It has been suggested previously that alkylresorcinols are effective biomarkers of whole grain intake. Alkylresorcinols are phenolic lipids found in high concentrations in the bran fraction of wheat and rye, but only in low concentrations in the endosperm. Because white flour excludes the bran fraction of cereals and uses only the endosperm, the alkylresorcinols content of white flour products are low. Whole grains in contrast possess the same bran to endosperm ratio as in the original plant, and so contain higher concentrations of alkylresorcinols. Therefore, alkylresorcinol intake should increase with increasing whole grain consumption and decrease as more refined grains are consumed. Previous research (here) has measured plasma levels of alkylresorcinols and found a correlation between intakes and whole grain consumption. This is useful because it provides a clinical biomarker to allow a more effective way to measure whole grain intakes in clinical and epidemiological research.
Other researchers1 have now investigated the use of alkylresorcinols in determining the self-reported whole grain intake of individuals, using a large parallel group dietary intervention study involving 316 overweight individuals. The subjects, who had whole grain intakes of less than 30 g/d, were assigned to receive either 60 g/d whole grains for 16 weeks, 60 g/d whole grains for 8 weeks followed by 120 g/d whole grains for 8 weeks, or their present diet for 16 weeks (control). Fasting blood samples were collected at baseline and at 8 and 16 weeks. The results showed that total plasma alkylresorcinols increased with increasing whole grain intake, and the levels were such that subjects who took 60 or 120 mg/d could be differentiated. The authors also reported that plasma alkylresorcinols were higher in men that women and correlated positively with plasma triglyceride concentrations, and negatively with non-esterified fatty acids.
This study suggests that the use of plasma alkylresorcinols as a biomarker of whole grain intake could be useful as a clinical tool. As with previous studies investigating the usefulness of plasma alkylresorcinols, the authors of this study reported large inter subject variability, suggesting that alkylresorcinol absorption and metabolism may vary from person to person. The sex differences shown in this study are interesting and highlight the differing rates for lipid metabolism in men and women. Metabolism of the vitamin E vitamer γ-tocopherol has also been shown to differ between sexes, with females having significantly faster γ-tocopherol metabolism. Both γ-tocopherol and alkylresorcinols are metabolised in a similar manner, and this might explain the lower levels of the alkylresorcinols found in this study in women. The differences in fat distribution may also contribute to these effects, but more data is required to draw conclusions.
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