Release from food structures maximising availability for absorption

4 Release from food structures maximising availability for absorption 

Comparative carotenoid intake across five European countries Aipha carotene Lycopene Lutein 

From the above description it will be appreciated that the efficiency of release of nutrients from ingested plant material is dependent upon the ease with which the digestive enzymes can penetrate the cell wall to release the nutrients so that they can diffuse out of the structure to be absorbed. Thus tissue maturity, cooking, macerating, mastication and mode of tissue failure, all of which control particle size, cell wall softening or cell disruption, are key features which regulate nutrient release. 

With few exceptions, small particles of vegetable foods are generally stripped of their more accessible nutrients during digestion in the GI tract. In this way starch, protein, fat and water-soluble small components (sugars, minerals) are usually well absorbed. This is not always the case, however, for larger food particles or for molecules that cannot diffuse out of the celF tissue. Neither is it the case for the lipid-soluble components. These need to be dissolved in lipid before they can be physically removed from the cell to the absorptive surface, since the cell wall is unlikely to be permeable to lipid emulsions or micelles, and the presence of lipases will strip away the solvating lipid. 

It will be appreciated that the delivery of nutrients from foods is attenuated by the structure of the food and the way in which it is digested. Thus, delivery from the food structure occurs over the same timescale as gastric emptying. Carotenoids, and other compounds, isolated from the food structure are generally emptied from the stomach and absorbed more rapidly. These different rates of delivery may have profound effects on subsequent metabolism. 

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