Plasma alkylresorcinol concentrations, biomarkers of whole-grain wheat and rye intake, in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort

Bioavailability and Bioactivity of Alkylresorcinols from Different Cereal Products

Cereal products are the most important dietary source for energy intake and several bioactive compounds with high concentrations in the bran and the germ. Different cereal products provide a rich source of bioactive phytochemicals, namely, phenolic acids, carotenoids, tocopherols, alkylresorcinols, benzoxazines, phytosterols, and lignans. The bioactive substance alkylresorcinols (ARs) present in the whole cereal can inhibit enzyme activity, prevent bacterial or fungal infection, reduce cholesterol absorption, prevent cancer, and resist oxidation. In this paper, we discussed the biological activity of ARs in whole cereal products. Understanding the effects of processing on cereal phytochemicals will help us to develop improved processes for processing cereal foods with higher retention rates of bioactive compounds.

Biomarkers of cereal food intake

Background/objectives

Cereal foods are major contributors to the daily energy, protein, and dietary fiber intake all over the world. The role of cereals in human health is dependent on whether they are consumed as refined or whole grain and on cereal species. To unravel the underlying mechanisms of health effects attributed to specific cereal foods and to provide more precise dietary advice, there is a need for improved dietary assessment of whole-grain intake. Dietary biomarkers of specific cereals, different fractions or cereal-containing foods could offer such a possibility. The aim of this review was to summarize the current status on biomarkers of different cereals, fractions, and specific cereal foods.

Subjects and methods

A literature review was conducted and putative biomarkers of different cereals and pseudo-cereals (wheat, oats, rye, barley, rice, and quinoa) as well as for different grain fractions (whole grain, refined grain, bran) and foods were summarized and discussed.

Results

Several putative biomarkers have been suggested for different cereals, due to their unique presence in these grains. Among the biomarkers, odd-numbered alkylresorcinols are the most well-studied and -evaluated biomarkers and reflect whole-grain wheat and rye intake. Even-numbered alkylresorcinols have been suggested to reflect quinoa intake. Recent studies have also highlighted the potential of avenanthramides and avenacosides as specific biomarkers of oat intake, and a set of biomarkers have been suggested to reflect rice bran intake. However, there are yet no specific biomarkers of refined grains. Most biomarker candidates remain to be evaluated in controlled interventions and free-living populations before applied as biomarkers of intake in food and health studies.

Conclusion

Several putative biomarkers of different cereals have been suggested and should be validated in human studies using recently developed food intake biomarker validation criteria.

Use of a Web-Based Dietary Assessment Tool (RiksmatenFlex) in Swedish Adolescents: Comparison and Validation Study

Background

A Web-based dietary assessment tool—RiksmatenFlex—was developed for the national dietary survey of adolescents in Sweden.

Objective

This study aimed to describe the Web-based method RiksmatenFlex and to test the validity of the reported dietary intake by comparing dietary intake with 24-hour dietary recalls (recall interviews), estimated energy expenditure, and biomarkers.

Methods

Adolescents aged 11-12, 14-15, and 17-18 years were recruited through schools. In total, 78 students had complete dietary information and were included in the study. Diet was reported a few weeks apart with either RiksmatenFlexDiet (the day before and a random later day) or recall interviews (face-to-face, a random day later by phone) in a cross-over, randomized design. At a school visit, weight and height were measured and blood samples were drawn for biomarker analyses. Students wore an accelerometer for 7 days for physical activity measurements. Dietary intake captured by both dietary methods was compared, and energy intake captured by both methods was compared with the accelerometer-estimated energy expenditure (EEest). Intake of whole grain wheat and rye and fruit and vegetables by both methods was compared with alkylresorcinol and carotenoid concentrations in plasma, respectively.

