to a family history of prostate cancer. Race appears to be an important determinant of risk; African-American men are at high risk, whereas men of oriental ancestry are at lower risk. The bases of these racial differences remain obscure but may be related to hormonal differences. Modifiable risk factors are most important from a public health perspective. Diet or closely related factors appear to hold the most promise for prevention, although the precise factors are unknown. The strongest evidence indicates that some component of animal fat intake appears to act as a promoter of prostate cancer. Other dietary factors, including vitamin D, vitamin E, and beta-carotene and lycopene, may confer protection, but these require more study. Many but not all studies that have examined long-term effects of vasectomy suggest that this procedure may increase risk of prostate cancer, but whether this association is causal is not established. Occupational factors, smoking, and physical activity level do not appear to be major determinants of prostate cancer risk.

Dietary factors and risk of prostate cancer: a case-control study in Ontario, Canada

The relationship between risk of prostate cancer and dietary intake of energy, fat, vitamin A, and other nutrients was investigated in a case-control study conducted in Ontario, Canada. Cases were men with a recent, histologically confirmed diagnosis of adenocarcinoma of the prostate notified to the Ontario Cancer Registry between April 1990 and April 1992. Controls were selected randomly from assessment lists maintained by the Ontario Ministry of Revenue, and were frequency-matched to the cases on age. The study included 207 cases (51.4 percent of those eligible) and 207 controls (39.4 percent of those eligible), and information on dietary intake was collected from them by means of a quantitative diet history. There was a positive association between energy intake and risk of prostate cancer, such that men at the uppermost quartile level of energy intake had a 75 percent increase in risk. In contrast, there was no clear association between the non-energy effects of total fat and monounsaturated fat intake and prostate cancer risk. There was some evidence for an inverse association with saturated fat intake, although the dose-response pattern was irregular. There was a weak (statistically nonsignificant) positive association between polyunsaturated fat intake and risk of prostate cancer. Relatively high levels of retinol intake were associated with reduced risk, but there was essentially no association between dietary beta-carotene intake and risk. There was no alteration in risk in association with dietary fiber, cholesterol, and vitamins C and E. Although these patterns were evident both overall and within age-strata, and persisted after adjustment for a number of potential confounding factors, they could reflect (in particular) the effect of nonrespondent bias.

Chemoprevention of prostate cancer

Primary prevention of prostate cancer is a relatively new concept. Through large-scale studies it is possible that we may be able to define better the risk for prostate cancer and identify those who would benefit from an intervention to lower their risk of disease. As risk for prostate cancer is better defined, a number of interventions may eventually be tested. Several interventions are sufficiently mature that they can be implemented in large-scale trials. Diet modification is an intervention that is ready for evaluation. It may also have additional benefits by decreasing mortality from other malignancies and cardiac disease. 5 alpha-reductase inhibitors are also ready for testing. The National Cancer Institute and its clinical cooperative groups have begun a large trial to assess finasteride in the prevention of prostate cancer.

Fruit, vegetables, and cancer prevention: a review of the epidemiological evidence

Approximately 200 studies that examined the relationship between fruit and vegetable intake and cancers of the lung, colon, breast, cervix, esophagus, oral cavity, stomach, bladder, pancreas, and ovary are reviewed. A statistically significant protective effect of fruit and vegetable consumption was found in 128 of 156 dietary studies in which results were expressed in terms of relative risk. For most cancer sites, persons with low fruit and vegetable intake (at least the lower one-fourth of the population) experience about twice the risk of cancer compared with those with high intake, even after control for potentially confounding factors. For lung cancer, significant protection was found in 24 of 25 studies after control for smoking in most instances. Fruits, in particular, were significantly protective in cancers of the esophagus, oral cavity, and larynx, for which 28 of 29 studies were significant. Strong evidence of a protective effect of fruit and vegetable consumption was seen in cancers of the pancreas and stomach (26 of 30 studies), as well as in colorectal and bladder cancers (23 of 38 studies). For cancers of the cervix, ovary, and endometrium, a significant protective effect was shown in 11 of 13 studies, and for breast cancer a protective effect was found to be strong and consistent in a meta analysis. It would appear that major public health benefits could be achieved by substantially increasing consumption of these foods.

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

The relationship between intake of various indicator foods and beverages and risk of prostatic cancer was assessed in 271 cases of prostatic cancer and 685 hospital controls recruited in two areas of northern Italy, the province of Pordenone and the greater Milan area. Increased risks were found for more frequent intake of meat [odds ratio (OR) in the highest vs. lowest consumption tertile = 1.4, 95% confidence interval (CI) 1.0-2.0], milk (OR = 1.6, 95% CI 1.1-2.4), fresh fruit (OR = 1.4, 95% CI 1.0-2.1), and vegetables (OR = 1.4, 95% CI 0.9-2.2). After allowance for the reciprocal confounding effect of various dietary habits, only frequent intake of milk seemed to be a significant independent indicator of prostatic cancer risk. There was also a clue that the unfavorable influence of frequent intake of a few food items (i.e. meat, fish, liver, ham and salami, milk and butter, and retinol) may be greater or restricted to older individuals (i.e., > or = 70 yrs of age). In conclusion, the present study confirms the presence of a moderate adverse effect of high intake of foods of animal origin, chiefly milk, while it suggests that a diet rich in fresh fruit and vegetables does not convey a protection.

Diet, nutritional status, and cancer risk in American blacks

About 35% (10-70%) of all cancers may be associated with nutritional causes (1). However, while natural or added substances in foods may be carcinogenic, nutritional deficiencies or excesses may promote carcinogenesis. We compared data from blacks and whites using dietary and nutritional status surveys in the United States to determine whether the poorer dietary patterns and nutritional status of American blacks may be associated with their higher incidence and mortality from certain cancers (compared with whites). Our review indicates that blacks eat more nitrate and animal foods and not enough fiber in relation to protein, fat, and carbohydrate. Blacks also have poorer nutritional status with respect to getting enough thiamine, riboflavin, vitamins A and C, and iron, to being obese (females), and to being underweight (males). This is in agreement with hypotheses regarding the interactions between diet and cancer (associations found in whites) and dose-response relationships reported for some cancers for which blacks have a higher incidence and mortality than whites. More large-scale prospective case-control and cohort studies are needed in both blacks and whites to elucidate the contribution of specific dietary and nutritional factors to the risk of specific cancers in these population groups. However, such studies must be preceded by methodological research to obtain more valid measures of dietary and nutritional status.

Cooking methods, carcinogens, and diet-cancer studies

A neglect of natural, preservative, and cooking-induced carcinogens or mutagens in food, along with a neglect of dietary patterns during the first portion of a person's lifetime, may be responsible for the many conflicting epidemiological reports dealing with dietary factors and cancer. From animal and occupational studies, we know that the two most important factors in the study of cancer are the dose of carcinogen and allowance for a long latent period. Most of the recent nutrition and cancer studies have ignored both factors. Some bile acids or other endogenous factors may be influenced by diet and may act as cancer-promoting agents, but promoting agents cannot be studied in the absence of knowledge about, or control of, the cancer-initiating events with which they must interact.