Intake of specific carotenoids and flavonoids and the risk of lung cancer in women in Barcelona, Spain

Phytochemicals in Cancer Treatment and Cancer Prevention-Review on Epidemiological Data and Clinical Trials

Phytochemicals are a non-nutritive substances that are present in plants and contribute significantly to their flavor and color. These biologically active compounds are classified into five major groups, namely phenolics, carotenoids, organosulfur compounds, nitrogen-containing compounds, and alkaloids, and are known for their potential health benefits in the prevention of various diseases, including cancer. The purpose of this review article is to explore the potential therapeutic benefits of the dietary phytochemicals, such as flavonoids, phenolic acids, phytosterols, carotenoids, and stilbenes, in cancer treatment and prevention based on the epidemiological studies and clinical trials. Although the majority of epidemiological studies report a significant advantage of the heightened phytochemical consumption and increased serum levels of these compounds, linking increased exposure with a lower cancer risk across most cancer types, these effects could not be replicated in the most available clinical trials. In fact, many of these trials were withdrawn early due to a lack of evidence and/or risk of harm. Despite the strong anticancer effect of phytochemicals, as well as their proven efficacy in multiple epidemiological studies, there is still a great need for human studies and clinical trials, with great caution regarding the safety measures. This review article provides an overview of the epidemiological and clinical evidence supporting the potential chemopreventive and anticancer properties of phytochemicals, with a focus on the need for further research in this area.

Higher Fruits and Vegetables Consumption Is not Associated with Risk of Breast Cancer in Iranian Women

We aimed to investigate the association of fruits and vegetables (FVs) and their all subgroups intakes with breast cancer (BC) risk in Iranian women.

The present case-control study conducted on 150 age-matched women with newly diagnosed BC and apparently healthy controls. Anthropometric measures were collected and eventually, the mean intakes of total FVs and each subgroup were obtained from a validated 147-item food frequency questionnaire. Multivariate regression analysis was used to estimate odds ratios (OR) with 95% confidence intervals (CI).

Our findings revealed that the intake of only dark yellow vegetable was significantly higher in BC patients (P = 0.03) after controlling for covariates. OR of BC across tertiles of FVs intake, showed that there was not any statistical association of total FVs (OR: 1.83, CI: 0.54-6.24, P-trend = 0.3) and their subgroups intakes with BC risk. Except for berry fruits intake which was adversely associated with BC risk (OR: 0.36, CI: 0.09-1.37, P-trend = 0.02).

Our findings did not support the hypothesis that higher total FVs and their subgroups intakes reduce BC risk and suggested that only higher berry fruits intake may have an association with lower BC risk.

Phytoestrogens for Cancer Prevention and Treatment

Phytoestrogens are a large group of natural compounds found in more than 300 plants. They have a close structural similarity to estrogens, which allow them to bind to both estrogen receptors (ER), ERα and ERβ, presenting a weak estrogenic activity. Phytoestrogens have been described as antioxidant, anti-inflammatory, anti-thrombotic, anti-allergic, and anti-tumoral agents. Their role in cancer prevention has been well documented, although their impact on treatment efficiency is controversial. Several reports suggest that phytoestrogens may interfere with the effect of anti-cancer drugs through the regulation of oxidative stress and other mechanisms. Furthermore, some phytoestrogens could exert a protective effect on healthy cells, thus reducing the secondary effects of cancer treatment. In this review, we have studied the recent research in this area to find evidence for the role of phytoestrogens in cancer prevention and therapy efficacy.

Improving Flavonoid Metabolism in Blackberry Leaves and Plant Fitness by Using the Bioeffector Pseudomonas fluorescens N 21.4 and Its Metabolic Elicitors: A Biotechnological Approach for a More Sustainable Crop

Beneficial rhizobacterium Pseudomonas fluorescens N 21.4 and its metabolic elicitors inoculated to cultivars of blackberry (Rubus spp. Var. Loch Ness) reinforced the plants' immune system and improved their fitness by increasing photosynthesis, decreasing oxidative stress, and activating pathogenesis-related proteins. They also triggered the leaves' flavonoid metabolism, enhancing the accumulation of beneficial phenolic compounds such as kaempferols and quercetin derivatives. The elicitation of leaf secondary metabolism allows one to take advantage of the blackberry leaves (a current crop waste), following the premises of the circular economy, to isolate and obtain high added value compounds. The results of this work suggest the use of N 21.4 and/or its metabolic elicitors as plant inoculants as an effective and economically and environmentally friendly agronomic alternative practice in the exploitation of blackberry crops to obtain plants with a better immune system and to revalorize the leaf pruning as a potential source of polyphenols.

Identification of Drug Candidates to Suppress Cigarette Smoke-induced Inflammation via Connectivity Map Analyses

Cigarette smoking is the main risk factor for chronic obstructive pulmonary disease, and to date, existing pharmacologic interventions have been ineffective at controlling inflammatory processes associated with the disease. To address this issue, we used the Connectivity Map (cMap) database to identify drug candidates with the potential to attenuate cigarette smoke-induced inflammation. We queried cMap using three independent in-house cohorts of healthy nonsmokers and smokers. Potential drug candidates were validated against four publicly available human datasets, as well as six independent datasets from cigarette smoke-exposed mice. Overall, these analyses yielded two potential drug candidates: kaempferol and bethanechol. Subsequently, the efficacy of each drug was validated in vivo in a model of cigarette smoke-induced inflammation. BALB/c mice were exposed to room air or cigarette smoke and treated with each of the two candidate drugs either prophylactically or therapeutically. We found that kaempferol, but not bethanechol, was able to reduce cigarette smoke-induced neutrophilia, both when administered prophylactically and when administered therapeutically. Mechanistically, kaempferol decreased expression of IL-1α and CXCL5 concentrations in the lung. Our data suggest that cMap analyses may serve as a useful tool to identify novel drug candidates against cigarette smoke-induced inflammation.

Nutritional Relevance of Flavonoids in Disease Prevention

Flavonoids are not essential nutrients in that their absence from the diet does not produce deficiency conditions in animals and man. However, many have important similarities to pharmacological agents used in the treatment of disease. Their role as dietary components in disease prevention is less clear. Many potentially anti-carcinogenic and anti-atherogenic effects observed in cell cultures will not be of nutritional relevance unless flavonoids gain access to appropriate cellular sites. The bioavailability of flavonoids will depend on numerous factors including molecular structure, the amount consumed, the food matrix, degree of bioconversion in the gut and tissues, the nutrient status of the host and genetic factors. Moreover, extensive and rapid intestinal and hepatic metabolism of flavonoids suggests that the body may treat them as xenobiotic and potentially toxic compounds requiring rapid elimination. Consequently, in addition to potential health benefits, possible adverse effects of flavonoids in the diet also need to be considered when assessing their roles in the prevention of degenerative diseases.

