With the introduction of solid foods, some galactose will inevitably be introduced into the diet, as many foods, such as fruit and vegetables, bread, legumes, and offal, contain trace amounts of galactose (Gross and Acosta
1991; Acosta and Gross
1995). Bound galactose is found in many vegetables as part of raffinose and stachyose. How much of this bound galactose can be broken down in the gut is not known. No significant contribution to the intake of galactose, or effect on biochemical parameters, has been demonstrated (Wiesmann et al.
1995).
There are major controversies concerning the daily allowance of galactose during long-term treatment. Many European metabolic centers recommend a very strict diet, also restricting galactose containing fruits and vegetables. Other centers, e.g., in the UK, Germany, The Netherlands, and the USA, are more liberal, advising only a lactose-free diet. There is limited knowledge of the tolerance for exogenous galactose in patients with classic galactosemia. A newborn infant with galactosemia ingesting 300 ml of formula or breast milk per day in the first days of life, equivalent to >7,000 mg of galactose, will develop severe illness. As soon as the diagnosis is suspected, the galactose intake will be restricted as much as possible. Patients on a lactose-free diet with no restrictions of fruit and vegetables will have a daily intake of galactose <30 mg (Berry et al.
1993; Bosch et al.
2004a). On a diet enriched in fruit and vegetables, this intake increases to an average of 54 mg of galactose per day (Berry et al.
1993). In one study, three adolescents ingested up to 600 mg of galactose per day for 6 weeks without any effect on clinical or laboratory parameters (Bosch et al.
2004a). Of importance is the strong contrast between the exogenous intake of galactose in the lactose-restricted diet, with an average intake of 54 mg of galactose per day with a diet enriched in galactose-containing fruit and vegetables and the endogenous production of galactose in adult patients, amounting to 1,000 mg per day (Berry et al.
2004, Huidekoper et al.
2005). This fact is an argument not to restrict fruit and vegetables from the diet. Also, after the introduction of a less restricted diet in Australia, no increases in gal-1-p values were detected (Thompson et al.
2003). Furthermore, in the UK, where fruit and vegetables are not restricted from the diet, no new cataracts or liver diseases have been reported in the literature. It has been demonstrated that the endogenous production of galactose is not affected by the exogenous intake from the diet. (Huidekoper et al.
2005)