Epithelial ovarian cancer and exposure to dietary nitrate and nitrite in the NIH-AARP Diet and Health Study

Spatial distribution, geochemical processes of high-content fluoride and nitrate groundwater, and an associated probabilistic human health risk appraisal in the Republic of Djibouti

In the northern East African Rift System, the Republic of Djibouti relies exclusively on groundwater, with levels of fluoride (up to 14 mg/L) and nitrate (up to 256 mg/L) posing potential health risks. To address this, 362 samples were considered, including 133 shallow groundwater samples, along with new and previously published data dating back to 2012 on deep (88) and thermal (141) groundwater samples. To understand the enrichment mechanisms, dissolved anion and cation constituents, geochemical and thermodynamic tools, and stable isotope ratios, such as δ2H(H2O), δ18O(H2O), δ15N(NO3-), and δ18O(NO3-), were used. In particular, two activity diagrams (Mg2+ vs. Ca2+ and Na+ vs. Ca2+), focused on aqueous and solid fluoride species in an updated thermodynamic dataset of 15 fluoride-bearing minerals, are shown for the first time. The dataset offers new and valuable insights into fluoride geochemistry (classic thermodynamic datasets combined with geochemical codes rely solely on fluorapatite and fluorite F-bearing minerals). Activity diagrams and geochemical modeling indicate that mineral dissolution primarily drives groundwater fluoride enrichment in all water types, whereas the elevated nitrate levels may stem from organic fertilizers like animal manure, as indicated by nitrate isotopes and NO3-/Cl- vs Cl- diagrams. Despite the arid climate and 2H18O enrichment in shallow waters, evaporation seems to play a minor role. Monte Carlo simulations and sensitivity analysis were used to assess the health risks associated with elevated F- and NO3- concentrations. Mapping-related spatial distribution analysis identified regional contamination hotspots using a global Moran's I and GIS tools. One fluoride and three nitrate contamination hotspots were identified at a p-value of 0.05. Groundwater chemistry revealed that 88 % of groundwater being consumed exceeded the permissible levels for fluoride and nitrate, posing potential health risks, particularly for teenagers and children. This study pinpoints specific areas with excessive nitrate and fluoride contamination, highlighting a high non-carcinogenic risk.

Dietary Nitrate Intake Is Associated with Decreased Incidence of Open-Angle Glaucoma: The Rotterdam Study

Previous studies suggest that nitric oxide is involved in the regulation of the intraocular pressure (IOP) and in the pathophysiology of open-angle glaucoma (OAG). However, prospective studies investigating the association between dietary nitrate intake, a source of nitric oxide, and incident (i)OAG risk are limited. We aimed to determine the association between dietary nitrate intake and iOAG, and to evaluate the association between dietary nitrate intake and IOP. From 1991 onwards, participants were followed each five years for iOAG in the Rotterdam Study. A total of 173 participants developed iOAG during follow-up. Cases and controls were matched on age (mean ± standard deviation: 65.7 ± 6.9) and sex (%female: 53.2) in a case:control ratio of 1:5. After adjustment for potential confounders, total dietary nitrate intake was associated with a lower iOAG risk (odds ratio (OR) with corresponding 95% confidence interval (95% CI): 0.95 (0.91-0.98) for each 10 mg/day higher intake). Both nitrate intake from vegetables (OR (95% CI): 0.95 (0.91-0.98) for each 10 mg/day higher intake) and nitrate intake from non-vegetable food sources (OR (95% CI): 0.63 (0.41-0.96) for each 10 mg/day higher intake) were associated with a lower iOAG risk. Dietary nitrate intake was not associated with IOP. In conclusion, dietary nitrate intake was associated with a reduced risk of iOAG. IOP-independent mechanisms may underlie the association with OAG.

Association between Dietary Nitrate, Nitrite Intake, and Site-Specific Cancer Risk: A Systematic Review and Meta-Analysis

BACKGROUND

People consume nitrates, nitrites, nitrosamines, and NOCs compounds primarily through processed food. Many studies have yielded inconclusive results regarding the association between cancer and dietary intakes of nitrates and nitrites. This study aimed to quantify these associations across the reported literature thus far.

METHODS

We performed a systematic review following PRISMA and MOOSE guidelines. A literature search was performed using Web of Science, Embase, PubMed, the Cochrane library, and google scholar up to January 2020. STATA version 12.0 was used to conduct meta-regression and a two-stage meta-analysis.

RESULTS

A total of 41 articles with 13 different cancer sites were used for analysis. Of these 13 cancer types/sites, meta-regression analysis showed that bladder and stomach cancer risk was greater, and that pancreatic cancer risk was lower with increasing nitrite intakes. Kidney and bladder cancer risk were both lower with increasing nitrate intakes. When comparing highest to lowest (reference) categories of intake, meta-analysis of studies showed that high nitrate intake was associated with an increased risk of thyroid cancer (OR = 1.40, 95% CI: 1.02, 1.77). When pooling all intake categories and comparing against the lowest (reference) category, higher nitrite intake was associated with an increased risk of glioma (OR = 1.12, 95% CI: 1.03, 1.22). No other associations between cancer risk and dietary intakes of nitrates or nitrites were observed.