Estimation of daily intake of flavonoids and major food sources in middle-aged Australian men and women

Flavonoid consumption has reported health benefits such as reducing cardiovascular disease risk factors, improving endothelial function, and delaying age-related cognitive decline. However, there are little dietary intake data for Australians, which limit our ability to make dietary recommendations to increase intakes to a level where health benefits are seen. The aim of this cross-sectional study was to determine the intake of flavonoids, flavonoid classes, and flavonoid subclasses of 1183 Australians aged 39 to 65 years using a validated 215-item food frequency questionnaire. Based on limited global flavonoid intake data, flavanols are the major dietary flavonoid and are found predominantly in tea and cocoa. As Australians are large tea drinkers, we anticipated that flavanols would be the major flavonoid in the Australian diet. The flavonoid content of foods was determined using a combination of the United States Department of Agriculture Databases and the Phenol-Explorer Database. One-way analysis of variance was undertaken to examine differences between flavonoid intake between men and women. Total flavonoid intake was 626 ± 579 mg/d. Men and women consumed 566 ± 559 mg and 660 ± 588 mg of total flavonoids per day, respectively. Thearubigin accounted for 58% of the flavonoid intake. Women consumed more total flavonoids, thearubigins (both P < .01), anthocyanidins (P < .0001), flavan-3-ols, flavones, and flavonols (all P < .05) than men, whereas men consumed more flavanones than women (P = .01). There was no difference between sexes for the consumption of isoflavones. The data indicated that flavan-3-ols, predominantly thearubigin from tea, were the main flavonoid consumed by Australians. This information contributes to population flavonoid intakes, which should be considered when exploring flavonoid and health relationships.

Intake of Individual Flavonoids and Risk of Carcinogenesis: Overview of Epidemiological Evidence

Several epidemiological findings have demonstrated that specific flavonoids can be responsible for reduction of the risk of certain cancer types. However, these results are still rather limited, inconclusive and controversial. Therefore, in this comprehensive review article the findings reported to date about the associations between dietary intake of individual flavonoid compounds and cancer incidence are compiled and analyzed. Also, the possible reasons for inconsistencies are brought forth and discussed. As diet is a potentially modifiable factor in our behavioral choices, further large-scale prospective studies with longer follow-up times, different populations, various doses and exposure timing as well as diverse well-controlled confounders are highly needed to confirm or disprove the current epidemiological knowledge about the role of flavonoids on cancer risk. Regarding the promising data to date, more research on bioavailability, metabolism and biological action mechanisms of these plant secondary metabolites is also encouraged.

Inhibition of transmembrane member 16A calcium-activated chloride channels by natural flavonoids contributes to flavonoid anticancer effects

BACKGROUND AND PURPOSE

Natural flavonoids are ubiquitous in dietary plants and vegetables and have been proposed to have antiviral, antioxidant, cardiovascular protective and anticancer effects. Transmembrane member 16A (TMEM16A)-encoded Ca²⁺ -activated Cl^- channels play a variety of physiological roles in many organs and tissues. Overexpression of TMEM16A is also believed to be associated with cancer progression. Therefore, inhibition of TMEM16A current may be a potential target for cancer therapy. In this study, we screened a broad spectrum of flavonoids for their inhibitory activities on TMEM16A currents.

EXPERIMENTAL APPROACH

A whole-cell patch technique was used to record the currents. The BrdU assay and transwell technique were used to investigate cell proliferation and migration.

KEY RESULTS

At a concentration of 100 μM, 10 of 20 compounds caused significant (>50%) inhibition of TMEM16A currents. The four most potent compounds - luteolin, galangin, quercetin and fisetin - had IC₅₀ values ranging from 4.5 to 15 μM). To examine the physiological relevance of these findings, we also studied the effects of these flavonoids on endogenous TMEM16A currents in addition to cell proliferation and migration in LA795 cancer cells. Among the flavonoids tested, we detected a highly significant correlation between TMEM16A current inhibition and cell proliferation or reduction of migration.

CONCLUSIONS AND IMPLICATIONS

This study demonstrates that flavonoids inhibit TMEM16A currents and suggests that flavonoids could have anticancer effects via this mechanism.

EBV reactivation as a target of luteolin to repress NPC tumorigenesis

Nasopharyngeal carcinoma (NPC) is a malignancy derived from the epithelial cells of the nasopharynx. Although a combination of radiotherapy with chemotherapy is effective for therapy, relapse and metastasis after remission remain major causes of mortality. Epstein-Barr virus (EBV) is believed to be one of causes of NPC development. We demonstrated previously that EBV reactivation is important for the carcinogenesis of NPC. We sought, therefore, to determine whether EBV reactivation can be a target for retardation of relapse of NPC. After screening, we found luteolin is able to inhibit EBV reactivation. It inhibited EBV lytic protein expression and repressed the promoter activities of two major immediate-early genes, Zta and Rta. Furthermore, luteolin was shown to reduce genomic instability induced by recurrent EBV reactivation in NPC cells. EBV reactivation-induced NPC cell proliferation and migration, as well as matrigel invasiveness, were also repressed by luteolin treatment. Tumorigenicity in mice, induced by EBV reactivation, was decreased profoundly following luteolin administration. Together, these results suggest that inhibition of EBV reactivation is a novel approach to prevent the relapse of NPC.

Kaempferol - A dietary anticancer molecule with multiple mechanisms of action: Recent trends and advancements

The consumption of diet-based naturally bioactive metabolites is preferred to synthetic material in order to avert health-associated disorders. Among the plant-derived polyphenols, kaempferol (KMF) is considered as a valuable functional food ingredient with a broad range of therapeutic applications such as anti-cancer, antioxidant and anti-inflammatory uses. KMF acts on a range of intracellular as well as extracellular targets involved in the cell signaling pathways that in turn are known to regulate the hallmarks of cancer growth progressions like apoptosis, cell cycle, invasion or metastasis, angiogenesis and inflammation. Importantly, the understanding of mechanisms of action of KMF-mediated therapeutic effects may help the scientific community to design novel strategies for the treatment of dreadful diseases. The current review summarizes the various types of molecular targets of KMF in cancer cells as well as other health-associated disorders. In addition, this review also highlights the absorption, metabolism and epidemiological findings.

Can the Consumption of Tomatoes or Lycopene Reduce Cancer Risk?

