Micronutrient Bioavailability From Wheat

This research project is a short-term dietary intervention study to investigate the bio-availability of iron and zinc from wheat. Approximately 50% of iron and 30% of zinc in the United Kingdom diet is provided by cereals and cereal products (e.g. bread and breakfast cereals). The localisation of both iron and zinc metals in wheat is largely confined to the aleurone layer, a single layer of cells located between the centre (endosperm) and outer layers (testa and pericarp). The aleurone layer is removed during the production of white flour. For this reason, since 1953 it has been mandatory to add iron to flours at the mill to restore iron to levels present in wholegrain flour (The Bread and Flour Regulations, 1998).

The investigators have shown that aleurone cells are resistant to physical disruption and digestion as they pass along the gastrointestinal tract and are excreted intact in faeces. The investigators believe that disruption of wheat aleurone cell walls prior to food manufacturing would therefore increase iron and zinc availability. Using wholegrain flour and purified wheat aleurone flour the investigators have shown that micro-milling, a process which reduces particle size of flour from approximately 100μm to 10μm, ruptures the aleurone cell walls, and increases iron availability, i.e. the amount absorbed by intestinal cells, compared with flour produced using standard milling techniques (which does not break down the aleurone layer).

Based on these initial findings, the current study therefore has 2 main aims:

(i) to determine whether physical disruption of the aleurone (by micro-milling) in wholegrain flour increases iron and zinc availability from wholegrain bread.

(ii) to determine whether addition of micro-milled aleurone flour to white flour increases iron availability from white bread.