Hidden sources of galactose in the environment

A galactose-restricted diet free of lactose is lifesaving in patients with galactose-1-phosphate uridyl transferase (GALT) deficiency, but does not prevent long-term complications such as developmental delay, abnormal speech, poor growth and, in females, ovarian failure. Lactose, found in dairy products and as an extender in drugs, has been considered the primary source of galactose in the diet. Two recent publications reported that small amounts of galactose are present in many fruits and vegetables. We report the presence of considerable amounts of free galactose in some legumes (dried beans and peas) and the presence of bound galactose in many food plants. Galactose, in various glycosidic linkages, such as alpha-1,6, beta-1,3 and beta-1,4, and as a component of lipids, is ubiquitous in animals and plants. The bioavailability of alpha-1,6 and beta-1,3 linked galactose in foods is unknown. However, alpha-galactosidases found in plant and animal tissues may release galactose in alpha-1,6 linkage, and from diagalactosyldiacylglycerol. Galactose in beta-1,4 linkage and as monogalactosyldiacylglycerol may be released by beta-galactosidases in animal and plant tissues. Foods fermented by microorganisms for preparation or preservation purposes may contain free galactose. The role of free and bound galactose in cereals, fruits, legumes, nuts, organ meats, seeds, and vegetables in the poor outcome seen in some patients with GALT deficiency is unknown. It is certain that no patients with GALT deficiency have ever ingested a galactose-free diet.