CONCLUSION

This study showed varied associations between site-specific cancer risks and dietary intakes of nitrate and nitrite. Glioma, bladder, and stomach cancer risks were higher and pancreatic cancer risk was lower with higher nitrite intakes, and thyroid cancer risk was higher and kidney cancer risk lower with higher nitrate intakes. These data suggest type- and site-specific effects of cancer risk, including protective effects, from dietary intakes of nitrate and nitrite.

Dietary nitrate and nitrite and human health: a narrative review by intake source

Nitrate and nitrite are plant nutrients that, although ubiquitous in plant foods, are highly controversial substances in human nutrition because they are also used as additives in processed foods and may be found as contaminants in drinking water. The aim for this narrative review is to provide a thorough insight into the current literature on the relationship between dietary nitrate and nitrite and the health risks and benefits by source of intake. The results highlight beneficial effects of nitrate and nitrite consumption from plant origin on cardiovascular disease and, to date, no positive correlation has been reported with cancer. On the contrary, high intake of these compounds from processed animal-based foods is related to an increased risk of gastro-intestinal cancer. Nitrate in drinking water also raises some concern, because it appears to be related to adverse health effects. The up-to-date debate on the role of nitrate and nitrite in human nutrition seems to be justified and more research is required to verify safe consumption.

Association between dietary intake and risk of ovarian cancer: a systematic review and meta-analysis

PURPOSE

It is unclear how dietary intake influences the ovarian cancer. The present paper sets out to systematically review and meta-analyze research on dietary intake to identify cases having high- or low-risk ovarian cancer.

METHODS

Scopus, PubMed, and Wiley Online Libraries were searched up to the date November 24, 2019. Two reviewers were requested to independently extract study characteristics and to assess the bias and applicability risks with reference to the study inclusion criteria. Meta-analyses were performed to specify the relationship between dietary intake and the risk of ovarian cancer identifying 97 cohort studies.

RESULTS

No significant association was found between dietary intake and risk of ovarian cancer. The results of subgroup analyses indicated that green leafy vegetables (RR = 0.91, 95%, 0.85-0.98), allium vegetables (RR = 0.79, 95% CI 0.64-0.96), fiber (RR = 0.89, 95% CI 0.81-0.98), flavonoids (RR = 0.83, 95% CI 0.78-0.89) and green tea (RR = 0.61, 95% CI 0.49-0.76) intake could significantly reduce ovarian cancer risk. Total fat (RR = 1.10, 95% CI 1.02-1.18), saturated fat (RR = 1.11, 95% CI 1.01-1.22), saturated fatty acid (RR = 1.19, 95% CI 1.04-1.36), cholesterol (RR = 1.13, 95% CI 1.04-1.22) and retinol (RR = 1.14, 95% CI 1.00-1.30) intake could significantly increase ovarian cancer risk. In addition, acrylamide, nitrate, water disinfectants and polychlorinated biphenyls were significantly associated with an increased risk of ovarian cancer.

CONCLUSION

These results could support recommendations to green leafy vegetables, allium vegetables, fiber, flavonoids and green tea intake for ovarian cancer prevention.

No. 344-Opportunistic Salpingectomy and Other Methods of Risk Reduction for Ovarian/Fallopian Tube/Peritoneal Cancer in the General Population

OBJECTIVE

This guideline reviews the potential benefits of opportunistic salpingectomy to prevent the development of high grade serous cancers (HGSC) of the ovary/fallopian tube/peritoneum based on current evidence supporting the fallopian tube origin of disease.

INTENDED USERS

Gynaecologists, obstetricians, family doctors, registered nurses, nurse practitioners, residents, and health care providers.

TARGET POPULATION

Adult women (18 and older): OPTIONS: Women considering hysterectomy who wish to retain their ovaries in situ have traditionally also retained their fallopian tubes. In addition, women undergoing permanent surgical sterilization have usually undergone tubal ligation using various methods rather than undergoing surgical removal of the entire fallopian tube.