Lycopene, a natural antioxidant found predominantly in to mato products, is attracting attention as a cancer prevention agent. Serum and dietary lycopene levels have been found to be inversely related to the incidence of several types of cancer, including prostate cancer. Although the antioxidant properties of lycopene are thought to be primarily responsible for its apparent beneficial effects, other mechanisms may also be involved. We outline the possible mechanisms of action of lycopene and review the current findings of in vitroand in vivostudies in cancer prevention and to some extent treatment. We examine the epidemiologic evidence regarding consumption of tomato and tomato products with the risk of cancer at various sites. Data suggest lycopene may account for or contribute to chemoprevention, but this hypothesis requires further study. Numerous other potentially beneficial compounds are present in tomatoes and complex interactions among multiple components may contribute to the anticancer properties of tomatoes.

Phytochemicals Mediate the Expression and Activity of OCTN2 as Activators of the PPARγ/RXRα Pathway

Many phytochemicals exert activities as agonists of peroxisome proliferator-activated receptor gamma (PPARγ). This study aims to investigate whether phytochemicals are agonists of the PPARγ/RXRα pathway and modulate the target gene OCTN2. In this study, a luciferase reporter gene system was used to screen novel OCTN2 activators from 39 phytochemicals. Kaempferol, curcumin, and puerarin were found to show the significant PPRE-mediated luciferase activities (>150%) at 20 μM and showed a dose-dependent manner. Phytochemicals also elevated the mRNA and protein expression of OCTN2 in a dose-dependent fashion in colorectal cancer SW480 cells. These induction effects were gradually inhibited by PPARγ antagonist GW9662 in the luciferase reporter gene system and in SW480 cells. Moreover, the results of cell viability assay imply that three phytochemicals probably induce OCTN2 expression leading to the enhanced uptake of its substrate, oxaliplatin, thereby making cells more sensitive to oxaliplatin. The molecular docking study showed the possible binding sites of phytochemicals in PPARγ protein, and all of the docked phytochemicals fitted the same active pocket in PPARγ as troglitazone. All three phytochemicals exhibited hydrogen bonds between their polar moieties and the amino acid residues. Thus, we identified three phytochemicals as PPARγ ligands, which potentiated the expression and activity of OCTN2.

Induction of cellular and molecular immunomodulatory pathways by vitamin A and flavonoids

INTRODUCTION

A detailed study of reports on the immunomodulatory properties of vitamin A and select flavonoids may pave the way for using these natural compounds or compounds with similar structures in novel drug and vaccine designs against infectious and autoimmune diseases and cancers.

AREAS COVERED

Intracellular transduction pathways, cellular differentiation and functional immunomodulatory responses have been reviewed. The reported studies encompass in vitro, in vivo preclinical and clinical studies that address the role of vitamin A and select flavonoids in induction of innate and adaptive B- and T-cell responses, including TH1, TH2 and regulatory T cells (Treg).

EXPERT OPINION

While the immunomodulatory role of vitamin A, and related compounds, is well-established in many preclinical studies, its role in humans has begun to gain wider acceptance. In contrast, the role of flavonoids is mostly controversial in clinical trials, due to the diversity of the various classes of these compounds, and possibly due to the purity and the selected doses of the compounds. However, current preclinical and clinical studies warrant further detailed studies of these promising immunomodulatory compounds.

Recent advances in pancreatic cancer: biology, treatment, and prevention

Pancreatic cancer (PC) is the fourth leading cause of cancer-related death in United States. Efforts have been made towards the development of the viable solution for its treatment with constrained accomplishment because of its complex biology. It is well established that pancreatic cancer stem cells (CSCs), albeit present in a little count, contribute incredibly to PC initiation, progression, and metastasis. Customary chemo and radiotherapeutic alternatives, however, expands general survival, the related side effects are the significant concern. Amid the most recent decade, our insight about molecular and cellular pathways involved in PC and role of CSCs in its progression has increased enormously. Presently the focus is to target CSCs. The herbal products have gained much consideration recently as they, usually, sensitize CSCs to chemotherapy and target molecular signaling involved in various tumors including PC. Some planned studies have indicated promising results proposing that examinations in this course have a lot to offer for the treatment of PC. Although preclinical studies uncovered the importance of herbal products in attenuating pancreatic carcinoma, limited studies have been conducted to evaluate their role in clinics. The present review provides a new insight to recent advances in pancreatic cancer biology, treatment and current status of herbal products in its anticipation.

Flavonoid intake and all-cause mortality

BACKGROUND

Flavonoids are bioactive compounds found in foods such as tea, chocolate, red wine, fruit, and vegetables. Higher intakes of specific flavonoids and flavonoid-rich foods have been linked to reduced mortality from specific vascular diseases and cancers. However, the importance of flavonoids in preventing all-cause mortality remains uncertain.

OBJECTIVE

The objective was to explore the association between flavonoid intake and risk of 5-y mortality from all causes by using 2 comprehensive food composition databases to assess flavonoid intake.

DESIGN

The study population included 1063 randomly selected women aged >75 y. All-cause, cancer, and cardiovascular mortalities were assessed over 5 y of follow-up through the Western Australia Data Linkage System. Two estimates of flavonoid intake (total flavonoidUSDA and total flavonoidPE) were determined by using food composition data from the USDA and the Phenol-Explorer (PE) databases, respectively.

RESULTS

During the 5-y follow-up period, 129 (12%) deaths were documented. Participants with high total flavonoid intake were at lower risk [multivariate-adjusted HR (95% CI)] of 5-y all-cause mortality than those with low total flavonoid consumption [total flavonoidUSDA: 0.37 (0.22, 0.58); total flavonoidPE: 0.36 (0.22, 0.60)]. Similar beneficial relations were observed for both cardiovascular disease mortality [total flavonoidUSDA: 0.34 (0.17, 0.69); flavonoidPE: 0.32 (0.16, 0.61)] and cancer mortality [total flavonoidUSDA: 0.25 (0.10, 0.62); flavonoidPE: 0.26 (0.11, 0.62)].

CONCLUSIONS

Using the most comprehensive flavonoid databases, we provide evidence that high consumption of flavonoids is associated with reduced risk of mortality in older women. The benefits of flavonoids may extend to the etiology of cancer and cardiovascular disease.

An Evidence-Based Systematic Review of Lutein by the Natural Standard Research Collaboration

An evidence-based systematic review of lutein by the Natural Standard Research Collaboration consolidates the safety and efficacy data available in the scientific literature using a validated, reproducible grading rationale. This article includes written and statistical analysis of clinical trials, plus a compilation of expert opinion, folkloric precedent, history, pharmacology, kinetics/dynamics, interactions, adverse effects, toxicology, and dosing.

