What You Eat as a Baby Could Affect Your Brain Decades Later, Study Finds

What happens during the first few years of life may have consequences that last for decades. A new study has found that people who were exposed to lower sugar intake during the first 1,000 days of life had a lower risk of developing dementia and Alzheimer's disease later in life.

The researchers reached this conclusion by examining people born in Britain around the period when the country had wartime sugar rationing. Rather than having detailed records of what each person ate as a baby, researchers used their birth dates to determine whether they were born during the rationing period.

The findings suggest that early-life sugar exposure may be associated with brain health many decades later, although the study does not prove that eating sugar directly causes dementia.

Researchers Used Britain's Wartime Sugar Rationing as a Natural Experiment

Britain began rationing sugar in January 1940, several months after the Second World War began. Families received coupons that limited how much sugar they could purchase each week.

The ration continued for years after the war and was finally ended in September 1953. When the restrictions disappeared, British households purchased more than 50% more sugar, while their overall calorie intake increased by around 5%.

This gave researchers an unusual opportunity to compare people who were born during periods of lower sugar availability with people born after rationing ended.

The study was led by Jiazhen Zheng, a researcher at The Hong Kong University of Science and Technology, and included three co-authors. The team examined 64,737 people born in Britain between 1951 and 1956.

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

Importantly, the study did not have records showing exactly how much sugar each individual consumed. Instead, participants were grouped according to their birth dates and whether they experienced sugar rationing during those early years.

Lower Early-Life Sugar Intake Was Linked to Lower Dementia Risk

The participants were part of the U.K. Biobank, which recruited hundreds of thousands of British adults between 2006 and 2010 and has followed their health records.

Of the people included in the analysis, 40,963 experienced sugar rationing during some part of their first 1,000 days after conception, while 23,774 did not. Researchers then tracked dementia diagnoses through July 2023.

Among those who were not exposed to rationing, 504 developed dementia. Among the 15,256 people who experienced rationing from conception through their second birthday, 456 developed dementia.

Researchers adjusted their analysis for factors including age, sex, income, smoking, blood pressure and diabetes, along with other measures related to food and the period in which people were born.

The results showed that people who experienced rationing from conception through their first year had a 21% lower risk of dementia compared with people conceived after rationing ended.

Those exposed to rationing through their second year had a slightly greater reduction, at 23% lower dementia risk.

The researchers also found that the rationed groups developed dementia later in life. Those exposed through age two developed dementia about 2.55 years later on average.

Alzheimer's Disease Also Showed a Similar Pattern

The researchers looked separately at Alzheimer's disease.

People who experienced sugar rationing during their first year had 23% less Alzheimer's disease, while those exposed through their second year had 28% less.

However, the researchers noted that the first of these figures was borderline.

The groups also experienced fewer cases of vascular dementia, which is associated with damage to blood vessels in the brain. But the number of cases was too small for the researchers to rule out the possibility that this finding could have occurred by chance.

The association was stronger among women than men.

Interestingly, people carrying APOE e4, the genetic variant most strongly associated with Alzheimer's disease, showed the pattern at roughly the same strength as the overall group.

As another check, researchers looked at two conditions that do not have a plausible connection to early sugar exposure: type 1 diabetes and melanoma.

The groups showed roughly similar results for both conditions, which the researchers used as an additional test of their analysis.

Brain Scans Revealed Some Differences

The researchers also examined brain scans from a smaller group of 7,724 participants, who returned for brain imaging at an average age of 62.

After making the same statistical adjustments, people exposed to sugar rationing had an average of about 3 cubic centimetres more gray matter. Gray matter contains the cell bodies of nerve cells.

The researchers also found that the rationed group had about 0.6 cubic centimetres less white matter hyperintensity volume. These bright areas can appear on brain scans and are mainly associated with damage involving small blood vessels.

However, the two groups did not differ in total brain volume, overall white matter or the size of the hippocampus, a brain structure involved in memory.

On certain cognitive tests, the rationed group performed slightly better in tasks involving matching symbols to numbers, reasoning puzzles and connecting numbered circles.

The groups performed similarly on tests of working memory and word recall.

Could Blood Pressure and Diabetes Explain Part of the Link?

Researchers then looked at possible pathways connecting early sugar exposure with dementia later in life.

They estimated that 18% of the dementia association could be attributed to new type 2 diabetes during follow-up, while 11.6% was linked to high blood pressure and 2.7% to birth weight.

According to Zheng, type 2 diabetes and hypertension together explained around one-quarter of the association.

That suggests metabolic and vascular health may play a role, although the researchers stressed that their study did not directly establish the underlying mechanisms. The remaining association could not be explained by these factors.

What Should Parents Take From the Study?

The researchers said the findings support limiting added and free sugars during pregnancy and early childhood in line with existing dietary guidelines, while still maintaining adequate overall energy and essential nutrients.

Free sugars include sugars added during food preparation or manufacturing, as well as sugars found in honey, syrups and fruit juices.

The World Health Organization advises keeping free sugars below 10% of daily calories, which the article gives as approximately 12 teaspoons for an adult consuming 2,000 calories a day.

However, the study should not be interpreted as proof that reducing sugar during infancy will definitely prevent dementia decades later.

The Study Has Important Limitations

One of the biggest limitations is that researchers did not know exactly how much sugar individual participants consumed.

Instead, they used birth dates to determine exposure to the rationing period. Because of that, the study can show an association but cannot establish that sugar itself caused the later differences in dementia risk.

The U.K. Biobank participants also tend to be healthier and more financially advantaged than the British population overall. About 96% of this particular group was white, which limits how broadly the findings can be applied.

Another limitation is age. The records ended in 2023, when participants were only 67 to 71 years old, while most dementia diagnoses occur later in life.

The researchers also had to account for many other changes that occurred in Britain after the war, not just sugar availability.

When they performed additional analyses using older adults in England and Americans born during the same period, the researchers continued to see a lower overall dementia association among the rationed group. However, in one final analysis accounting for people who had died from other causes first, the difference in Alzheimer's disease disappeared.

What Happens Next?

The researchers say the next step is to conduct practical trials examining safe, guideline-level reductions in added sugar during pregnancy and early childhood.

Such research could potentially track brain development, metabolism and brain health much earlier in life rather than waiting decades for dementia diagnoses.

For now, the strongest evidence connecting early-life sugar exposure with dementia comes from an unusual historical experiment created by Britain's wartime food rationing.

The study was published in the journal Neurology.