EVIDENCE

For the sections "Evidence Supporting the Hypothesis That HGSC Originates in the Fallopian Tube" and "Current Literature on the Effects and Safety of Opportunistic Salpingectomy," relevant studies were searched in PubMed, Medline, and the Cochrane Systematic Reviews using the following terms, either alone or in combination, with the search limited to English language materials: "high grade serous cancers ovary," "fallopian tube," "peritoneum," "opportunistic salpingectomy," "epithelial ovarian cancers," "origin," "tubal carcinoma in situ," "BRCA mutation," "prophylactic salpingectomy," "inflammation," "clear cell," and "endometrioid." The initial search was performed in March 2015 with a final literature search in March 2016. Relevant evidence was selected for inclusion in the following order: meta-analyses, systematic reviews, guidelines, randomized controlled trials, prospective cohort studies, observational studies, non-systematic reviews, case series, and reports. The total number of studies identified was 458, and 56 studies were included in this review. For the section "Other Factors Influencing the Risk of Developing "Ovarian" Cancers" a general Medline search was carried out using the terms "ovarian neoplasm" and "prevention." The search included papers published from December 2005 to March 2016. Meta-analyses were preferentially selected except where no such review was found. Additional searches for each subheading were also conducted (e.g., "ovarian neoplasm" and "tubal ligation.") Additional significant articles were identified through cross-referencing the identified reviews. For the search for "ovarian neoplasm" and "prevention," 10 meta-analyses were identified. For the search for "ovarian neoplasm" and "tubal ligation," an additional 4 meta-analyses were identified.

VALIDATION METHODS

The content and recommendations were drafted and agreed on by the principal authors. The Executive and Board of the Society of Gynecologic Oncology of Canada reviewed the content and submitted comments for consideration, and the Board of the SOGC approved the final draft for publication. The quality of evidence was rated using the criteria described in the Grading of Recommendations Assessment, Development and Evaluation methodology framework (Table 1). The interpretation of strong and weak recommendations is described in Table 2. The summary of findings is available on request.

BENEFITS, HARMS, AND/OR COSTS

The addition of opportunistic salpingectomy to a planned hysterectomy or permanent sterilization did not increase rates of hospital readmission (OR 0.91, 95% CI 0.75 to 1.10 and OR 0.8, 95% CI 0.56 to 1.21, respectively) or blood transfusions (OR 0.86, 95% CI 0.67 to 1.10 and OR 0.75, 95% CI 0.32 to 1.73, respectively) but did increase the overall operating time (by 16 minutes and 10 minutes, respectively) in a retrospective review of 43 931 women. The risk of repeat surgery for tubal pathology among women with retained fallopian tubes after hysterectomy was at least doubled (OR 2.13, 95% CI 1.88 to 2.42 in a population-based study of 170 000 women). If general gynaecologists were to consider removal of fallopian tubes at the time of every hysterectomy and sterilization procedure with referral of all patients with HGSC for hereditary cancer counselling and genetic testing, experts project a potential reduction in the rate of HGSC by 40% over the next 20 years.

GUIDELINE UPDATE

Evidence will be reviewed 5 years after publication to decide whether all or part of the guideline should be updated. However, if important new evidence is published prior to the 5-year cycle, the review process may be accelerated for a more rapid update of some recommendations.

SPONSORS

This guideline was developed with resources funded by the Society of Gynecologic Oncology of Canada and SOGC.

SUMMARY STATEMENTS

RECOMMENDATIONS.

Assessment of dietary nitrate intake in humans: a systematic review

Background

The nitrate content of foods and water is highly variable, which has implications for the compilation of food-composition databases and assessment of dietary nitrate intake.

Objective

A systematic review was conducted to ascertain the dietary assessment methods used and to provide estimates of daily nitrate intake in humans.

Design

Relevant articles were identified by a systematic search of 3 electronic databases (PubMed, Web of Science, and Embase) from inception until February 2018. Observational studies conducted in adult populations and reporting information on dietary assessment methods and daily nitrate intake were included. Ecological analyses were conducted to explore the association of nitrate intake with indexes of economic development [Gross Domestic Product (GDP) and KOF Index of Globalization].

Results

A total of 55 articles were included. Forty-two studies investigated associations between nitrate intake and disease risk; 36 (87%) of these studies examined the association between nitrate intake and cancer risk, whereas only 6 studies explored the association of nitrate intake with the risk of diabetes, glaucoma, kidney failure, hypertension, and atherosclerotic vascular disease. The majority of studies used food-frequency questionnaires to assess nitrate intake (n = 43). The median daily nitrate intakes in healthy and patient populations were 108 and 110 mg/d, respectively. We found a significant inverse correlation of nitrate intake with GDP (r = -0.46, P < 0.001) and KOF index (r = -0.31, P = 0.002).

Conclusions

The median estimated daily nitrate intakes by healthy and patient populations were similar, and these values were below the safe upper intake of daily intake (3.7 mg nitrate ion/kg body weight). However, there is considerable heterogeneity in the application of food-composition tables, which may have implications for the accuracy of estimated daily nitrate intake. The association between nitrate intake and risk of cardiometabolic diseases needs further investigation. The protocol for this systematic review has been registered in the PROSPERO database (https://www.crd.york.ac.uk/prospero; CRD number: 42017060354).

Does nitrite and nitrate levels in drinking water impact the health of people in Dakahlia governorate, Egypt?

