High doses of vitamin A impair iron absorption

Abstract

Objective:

The present study aimed to determine the influence of vitamin A on iron absorption when vitamin A and iron are administered together orally compared with the administration of iron alone.

Methods:

This was a randomized double-blind clinical trial conducted on healthy men with normal red blood cell indices. Five experiments were performed, with iron (10 mg); iron (10 mg) plus vitamin A (450, 900 and 1800 μg), and placebo. After an 8-hour fast, basal (T0) blood samples were collected: basal (T0), 2 hours (T1), and 4 hours (T2) after the ingestion of the compounds to be studied. Iron was determined by inductively coupled plasma mass spectrometry. Serum ferritin was determined by an immunometric method, ie, by chemoluminescent enzyme immunoassay. Plasma retinol was measured by high-pressure liquid chromatography. Serum curves and the sum of the area under the curve adjusted to the mixed effects linear model were determined (P < 0.05).

Results:

Vitamin A at the doses of 450 and 900 μg had a stimulating effect, which, however, did not differ significantly from that of experiment 1 in which iron was used alone. At the dose of 1800 μg, vitamin A had a negative effect on iron absorption.

Conclusion:

High doses of vitamin A may cause lower serum iron levels, whereas a low dose favors iron absorption.

Keywords::

• iron absorption
• serum iron
• vitamin A
• oral iron
• oral supplement