- Sugar consumed during pregnancy or early childhood may harm brain development, especially memory and learning.
- The effect seems to run through the gut microbiome, which sends signals disrupting the hippocampus.
- Human studies link maternal sugar intake to altered infant brain structure and lower cognitive scores later.
- Timing and amount matter — chronic sugar harms cognition, but a quick glucose hit can briefly boost memory.
- Health bodies (WHO, AHA, AAP) now recommend strict sugar limits for young children based on this evidence.
Warnings about sugar have been about the waistline and teeth for decades. But a new wave of studies is emerging that points towards a place less obvious today: the developing brain. Scientists are more and more sure that the food consumed by a mother in her womb or a child while growing up during this explosive time of brain development imprints a lasting memory, learning and even mental health on the brain, which can have impacts in the decades that follow.
A Brain Under Construction
The human brain isn’t built in one fell swoop and then abandoned; it is put together piece by piece, and certain sections continue to be in construction quite into adolescence. One of the slowest developing brain regions is the hippocampus, the seahorse-shaped region that is the anchor of memory and learning; this area is also one of the most susceptible to nutritional disruption. With a team from the University of Southern California, researchers at the University of Georgia wanted to find out what happens to this region if young animals are allowed to drink sugar-sweetened beverages regularly. The results of their several-year study of the hippocampus were surprising: although food intake or anxiety-like behaviour was not different, chronic sugar intake during adolescence reduced memory function in the hippocampus in adulthood. That is, the injury was not apparent on the bathroom scale, but only in tests of memory and learning.
The Gut-Brain Detour
The scientists found a pathway, which is interesting because of this research. It was not sugar being fed directly to the brain cells, but sugar going to the gut microbiome which then sent signals to the brain. The researchers discovered that early sugar consumption altered the composition of gut bacteria, and specifically increased a genus called Parabacteroides. The impact of sugar consumption during early life was clear, said lead researcher Emily Noble: “some learning and memory seems to be selectively disrupted by early-life sugar consumption, and that is related to learning and memory that rely on the hippocampus. The researchers raised the amount of Parabacteroides in the animals but didn’t give them any sugar, and even then, cognitive impairments emerged a powerful suggestion that the gut microbiome has a role to play in the cognitive changes and is not just a byproduct.
A follow-up study on early-life stress and diet took it one step further: mice that were stressed by maternal separation but fed a high-sucrose diet exhibited hippocampal changes remarkably comparable to those observed in stressed animals alone, such as changes in neurogenesis and inflammation. This indicates that sugar is not a silent partner in a stressed or developing brain but rather can serve to enhance the biological markers of stress.
The Story in Human Infants
Animal data are compelling, but the more pressing issue is whether this is also the case for humans. In this instance, the evidence is newer and thinner but still agrees. In a study presented at the meeting, researchers applied a specialized MRI technique called diffusion tensor imaging to the brains of three-week-old babies, whose mothers had reported their consumption of sugar during pregnancy. Even after researchers took into account the baby’s age, sex and birth weight, they found that higher maternal intake of total and added sugar was associated with a widespread pattern of differences in organization of brain tissue across the cortex, including the frontal lobes. The same research group reported earlier in the study that moms who consumed more sugary drinks during pregnancy had children with verbal test scores that were a little lower, and sugary drinks eaten during breastfeeding were linked to lower cognitive scores when the kids were two years old.
Another long-term American study, Project Viva, followed more than 1,000 mom and baby dyads from the 20th week of pregnancy through adulthood. It discovered that mothers who drank more sucrose while they were pregnant had children that performed worse on nonverbal intelligence tests years later, when they were mid-childhood even after taking account of other factors concerning the mother and the child. Curiously, the same study revealed a silver lining: Foetuses were more likely to score higher if their mothers ate more whole fruit during pregnancy, suggesting that natural sugars found in whole fruit are very different from free sugars that can be poured out of a bottle.
Recent studies also have extended that time period to adulthood. By exploiting a quirk of history, in the UK during the Second World War sugar was rationed until 1953, a time when a large number of Biobank participants were born, or just after, allowing for a natural experiment in early-life sugar exposure. A team is currently studying whether that early exposure – or lack of exposure – is associated with differences in brain structure and mental health risk decades later, avoiding many of the biases of normal dietary recall studies.
What the Broader Evidence Shows
In 2023, a systematic review and meta-analysis was carried out to summarize the results of 77 studies examining the influence of sugar on cognition in humans. Nearly all of the reviewed cohort and cross-sectional studies indicated a positive link between increased added sugar intake and cognitive impairment risks. The short-term laboratory experiments revealed that a rapid injection of glucose may have a positive effect by improving the ability to retrieve memories. Therefore, the effect of sugar on cognition cannot be considered negative in all cases as it depends on the amount, timing, and chronicity of its action.
Why the Early Window Matters So Much
Multiple biological theories point in this direction. First, hyperglycaemia, or consistently elevated blood glucose levels, have been found in neuroimaging research to impair the connectivity of different parts of the brain and also be linked with brain volume reduction. It can be suggested that the constant metabolic stress in such conditions hampers the connections from being established in the case of a growing and forming brain. This needs to be supplemented by the gut microbiota mechanism, the increase in stress response gene activity, and, finally, the fact that sweet tastes acquired in early childhood set one’s taste preferences for life.
The Practical Takeaway
In fact, public health authorities have already started acting on this evidence. The American Heart Association and the American Academy of Paediatrics advise against adding any sugar to foods and beverages intended for consumption by children younger than two, while those over two should keep their sugar intake down to around six teaspoons a day – that is a small fraction of what the average child eats today. Similarly, the World Health Organization recommends restricting sugar consumption to 10 percent of daily calories, and even less is preferable.
Of course, it does not mean that sugar is an outright villain, which should be avoided at all costs. Natural sugars, occurring in fruits together with fibre, seem to act differently than free sugars, found in soda drinks, juices, and other processed products. Nevertheless, the emerging consensus for parents, pregnant women, and paediatricians is unmistakable: the sweet taste introduced in the early days of a child’s life could be remembered for many years to come.
Clear Cut Education, Health Desk
New Delhi, UPDATED: August 19, 2026 18:30 IST
Written By: Subhanshu Jaiswal
Designation: Assistant Manager – MLE at DevInsights