A total of 1291 drinking water samples were examined for nitrite and nitrate during 6 months from December, 2015 to May, 2016 at 17 cities of Dakahlia governorate (Nile Delta, north of Egypt), and the results were utilized for assessment of health risk of the exposure from drinking water by calculating average daily intake (ADI), hazard quotient (HQ), and the hazard index (HI). The nitrite and nitrate in drinking water had a concentration range of 0.030-0.113 and 2.41-8.70 mg L^-1, with mean values of 0.059 ± 0.014 and 5.25 ± 1.61 mg L^-1, respectively. Nitrite and nitrate levels in rural areas and ground water samples were significantly higher than that in the urban ones. None of the analyzed samples exceeded WHO guideline values that set out to prevent methemoglobinemia. The values of HQ and HI for all age groups do not exceed unity indicating a low risk of methaemoglobinaemia for the population in this area. Results of the present study indicate that there is no health risk of residents from nitrite and nitrate through drinking water in the studied area. However, the other sources of exposure to nitrite and nitrate should be investigated in further studies.

Association between dietary nitrate and nitrite intake and sitespecific cancer risk: evidence from observational studies

Epidemiological studies have reported inconsistent findings on the association between dietary nitrate and nitrite intake and cancer risk. We performed a meta-analysis of epidemiological studies to summarize available evidence on the association between dietary nitrate and nitrite intake and cancer risk from published prospective and case-control studies. PubMed database was searched to identify eligible publications through April 30^th, 2016. Study-specific relative risks (RRs) with corresponding 95% confidence interval (CI) from individual studies were pooled by using random- or fixed- model, and heterogeneity and publication bias analyses were conducted.

Data from 62 observational studies, 49 studies for nitrates and 51 studies for nitrites, including a total of 60,627 cancer cases were analyzed. Comparing the highest vs. lowest levels, dietary nitrate intake was inversely associated with gastric cancer risk (RR = 0.78; 95%CI = 0.67-0.91) with moderate heterogeneity (I² = 42.3%). In contrast, dietary nitrite intake was positively associated with adult glioma and thyroid cancer risk with pooled RR of 1.21 (95%CI = 1.03-1.42) and 1.52 (95%CI = 1.12-2.05), respectively. No significant associations were found between dietary nitrate/nitrite and cancers of the breast, bladder, colorectal, esophagus, renal cell, non-Hodgkin lymphoma, ovarian, and pancreas. The present meta-analysis provided modest evidence that positive associations of dietary nitrate and negative associations of dietary nitrite with certain cancers.

Re-evaluation of sodium nitrate (E 251) and potassium nitrate (E 252) as food additives

The Panel on Food Additives and Nutrient Sources added to Food (ANS) provided a scientific opinion re-evaluating the safety of sodium nitrate (E 251) and potassium nitrate (E 252) when used as food additives. The current acceptable daily intakes (ADIs) for nitrate of 3.7 mg/kg body weight (bw) per day were established by the SCF (1997) and JECFA (2002). The available data did not indicate genotoxic potential for sodium and potassium nitrate. The carcinogenicity studies in mice and rats were negative. The Panel considered the derivation of an ADI for nitrate based on the formation of methaemoglobin, following the conversion of nitrate, excreted in the saliva, to nitrite. However, there were large variations in the data on the nitrate-to-nitrite conversion in the saliva in humans. Therefore, the Panel considered that it was not possible to derive a single value of the ADI from the available data. The Panel noticed that even using the highest nitrate-to-nitrite conversion factor the methaemoglobin levels produced due to nitrite obtained from this conversion would not be clinically significant and would result to a theoretically estimated endogenous N-nitroso compounds (ENOC) production at levels which would be of low concern. Hence, and despite the uncertainty associated with the ADI established by the SCF, the Panel concluded that currently there was insufficient evidence to withdraw this ADI. The exposure to nitrate solely from its use as a food additive was estimated to be less than 5% of the overall exposure to nitrate in food based on a refined estimated exposure scenario. This exposure did not exceed the current ADI (SCF, 1997). However, if all sources of exposure to dietary nitrate are considered (food additive, natural presence and contamination), the ADI would be exceeded for all age groups at the mean and the highest exposure.

Re-evaluation of potassium nitrite (E 249) and sodium nitrite (E 250) as food additives

