Bioavailability of Food Folates and Evaluation of Food Matrix Effects with a Rat Bioassay

Abstract

Folate bioavailability of beef liver, lima beans, peas, spinach, mushrooms, collards, orange juice and wheat germ was estimated with a protocol of folate depletion-repletion using growth and liver, serum and erythrocyte folate of weanling male rats. Diets with 125, 250 and 375 micrograms folic acid/kg were standards. Individual foods were incorporated into a folate-free amino acid-based diet alone (250 micrograms folate/kg diet from food) or mixed with folic acid (125 micrograms folate from food + 125 micrograms folic acid) to evaluate folate bioavailability and effects of food matrix. Beef liver and orange juice folates were as available as folic acid, whereas those of wheat germ were less bioavailable. Folates of peas and spinach were also less available than folic acid using liver and serum folate concentrations and total liver folate as response criteria, but they were not lower when based on growth and erythrocyte folate concentrations. Lima bean, mushroom and collard folates were as available as folic acid using four of five response criteria. Folate bioavailability of all foods generally exceeded 70%. All response criteria gave approximately equivalent results, indicating that growth and tissue folate levels are appropriate criteria. No food matrix effects were observed for any food except lima beans. Foods rich in polyglutamyl folates were less bioavailable than those of foods rich in short-chain folates.

Comparative nutrient composition of selected wild edible mushrooms from two agro-ecological zones, Uganda

“…This value is almost of the same magnitude as that generally found in some vegetables, higher than that of fruits (3–23 μg/100 g) (FAO 1972) and lower than in other wild mushrooms (1,222–1,412 μg/100 g dry weight) (Bano and Rajarathnam 1988). Fortunately, folic acid bioavailability in mushrooms is good compared to some vegetables, such as peas and spinach (Clifford et al 1991). …”

Mushrooms as therapeutic agents

“…Mushrooms contain moderately high amounts of folates at concentrations that are of the same magnitude as is generally found in vegetables. Furthermore, the bioavailability of folates is as good as that for folic acids (Clifford et al, 1991) with a content of 300-1412 μg/100 g. In addition to riboflavin, niacin and folates, cultivated mushrooms also contain small amounts of vitamin C and vitamin B1 and traces of vitamins B12 and D2 (Mattila et al, 2001).…”

Folates - food sources, analyses, retention and bioavailability

“…Cliflord et al (88,89), using a rat bioassay model, reported folate bioavailability between 70 and 120% from food items like lyophilised orange juice, cooked lima beans, cooked leafy vegetables, wheat germ, eggs and mushrooms. These figures are higher than usually found in human studies based on similar food items.…”