Results

The mean of the reported energy intake was 8.92 (SD 2.77) MJ by RiksmatenFlexDiet and 8.04 (SD 2.67) MJ by the recall interviews (P=.01). Intake of fruit and vegetables was 224 (169) g and 227 (150) g, and whole grain wheat and rye intake was 12.4 (SD 13.2) g and 12.0 (SD 13.1) g, respectively; the intakes of fruit and vegetables as well as whole grain wheat and rye did not differ between methods. Intraclass correlation coefficients ranged from 0.57 for protein and carbohydrates to 0.23 for vegetables. Energy intake by RiksmatenFlexDiet was overreported by 8% (P=.03) but not by the recall interviews (P=.53) compared with EEest. The Spearman correlation coefficient between reported energy intake and EEest was 0.34 (P=.008) for RiksmatenFlexDiet and 0.16 (P=.21) for the recall interviews. Spearman correlation coefficient between whole grain wheat and rye and plasma total alkylresorcinol homologs was 0.36 (P=.002) for RiksmatenFlexDiet and 0.29 (P=.02) for the recall interviews. Spearman correlations between intake of fruit and vegetables and plasma carotenoids were weak for both dietary tools. The strongest correlations were observed between fruit and vegetable intake and lutein/zeaxanthin for RiksmatenFlexDiet (0.46; P<.001) and for recall interviews (0.28; P=.02).

Conclusions

RiksmatenFlexDiet provides information on energy, fruit, vegetables, and whole grain wheat and rye intake, which is comparable with intake obtained from recall interviews in Swedish adolescents. The results are promising for cost-effective dietary data collection in upcoming national dietary surveys and other studies in Sweden. Future research should focus on how, and if, new technological solutions could reduce dietary reporting biases.

Whole Grain Consumption for the Prevention and Treatment of Breast Cancer

Breast cancer is one of the most common and malignant cancers among females worldwide. Several epidemiological studies have indicated the inverse correlation between the intake of whole grains and the incidence of breast cancer. Whole grains are the most fundamental and important food source of bioactive phytochemicals, which have well-defined roles in the management of each stage of breast carcinogenesis. To better understand the value of whole grains in future prevention and treatment of breast cancer, the effects and possible mechanisms of six different whole grain cereals, which are the most commonly consumed throughout the world, are introduced in the current review. Moreover, the bioactive compounds extracted from whole grains are adequately formulated and the underlying mechanism of action is illustrated. In addition, the present limitations and future perspective of whole grain consumption for breast cancer are also concluded. The objective of this review is to promote the development of nutraceutical and functional food from whole grains and its application for reducing the risk of breast cancer.

Long-Term Whole Grain Wheat and Rye Intake Reflected by Adipose Tissue Alkylresorcinols and Breast Cancer: A Case-Cohort Study

Whole grain rye (WGR) and whole grain wheat (WGW) have been suggested to protect against the development of breast cancer. In this study, we estimated long-term intake of WGR and WGW, using both a food frequency questionnaire (FFQ) and alkylresorcinol concentrations in adipose tissue biopsies, in relation to the risk of developing invasive breast cancer in a case-cohort study (n = 414 in the case group, n = 933 in the subcohort group) on the Danish “Diet, Cancer and Health” cohort. The median follow-up time of the subcohort was 5.3 years. Total WGR and WGW intake estimated with FFQ or reflected by total alkylresorcinol concentration in adipose tissue was not significantly associated with risk of breast cancer. However, after adjustment for total WGR and WGW intake, women in the highest quartile of relative WGR intake, reflected by the alkylresorcinol C17:0/C21:0 ratio, had a higher risk of overall breast cancer and estrogen-receptor-positive (ER+) breast cancer than women in the lowest quartile of relative WGR intake, while the risk of estrogen-receptor-negative (ER-) breast cancer incidence was unaffected. Similar results were obtained with the FFQ data. Based on these data, further investigation of the role of specific grain types in reducing or increasing breast cancer risk, and their overall impact on health, is warranted.