The Panel on Food Additives and Nutrient Sources added to Food (ANS) provided a scientific opinion re-evaluating the safety of potassium nitrite (E 249) and sodium nitrite (E 250) when used as food additives. The ADIs established by the SCF (1997) and by JECFA (2002) for nitrite were 0-0.06 and 0-0.07 mg/kg bw per day, respectively. The available information did not indicate in vivo genotoxic potential for sodium and potassium nitrite. Overall, an ADI for nitrite per se could be derived from the available repeated dose toxicity studies in animals, also considering the negative carcinogenicity results. The Panel concluded that an increased methaemoglobin level, observed in human and animals, was a relevant effect for the derivation of the ADI. The Panel, using a BMD approach, derived an ADI of 0.07 mg nitrite ion/kg bw per day. The exposure to nitrite resulting from its use as food additive did not exceed this ADI for the general population, except for a slight exceedance in children at the highest percentile. The Panel assessed the endogenous formation of nitrosamines from nitrites based on the theoretical calculation of the NDMA produced upon ingestion of nitrites at the ADI and estimated a MoE > 10,000. The Panel estimated the MoE to exogenous nitrosamines in meat products to be < 10,000 in all age groups at high level exposure. Based on the results of a systematic review, it was not possible to clearly discern nitrosamines produced from the nitrite added at the authorised levels, from those found in the food matrix without addition of external nitrite. In epidemiological studies there was some evidence to link (i) dietary nitrite and gastric cancers and (ii) the combination of nitrite plus nitrate from processed meat and colorectal cancers. There was evidence to link preformed NDMA and colorectal cancers.

N o 344-Salpingectomie opportuniste et autres méthodes pour réduire le risque de cancer de l'ovaire, de la trompe de Fallope et du péritoine dans la population générale

OBJECTIF

La présente directive clinique examine les avantages potentiels de la salpingectomie opportuniste pour prévenir le développement du cancer séreux de grade élevé de l'ovaire, de la trompe de Fallope et du péritoine à la lumière de données probantes actuelles selon lesquelles ce type de cancer prendrait naissance dans la trompe de Fallope.

UTILISATEURS CIBLES

Gynécologues, obstétriciens, médecins de famille, infirmières autorisées, infirmières praticiennes, résidents et fournisseurs de soins de santé.

POPULATION CIBLE

Femmes adultes (18 ans et plus) : OPTIONS: Les femmes envisageant une hystérectomie et souhaitant conserver leurs ovaires conservent généralement aussi leurs trompes de Fallope. De plus, celles qui subissent une chirurgie de stérilisation permanente subissent habituellement aussi une ligature des trompes selon des méthodes variées plutôt qu'un retrait chirurgical complet des trompes. RéSULTATS: Les sections « Données probantes appuyant l'hypothèse selon laquelle les CSGE prendraient naissance dans la trompe de Fallope » et « Articles récents sur les répercussions et la sûreté de la salpingectomie opportuniste » reposent sur des études pertinentes rédigées en anglais, qui ont été repérées dans PubMed, Medline et la Cochrane Database of Systematic Reviews à l'aide des termes suivants, seuls ou combinés : high grade serous cancers ovary, fallopian tube, peritoneum, opportunistic salpingectomy, epithelial ovarian cancers, origin, tubal carcinoma in situ, BRCA mutation, prophylactic salpingectomy, inflammation, clear cell et endometrioid. La recherche initiale a été menée en mars 2015, et une dernière recherche a été effectuée en mars 2016. Dans l'ordre, les données probantes pertinentes ont été tirées de méta-analyses, de revues de la littérature, de directives, d'essais cliniques randomisés, d'études de cohorte prospectives, d'études d'observation, de revues non systématiques, d'études de série de cas ainsi que de rapports. Au total, 458 études ont été repérées, et 56 ont été retenues pour la présente directive. Pour la section « Autres facteurs influant sur le risque de développer un cancer de ″l'ovaire″ », une recherche générale a été effectuée dans Medline à partir des termes ovarian neoplasm et prevention. Ont été inclus dans cette recherche des articles rédigés entre décembre 2005 et mars 2016. Les méta-analyses ont été privilégiées lorsque possible. Des recherches supplémentaires ont également été menées pour chaque sous-descripteurs (p. ex., ovarian neoplasm et tubal ligation). D'autres articles pertinents ont été ciblés au moyen d'une vérification des références des revues de la littérature retenues. Les termes ovarian neoplasm et prevention ont permis de repérer 10 méta-analyses; les termes ovarian neoplasm et tubal ligation, 4 méta-analyses. MéTHODES DE VALIDATION: Le contenu et les recommandations ont été rédigés et acceptés par les auteurs principaux. La direction et le conseil de la Société de gynéco-oncologie du Canada ont examiné le contenu et soumis des commentaires, puis le Conseil d'administration de la SOGC a approuvé la version finale avant publication. La qualité des données probantes a été évaluée à partir des critères de l'approche GRADE (Grading of Recommendations Assessment, Development and Evaluation) (tableau 1). L'interprétation des recommandations solides et conditionnelles est décrite dans le tableau 2. Le résumé des conclusions peut être fourni sur demande. AVANTAGES, INCONVéNIENTS ET COûTS: L'ajout d'une salpingectomie opportuniste à une hystérectomie ou à une procédure de stérilisation permanente prévue n'a pas entraîné une augmentation des taux de réadmission à l'hôpital (RC : 0,91; IC à 95 % : 0,75-1, 10 et RC : 0,8; IC à 95 % : 0,56-1,21, respectivement) ou de transfusion sanguine (RC : 0,86; IC à 95 % : 0,67-1,10 et RC : 0,75; IC à 95 % : 0,32-1,73, respectivement), mais il a entraîné une hausse de la durée des opérations (de 16 minutes et de 10 minutes, respectivement) selon une étude rétrospective portant sur 43 931 femmes. Le risque de subir des interventions répétées pour une pathologie tubaire chez les femmes ayant conservé leurs trompes de Fallope après une hystérectomie était au moins deux fois plus élevé (RC : 2,13; IC à 95 % : 1,88-2,42, selon une étude fondée sur une population de 170 000 femmes). Selon des experts, si les gynécologues généralistes envisageaient systématiquement de retirer les trompes de Fallope lors d'une hystérectomie ou d'une procédure de stérilisation et d'aiguiller toutes les patientes aux prises avec un CSGE vers une consultation en oncologie génétique et un dépistage génétique, le taux de CSGE pourrait diminuer de 40 % au cours des 20 prochaines années. MISE à JOUR DE DIRECTIVES CLINIQUES: Une revue des données probantes sera menée cinq ans après la publication de la présente directive clinique afin de déterminer si une mise à jour complète ou partielle s'impose. Cependant, si de nouvelles données probantes importantes sont publiées avant la fin du cycle de cinq ans, le processus pourrait être accéléré afin que certaines recommandations soient mises à jour rapidement.

