A new study has linked greater sugar exposure during the earliest stages of life with a higher risk of anxiety in adulthood, suggesting that nutritional conditions during pregnancy and the first two years of life may have effects that persist for decades.

Researchers from the University of Surrey examined data from 46,448 participants in the UK Biobank who were born between October 1951 and March 1956, a period spanning Britain's post-war sugar rationing and its eventual removal.

The researchers used the historical change in sugar availability as a natural experiment to investigate whether differences in early-life sugar exposure were associated with later mental-health outcomes.

The first 1,000 days

The study focused on the first 1,000 days after conception, broadly covering pregnancy and the first two years of a child's life.

Participants were grouped according to how long they were exposed to Britain's sugar-rationing system, including people who experienced rationing only in the womb and those who remained under rationing for up to 24 months after birth.

Researchers compared these groups with people who were born after sugar rationing had ended.

The study therefore did not rely on parents recalling what their children ate decades earlier. Instead, exposure was inferred from birth dates and the historical period during which sugar was rationed.

Lower anxiety risk among those exposed to longer rationing

The clearest association involved anxiety.

People who experienced the longest period of sugar rationing, from pregnancy through approximately their first two years of life, showed a lower hazard of developing anxiety in adulthood compared with participants who had not experienced sugar rationing.

In the fully adjusted analysis, the longest-rationed group had a hazard ratio of 0.67 compared with the reference group, corresponding to an approximately 33% lower hazard.

The researchers also found evidence of a duration-response pattern, with longer exposure to rationing generally associated with lower anxiety risk.

Later diet did not explain away the anxiety association

The researchers carried out additional analyses to examine whether the differences could simply be explained by how much sugar participants consumed as adults.

After adjusting for later-life free and total sugar consumption, the association between prolonged early-life rationing and lower anxiety risk remained statistically significant.

This suggests that the relationship observed in the study cannot be explained entirely by differences in adult sugar intake.

However, the authors stress that the study design still cannot rule out all other factors that may have differed between the historical groups.

Depression findings were less consistent

The researchers also investigated depression.

The longest period of early-life sugar rationing was initially associated with a lower risk of depression. However, that association became weaker and was no longer statistically significant after adjustment for later-life sugar consumption.

The researchers therefore regarded the evidence linking early-life sugar restriction with anxiety as more robust than the evidence relating to depression.

Participants were born during a unique historical period

The study was possible because Britain's post-war sugar rationing created a rare natural experiment.

Sugar was rationed for years before restrictions ended in September 1953. Sugar availability subsequently increased substantially, creating differences in exposure among people born at different points around the end of the rationing period.

This allowed researchers to compare groups who were otherwise born within a relatively narrow historical window.

The researchers also included comparison groups, including people born after rationing had ended and a group born in Ireland, to test whether their findings could simply reflect differences associated with birth timing.

Preference for sweet foods also differed

The study found that people who experienced the longest period of sugar rationing reported a lower preference for sweet foods in adulthood.

The differences were relatively modest, and the study did not find statistically significant differences in measured adult sugar consumption across all rationing groups.

This distinction is important because a preference for sweet foods is not the same as a direct measurement of how much sugar someone consumes.

Researchers also examined brain structure

The team analysed available brain-imaging data alongside the historical rationing exposure.

Significant differences in grey-matter volume were identified across 80 of the 139 brain regions examined when comparing the different rationing groups.

Further analysis found significant differences in 11 of those regions in comparisons involving most of the rationed groups and participants who had never experienced rationing. Some of the differences involved regions of the cerebellum.

The researchers suggest that brain development could be one possible pathway connecting early nutritional environments with later mental-health outcomes.

These imaging findings, however, are observational associations and do not establish that differences in sugar exposure directly caused the structural changes.

The study did not directly measure childhood sugar intake

One of the most important qualifications is that the researchers did not have direct dietary records showing exactly how much sugar every participant consumed during infancy.

Instead, sugar exposure was inferred from the duration of historical rationing.

The researchers acknowledge that other foods were also rationed during the same period, including items such as cheese, butter, cereals and meat, although sugar rationing ended at a different point and the researchers carried out additional analyses to address this issue.

This means that the findings should be interpreted as evidence from a natural experiment involving early-life sugar availability, rather than as a direct comparison of children consuming measured quantities of sugar.

The results do not prove that sugar causes anxiety

The study provides evidence of an association between early-life sugar exposure and later anxiety risk, but it does not establish that consuming a particular amount of sugar during childhood will cause anxiety later in life.

The authors acknowledge that the observational nature of the research means residual confounding remains possible.

The participants were also born in Britain during a very specific historical period, meaning the findings may not necessarily apply in the same way to children growing up under today's nutritional, social and healthcare conditions.

Further research would be needed to determine how much of the association is specifically attributable to sugar itself and what biological mechanisms might be involved.

What the researchers found overall

The study's principal finding was that longer exposure to sugar rationing during the first 1,000 days was associated with lower anxiety risk in adulthood.

Those exposed to rationing for the longest period also showed a lower preference for sweet foods later in life, while the study identified differences in a number of brain-imaging measures.

The association with depression was weaker and became non-significant after accounting for later-life sugar intake.

A long-term question about early nutrition

The findings add to research examining how nutrition during early development may be associated with health outcomes much later in life.

The first 1,000 days are already considered an important period of development, and the researchers argue that the historical British rationing period provides an unusual opportunity to examine possible long-term relationships between early nutritional environments and adult mental health.

For now, the study provides an association rather than a definitive cause-and-effect explanation. Its findings point to the potential importance of early-life nutrition while also highlighting the need for further research into the mechanisms behind the relationship between sugar exposure and anxiety.