Hereditary Fructose Intolerance (HFI)
Hereditary Fructose Intolerance (HFI) is a very rare congenital defect of the fructose metabolism which results in hypoglycaemia and serious damage to the liver and kidneys. HFI patients suffer severe symptoms, usually starting in their first year of life as soon as they are given supplementary food. A great many, but by no means all of them, take a dislike to anything sweet (fruit or vegetables) which protects them against eating fructose. In contrast to fructose malabsorption, a low-fructose diet is of no use if someone suffers from fructose intolerance; their intake must be strictly fructose-free.
People suspected of suffering from HFI should be warned against taking a Hydrogen Breath Test before any suspicious factors are cleared up; serious hypoglycemic reactions may occur during the test.
Hereditary fructose intolerance can, among other things, be diagnosed by molecular genetic analysis.
More information about the various kinds of sugar/sugars please see sugars.