Quantification of 38 dietary polyphenols in plasma by differential isotope labelling and liquid chromatography electrospray ionization tandem mass spectrometry

Polyphenols constitute one of the most complex classes of phytochemicals in the human diet and have been suggested to play a role in the prevention of chronic diseases such as cardiovascular diseases, diabetes and cancers. However, evidence from epidemiological studies is still needed to better understand their role in disease prevention. To do so, robust methods for the accurate measurement of these molecules in large series of samples are needed. We report here the development of a highly-sensitive method based on differential isotope labelling with 13C- and 12C-dansyl chloride for the analysis of 38 structurally diverse polyphenols in 50 μL plasma by tandem mass spectrometry with limits of quantification varying between 0.11 to 44 nmol/L. Full validation of the method was achieved for 37 compounds out of the 38 tested. The method showed intra- and inter-batch coefficients of variations of 2.3-9.0% and 2.8-20.3% respectively depending on polyphenols when applied to 1163 plasma samples from the European Prospective Investigation on Cancer and Nutrition (EPIC) study. For the first time this method allowed to quantify with high accuracy and reproducibility a large selection of compounds representative of the main classes of dietary polyphenols in low volumes of plasma.

Evaluation of alkylresorcinols in adipose tissue biopsies as a long-term biomarker of whole-grain wheat and rye intake in free-living Swedish men and women

OBJECTIVE

Wheat and rye, the most consumed whole grains (WG) in the Nordic countries, contain alkylresorcinols (AR) in their bran. AR concentrations in human adipose tissue might reflect long-term WG rye and wheat intake. We aimed to evaluate AR concentrations in adipose tissue biopsies as a long-term biomarker of WG wheat and rye intake in free-living Swedish men and women.

DESIGN

Cross-sectional study. AR concentrations in adipose tissue biopsies were analysed and compared with long-term WG intake assessed by three FFQ (repeated over a period of 14 years in men, 17 years in women) and with plasma AR concentrations.

SETTING

The Cohort of Swedish Men between 1997 and 2010 and the Swedish Mammography Cohort between 1987 and 2003, Sweden.

SUBJECTS

Men (n 149) and women (n 109).

RESULTS

Long-term WG rye intake estimated with repeated FFQ correlated (r=0·31-0·41, P<0·01) with adipose-tissue AR concentrations, while WG wheat intake correlated only weakly (r=0·17-0·33, P<0·05). Total AR concentration in adipose tissue was 61 % lower in women than in men at similar energy-adjusted WG wheat and rye intakes, but plasma concentrations were similar. AR concentrations in adipose tissue correlated well with plasma concentrations (r=0·49-0·81, P<0·001).

CONCLUSIONS

AR in adipose tissue reflected long-term WG rye but not WG wheat intake, probably due to poor precision in estimating WG wheat intake by FFQ. AR in adipose tissue appears promising as a biomarker of long-term WG rye intake but should be adjusted for sex.

Dietary intake of whole grains and plasma alkylresorcinol concentrations in relation to changes in anthropometry: the Danish diet, cancer and health cohort study

BACKGROUND/OBJECTIVES

Whole grain intake has been associated with a small but significant lower body weight gain in observational studies, but there is limited knowledge about the associations with specific whole grain types. The objective was to investigate the association between whole grains, different sources of whole grains and biomarkers of whole grain intake (alkylresorcinols) in relation to subsequent changes in waist circumference (WC) and body weight.

SUBJECTS/METHODS

Cohort study of 57 053 participants with baseline information on whole grain intake from questionnaires (FFQ) and biomarkers of whole grain rye and wheat intake, plasma alkylresorcinols, for a subset. WC and body weight were measured at baseline and again at follow-up. The associations were estimated using multiple linear regression analyses and logistic regression.

RESULTS

For women, overall whole grain intake was not related to changes in WC or body weight. For men, total whole grain intake was associated with gains in WC (ΔWC per 25 g increment: 0.44 cm, 95% CI: 0.34 cm; 0.54 cm) and body weight (Δweight per 25 g increment: 150 g, 95% CI: 78 g; 222 g), but the results changed to null or changed direction when adjusting for baseline anthropometry. For the different sources of whole grains, rye (women) and crispbread was significantly associated with gains in WC and body weight. Plasma alkylresorcinol concentration was associated with reduced WC, but not body weight, for women (ΔWC per 50 nmol/l increment: -0.69 cm, 95% CI:-1.26 cm;-0.13 cm), but no association was found for men.