PARRAINS

La présente directive clinique a été élaborée à l'aide de ressources financées par la Société de gynéco-oncologie du Canada et la SOGC. DéCLARATIONS SOMMAIRES: RECOMMANDATIONS.

Development and calibration of a dietary nitrate and nitrite database in the NIH-AARP Diet and Health Study

OBJECTIVE

Nitrate and nitrite are probable human carcinogens when ingested under conditions that increase the formation of N-nitroso compounds. There have been limited efforts to develop US databases of dietary nitrate and nitrite for standard FFQ. Here we describe the development of a dietary nitrate and nitrite database and its calibration.

DESIGN

We analysed data from a calibration study of 1942 members of the NIH-AARP (NIH-AARP, National Institutes of Health-AARP) Diet and Health Study who reported all foods and beverages consumed on the preceding day in two non-consecutive 24 h dietary recalls (24HR) and completed an FFQ. Based on a literature review, we developed a database of nitrate and nitrite contents for foods reported on these 24HR and for food category line items on the FFQ. We calculated daily nitrate and nitrite intakes for both instruments, and used a measurement error model to compute correlation coefficients and attenuation factors for the FFQ-based intake estimates using 24HR-based values as reference data.

RESULTS

FFQ-based median nitrate intake was 68·9 and 74·1 mg/d, and nitrite intake was 1·3 and 1·0 mg/d, in men and women, respectively. These values were similar to 24HR-based intake estimates. Energy-adjusted correlation coefficients between FFQ- and 24HR-based values for men and women respectively were 0·59 and 0·57 for nitrate and 0·59 and 0·58 for nitrite; energy-adjusted attenuation factors were 0·59 and 0·57 for nitrate and 0·47 and 0·38 for nitrite.

CONCLUSIONS

The performance of the FFQ in assessing dietary nitrate and nitrite intakes is comparable to that for many other macro- and micronutrients.

Red and processed meat, nitrite, and heme iron intakes and postmenopausal breast cancer risk in the NIH-AARP Diet and Health Study

Previous studies have shown inconsistent associations between red and processed meat intake and breast cancer risk. N-nitroso compounds and heme iron have been hypothesized as contributing factors. We followed 193,742 postmenopausal women in the NIH-AARP Diet and Health Study and identified 9,305 incident breast cancers (1995-2006). Dietary intake was assessed using a food frequency questionnaire at baseline. We adjusted daily intakes of meat, nitrite and heme iron for energy intake using the nutrient density method. We estimated multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) by quintiles of dietary exposures for all breast cancer, by stage (in-situ, localized, regional/distant) and by estrogen/progesterone receptor (ER/PR) status using Cox proportional hazards regression. Total red meat intake was positively associated with risk of regional/distant cancer (p-trend = 0.02). The risk was 25% higher in the highest vs. lowest intake quintile (95% CI = 1.03-1.52). Higher processed red meat intake (Q5 vs. Q1) was associated with 27% higher risk of localized breast cancer (95% CI = 1.01-1.27, p-trend = 0.03) and a 19% higher risk of regional/distant cancer (95% CI = 0.98-1.44, p-trend = 0.10). In addition, higher nitrite intake from processed red meat was positively associated with localized cancer (HR for Q5 vs. Q1 = 1.23, 95% CI = 1.09-1.39, p-trend < 0.0001). Heme iron intake was positively associated with breast cancer risk overall and all cancer stages (p-trend = 0.02-0.05). No heterogeneity was observed in risk associations by hormone receptor status. Our findings suggest that high consumption of red meat and processed meat may increase risk of postmenopausal breast cancer. Added nitrite and heme iron may partly contribute to these observed associations.

