A study led by researchers in Hong Kong, which looked at data from 65 000 UK Biobank participants, has concluded that people who consumed less sugar in utero and before the age of two, had a lower risk of developing dementia later in life, reports MedPage Today.
The study used the abrupt end of World War II sugar rationing in Britain as a natural experiment to test whether sugar exposure during different windows in the first 1 000 days from conception was tied to later all-cause dementia, Alzheimer’s disease, or vascular dementia.
Compared with people not exposed to sugar rationing, risks of all-cause dementia (HR 0.79, 95% CI 0.66-0.94) and Alzheimer’s disease (HR 0.77, 95% CI 0.59-1.00) were lower for people who had sugar rationing in utero and their first year of life, reported Jiazhen Zheng, PhD, of the Hong Kong University of Science and Technology in Guangzhou, China, and colleagues. Associations with vascular dementia were not significant.
Similar relationships emerged for in utero exposure to sugar rationing plus the first one to two years of life (all-cause dementia HR 0.77; Alzheimer’s disease HR 0.72), Zheng and co-authors wrote in Neurology.
Rationing in utero that extended to the ages of one to two years was tied to dementia being delayed by 2.55 years. Incident type 2 diabetes and hypertension jointly mediated 25.5% of the association.
In an imaging sub-study, early-life sugar rationing was associated with higher total grey matter volume, lower white matter hyperintensity volume, and better performance in processing speed and reasoning, the researchers added.
Several pathways may explain these findings, Zheng suggested.
“Excessive sugar exposure during pregnancy may contribute to maternal hyperglycaemia, insulin resistance, and inflammation, potentially affecting placental function and foetal brain development,” he told MedPage Today.
“Early-life nutrition may also shape synaptic maturation, myelination, and long-term cognitive reserve, although these potential mechanisms were not directly examined in our study. In our analysis, diabetes and hypertension jointly explained about one-quarter of the association, suggesting that metabolic and vascular health may also play an important role.”
Previous research has linked early-life sugar rationing to less risk of diabetes and hypertension in adults and better cardiovascular outcomes.
“Most of the work so far has gone into establishing that these long-term effects exist. What actually carries them is much less studied,” said Tadeja Gracner, PhD, of the University of Southern California in Los Angeles, who has researched this cohort but wasn’t involved with the current study.
“In our work, we’ve tried to pin down a few. One is that the diet itself persists: sweet preferences form early, and we find that people rationed as infants or toddlers were still eating less added sugar and more fibre 50 years later,” she noted.
“We also find that rationing shifted schooling, occupation, and wealth, and those could shape later health, including cognition.
“Interestingly, the effects do not seem evenly spread,” Gracner added. “They concentrate among people genetically predisposed to obesity: in our current work in progress, we showed that early sugar restriction narrowed the genetic gap in adult obesity by about 40%. None of these rules each other out, and how much each contributes is still very much open.”
Zheng and colleagues studied 64 737 UK Biobank participants who were born before and after World War II sugar rationing. Sugar became widely available again in 1953.
Other foods were rationed but sugar was the only one with a rapid rise in consumption when rationing ended, the researchers noted.
“According to National Food Survey data, sugar intake rose by more than 50% post-rationing, while fat consumption showed a modest increase, and most other commodities changed minimally,” they wrote.
The cohort included 56.4% women. Overall, 40 963 participants were exposed to sugar rationing during foetal or early childhood life, and 23 774 participants were unexposed.
Participants were 55 on average when they entered the study. ICD-10 codes from medical records were used to determine incident dementia diagnoses up to 15 years later. Brain MRI and cognitive function were assessed in a sub-cohort with a mean age of 62.
Sugar intake during rationing aligned with current US dietary guidelines and American Heart Association recommendations, the researchers noted.
The study findings do not support restricting overall calories or essential nutrients during pregnancy or infancy, Zheng emphasised.
“Rather, they suggest that guideline-consistent reductions in added and free sugars during the first 1 000 days may have long-term brain-health benefits,” he said. “As this was an observational natural experiment study, further research is needed before drawing causal conclusions.”
Study details
Association of sugar restriction in utero through age two years on dementia risk later in life
Zheng J, et al
Published in Neurology on 29 July 2026
Abstract
Background and Objectives
Excess sugar intake in early life may affect long-term brain health, but evidence for dementia is limited. We used the abrupt end of UK sugar rationing in September 1953 as a natural experiment to test whether exposure to sugar rationing during different windows within the first 1 000 days from conception was associated with adult risk of all-cause dementia, Alzheimer disease (AD), and vascular dementia (VaD).
Methods
We analysed UK Biobank participants born around the end of UK sugar rationing. Exposure was classified as rationing in utero only, in utero plus the first year of life, in utero plus 1–2 years of life, or no exposure. Incident dementia was identified from linked ICD-10 records. MRI of the brain and cognitive function were assessed in the imaging subcohort. Adjusted Cox and Gompertz models estimated HRs and 95% CIs, Fine–Gray models accounted for competing risk, and mediation analyses evaluated type 2 diabetes and hypertension.
Results
Among 64,737 participants included in the analysis, the mean age at recruitment was 54.6 years, and 56.4% were women; 40,963 were exposed to sugar rationing during fetal and/or early-childhood life, and 23,774 were unexposed. Compared with unexposed individuals, sugar rationing in utero plus the first year of life was associated with lower hazards of all-cause dementia (HR, 0.79; 95% CI 0.66–0.94) and AD (HR, 0.77; 95% CI 0.59–1.00). Similar or slightly stronger associations were observed for exposure in utero plus 1–2 years (all-cause dementia: HR, 0.77; 95% CI 0.63–0.95; AD: HR, 0.72; 95% CI 0.53–0.98). Exposure in utero plus 1–2 years was associated with delayed onset of all-cause dementia by 2.55 years, AD by 2.87 years, and VaD by 2.49 years. Early-life sugar rationing was also associated with higher total gray matter volume (β, 3.27; 95% CI 0.46–6.07), lower white matter hyperintensity volume (β, −0.64; 95% CI −0.97 to −0.31), and better performance in processing speed and reasoning. Incident type 2 diabetes and hypertension jointly mediated 25.5% of the association.
Discussion
Sugar restriction in the first 1,000 days was associated with lower dementia hazards, delayed onset, and more favourable brain-health profiles. These results support early-life sugar reduction as a potential strategy for dementia prevention.
See more from MedicalBrief archives:
Babies’ reduced sugar intake leads to lower later chronic disease risk – UK study
Sugar consumption in pregnancy linked to poorer childhood cognition