CONCLUSIONS

Overall, no strong relationship between whole grain intake, measured from questionnaires or using biomarkers was found in relation to changes in body weight and WC.

Intakes of whole grain in an Italian sample of children, adolescents and adults

PURPOSE

There is wide evidence that regular consumption of whole grain foods may reduce the risk of chronic diseases. The aim of this work was to quantify the intake of whole grains and identify main dietary sources in the Italian population.

METHODS

Whole grain intakes were calculated in a sample of 2830 adults/older adults and of 440 children/adolescents from the last national survey INRAN-SCAI 2005-06. Food consumption was assessed from a 3-day food record. The whole grain content of foods was estimated mainly from quantitative ingredient declarations on labels.

RESULTS

Mean whole grain intakes were 3.7 g/day in adults/older adults and 2.1 g/day in children/adolescents. Overall, 23 % of the sample reported consumption of whole grain foods during the survey, among which mean whole grain intakes ranged from 6.0 g/day in female children to 19.1 g/day in female older adults. The main sources of whole grains were breakfast cereals in children/adolescents (32 %) and bread in adults/older adults (46 %). Consumption of whole grain among adults was associated with significantly higher daily intakes and adequacy of dietary fibre, several vitamins (thiamine, riboflavin, vitamin B6) and minerals (iron, calcium, potassium, phosphorus, zinc, magnesium) compared to non-consumption. Among children, whole grain intake was associated with significantly higher intakes of iron and magnesium.

CONCLUSIONS

The study reveals very low whole grain intakes across all age groups of the Italian population. Considering the positive association in consumers between whole grain intakes and fibre and micro-nutrient intakes, public health strategies to increase whole grain consumption should be considered.

Quality of meal and appetite sensation

PURPOSE OF REVIEW

The scope of this review is to summarize recent studies assessing the role of meal composition on appetite sensation.

RECENT FINDINGS

Currently, data confirm a positive effect on appetite sensations following protein-rich meals, suggesting that at least 25-30-g protein/meal provide potential improvements on appetite, but further long-term studies are required to confirm the results. A greater interest has been showed in the interaction between short-chain fatty acids produced by gut microbiota, following dietary fiber consumption, and appetite sensation, but research is ongoing. Finally, as reflected in the recent literature, new systematic reviews should be carried out to assess the effect of dietary fibers on appetite sensation.

SUMMARY

Meal composition, in terms of nutrients, widely differs in the ability to affect appetite sensation. This mostly depends on the content of protein and dietary fibers in a meal. The effect of higher protein intake on appetite sensation has been well documented with positive results, whereas dietary fibers, although the majority of evidence suggests positive results, still show inconsistent data because of various methodological approaches. Generally, more research both in the short and long term is required to investigate the underlying mechanism associated with appetite sensation.

Mediterranean Diet and cancer risk: an open issue

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

Validation of Reported Whole-Grain Intake from a Web-Based Dietary Record against Plasma Alkylresorcinol Concentrations in 8- to 11-Year-Olds Participating in a Randomized Controlled Trial

BACKGROUND

Whole-grain (WG) intake is important for human health, but accurate intake estimation is challenging. Use of a biomarker for WG intake provides a possible way to validate dietary assessment methods.

OBJECTIVE

Our aim was to validate WG intake from 2 diets reported by children, using plasma alkylresorcinol (AR) concentrations, and to investigate the 3-mo reproducibility of AR concentrations and reported WG intake.

