The study, which took place in Australia, also reported a significant difference in the gut microbiome of toddlers who consumed synbiotics-fortified milk.
In particular, there was an increase in Bifidobacterium in their gut microbiome.
Writing in Frontier in Padiatrics, researchers from The University of Queensland and Danone Research and Innovation pointed out that toddlers taking the fortified milk have shown had significantly higher levels of serum iron and iron carrier.
The synbiotics-fortified milk used in the study contained 780m CFU of the probiotics strain Bifidobacterium breve M-16V, and prebiotics consisting of 1.8 grams of short-chain galactooligosaccharides and 0.2 grams of long-chain fructooligosaccharides per 100 ml.
It was also fortified with 1.3mg of iron and 1.2 µg of vitamin D and vitamin C to help increase the bioavailability of ferrous citrate – an iron-based phosphate binder that improves iron-deficiency anaemia.
Effects of the fortified milk on iron status were compared against a standard non-fortified milk in a 12-month double-blind randomised-controlled trial known as the Child Health and Residence Microbes (CHaRM).
The trial involved 48 toddlers aged one to two and they consumed two 150 mL servings of their respective formulas daily.
Their blood and faecal samples were collected before and after the trial for analysis on iron absorption status.
Findings showed that the intervention group had significant increase in their levels of iron carrier transferrin.
Transferrin transports iron through the blood to various tissues, such as the liver, spleen, and bone marrow. It is an essential biochemical marker of body iron status.
In this case, transferrin levels increased from an average of 10g/L at baseline to nearly 20g/L by the end of the study in the intervention group. There was, however, a reduction in transferrin levels in the control group by the end of the study.
Second, serum ferritin concentration was significantly higher in the intervention group as compared to the control group by the end of the study.
Ferritin is a blood protein containing iron.
Results also showed that ferritin concentration had significantly decreased from baseline in the control group.
Third, haemoglobin levels had significantly increased from baseline in both groups by the end of the study. However, the increase was greater in the intervention group as compared to the control group.
“At the end of the intervention, we observed significant differences in several blood parameters; serum iron, transferrin, and haemoglobin levels were higher in the Active (intervention) group at month 12 compared to baseline…
“Serum iron levels were higher in the Active group at month 12. This suggests that increased iron uptake coincided with increased iron carriers (transferrin) in the blood and ferritin stores were maintained in the body,” said the researchers.
On the other hand, serum vitamin D in the form of 25-hydroxyvitamin D was significantly reduced from baseline to the 12th month in both groups. However, the researchers said the levels were still within the healthy range for both groups.
Microbiome differences
The supplemented probiotic strain, Bifidobacterium breve M-16V, saw a significant increase between baseline and the 12th month in the intervention group.
In contrast, there was a significant decrease in the Bifidobacterium breve group in the control group from baseline to the 12th month. This decrease was not observed in the intervention group.
As a whole, Bifidobacterium had decreased significantly in the control group from 20.6 per cent at baseline to 7.9 per cent by the end of the study.
“The presence of the supplemented probiotic strain (B. breve M-16 V) was only detected in the Active group, as shown by the q-PCR results.
“Bifidobacterium is one of the most abundant genera in the gut of breastfed infants and is considered a true ‘keystone’ taxon with a strong eco-physiological impact on the microbiota composition,” said the researchers.
As iron supplementation has been associated with adverse effects such as an increase in opportunistic pathogenic bacteria, the researchers said that the use of pre, pro, or synbiotics could help mitigate these adverse effects, while supplementing iron at the same time.
“Several studies have shown modulation of the colonic microbiota by pre-, pro-, or synbiotics can mitigate these adverse effects of iron fortification on the gut microbiome.
“This study confirms changes in both the taxonomic composition and the relative abundances of predicted microbial functions over one year, indicative of a developing early-life microbiome.”
Mechanisms
The researchers hypothesised that Bifidobacterium may have improved iron bioavailability by a few mechanisms.
First, it could have improved iron bioavailability by lowering pH levels in the colon.
In addition, Bifidobacteria may have prevented opportunistic pathogenic bacteria from utilising the scarce amount of iron either by competitive exclusion or by reducing Fe2+ accessibility for other microorganisms by competitively binding it to their extracellular membranes.
“This study has provided us with a working hypothesis on the effect of synbiotics on toddler gut microbiota composition and microbial function. In the presence of synbiotics, iron absorption may be improved through the acidification of the gut.
“As the study aimed to compare the effects of synbiotic-supplemented formula with cow’s milk, which is a common practice, we were unable to independently differentiate the effects of iron fortification from the interaction of synbiotics with the microbiota composition.
“We propose that this hypothesis should be addressed using existing publicly available studies and in future clinical trials,” said the researchers.
Source: Frontier in Padiatrics
A young child formula supplemented with a synbiotic mixture of scGOS/lcFOS and Bifidobacterium breve M-16V improves the gut microbiota and iron status in healthy toddlers
doi: 10.3389/fped.2024.1193027
Authors: Charmaine Chew et al
