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Published on: December 17, 2018
Bioavailability of cadmium from infant diets in newborn rats
G Eklund1, K P Grawé, A Oskarsson
1Department of Pharmacology and Toxicology, Swedish University of Agricultural Sciences, BMC, PO Box 573, 751 23 Uppsala, Sweden. Gunilla.Eklund@farmtox.slu.se
Insights
Infant formulas expose babies to more cadmium (Cd) than breast milk. Cereal-based formulas show lower cadmium absorption in rat pups due to binding with fiber and phytic acid.
Area of Science:
- Environmental Toxicology
- Pediatric Nutrition
- Trace Element Metabolism
Background:
- Infants may receive higher cadmium (Cd) exposure from formulas compared to breast milk.
- Cadmium is a toxic heavy metal with potential adverse health effects, particularly in vulnerable populations like infants.
Purpose of the Study:
- To investigate the bioavailability and retention of cadmium (Cd) from different infant formulas in neonatal rat pups.
- To compare Cd absorption from cereal-based formulas versus cow's milk-based formula and water.
Main Methods:
- Neonatal rat pups were administered a single oral dose of 109Cd-labeled diets (cow's milk formula, soy formula, cereal-based formulas, or water).
- Whole-body, intestinal, and tissue retention of 109Cd was measured at various time points (2h to 12 days) using a gamma counter.
- Cadmium levels were quantified in the whole body, small intestine segments, liver, and kidneys.
Main Results:
- Whole-body retention of 109Cd was highest in pups consuming water or cow's milk formula.
- Retention of 109Cd in the small intestine was significantly higher in water and cow's milk formula groups compared to cereal-based formulas.
- Cadmium retention in the kidneys increased throughout the 12-day study period, indicating accumulation.
Conclusions:
- Cereal-based infant formulas demonstrate lower cadmium bioavailability in neonatal rats, likely due to binding with dietary fiber and phytic acid.
- Prolonged cadmium retention in the small intestine of neonates highlights the need for long-term studies to assess potential kidney accumulation.
- Findings underscore the importance of evaluating infant formula composition for heavy metal bioavailability and potential health risks.
Abstract:
Infants are exposed to higher levels of cadmium (Cd) from infant and follow-on formulas than from breast milk. We studied the bioavailability of 109CdCl2 from cows' milk formula, soy formula, wheat/oat/milk formula, wholemeal/milk formula and water in 11-day-old rat pups. The pups received a single oral dose of one diet labelled with 109Cd, 0.1 or 0.3 mg Cd/kg body weight. After 2 or 24 h or 4, 9 or 12 days the fractional retention of 109Cd in the whole body, in segments of rinsed small intestine and in tissue was measured in a gamma counter. Pups receiving 109Cd in water or cows' milk formula had the highest mean whole-body retention. It ranged from 67% of the dose in the water group to 52% in the wholemeal/milk formula group 4 days after dosing. The retention of 109Cd in the rinsed small intestine was significantly higher in the water group and the cows' milk formula group than in the cereal-based formula groups at 24 h and 4 days after dosing. It was still high in all groups on day 9, ranging from 26 to 11%. Initially most of the 109Cd was retained in the duodenum but by day 4 it had moved further down into the jejunum. In the liver, the highest and lowest retention on day 4 was 16%, and 3 per thousand of the dose in the water group and wholemeal/milk formula group, respectively. In the kidney, 109Cd was still increasing 12 days after exposure in all groups. Whole-body retention and tissue levels were higher than previously reported in adult animals. The lower bioavailability of 109Cd from the cereal-based formulas compared to water and cows milk formula on the longer survival times is most likely explained by Cd binding to dietary fibre and phytic acid in the cereal-based formulas reducing the intestinal binding and decreasing the bioavailability of Cd. The high retention of 109Cd in the small intestine, leading to a prolonged absorption period, emphasizes the importance of extending studies on neonatal Cd absorption over a long time period in order to detect for example, endpoints, accumulation of Cd in the kidney.