Nitrate and nitrite ingestion and risk of ovarian cancer among postmenopausal women in Iowa

Nitrate and nitrite are precursors in the endogenous formation of N-nitroso compounds (NOC), potential human carcinogens. We evaluated the association of nitrate and nitrite ingestion with postmenopausal ovarian cancer risk in the Iowa Women's Health Study. Among 28,555 postmenopausal women, we identified 315 incident epithelial ovarian cancers from 1986 to 2010. Dietary nitrate and nitrite intakes were assessed at baseline using food frequency questionnaire data. Drinking water source at home was obtained in a 1989 follow-up survey. Nitrate-nitrogen (NO3 -N) and total trihalomethane (TTHM) levels for Iowa public water utilities were linked to residences and average levels were computed based on each woman's duration at the residence. We computed multivariable-adjusted hazard ratios (HR) and 95% confidence intervals (CI) using Cox proportional hazards regression. We tested interactions of nitrate with TTHMs and dietary factors known to influence NOC formation. Ovarian cancer risk was 2.03 times higher (CI = 1.22-3.38, ptrend  = 0.003) in the highest quartile (≥2.98 mg/L) compared with the lowest quartile (≤0.47 mg/L; reference) of NO3 -N in public water, regardless of TTHM levels. Risk among private well users was also elevated (HR = 1.53, CI = 0.93-2.54) compared with the same reference group. Associations were stronger when vitamin C intake was <median (pinteraction  = 0.01 and 0.33 for private well and public supplies, respectively). Dietary nitrate was inversely associated with ovarian cancer risk (ptrend  = 0.02); whereas, dietary nitrite from processed meats was positively associated with the risk (ptrend  = 0.04). Our findings indicate that high nitrate levels in public drinking water and private well use may increase ovarian cancer risk among postmenopausal women.

Nitrate and nitrite in the diet: how to assess their benefit and risk for human health

Nitrate is a natural constituent of the human diet and an approved food additive. It can be partially converted to nitrogen monoxide, which induces vasodilation and thereby decreases blood pressure. This effect is associated with a reduced risk regarding cardiovascular disease, myocardial infarction, and stroke. Moreover, dietary nitrate has been associated with beneficial effects in patients with gastric ulcer, renal failure, or metabolic syndrome. Recent studies indicate that such beneficial health effects due to dietary nitrate may be achievable at intake levels resulting from the daily consumption of nitrate-rich vegetables. N-nitroso compounds are endogenously formed in humans. However, their relevance for human health has not been adequately explored up to now. Nitrate and nitrite are per se not carcinogenic, but under conditions that result in endogenous nitrosation, it cannot be excluded that ingested nitrate and nitrite may lead to an increased cancer risk and may probably be carcinogenic to humans. In this review, the known beneficial and detrimental health effects related to dietary nitrate/nitrite intake are described and the identified gaps in knowledge as well as the research needs required to perform a reliable benefit/risk assessment in terms of long-term human health consequences due to dietary nitrate/nitrite intake are presented.

Meat, dairy, and cancer

In 2007 the World Cancer Research Fund and American Institute for Cancer Research (WCRF/AICR) report judged that the evidence for an association between red and processed meat consumption and colorectal cancer was convincing. In addition, the effect of other animal products on cancer risk has been studied, and the WCRF/AICR report concluded that milk probably decreases the risk of colorectal cancer but diets high in calcium probably increase the risk of prostate cancer, whereas there was limited evidence for an association between milk and bladder cancer and insufficient evidence for other cancers. There are several potential mechanisms relating meat to cancer, including heterocyclic amines, polycyclic aromatic hydrocarbons, N-nitroso compounds, and heme iron. Although the evidence in favor of a link between red and processed meat and colorectal cancer is convincing, the relations with other cancers are unclear. In this review, we summarize cohort studies conducted by the National Cancer Institute on meat and dairy intake in relation to cancer since the 2007 WCRF/AICR report. We also report the findings of meta-analyses published since 2007.

Dietary intake and ovarian cancer risk: a systematic review

Ovarian cancer is a leading cause of gynecological cancer death. There is a need to identify modifiable dietary risk factors for this disease. To evaluate the role of diet in ovarian cancer risk, we performed a PRISMA-directed systematic review that included prospective cohort studies with >200 cases (n = 24). Higher risk for ovarian cancer was shown for total, animal, and dairy fat (five of nine studies), as well as total nitrate and possibly total vitamin C. No associations were demonstrated for red meat, fiber, vitamin A, vitamin E, β-carotene, or folate. Vegetables were associated with lower risk in one of three studies; fruit showed no association, although risk estimates were all greater than 1.0. Isoflavones and flavonoids were associated with modestly lower risk in two studies and tea intake was associated with lower risk in one of two studies. This review suggests that no specific dietary factors are consistently associated with ovarian cancer risk. Data by tumor subtypes are limited, but suggest that differential associations by tumor subtype may exist and should be evaluated. Studies of ample sample size, varied exposure, which can better control for dietary measurement error, are needed to fully define dietary recommendations for ovarian cancer prevention.

