Whole grains have been shown to confer health benefits and may lower the risk of developing obesity and cardiovascular disease. Epidemiological studies showing inverse association between whole grain intakes and certain diseases have traditionally relied on the use of food questionnaires and food diaries to ascertain the intakes of whole grain foods. Although progress has been made in increasing the reliability of such recall methods for estimating food intake, controversy still surround their ultimate reliability. Alkylresorcinols are a group of phenolic lipids that are exclusively found in the outer parts of rye and wheat and are possibly therefore a useful biomarker for whole grain intake. Some studies have reported strong associations between whole grain intake and alkylresorcinols, suggesting that they are indeed useful in determining short-term intakes. More recently, longitudinal studies have reported that alkylresorcinols may be reliable medium-term biomarkers for whole grain intake.
For example researchers1 have investigated the medium-term use of plasma alkylresorcinols as biomarkers of whole grain intake by comparing weighed food records of 72 Swedish adults with their plasma concentrations of alkylresorcinols on 2 test occasions separated by 2 to 3 months. Plasma alkylresorcinols were higher during nonfasting compared to fasting conditions (210nmol/L and 99nmols/L, respectively). The mean whole grain intake was 70 grams per day, mostly from rye, wheat and oats, and total daily intake of alkylresorcinols was 0.5 to 124mg/d with strong positive correlation between whole grain intake and alkylresorcinols (Spearman’s rank order coefficient = 0.49 to 0.82). Between the 2 test occasions, the intraclass correlation coefficients (a measure of how strongly units in the same group resemble each other) were 0.44 for total whole grain intake and 0.47 for fasting plasma total alkylresorcinol concentration, values that only represent a moderate correlation.
Taken as a whole these results suggest that plasma alkylresorcinol concentrations do vary over time and the medium-term correlation with the whole grain intake is moderate. Plasma alkylresorcinols could therefore be useful in studies as a biomarker of whole grain intake, particularly in populations with a more consistent intake of whole grains that is relatively high. The intake of whole grains amongst the subjects was higher than expected, possibly due to selection bias, with the type of individual likely to enrol in such a study being more likely to have an interest in a healthy lifestyle. In this study, rye showed a higher correlation with fasting plasma alkylresorcinols compared to wheat, which is explained by the higher content of alkylresorcinols in rye. Fasting alkylresorcinols therefore show moderate medium-term reproducibility and are well correlated with self-reported rye and wheat whole grain intakes, making them potentially useful biomarkers.
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