The government started rationing sugar in January 1940, a few months into the Second World War, when supplies from overseas ran short.
Consuming less sugar in the first 1,000 days of life is linked to a lower risk of dementia and Alzheimer’s disease decades later.
After the same adjustments, the rationed group averaged about 3 cubic centimeters (0.2 cubic inches) more gray matter.
On thinking tests, the rationed group was slightly faster at matching symbols to numbers, better at reasoning puzzles, and quicker at connecting numbered circles in order.
They also repeated the analysis in older adults in England and in Americans born during the same years, who never faced sugar rationing.
Babies who spent their first years under Britain’s wartime sugar ration have a lower risk of dementia than the children conceived once it ended.
The government started rationing sugar in January 1940, a few months into the Second World War, when supplies from overseas ran short.
Every household got a book of coupons and a fixed weekly allowance. Britain kept that allowance in place for eight years after the war, and ended it in September 1953.
No one wrote down what those children ate, or what their mothers ate while pregnant. The researchers had only the date that each of them was born, but they built the whole comparison on it.
Jiazhen Zheng, a researcher at The Hong Kong University of Science and Technology (HKUST), worked with three co-authors.
The team sorted 64,737 people born in Britain between 1951 and 1956 by the day they were born.
Consuming less sugar in the first 1,000 days of life is linked to a lower risk of dementia and Alzheimer’s disease decades later.
Zheng said sugar intake during pregnancy may also matter, and in the two years after it.
“We were particularly struck by the persistence of the association,” Zheng told Earth.com.
Rationing cut sugar, not calories
Families under the ration still ate. Once the coupons stopped, British households bought more than 50 percent more sugar. Their total calories rose by about 5 percent.
Households in the government’s National Food Survey kept a seven-day diary of everything they brought home, and both of those figures come from those records.
Researchers who study famines look at people who lost everything at once. During rationing, these families had less sugar, and a little less fat. Most other foods barely changed.
People under rationing ate about as much sugar as the World Health Organization, the U.S. Dietary Guidelines and the American Heart Association now advise, noted Zheng.
In 2024, Tadeja Gracner, Claire Boone, and Paul Gertler reported in Science on the same set of British births.
People rationed from conception to age two had roughly 35 percent less type 2 diabetes as adults. Their blood pressure was about 20 percent lower.
Zheng’s team went back to the same group of births, this time to look for lasting effects on the brain.
Dementia risk drops with less sugar
Everyone in the analysis had joined U.K. Biobank, which recruited half a million British adults between 2006 and 2010 and has tracked their health records since.
Of them, 40,963 were rationed for some part of the first 1,000 days after conception, and 23,774 were not.
The researchers tracked dementia diagnoses in those records through July 2023.
Among the people who missed rationing entirely, 504 developed dementia. Among the 15,256 rationed from conception to their second birthday, 456 did.
The team had to correct for age first. The rationed participants were about two years older than the comparison group, and dementia becomes far more common with each year past 65.
The team then accounted for age, sex, income, smoking, blood pressure and diabetes. They added the national average fat intake in each person’s birth year, and the price of food then, adjusted for inflation.
People rationed from conception through their first year had a 21 percent lower risk of dementia than those conceived after rationing ended.
People rationed through their second year came out slightly lower again, at 23 percent.
Sugar rationing link to Alzheimer’s
The same two groups had 23 and 28 percent less Alzheimer’s disease, though the first of those two figures was borderline.
Both of those groups also had fewer cases of vascular dementia, the kind caused by damaged blood vessels in the brain. Too few people developed it for the team to rule out chance.
Those rationed through age two also developed dementia later, by 2.55 years on average for dementia of any kind, 2.87 years for Alzheimer’s, and 2.49 years for vascular dementia.
Women showed the pattern more strongly than men. People carrying APOE e4, the gene variant most strongly tied to Alzheimer’s, showed it about as strongly as everyone else.
As a check, Zheng’s team ran the same comparison on two conditions that early sugar has no plausible connection to: type 1 diabetes and melanoma. The two groups came out about the same on both.
What the brain scans revealed
A smaller group, 7,724 people, went back for brain scans at an average age of 62.
After the same adjustments, the rationed group averaged about 3 cubic centimeters (0.2 cubic inches) more gray matter. This is the tissue where nerve cell bodies are packed together.
The average brain in that group held about 619 cubic centimeters (38 cubic inches) of it, so the difference is half of one percent, or two-thirds of a teaspoon. The team saw that gap only after the adjustments.
Bright patches also turn up on these scans, mostly where the smallest blood vessels have been damaged. Radiologists call them white matter hyperintensities.
In the same models, the rationed group had about 0.6 cubic centimeters (0.04 cubic inches) less of them, out of an average of 3.7.
The two groups did not differ on total brain volume, on white matter overall, or on the hippocampus, the seahorse-shaped structure at the center of memory.
On thinking tests, the rationed group was slightly faster at matching symbols to numbers, better at reasoning puzzles, and quicker at connecting numbered circles in order.
The two groups scored the same on working memory and word recall.
High blood pressure and diabetes
The team then looked for the steps in between. They put 18 percent of the dementia link down to new type 2 diabetes during follow-up, 11.6 percent to high blood pressure, and 2.7 percent to birth weight.
“Type 2 diabetes and hypertension jointly explained about one quarter of the association, suggesting that metabolic and vascular health may be part of the pathway, although the underlying mechanisms were not directly established by our study,” Zheng said.
He and his co-authors cannot account for the other three quarters, and in the paper they list candidates from earlier work.
Earth.com asked Zheng what expectant parents and parents of babies should take from the work in practice.
“Our findings support limiting added and free sugars in line with current dietary guidelines during pregnancy and early childhood, while maintaining adequate overall energy and essential nutrients,” he said.
Free sugars are the ones added by a manufacturer, a cook, or whoever is holding the spoon, plus what is in honey, syrups and fruit juices.
The World Health Organization advises keeping them under 10 percent of daily calories, which equals about 12 teaspoons for an adult eating 2,000 calories a day.
Limitations of the study
Nothing here measured how much sugar any individual actually ate. Participants were assigned to groups by birth date, so the study cannot show that sugar itself caused the differences.
U.K. Biobank volunteers tend to be healthier and better off than the British population overall, and 96 percent of this group was white.
Everyone also had to survive into their 50s and attend an appointment. The team excluded 6,582 people born outside the U.K. and 2,424 twins and triplets.
Postwar Britain changed in many ways besides sugar. To account for shifts over time, the researchers compared people born in six-month blocks.
They also repeated the analysis in older adults in England and in Americans born during the same years, who never faced sugar rationing.
In a final check that accounted for people who died of other causes first, the rationed group still had less dementia overall, but the difference in Alzheimer’s disease disappeared.
The records end in 2023, when participants were only 67 to 71 years old. Most dementia is diagnosed later in life.
Future research directions
Researchers have never taken a group of pregnant women, kept added sugar low through the child’s second birthday, and then followed those children into old age.
In an interview with Earth.com, Zheng said the next step is practical trials of safe, guideline-level cuts to added sugar in pregnancy and early childhood.
Along the way, researchers could measure brain development, metabolism and brain health, decades before any dementia diagnosis.
Until one of those trials, the strongest evidence tying early sugar to dementia comes from a ration book that expired more than 70 years ago.
The full study was published in the journal Neurology.
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