Abstract:
Dietary fiber has been suggested as interfering with
mineral utilization. The influence of broccoli florets and
wastes, cauliflower heads and wastes, wheat bran and Metamucil
on mineral uptake by the rat was determined using
balance studies. All results were compared to control
animals fed diets containing 10% hydrolyzed cellulose.
Utilization of Ca, Mg, Cu, Zn and Fe were determined to be
62, 33, 23, 42, and 52% respectively for control animals.
The uptake of Mg, Zn and Fe were significantly reduced to 12,
16 and 18% respectively from broccoli florets. Broccoli
wastes decreased absorption of Zn to 14% and created a negative
iron balance. Cauliflower heads improved Zn assimilation
to 61%. Cauliflower wastes depressed Ca absorption to
26% and caused Mg balance to be negative. Wheat bran improved
utilization of Ca and Zn to 88 and 54% respectively.
Metamucil increased uptake of Ca to 88% and Mg to 53%. Copper
balance was unaffected by any test diet. To better understand results of balance trials, the bioavailability of
Fe from some sources was measured. The relative biological
values (RBV) of endogenous Fe in broccoli, cauliflower,
Brussel sprouts and wheat bran were determined to be 93, 88,
83, 98% respectively. These values were obtained using rats
fed control diets containing 5% hydrolyzed cellulose and
ferrous sulfate (RBV = 100). The efficiency - true bioavailability
of utilizing dietary Fe is approximately one-half
of the RBV. These values agree well with apparent uptake
of iron by animals in the balance trials for all diets
except broccoli. This exception may be due to differences
in the amount and source of broccoli fed. High dietary
levels of broccoli florets and wastes appear to interfere
with utilization of Fe and Zn. Cauliflower wastes depress
absorption of Ca and Mg. With the exceptions noted, dietary
fiber from plant sources does not appear to decrease the
utilization of minerals by the rat. The nature of mineral
complexes in plants may be more important in defining the
degree of its absorption.