Vascular effects of dietary nitrate (as found in green leafy vegetables and beetroot) via the nitrate-nitrite-nitric oxide pathway

The discovery that dietary (inorganic) nitrate has important vascular effects came from the relatively recent realization of the 'nitrate-nitrite-nitric oxide (NO) pathway'. Dietary nitrate has been demonstrated to have a range of beneficial vascular effects, including reducing blood pressure, inhibiting platelet aggregation, preserving or improving endothelial dysfunction, enhancing exercise performance in healthy individuals and patients with peripheral arterial disease. Pre-clinical studies with nitrate or nitrite also show the potential to protect against ischaemia-reperfusion injury and reduce arterial stiffness, inflammation and intimal thickness. However, there is a need for good evidence for hard endpoints beyond epidemiological studies. Whilst these suggest reduction in cardiovascular risk with diets high in nitrate-rich vegetables (such as a Mediterranean diet), others have suggested possible small positive and negative associations with dietary nitrate and cancer, but these remain unproven. Interactions with other nutrients, such as vitamin C, polyphenols and fatty acids may enhance or inhibit these effects. In order to provide simple guidance on nitrate intake from different vegetables, we have developed the Nitrate 'Veg-Table' with 'Nitrate Units' [each unit being 1 mmol of nitrate (62 mg)] to achieve a nitrate intake that is likely to be sufficient to derive benefit, but also to minimize the risk of potential side effects from excessive ingestion, given the current available evidence. The lack of data concerning the long term effects of dietary nitrate is a limitation, and this will need to be addressed in future trials.

Plasma levels of nitrate and risk of prostate cancer: a prospective study

BACKGROUND

Nitrate and nitrite supplements have recently been shown to improve cardiovascular health, but there is concern that these supplements could contribute to the development of cancer. Previous small, cross-sectional studies reported positive associations between circulating nitrate/nitrite levels and cancer. Prospective studies examining the association between plasma nitrate and cancer, especially prostate cancer, are lacking.

METHODS

We conducted a nested case-control study within the Health Professionals Follow-up Study. Baseline blood samples were collected in 1994, and incident cases of prostate cancer were identified from 1997 to 2005. Baseline plasma levels of nitrate were measured in the 630 cases and 630 matched controls.

RESULTS

We have found that baseline levels of plasma nitrate were not associated with risk of prostate cancer. Compared to quintile 1, the relative risk from quintiles 2 to 5 were 1.13 [95% confidence interval (CI), 0.78-1.63], 0.93 (95% CI, 0.63-1.38), 0.95 (95% CI, 0.65-1.39), and 0.99 (95% CI, 0.68-1.48); Ptrend was 0.9 after adjustment of multivariate risk factors. When analyses were restricted to men fasting more than 6 hours, the trend was similar. Furthermore, plasma nitrate seemed to be inversely associated with advanced-stage prostate cancer. The relative risk across extreme quartiles was 0.44 (95% CI, 0.17-1.12; Ptrend = 0.07) for the whole dataset and 0.30 (95% CI, 0.09-0.99; Ptrend = 0.05) for the fasting dataset.

CONCLUSIONS

In summary, we did not find an increased risk of prostate cancer associated with higher plasma nitrate levels. A potential protective association between nitrate and aggressive forms of prostate cancer requires confirmation.

IMPACT

Nitrate-nitrite-nitric oxide pathway has emerged as a new therapeutic pathway for chronic diseases. The results of this study certainly merit replications in other prospective studies.

USDA food and nutrient databases provide the infrastructure for food and nutrition research, policy, and practice

The USDA food and nutrient databases provide the basic infrastructure for food and nutrition research, nutrition monitoring, policy, and dietary practice. They have had a long history that goes back to 1892 and are unique, as they are the only databases available in the public domain that perform these functions. There are 4 major food and nutrient databases released by the Beltsville Human Nutrition Research Center (BHNRC), part of the USDA's Agricultural Research Service. These include the USDA National Nutrient Database for Standard Reference, the Dietary Supplement Ingredient Database, the Food and Nutrient Database for Dietary Studies, and the USDA Food Patterns Equivalents Database. The users of the databases are diverse and include federal agencies, the food industry, health professionals, restaurants, software application developers, academia and research organizations, international organizations, and foreign governments, among others. Many of these users have partnered with BHNRC to leverage funds and/or scientific expertise to work toward common goals. The use of the databases has increased tremendously in the past few years, especially the breadth of uses. These new uses of the data are bound to increase with the increased availability of technology and public health emphasis on diet-related measures such as sodium and energy reduction. Hence, continued improvement of the databases is important, so that they can better address these challenges and provide reliable and accurate data.