However, the supplementation did not lead to benefits in other areas of neurocognitive development, including motor and visual development.
Writing in the Annals of the New York Academy of Sciences, the researchers also found that prior to the supplementation regime, a higher baseline concentration of vitamin B1 in breastmilk was associated with more advanced development in the infants' fine motor, receptive language and expressive language abilites.
This could be because neurocognitive development begins before birth and then progresses rapidly from birth onward, the researchers explained.
“This finding provides preliminary evidence that infants’ neurocognitive development may benefit most if maternal thiamine supplementation begins prenatally,” they said.
The RCT was conducted between September 2018 and December 2019 in the Kampong Thom province in Cambodia – where there is a high risk of thiamine deficiency due to low maternal thiamine intake during lactation.
A double blind, four-parallel-arm RCT, 335 mothers who fed their infants only with breastmilk were recruited and randomised into four groups.
The mothers took in a capsule containing no vitamin, 1.2mg of vitamin B1, which is the estimated average requirement (EAR), or double the EAR at 2.4mg, or 10mg daily when their babies were between two and 24 weeks old.
Two assessments, namely the Mullen Scales of Early Learning (MSEL) and the Caregiver Reported Early Development Instrument (CREDI), were then conducted on the infants at the start of the trial and when they turned 12, 24, and 52 weeks old.
Vitamin B1, also known as thiamine, plays a crucial role in the cognitive development of children.
In 2003, Israel reported several cases of hospitalisation among infants who consumed a soy-based infant formula that was erroneously manufactured without vitamin B1.
These infants developed serious symptoms including developmental delay, respiratory symptoms, diarrhoea, vomiting, and abdominal distension. They were subsequently treated with an injection of 50mg of vitamin B1 per day for two weeks and switching to another infant formula.
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What happens when supplementation stops?
The researchers found that once the mothers stopped taking vitamin B1, language development began to slow down in their kids.
In this study, the mothers stopped taking vitamin B1 when their kids turned 24 weeks old, and the kids' neurocognitive development was assessed and compared with kids of similar age in the US.
It was found that by the 52nd week, their language development decreased by about 1.5 standard deviations from their 24-week standardised score and was approximately a full standard deviation below the US norms.
“It is important to recognise that the magnitude of this developmental slowing observed across our sample was not trivial.
“Infants whose mothers had received higher doses of thiamine in previous months tended to display more precipitous rates of decline in language development once supplementation ended, with all protection conferred by thiamine supplementation during the first 6 months nullified by 52 weeks,” the researchers said.
While the decline was mainly seen in language development and not on motor and visual development, they also cautioned that the declines in these domains might emerge later as seen from existing studies.
Based on the findings, they suggested that maternal thiamine supplementation and/or integration of nutrient-rich complementary foods for a prolonged period might be necessary to sustain neurocognitive gains in infants.
“One possible perspective on these findings is that they provide yet further indication that infants’ developing language systems require adequate thiamine.
“In sum, it is not yet possible to draw clear conclusions regarding the precise implications of infants’ declining trajectory in language development between the conclusion of the intervention at 24 weeks to the 52-week post-intervention time point.
“Further investigation of this important issue is clearly warranted,” the researchers said.
Sufficiency is not enough
Having a sufficient vitamin B1 status amongst breastfeeding mothers is not enough to drive language development in infants, the study also found.
A daily supplementation of 1.2mg of vitamin B1 was sufficient to increase breast milk vitamin B1 concentration. However, it was not enough to help infants, especially those from low- and middle-income countries, in catching up with infants from more advantaged countries in terms of language development.
For future studies, the researchers proposed to find out the appropriate duration of vitamin B1 supplementation and/or fortification programs during pregnancy, infancy, and beyond.
Source: Annals of the New York Academy of Sciences
Thiamine supplementation holds neurocognitive benefits for breastfed infants during the first year of life
Authors: Jeffrey R. Measelle et al