Date of Award:

1989

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Nutrition, Dietetics, and Food Sciences

Department name when degree awarded

Nutrition and Food Sciences

Advisor/Chair:

Deloy G. Hendricks

Abstract

Methods currently used to determine iron bioavailability have disadvantages for both the subjects and researchers involved. One safe and simple method that needs further evaluation, the serum iron absorption method, involves an initial blood drawing, dosage s of iron, and blood drawings taken at intervals thereafter. Generally, the rise in serum iron or area under the curve is used to determine iron uptake. Two experiments were conducted using the serum iron absorption method in an effort to improve the utility of this method for the measurement of iron bioavailability. With this effort in mind, an equation adjusting for dose of iron (0.5-8 mg) and blood volume was used to estimate serum iron absorption and allow for adequate comparisons of other iron absorption data obtained with this method and others.

One very significant result was that low serum ferritin was found to be a predictor of high serum estimated iron absorption (SEIA). Similarly, low serum ferritin levels were also highly correlated to iron absorption when radioiron methods were used.

In Experiment I, college-aged women (n=11) with low serum ferritin levels (average 11 ng/ml) participated in four serum iron trials in which four iron sources were used as iron dosages. Ferrous sulfate in orange juice (2.2 mg iron), ground beef (0.62 mg iron), cereal (6.6 mg iron), and ground beef and cereal together (3.6 mg iron) were used. Comparisons were made between the results obtained using this serum iron absorption data and other radioiron absorption data for similar iron sources, and the results were quite similar to iron absorption levels reported in the literature. In Experiment I, the ferrous sulfate (40%) and ground beef treatments (46%) had the highest serum estimated iron absorption (SEIA) and the cereal/ground beef (5%) and cereal treatments (3%) had significantly less.

Experiment II involved 28 college-aged women who participated in four serum iron absorption trials. For these four trials the iron dose was the same (2 mg iron as ferrous sulfate in orange juice). However, pre-trial supplements containing either (1) 30 mg iron, 60 mg ascorbic acid, (2) 30 mg iron, no ascorbic acid, (3) no iron, 60 mg ascorbic acid, or (4) a placebo were given (one per day) on each of the three days prior to the weekly serum iron absorption trials. During each pre-trial supplementation period, three daily diet records were kept by subjects to determine if the previous intake of nutrients (from food or pre-trial supplements) influenced the outcome of the serum iron absorption trial. Pre-trial supplementation of 30 mg iron, no ascorbic acid caused a significantly lower SEIA. Dietary nutrients did not cause a significant effect on SEIA. Mean SEIA following combined iron supplements was lower (p=0.081) 16% vs. 23% following non-iron containing supplements. For this experiment, the SEIA was higher in subjects with low serum ferritin (20 ng/ml).

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