METHODS

AR concentrations were analyzed in fasting blood plasma samples, and WG intake was estimated in a 7-d web-based diary by 750 participants aged 8-11 y in a 2 school meal × 3 mo crossover trial. Reported WG intake and plasma AR concentrations were compared when children ate their usual bread-based lunch (UBL) and when served a hot lunch meal (HLM). Correlations and cross-classification were used to rank subjects according to intake. The intraclass correlation coefficients (ICCs) between subjects' measurements at baseline and after the UBL were used to assess reproducibility.

RESULTS

Correlations between reported WG wheat + rye intake and plasma AR were 0.40 and 0.37 (P < 0.001) for the UBL and the HLM diets, and 78% and 77% were classified in the same or adjacent quartiles for the UBL and HLM diets, respectively. The ICC over 3 mo was 0.47 (95% CI: 0.38, 0.55) for plasma total ARs and 0.64 (95% CI: 0.58, 0.70) for reported WG intake. Correlations were higher when using the AR C17:0 homolog as a biomarker, reflecting rye intake instead of plasma total ARs [UBL: r = 0.47; HLM: r = 0.43, P < 0.001; ICC = 0.51 (95% CI: 0.43, 0.59)].

CONCLUSIONS

Self-reported WG wheat + rye intake among children showed moderate correlations with plasma AR concentrations. Substantial intraindividual variation was found in WG intake and plasma AR concentrations. The AR homolog C17:0 may be used as a biomarker for WG intake when the WG intake primarily comes from rye as in the present study. This trial was registered at clinicaltrials.gov as NCT01457794.

A high-throughput method for liquid chromatography-tandem mass spectrometry determination of plasma alkylresorcinols, biomarkers of whole grain wheat and rye intake

Plasma alkylresorcinols are increasingly analyzed in cohort studies to improve estimates of whole grain intake and their relationship with disease incidence. Current methods require large volumes of solvent (>10 ml/sample) and have relatively low daily sample throughput. We tested five different supported extraction methods for extracting alkylresorcinols from plasma and improved a normal-phase liquid chromatography coupled to a tandem mass spectrometer method to reduce sample analysis time. The method was validated and compared with gas chromatography-mass spectrometry analysis. Sample preparation with HybridSPE supported extraction was most effective for alkylresorcinol extraction, with recoveries of 77-82% from 100 μl of plasma. The use of 96-well plates allowed extraction of 160 samples per day. Using a 5-cm NH2 column and heptane reduced run times to 3 min. The new method had a limit of detection and limit of quantification equivalent to 1.1-1.8 nmol/L and 3.5-6.1 nmol/L plasma, respectively, for the different alkylresorcinol homologues. Accuracy was 93-105%, and intra- and inter-batch precision values were 4-18% across different plasma concentrations. This method makes it possible to quantify plasma alkylresorcinols in 100 μl of plasma at a rate of at least 160 samples per day without the need for large volumes of organic solvents.

Determination of alkylresorcinols and their metabolites in biological samples by gas chromatography-mass spectrometry

High throughput GC-MS methods for quantification of alkylresorcinols (AR), biomarkers of whole grain wheat and rye intake, in plasma and adipose tissue and their metabolites in urine were developed and optimised. Alkylresorcinols in plasma (200μL) and adipose tissues (10-50mg) were extracted with diethyl ether, whereas main AR metabolites such as DHBA and DHPPA and newly identified metabolites in urine (50μL) were extracted with ethyl acetate after enzymatic deconjugation. All extracts were purified on OASIS-MAX solid phase extraction cartridges. Plasma and adipose tissue sample extracts were then derivatised with trifluoroacetic anhydride and reconstituted in undecane, whereas AR metabolites in urine samples were derivatised with BSTFA+TMCS (99:1, v/v, 100μL). Prepared samples were quantified by GC-MS (EI-SIM). Analysis of all compounds in the different matrices showed good selectivity, sensitivity, linearity, precision (<15% within and between batches), adequate recovery (75-108%), and short total run time (10-12min). The methods developed are applicable to large-scale sample sets such as epidemiological studies.

