absorption

Absorption is the process by which nutrients in the gut are taken into the blood-stream so that body cells can use them. For a nutrient to be absorbed, it has to be broken down into substances small enough to pass through the gut wall. Despite eating a balanced meal rich in nutrients, a person may still be malnourished if he or she lacks the enzymes required to break down the food into absorbable components (lack of the enzyme lactase, for example, will result in an inability to digest milk sugar (see lactose). Malnutrition may also result from damage to the intestinal wall, as happens in people intolerant to gluten (see coeliac disease), or when one food item interferes with the absorption of another. Absorption of iron and other minerals, for example, may be impaired by drinking tea and coffee, or by eating soya protein, wheat bran, calcium supplements, and fibre. Alternatively, high levels of vitamin C in the diet enhances iron absorption. See also phytic acid.