The enrichment of eggs with folic acid through supplementation of the laying hen diet.
In light of evidence supporting a need for humans to increase their dietary folate intakes, experiments were conducted to evaluate the extent to which egg folate levels could be increased. In Study 1, Hyline W36 hens (n = 6/diet) received a barley-based diet, containing 0 or 10 mg/kg of crystalline folic acid, to establish the potential for folate incorporation into table eggs. In Study 2, 70 hens were divided into seven treatment groups (n = 10 hens/diet) and received diets supplemented with 0, 1, 2, 4, 8, 16, or 32 mg folic acid/kg diet. In Study 3, 64 hens received the barley-based diet with or without 4 mg folic acid/kg diet. Eggs were collected and stored for 0, 7, 14, 21, or 28 d, prior to folate determinations. The folate content of eggs was determined by HPLC for 5-methyltetrahydrofolate (the sole form of folate in egg yolk). Results from Study 1 showed that a 10 mg/kg inclusion of folic acid increased folate incorporation into egg yolk (41.0 +/- 0.7 microg /egg) over that of an unsupplemented diet (17.5 +/- 0.7 microg /egg; P = 0.0001). In Study 2, the response of egg folate to dietary folic acid supplementation was saturable, with 90% of maximal egg folate levels established at approximately 4 mg folic acid/ kg diet. Results from Study 3 showed that folate levels are stable, in control and fortified eggs, during 28 d of storage at 4 C. In terms of its nutritional value, one large egg collected from a folic acid-supplemented hen provided approximately 12.5% of the recommended dietary allowance (RDA) for adult humans (RDA = 400 mg/d).