Dietary flavonoid intake and smoking-related cancer risk: a meta-analysis

Purpose

To systematically investigate the effects of dietary flavonoids and flavonoid subclasses on the risk of smoking-related cancer in observational studies.

Methods

Summary estimates and corresponding standard errors were calculated using the multivariate-adjusted odds ratio (OR) or relative risk (RR) and 95% CI of selected studies and weighted by the inverse variance.

Results

A total of 35 studies, including 19 case-controls (9,525 cases and 15,835 controls) and 15 cohort studies (988,082 subjects and 8,161 cases), were retrieved for the meta-analysis. Total dietary flavonoids and most of the flavonoid subclasses were inversely associated with smoking-related cancer risk (OR: 0.82, 95% CI: 0.72-0.93). In subgroup analyses by cancer site, significant associations were observed in aerodigestive tract and lung cancers. Total dietary flavonoid intake was significantly associated with aerodigestive tract cancer risk (OR: 0.67, 95% CI: 0.54-0.83) marginally associated with lung cancer risk (OR: 0.84, 95% CI: 0.71-1.00). Subgroup analyses by smoking status showed significantly different results. The intake of total flavonoids, flavonols, flavones, and flavanones, as well as the flavonols quercetin and kaempferol was significantly associated with decreased risk of smoking-related cancer in smokers, whereas no association was observed in non-smokers, except for flavanones. In meta-analysis for the effect of subclasses of dietary flavonoids by cancer type, aerodigestive tract cancer was inversely associated with most flavonoid subclasses.

Conclusion

The protective effects of flavonoids on smoking-related cancer risk varied across studies, but the overall results indicated that intake of dietary flavonoids, especially flavonols, was inversely associated with smoking-related cancer risk. The protective effects of flavonoids on smoking-related cancer risk were more prominent in smokers.

Signal transduction and molecular targets of selected flavonoids

SIGNIFICANCE

Diet exerts a major influence on the risk for developing cancer and heart disease. Food factors such as flavonoids are alleged to protect cells from premature aging and disease by shielding DNA, proteins, and lipids from oxidative damage.

RECENT ADVANCES

Our work has focused on clarifying the effects of dietary components on cancer cell proliferation and tumor growth, discovering mechanisms to explain the effects, and identifying the specific molecular targets of these compounds. Our strategy for identifying specific molecular targets of phytochemicals involves the use of supercomputer technology combined with protein crystallography, molecular biology, and experimental laboratory verification.

CRITICAL ISSUES

One of the greatest challenges for scientists is to reduce the accumulation of distortion and half truths reported in the popular media regarding the health benefits of certain foods or food supplements. The use of these is not new, but interest has increased dramatically because of perceived health benefits that are presumably acquired without unpleasant side effects. Flavonoids are touted to exert many beneficial effects in vitro. However, whether they can produce these effects in vivo is disputed.

FUTURE DIRECTIONS

The World Health Organization indicates that one third of all cancer deaths are preventable and that diet is closely linked to prevention. Based on this idea and epidemiological findings, attention has centered on dietary phytochemicals as an effective intervention in cancer development. However, an unequivocal link between diet and cancer has not been established. Thus, identifying cancer preventive dietary agents with specific molecular targets is essential to move forward toward successful cancer prevention.

Citrus fruit intake and breast cancer risk: a quantitative systematic review

PURPOSE

We investigated the association between dietary intake of citrus fruits and breast cancer risk.

METHODS

The PubMed and EMBASE were searched for relevant articles on diet and breast cancer up to January 2012. All of the epidemiological studies that assessed dietary intake of citrus fruits and presented risk estimates of the association between citrus fruits intake and risk of breast cancer were reviewed. Multivariable-adjusted odds ratios (OR) and associated 95% confidence intervals (CI) for highest versus lowest intake of dietary citrus fruits level were extracted. Overall summary OR was calculated by using a fixed-effect meta-analysis.

RESULTS

Six case-control studies out of five articles were eligible. Overall summary OR showed a 10% reduction in risk of breast cancer associated with high intake of citrus fruits (summary OR, 0.90; 95% CI, 0.85-0.96; p<0.001); results were consistent across the studies (I (2)=0). Visual inspection of the results did not suggest a publication bias.

CONCLUSION

Pooled results from observational studies showed an inverse association between citrus fruits intake and the risk of breast cancer.

The risk of lung cancer related to dietary intake of flavonoids

It has been hypothesized that flavonoids in foods and beverages may reduce cancer risk through antioxidation, inhibition of inflammation, and other antimutagenic and antiproliferative properties. We examined associations between intake of 5 flavonoid subclasses (anthocyanidins, flavan-3-ols, flavones, flavonols, and flavanones) and lung cancer risk in a population-based case-control study in Montreal, Canada (1061 cases and 1425 controls). Flavonoid intake was estimated from a food frequency questionnaire that assessed diet 2 yr prior to diagnosis (cases) or interview (controls). Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using unconditional logistic regression. Overall, total flavonoid intake was not associated with lung cancer risk, the effect being similar regardless of sex and smoking level. However, low flavonoid intake from food, but not from beverages, was associated with an increased risk. The adjusted ORs (95% CIs) comparing the highest vs. the lowest quartiles of intake were 0.63 (0.47-0.85) for total flavonoids, 0.82 (0.61-1.11) for anthocyanidins, 0.67 (0.50-0.90) for flavan-3-ols, 0.68 (0.50-0.93) for flavones, 0.62 (0.45-0.84) for flavonols, and 0.70 (0.53-0.94) for flavanones. An inverse association with total flavone and flavanone intake was observed for squamous cell carcinoma but not adenocarcinoma. In conclusion, low flavonoid intake from food may increase lung cancer risk.

