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An investigation of the functional significance of marginal riboflavin status in young women (RIBOFEM)
Project Code: N05061
University of Sheffield
Powers, H ; Williams, E; Hill, M; Mushtaq, S
The most recent National Diet and Nutrition Surveys (NDNS) of the United Kingdom have revealed a high prevalence of poor riboflavin status in certain population groups, and, in some instances, some discrepancy between measures of riboflavin status and estimates of riboflavin intakes. This study provides information regarding the functional significance of marginal riboflavin deficiency in young women. The study focuses on haematological status and iron handling as the key functional effect of marginal riboflavin status because this outcome has the strongest evidence base.
Summary of main findings
Improving riboflavin status leads to an improvement in some measures of haematological status, including haemoglobin and red blood cell numbers.
There was a highly significant improvement in EGRAC in response to both levels of supplement, with a significant dose-response. Improving riboflavin status elicited an increase in haemoglobin and red blood cell numbers. EGRAC value at baseline was an important determinant of the magnitude of the increase in haemoglobin, such that there was a significant inverse association between baseline EGRAC and change in haemoglobin concentration. Women in the lowest tertile of riboflavin status at baseline (EGRAC >1.65), showed a significantly greater increase in haemoglobin (0.48g/dl) than women in the first and second tertiles. These women also showed a significant increase in number of circulating red blood cells. There
were no changes in dietary iron intake and it is postulated that improving riboflavin status enhanced mobilisation of iron from body stores and that this iron fuelled the observed increase in red blood cell numbers and haemoglobin concentration.
Improving riboflavin status does not increase iron bioavailability
In the sub group of women who completed the iron bioavailability study, riboflavin supplements elicited an increase in haemoglobin and red blood cell numbers, as seen in the main study. The increase in circulating iron appears to come from iron stores. Taking the sub group as a whole there was no significant effect of riboflavin supplementation on iron absorption, as measured by red blood cell incorporation of iron. However, in those women with an initial haemoglobin value above the median for the whole group, improving riboflavin status significantly down regulated iron absorption. This reflects the body’s attempt to maintain iron homeostasis.
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