The Influence of Iron and Zinc Supplementation on Iron Apparent Absorption in Rats Fed Vitamins and Minerals Reduced Diets

Deficient human diet is usually reduced in many nutrients, but animal studies on iron absorption have been only carried out for rats fed well-balanced (control) and iron-deficient diets. The aim of this study was to evaluate the effect of iron or iron/zinc supplementation on iron apparent absorption (IAA) in rats fed a diet reduced in all vitamins and minerals (R). The study was conducted on 77, 6-week-old male Wistar rats in 3 stages as follows: stage I, 4-week period of adaptation to R diet (50% less vitamins and minerals compared to AIN-93M recommendations); stage II, 4-week supplementation period with iron (RSFe) or iron/zinc (RSFeZn); stage III, 2-week post-supplementation period (rats fed R diet). Feces samples to IAA determination were collected at the 20–22nd days of stage I and II and the 10–12th days of stage III. To determine the changes in IAA after introducing and discontinuation of supplementation, feces were collected for 3 days after introducing (stage II) and 5 days after the supplementation discontinuation (stage III). At the end of stage II, compared to R rats, the IAA was statistically significantly higher in RSFe and RSFeZn rats (30.3 ± 2.0% vs. 47.4 ± 1.2% and 51.0 ± 1.7%, respectively). After introducing iron or iron/zinc supplementation, the IAA stabilized fast already in the first day, while after discontinuation of the supplementation, at least 4 days was required to the stabilization. At the end of stage III, the IAA was significantly lower in RSFe (15.8 ± 6.6%) than in RSFeZn rats (43.4 ± 5.9%). In conclusion, to confirm that iron and zinc supplementation is more beneficial than iron supplementation only, especially after discontinuation of supplementation, further research among humans is necessary.