A superoxide-mediated mitogen-activated protein kinase phosphatase-1 degradation and c-Jun NH(2)-terminal kinase activation pathway for luteolin-induced lung cancer cytotoxicity

Although luteolin is identified as a potential cancer therapeutic and preventive agent because of its potent cancer cell-killing activity, the molecular mechanisms by which its cancer cell cytotoxicity is achieved have not been well elucidated. In this report, luteolin-induced cellular signaling was systematically investigated, and a novel pathway for luteolin's lung cancer killing was identified. The results show that induction of superoxide is an early and crucial step for luteolin-induced apoptotic and nonapoptotic death in lung cancer cells. The c-Jun N-terminal kinase (JNK) was potently activated after superoxide accumulation. Suppression of superoxide completely blocked luteolin-induced JNK activation, which was well correlated to alleviation of luteolin's cytotoxicity. Although luteolin slightly stimulated the JNK-activating kinase mitogen-activated protein kinase kinase 7, the latter was not dependent on superoxide. We further found that luteolin triggers a superoxide-dependent rapid degradation of the JNK-inactivating phosphatase mitogen-activated protein kinase phosphatase-1 (MKP-1). Introduction of a degradation-resistant MKP-1 mutant effectively attenuated luteolin-induced JNK activation and cytotoxicity, suggesting that inhibition of the JNK suppressor MKP-1 plays a major role in luteolin-induced lung cancer cell death. Taken together, our results unveil a novel pathway consisting of superoxide, MKP-1, and JNK for luteolin's cytotoxicity in lung cancer cells, and manipulation of this pathway could be a useful approach for applying luteolin for lung cancer prevention and therapy.

Tomato lycopene and lung cancer prevention: from experimental to human studies

Increasing evidence suggests that tomato lycopene may be preventive against the formation and the development of lung cancer. Experimental studies demonstrated that lycopene may inhibit the growth of several cultured lung cancer cells and prevent lung tumorigenesis in animal models through various mechanisms, including a modulation of redox status, cell cycle arrest and/or apoptosis induction, a regulation of growth factor signaling, changes in cell growth-related enzymes, an enhancement of gap junction communication and a prevention of smoke-induced inflammation. In addition, lycopene also inhibited cell invasion, angiogenesis, and metastasis. Several lycopene metabolites have been identified, raising the question as to whether the preventive effects of lycopene on cancer risk is, at least in part, due to its metabolites. Despite these promising reports, it is difficult at the moment to directly relate available experimental data to human pathophysiology. More well controlled clinical intervention trials are needed to further clarify the exact role of lycopene in the prevention of lung cancer cell growth. Such studies should take into consideration subject selection, specific markers of analysis, the levels of carotenoids being tested, metabolism and isomerization of lycopene, interaction with other bioactive food components. This article reviews data on the cancer preventive activities of lycopene, possible mechanisms involved, and the relationship between lycopene consumption and human cancer risk.

Estimation of dietary sources and flavonoid intake in a Spanish adult population (EPIC-Spain)

BACKGROUND

Epidemiologic studies have suggested associations between flavonoid intake and health benefits. Traditional Mediterranean diets consist of a high consumption of plant products rich in flavonoids.

OBJECTIVE

This study estimates dietary flavonoid intake and main food sources in a Mediterranean population (Spanish adults).

DESIGN

The study included 40,683 subjects aged 35 to 64 years from northern and southern regions of Spain who were included in the European Prospective Investigation into Cancer and Nutrition study Spanish cohort. Usual food intake was assessed by personal interviews using a computerized version of a validated diet history method. Expanded US Department of Agriculture databases for the flavonoid, isoflavone, and proanthocyanidin content were used.

RESULTS

The median and mean of total flavonoids were 269.17 and 313.26 mg/day, respectively. The most abundant flavonoid subgroup was proanthocyanidins (60.1%), followed by flavanones (16.9%), flavan-3-ols (10.3%), flavonols (5.9%), anthocyanidins (5.8%), flavones (1.1%), and isoflavones (<0.01%). The main sources of total flavonoid intake were apples (23%), red wine (21%), unspecified fruit (12.8%), and oranges (9.3%).

CONCLUSIONS

These results should be very useful for evaluating the relationships between flavonoid intake and several diseases.

Dietary quercetin, quercetin-gene interaction, metabolic gene expression in lung tissue and lung cancer risk

Epidemiological and mechanistic evidence on the association of quercetin-rich food intake with lung cancer risk and carcinogenesis are inconclusive. We investigated the role of dietary quercetin and the interaction between quercetin and P450 and glutathione S-transferase (GST) polymorphisms on lung cancer risk in 1822 incident lung cancer cases and 1991 frequency-matched controls from the Environment And Genetics in Lung cancer Etiology study. In non-tumor lung tissue from 38 adenocarcinoma patients, we assessed the correlation between quercetin intake and messenger RNA expression of the same P450 and GST metabolic genes. Multivariate odds ratios (ORs) and 95% confidence intervals (CIs) for sex-specific quintiles of intake were calculated using unconditional logistic regression adjusting for putative risk factors. Frequent intake of quercetin-rich foods was inversely associated with lung cancer risk (OR = 0.49; 95% CI: 0.37-0.67; P-trend < 0.001) and did not differ by P450 or GST genotypes, gender or histological subtypes. The association was stronger in subjects who smoked >20 cigarettes per day (OR = 0.35; 95% CI: 0.19-0.66; P-trend = 0.003). Based on a two-sample t-test, we compared gene expression and high versus low consumption of quercetin-rich foods and observed an overall upregulation of GSTM1, GSTM2, GSTT2, and GSTP1 as well as a downregulation of specific P450 genes (P-values < 0.05, adjusted for age and smoking status). In conclusion, we observed an inverse association of quercetin-rich food with lung cancer risk and identified a possible mechanism of quercetin-related changes in the expression of genes involved in the metabolism of tobacco carcinogens in humans. Our findings suggest an interplay between quercetin intake, tobacco smoking, and lung cancer risk. Further research on this relationship is warranted.

Food-frequency questionnaires: a review of their design, validation and utilisation

A review of the literature concerning the design, utilisation and validation of food-frequency questionnaires (FFQ) has been carried out using a semi-systematic approach to obtaining, reviewing and extracting data from articles. Databases were searched from 1980 to 1999. The present review identified 227 validation (from 1980 to September 1999) and 164 utilisation (for 1998 only) studies. A number of design issues have been evaluated through the present review. These include: the need to consider how portion sizes have been described, self-defined giving higher mean correlations; how an FFQ was administered, interviewer-administered giving higher mean correlations for some nutrients; how many items to include on an FFQ, those with the largest number of items having higher correlations. Validation techniques were described. Most validation studies involved comparing an FFQ against another dietary assessment method; only 19 % compared an FFQ to a biomarker. Measurement differences were most commonly assessed by correlation coefficients as opposed to other more appropriate methods. Mean correlation coefficients were highest for Ca and fat, and lowest for vitamin A and vegetables. The utilisation studies showed that FFQ were most commonly used in cross-sectional surveys, with ninety-three of the FFQ being designed to be disease-specific. The present review results were presented to a group of experts and a consensus arrived at concerning the development, validation and use of FFQ. Recommendations derived from the consensus arising from the literature review are presented as an appendix to the present paper.

