Define the Enzyme deficiency or defects?
A food sensitivity or intolerance can occur when the body has difficulty in digesting a particular food and therefore reacts against it. Let us understand this mechanism in details. In normal digestion, the foods we eat are broken down (though chewing and the action of the acids etc. in our stomach and our intestines) into their component parts. The useful ones (the nutrients) are absorbed into the bloodstream through the digestive tract (or 'gut wall'), the redundant ones are flushed out through the bowel. However, if the foods are not properly broken down through some digestive malfunction the body either will not be able to absorb them properly or, since they have not been properly 'processed', may react against them. In the case of lactose intolerance, for example, the body fails to manufacture the enzyme lactase that is needed to digest the lactose sugar in mill<. Without lactase, the digestion cannot process the lactose sugar in the milk.
The digestion cannot cope with the raw lactose sugar so reacts against it in the form of cramps, vomiting, diarrhoea, abdominal pain etc. One other example is phenylketonuria (PKU), which is an inborn error of metabolism. In normal people the enzymephenylalanirze Izydronylase converts phenylalanine (an amino acid) to tyrosine (another amino acid), which is then utilized by the body. In PKU since phenylalanine cannot be hydroxylated to tyrosine, its metabolites accumulate and cause damage to the central nervous system and result in unusual irritability, eczema etc. Galactosemia due to deficiency of the enzyme galactose-1 -phospahte uridyl ti-ansferase which converts galactose-l- phosphate to glucose-1-phosphate leads to accumulation of galactose causing various symptoms such as vomiting, fever, jaundice etc.