Plasma alkylresorcinols, biomarkers of whole-grain intake, are not associated with progression of coronary artery atherosclerosis in postmenopausal women with coronary artery disease

Objective

The objective of the present study was to examine the relationship between plasma alkyresorcinol (AR) concentrations, which are biomarkers of whole-grain intake, and atherosclerotic progression over 3 years in postmenopausal women with coronary artery disease.

Design

Plasma AR concentrations were measured by a validated GC–MS method in fasting plasma samples. Atherosclerosis progression was assessed using change in mean minimal coronary artery diameter (MCAD) and percentage diameter stenosis (%ST), based on mean proximal vessel diameter across up to ten coronary segments. Dietary intake was estimated using a 126-item interviewer-administered FFQ.

Setting

A prospective study of postmenopausal women participating in the Estrogen Replacement and Atherosclerosis trial.

Subjects

For the analysis of plasma AR concentrations and atherosclerotic progression, plasma samples and follow-up data on angiography were available for 182 women.

Results

Mean whole-grain intake was 9·6 (se 0·6) servings per week. After multivariate adjustment, no significant associations were observed between plasma AR concentrations and change in mean MCAD or progression of %ST. Plasma AR concentrations were significantly correlated with dietary whole grains (r=0·35, P<0·001), cereal fibre (r=0·33, P<0·001), bran (r=0·15, P=0·05), total fibre (r=0·22, P=0·003) and legume fibre (r=0·15, P=0·04), but not refined grains, fruit fibre or vegetable fibre.

Conclusions

Plasma AR concentrations were not significantly associated with coronary artery progression over a 3-year period in postmenopausal women with coronary artery disease. A moderate association was observed between plasma AR concentrations and dietary whole grains and cereal fibre, suggesting it may be a useful biomarker in observational studies.

Simultaneous pharmacokinetic modeling of alkylresorcinols and their main metabolites indicates dual absorption mechanisms and enterohepatic elimination in humans

BACKGROUND

Alkylresorcinols have proven to be useful biomarkers of whole-grain wheat and rye intake in many nutritional studies. To improve their utility, more knowledge regarding the fate of alkylresorcinols and their metabolites after consumption is needed.

OBJECTIVE

The objective of this study was to develop a combined pharmacokinetic model for plasma concentrations of alkylresorcinols and their 2 major metabolites, 3,5-dihydroxybenzoic acid (DHBA) and 3-(3,5-dihydroxyphenyl)-propanoic acid (DHPPA).

METHODS

The model was established by using plasma samples collected from 3 women and 2 men after a single dose (120 g) of rye bran and validated against fasting plasma concentrations from 8 women and 7 men with controlled rye bran intake (23, 45, or 90 g/d). Alkylresorcinols in the lymph and plasma of a pig fed a single alkylresorcinol dose (1.3 mmol) were quantified to assess absorption. Human ileostomal effluent and pig bile after high and low alkylresorcinol doses were analyzed to evaluate biliary alkylresorcinol metabolite excretion.

RESULTS

The model contained 2 absorption compartments: 1 that transferred alkylresorcinols directly to the systematic circulation and 1 in which a proportion of absorbed alkylresorcinols was metabolized before reaching the systemic circulation. Plasma concentrations of alkylresorcinols and their metabolites depended on absorption and formation, respectively, and the mean ± SEM terminal elimination half-life of alkylresorcinols (1.9 ± 0.59 h), DHPPA (1.5 ± 0.26 h), and DHBA (1.3 ± 0.22 h) did not differ. The model accurately predicted alkylresorcinol and DHBA concentrations after repeated alkylresorcinol intake but DHPPA concentration was overpredicted, possibly because of poorly modeled enterohepatic circulation. During the 8 h following administration, <2% of the alkylresorcinol dose was recovered in the lymph. DHPPA was identified in both human ileostomal effluent and pig bile, indicating availability of DHPPA for absorption and enterohepatic circulation.

CONCLUSION

Intact alkylresorcinols have advantages over DHBA and DHPPA as plasma biomarkers for whole-grain wheat and rye intake because of lower susceptibility to factors other than alkylresorcinol intake.