Luteolin, a flavonoid with potential for cancer prevention and therapy

Luteolin, 3',4',5,7-tetrahydroxyflavone, is a common flavonoid that exists in many types of plants including fruits, vegetables, and medicinal herbs. Plants rich in luteolin have been used in Chinese traditional medicine for treating various diseases such as hypertension, inflammatory disorders, and cancer. Having multiple biological effects such as anti-inflammation, anti-allergy and anticancer, luteolin functions as either an antioxidant or a pro-oxidant biochemically. The biological effects of luteolin could be functionally related to each other. For instance, the anti-inflammatory activity may be linked to its anticancer property. Luteolin's anticancer property is associated with the induction of apoptosis, and inhibition of cell proliferation, metastasis and angiogenesis. Furthermore, luteolin sensitizes cancer cells to therapeutic-induced cytotoxicity through suppressing cell survival pathways such as phosphatidylinositol 3'-kinase (PI3K)/Akt, nuclear factor kappa B (NF-kappaB), and X-linked inhibitor of apoptosis protein (XIAP), and stimulating apoptosis pathways including those that induce the tumor suppressor p53. These observations suggest that luteolin could be an anticancer agent for various cancers. Furthermore, recent epidemiological studies have attributed a cancer prevention property to luteolin. In this review, we summarize the progress of recent research on luteolin, with a particular focus on its anticancer role and molecular mechanisms underlying this property of luteolin.

Long-term use of beta-carotene, retinol, lycopene, and lutein supplements and lung cancer risk: results from the VITamins And Lifestyle (VITAL) study

High-dose beta-carotene supplementation in high-risk persons has been linked to increased lung cancer risk in clinical trials; whether effects are similar in the general population is unclear. The authors examined associations of supplemental beta-carotene, retinol, vitamin A, lutein, and lycopene with lung cancer risk among participants, aged 50-76 years, in the VITamins And Lifestyle (VITAL) cohort Study in Washington State. In 2000-2002, eligible persons (n = 77,126) completed a 24-page baseline questionnaire, including detailed questions about supplement use (duration, frequency, dose) during the previous 10 years from multivitamins and individual supplements/mixtures. Incident lung cancers (n = 521) through December 2005 were identified by linkage to the Surveillance, Epidemiology, and End Results cancer registry. Longer duration of use of individual beta-carotene, retinol, and lutein supplements (but not total 10-year average dose) was associated with statistically significantly elevated risk of total lung cancer and histologic cell types; for example, hazard ratio = 2.02, 95% confidence interval: 1.28, 3.17 for individual supplemental lutein with total lung cancer and hazard ratio = 3.22, 95% confidence interval: 1.29, 8.07 for individual beta-carotene with small-cell lung cancer for >4 years versus no use. There was little evidence for effect modification by gender or smoking status. Long-term use of individual beta-carotene, retinol, and lutein supplements should not be recommended for lung cancer prevention, particularly among smokers.

Dietary intake of selected flavonols, flavones, and flavonoid-rich foods and risk of cancer in middle-aged and older women

BACKGROUND

Flavonoids may protect against cancer development through several biological mechanisms. However, epidemiologic studies on dietary flavonoids and cancer risk have yielded inconsistent results.

OBJECTIVE

We prospectively investigated the association between the intake of selected flavonoids and flavonoid-rich foods and risk of cancers in the Women's Health Study.

DESIGN

A total of 3234 incident cancer cases were identified during 11.5 y of follow-up among 38,408 women aged > or = 45 y. Intake of individual flavonols (quercetin, kaempferol, and myricetin) and flavones (apigenin and luteolin) was assessed from food-frequency questionnaires. Cox regression models were used to estimate the relative risk (RR) of total and site-specific cancer across increasing intakes of total and individual selected flavonoids and flavonoid-rich foods (tea, apple, broccoli, onion, and tofu).

RESULTS

The multivariate RRs of total cancer across increasing quintiles of total quantified flavonoid intake were 1.00, 1.00, 0.93, 0.94, and 0.97 (P for trend = 0.72). For site-specific cancers, the multivariate RRs in the highest quintile of total quantified flavonoid intake compared with the lowest quintile were 1.03 for breast cancer, 1.01 for colorectal cancer, 1.03 for lung cancer, 1.15 for endometrial cancer, and 1.09 for ovarian cancer (all P > 0.05). The associations for the individual flavonoid intakes were similar to those for the total intake. There was also no significant association between intake of flavonoid-rich foods and the incidence of total and site-specific cancers.

CONCLUSION

Our results do not support a major role of 5 common flavonols and flavones or selected flavonoid-rich foods in cancer prevention.

Anti-carcinogenic effects of the flavonoid luteolin

Luteolin is a flavonoid which is part of our daily nutrition in relatively low amounts (less than 1 mg/day). Nevertheless, some epidemiological studies suggest an inverse correlation between luteolin intake and the risk of some cancer types. Luteolin displays specific anti-inflammatory and anti-carcinogenic effects, which can only partly be explained by its anti-oxidant and free radical scavenging capacities. Luteolin can delay or block the development of cancer cells in vitro and in vivo by protection from carcinogenic stimuli, by inhibition of tumor cell proliferation, by induction of cell cycle arrest and by induction of apoptosis via intrinsic and extrinsic signaling pathways. When compared to other flavonoids, luteolin was usually among the most effective ones, inhibiting tumor cell proliferation with IC(50) values between 3 and 50 microM in vitro and in vivo by 5 to 10 mg/kg i.p., intragastric application of 0.1-0.3 mg/kg/d, or as food additive in concentrations of 50 to 200 ppm. Luteolin has been shown to penetrate into human skin, making it also a candidate for the prevention and treatment of skin cancer.

A review of the epidemiological evidence on tea, flavonoids, and lung cancer

Tea and its main bioactive ingredients, the flavonoids, have been associated with human cancer for several decades. In this article, an overview is provided of observational epidemiological studies of lung cancer incidence in relation to intake of green tea, black tea, flavonols/flavones, and catechins. A PubMed search was conducted in September 2007. Articles were selected if they provided risk ratios (relative risk or odds ratio) for lung cancer and were of observational design (cohort, case-control, or case-cohort). Three of 12 studies reported a significantly lower risk of lung cancer with a high intake of flavonoids, whereas 1 study reported a significantly increased risk. After stratification by type of flavonoid, catechin intake was no longer associated with lung cancer risk in 3 of 4 studies available. For tea, 4 of 20 studies reported significantly reduced risks with high intake. Two studies found significantly increased risk ratios, but both were older studies. Findings were similar for green and black tea but became more significant when only methodologically sounder cohort studies were considered. When tea intake and lung cancer were studied among never- or former smokers to eliminate the confounding effect of smoking, 4 of 7 reported associations were significantly protective. In general, the studies on tea, flavonoids, and lung cancer risk indicate a small beneficial association, particularly among never-smokers. More well-designed cohort studies, in particular for catechins, are needed to strengthen the evidence on effects of long-term exposure to physiological doses of dietary flavonoids.

