Researchers identified the connection by leveraging the abrupt end of UK sugar rationing, in 1953. The termination of this World War II–related austerity measure created a rare opportunity to compare people born just before and after sugar became widely available again.
The analysis revealed that less exposure to sugar in utero and early childhood was linked to delaying the onset of dementia by about two and a half years.
“This study raises the possibility that nutrition during the first 1,000 days of life — a critical period for brain development — may influence brain health much earlier than we previously appreciated,” says Kaitlin Seibert, MD, a behavioral neurologist at the Cleveland Clinic Center for Brain Health in Ohio, who wasn’t involved in the research.
How a Wartime Sugar Rule Became a Brain Health Study
During and after World War II, the United Kingdom rationed sugar and sweets. The ration kept sugar intake below 40 grams (g) a day for adults — roughly 10 teaspoons (tsp) — and below 15 g for young children. Children younger than 2 received no sugar or sweets ration.
After rationing ended in September 1953, average adult consumption climbed from about 41 g to 80 g a day, or roughly 10 to 20 tsp.
Researchers analyzed nearly 65,000 UK Biobank participants and grouped them by whether sugar rationing was in effect while they were in the womb, during their first one or two years of life, or not at all.
The study design is a natural experiment, says Victor Henderson, MD, a professor of epidemiology and neurology at Stanford Neuroscience Health Center in California who wasn’t involved in the new research.
In a natural experiment, researchers don’t assign people to groups — real-world circumstances do. Here, the dividing line was birth date: whether someone was in the womb or was a young child before or after UK sugar rationing ended, says Dr. Henderson.
Longer Rationing Was Linked to Lower Dementia Risk
Prenatal sugar exposure wasn’t clearly associated with lower dementia risk; the strongest findings appeared when lower sugar exposure continued after birth, according to the authors.
Compared with people born after sugar rationing ended:
- Those whose time in the womb and first year of life occurred during the rationing period had a 21 percent lower risk of all-cause dementia and a 23 percent lower risk of Alzheimer’s disease.
- Those whose time in the womb and first two years of life occurred during the rationing period had a 23 percent lower risk of all-cause dementia and a 28 percent lower risk of Alzheimer’s disease.
- Vascular dementia showed a similar trend, but the results weren’t statistically significant — the difference could have been due to chance.
Researchers estimated that rationing through age 2 delayed the onset of all-cause dementia by 2.55 years, Alzheimer’s disease by 2.87 years, and vascular dementia by 2.49 years.
How Significant Are These Findings?
“The magnitude of reported differences in dementia risk and age at diagnosis is certainly clinically meaningful,” says Henderson.
Given that the average American consumes 1.5 to 2 times the recommended daily allowance of sugar, the study results have important public health relevance, says Elinor Sullivan, PhD, a professor of psychiatry and behavioral sciences and the director of the Prenatal Environment and Child Health Lab at Oregon Health & Science University in Portland, who wasn’t involved in the study.
If limiting sugar helped delay dementia, that would be “substantial for quality of life and the burden on the healthcare system,” says Dr. Sullivan.
What Might Connect Sugar Exposure Early in Life to Increased Dementia Risk?
Previous studies have linked higher sugar exposure during pregnancy or infancy with childhood cognition, newborn brain organization, and memory changes in animals, Sullivan says.
This is the first study to look at the connection between sugar early in life with dementia risk decades later, she adds.
Researchers drilled down further and found that type 2 diabetes and hypertension jointly explained 25.5 percent of the association. “Diabetes is a well-established risk factor for stroke and cardiovascular disease, and diabetes is also linked to dementia,” says Sullivan.
The proposed pathways driving the majority of the risk are inflammation and impaired placental function, says Sullivan.
Too much sugar may trigger inflammation in the mother’s bloodstream and placenta, potentially interfering with the development of new brain cells and the connections that allow the brain to learn and adapt, she says.
Excess maternal sugar could also lead to insulin resistance and placental impairment, which can impact nutrient delivery and influence fetal brain development, says Sullivan.
Why the Study Can’t Prove Sugar Rationing Prevented Dementia
Using sugar rationing to look at sugar consumption and dementia is a “clever but not infallible way to address the question of dietary sucrose early in life and later-life dementia,” says Henderson.
The large sample, the narrow window around the end of rationing, the extensive statistical adjustments, and the findings across medical records, brain scans, and cognitive tests strengthened the analysis. Researchers also checked the pattern in other UK and U.S. cohorts, Sullivan says.
But the study has limitations. Researchers didn’t know how much sugar any individual mother or child ate. The groups also differed in age, education, and some health conditions, and other parts of postwar life may have changed in ways the analysis couldn’t capture.
“The relatively small number of dementia cases and the unusually large reported reduction in Alzheimer’s disease also mean these findings should be viewed as hypothesis-generating until they are replicated in other populations,” says Dr. Seibert.
It Isn’t Too Late to Improve Your Brain Health
Experts agree that these findings alone aren’t enough to make recommendations on sugar intake for expectant mothers or infants to reduce dementia risk. But the findings should encourage more research into how nutrition can affect brain health decades later, says Seibert.
- Regular movement
- A balanced, plant-forward diet, such as a Mediterranean-style eating pattern
- Managment of high blood pressure, diabetes, and high cholesterol
- Adequate sleep and treatment for ongoing sleep problems
- Social and mental engagement
- Abstention from smoking and heavy alcohol use
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