Intake of flavonoids and risk of cancer in Finnish men: The Kuopio Ischaemic Heart Disease Risk Factor Study

Limited amount of evidence suggests that high intake of flavonoids could be associated with decreased risk of lung and colorectal cancer, but more studies are needed. In this prospective cohort study, we assessed the relation between the intakes of 26 flavonoids from 5 subclasses; flavonols, flavones, flavanones, flavan-3-ols and anthocyanidins, and the risk of lung, prostate and colorectal cancer. The study population consisted of 2,590 middle-aged eastern Finnish men of the prospective population-based Kuopio Ischaemic Heart Disease Risk Factor (KIHD) Study. The mean intake of flavonoids was 131.0 +/- 214.7 mg/day. During the mean follow-up time of 16.2 years, 62 lung, 138 prostate, and 55 colorectal cancers occurred. All lung cancer cases occurred among either current smokers (n = 50) or previous smokers (n = 12). After adjustment for age, examination years, body mass index, smoking status, pack-years of smoking, physical activity and intakes of alcohol, total fat, saturated fat, fiber, vitamin C and E, relative risk (RR) for lung cancer was 0.27 (95% CI: 0.11-0.66) for the highest quarter of total flavonoid intake as compared with the lowest quarter. Out of 5 flavonoid subclasses, flavonols and flavan-3-ols were associated with lung cancer, for the highest quarter of intake the RR were 0.29 (95% CI: 0.11-0.78) and 0.24 (95% CI: 0.09-0.64), respectively. No association between flavonoid intake and risk of prostate or colorectal cancer were found. We conclude that high intake of flavonoids is associated with decreased risk of lung cancer in middle-aged Finnish smoking men.

Lycopene in cancer prevention and treatment

Dietary intake of lycopene is inversely associated with the risk of many cancers. Preclinical studies show that lycopene has potent in vitro and in vivo antitumor effects, suggesting potential preventive and therapeutic roles for the compound. However, clinical trials with lycopene have only recently been started, and available clinical data preclude firm conclusions with regard to its use in cancer prevention and treatment. Further mechanistic studies and randomized controlled clinical intervention trials with lycopene involving cancer patients are warranted.

The U.S. Food and Drug Administration's evidence-based review for qualified health claims: tomatoes, lycopene, and cancer

Several studies have reported an inverse association between tomato and/or lycopene intake and the risk of some types of cancer. In 2004, the U.S. Food and Drug Administration (FDA) received two petitions for qualified health claims regarding tomatoes, lycopene, and the risk reduction for some forms of cancer. Health claims that characterize the relationship between a food or food component and a disease or health-related condition require premarket approval by FDA to be included on the labels of conventional foods and dietary supplements. Here we describe FDA's review of the scientific data for tomato and/or lycopene intake with respect to risk reduction for certain forms of cancer. The FDA found no credible evidence to support an association between lycopene intake and a reduced risk of prostate, lung, colorectal, gastric, breast, ovarian, endometrial, or pancreatic cancer. The FDA also found no credible evidence for an association between tomato consumption and a reduced risk of lung, colorectal, breast, cervical, or endometrial cancer. The FDA found very limited evidence to support an association between tomato consumption and reduced risks of prostate, ovarian, gastric, and pancreatic cancers.

Dietary flavonoids and the risk of colorectal cancer

In vitro and in vivo laboratory data point to chemoprotective effects of flavonoids on colorectal cancer. However, there has been limited epidemiologic research on the dietary intake of flavonoids and risk of colorectal cancer. Recent expansions of dietary databases to include flavonoid data now make such studies feasible. Association between the six main classes of flavonoids and the risk of colorectal cancer was examined using data from a national prospective case-control study in Scotland, including 1,456 incident cases and 1,456 population-based controls matched on age, sex, and residence area. Dietary, including flavonoid data, were obtained from a validated, self-administered food frequency questionnaire. Risk of colorectal cancer was estimated using conditional logistic regression models in the whole sample and stratified by sex, smoking status, and cancer site and adjusted for established and putative risk factors. After energy adjustment, reductions in colorectal cancer risk associated with the highest quartiles of intake (versus the lowest quartile) were 27% for flavonols [odds ratio (OR), 0.73; P(trend) = 0.012], 32% for quercetin (OR, 0.68; P(trend) = 0.001), 32% for catechin (OR, 0.68; P(trend) < 0.0005); 26% for epicatechin (OR, 0.74; P(trend) = 0.019), and 22% for procyanidins (OR, 0.78; P(trend) = 0.031). The significant dose-dependent reductions in colorectal cancer risk that were associated with increased consumption of flavonols, quercetin, catechin, and epicatechin remained robust after controlling for overall fruit and vegetable consumption or for other flavonoid intake. The risk reductions were greater among nonsmokers, but no interaction beyond a multiplicative effect was present. Sex-specific or cancer-type differences were not observed. No risk reductions were associated with intake of flavones (P(trend) = 0.64), flavonones (P(trend) = 0.22), and phytoestrogens (P(trend) = 0.26). This was the first of several a priori hypotheses to be tested in this large study and showed strong and linear inverse associations of flavonoids with colorectal cancer risk.

Effects of dietary flavonoids on apoptotic pathways related to cancer chemoprevention

Epidemiological studies have described the beneficial effects of dietary polyphenols (flavonoids) on the reduction of the risk of chronic diseases, including cancer. Moreover, it has been shown that flavonoids, such as quercetin in apples, epigallocatechin-3-gallate in green tea and genistein in soya, induce apoptosis. This programmed cell death plays a critical role in physiological functions, but there is underlying dysregulation of apoptosis in numerous pathological situations such as Parkinson's disease, Alzheimer's disease and cancer. At the molecular level, flavonoids have been reported to modulate a number of key elements in cellular signal transduction pathways linked to the apoptotic process (caspases and bcl-2 genes), but that regulation and induction of apoptosis are unclear. The aim of this review is to provide insights into the molecular basis of the potential chemopreventive activities of representative flavonoids, with emphasis on their ability to control intracellular signaling cascades responsible for regulating apoptosis, a relevant target in cancer-preventive approach.

Divergent effects of quercetin conjugates on angiogenesis

The present study reports the activities of quercetin and its main circulating conjugates in man (quercetin-3'-sulphate (Q3'S) and quercetin-3-glucuronide (Q3G)) on in vivo angiogenesis induced by vascular endothelial growth factor (VEGF) and examines the effects of these molecules on cultured endothelial cells. We found opposing effects of quercetin and its metabolites on angiogenesis. While quercetin and Q3G inhibited VEGF-induced endothelial cell functions and angiogenesis, Q3'S per se promoted endothelial cell proliferation and angiogenesis. The inhibitory effect elicited by Q3G was linked to inhibition of extracellular signal-regulated kinases 1/2 (ERK1/2) phosphorylation elicited by VEGF. The activation of endothelial cells by Q3'S was associated to stimulation of VEGF receptor-2 and to downstream signalling activation (phosphatidylinositol-3 kinase/Akt and nitric oxide synthase pathways), ultimately responsible for ERK1/2 phosphorylation. These data indicate that the effects of circulating quercetin conjugates on angiogenesis are different depending on the nature of the conjugate. Q3G and Q3'S are the two major conjugates in plasma, but their ratio is dependent on several factors, so that inhibition or activation of angiogenesis could be subtly shifted as a result of metabolism in vivo.

Flavonols, flavones, flavanones, and human health: epidemiological evidence

Polyphenolic flavonoids are among a wide variety of phytochemicals present in the human diet. Basic research, animal model, and human studies suggest flavonoid intake may reduce the risk of several age-related chronic diseases. The vast number of flavonoids and mixtures of their subclasses, including flavonols, flavones, and flavanones, and the variety of agricultural practices that affect their concentration in foods have presented a challenge to the development of adequate food composition databases for these compounds. Nonetheless, dietary assessments have been applied to cohort and case-control epidemiological studies, and several reveal an inverse association with risk of some forms of cancer, cardiovascular disease, and other chronic conditions. Those observational studies that have examined these relationships with regard to flavonols, flavones, and flavanones are reviewed. The requirement for caution in interpreting these studies is discussed with regard to the limited information available on the bioavailability and biotransformation of these flavonoids. As the totality of the available evidence on these flavonoids suggests a role in the prevention of cancer and cardiovascular disease, further research is warranted, particularly in controlled clinical trials.

Dietary polyphenols and the prevention of diseases

Polyphenols are the most abundant antioxidants in the diet and are widespread constituents of fruits, vegetables, cereals, dry legumes, chocolate, and beverages, such as tea, coffee, or wine. Experimental studies on animals or cultured human cell lines support a role of polyphenols in the prevention of cardiovascular diseases, cancers, neurodegenerative diseases, diabetes, or osteoporosis. However, it is very difficult to predict from these results the effects of polyphenol intake on disease prevention in humans. One of the reasons is that these studies have often been conducted at doses or concentrations far beyond those documented in humans. The few clinical studies on biomarkers of oxidative stress, cardiovascular disease risk factors, and tumor or bone resorption biomarkers have often led to contradictory results. Epidemiological studies have repeatedly shown an inverse association between the risk of myocardial infarction and the consumption of tea and wine or the intake level of some particular flavonoids, but no clear associations have been found between cancer risk and polyphenol consumption. More human studies are needed to provide clear evidence of their health protective effects and to better evaluate the risks possibly resulting from too high a polyphenol consumption.

Dietary flavonoids and cancer risk: evidence from human population studies

High dietary intake of fruits and vegetables is consistently associated with a reduced risk of common human cancers, including cancers of the lung, breast, prostate, and colon. It is unknown which bioactive compound or compounds in plant foods provide the chemoprotective effects. One class of compounds currently under investigation is flavonoids, a large group of compounds with similar structure, consisting of two phenolic benzene rings linked to a heterocyclic pyran or pyrone. Although there are numerous in vitro and animal model data suggesting that flavonoids influence important cellular and molecular mechanisms related to carcinogenesis, such as cell cycle control and apoptosis, there are limited data from human population studies. This article reviews data from four cohort studies and six case-control studies, which have examined associations of flavonoid intake with cancer risk. There is consistent evidence from these studies that flavonoids, especially quercetin, may reduce the risk of lung cancer. Further research using new dietary databases for food flavonoid content is needed to confirm these findings before specific public health recommendations about flavonoids can be formulated.

Lutein and Zeaxanthin and Their Potential Roles in Disease Prevention

Lutein and zeaxanthin are xanthophyll carotenoids found particularly in dark-green leafy vegetables and in egg yolks. They are widely distributed in tissues and are the principal carotenoids in the eye lens and macular region of the retina. Epidemiologic studies indicating an inverse relationship between xanthophyll intake or status and both cataract and age-related macular degeneration suggest these compounds can play a protective role in the eye. Some observational studies have also shown these xanthophylls may help reduce the risk of certain types of cancer, particularly those of the breast and lung. Emerging studies suggest as well a potential contribution of lutein and zeaxanthin to the prevention of heart disease and stroke. Even as the evidence for a role of lutein and zeaxanthin in disease prevention continues to evolve, particularly from human studies directed to their bioavailability, metabolism, and dose-response relationships with intermediary biomarkers and clinical outcomes, it is worth noting that recommendations to consume foods rich in xanthophylls are consistent with current dietary guidelines.

Nutrition and cancer: a review of the evidence for an anti-cancer diet

It has been estimated that 30–40 percent of all cancers can be prevented by lifestyle and dietary measures alone. Obesity, nutrient sparse foods such as concentrated sugars and refined flour products that contribute to impaired glucose metabolism (which leads to diabetes), low fiber intake, consumption of red meat, and imbalance of omega 3 and omega 6 fats all contribute to excess cancer risk. Intake of flax seed, especially its lignan fraction, and abundant portions of fruits and vegetables will lower cancer risk. Allium and cruciferous vegetables are especially beneficial, with broccoli sprouts being the densest source of sulforophane. Protective elements in a cancer prevention diet include selenium, folic acid, vitamin B-12, vitamin D, chlorophyll, and antioxidants such as the carotenoids (α-carotene, β-carotene, lycopene, lutein, cryptoxanthin). Ascorbic acid has limited benefits orally, but could be very beneficial intravenously. Supplementary use of oral digestive enzymes and probiotics also has merit as anticancer dietary measures. When a diet is compiled according to the guidelines here it is likely that there would be at least a 60–70 percent decrease in breast, colorectal, and prostate cancers, and even a 40–50 percent decrease in lung cancer, along with similar reductions in cancers at other sites. Such a diet would be conducive to preventing cancer and would favor recovery from cancer as well.