Eating less sugar during the earliest stage of life may be linked with a lower risk of dementia many decades later, according to a large study.
Researchers examined people who were born around the time Britain ended sugar rationing in the 1950s. The findings were published online July 29 in Neurology.
The first 1,000 days of life begin at conception and continue through roughly a child’s second birthday. This period is especially important because the brain and many other organs are developing rapidly. Nutrition during pregnancy and early childhood can influence growth and may have effects that remain visible much later in life.
Jiazhen Zheng of The Hong Kong University of Science and Technology and colleagues used a historical event as a natural experiment.
Britain restricted sugar during and after World War II, and these limits remained in place until September 1953. Children born just before and just after rationing ended therefore grew up in similar places and times but experienced different levels of sugar availability early in life.
The researchers studied 64,737 participants from the UK Biobank who were born around the end of sugar rationing. Of these, 40,963 had been exposed to rationing while developing in the womb, during early childhood, or both. Another 23,774 were born after the restrictions ended and were considered unexposed.
The team then examined later diagnoses of dementia. Dementia is not one single disease but a general term for severe declines in memory, thinking and other mental abilities that interfere with everyday life. Alzheimer’s disease is the most common cause, while vascular dementia is linked with problems in the blood vessels that supply the brain.
People exposed to sugar rationing before birth and during their first year had a lower rate of overall dementia than people who were not exposed. They also had a lower rate of Alzheimer’s disease. The reduction was about one-fifth for overall dementia and slightly greater for Alzheimer’s.
The association appeared somewhat stronger among people exposed from pregnancy through the first two years after birth. In this group, the rate of overall dementia was about 23% lower, while the rate of Alzheimer’s disease was about 28% lower than among people who had not experienced sugar rationing.
The researchers also found a difference in when dementia appeared. Exposure from pregnancy through the first two years was associated with the onset of overall dementia about 2.55 years later. Alzheimer’s disease appeared about 2.87 years later and vascular dementia about 2.49 years later.
Brain scans provided another clue. Participants exposed to early-life sugar rationing had a somewhat greater total volume of gray matter, the brain tissue containing many nerve cell bodies. They also had fewer changes in white matter that are often associated with aging and damage to small blood vessels.
Early exposure was also associated with better performance on tests of thinking speed and reasoning. These findings suggest that the association was not limited to recorded dementia diagnoses. Differences could also be seen in brain structure and some measures of mental performance.
The researchers investigated possible reasons for the connection. Type 2 diabetes and high blood pressure explained about one-quarter of the association between early sugar rationing and later dementia risk. Both conditions can damage blood vessels and have previously been linked with a higher risk of cognitive decline.
Too much added sugar can contribute to excess weight and poor metabolic health, although sugar is only one part of a person’s overall diet. The new study raises the possibility that nutrition during a particularly sensitive period of development could influence the body’s long-term handling of sugar and its later vulnerability to diabetes, high blood pressure and brain disease.
However, the study does not prove that giving babies or pregnant women less sugar directly prevents Alzheimer’s disease. It was an observational analysis based on a historical period rather than a controlled trial in which researchers assigned people to different diets. Families living under rationing may also have differed from later families in other ways that are difficult to measure completely.
Another limitation is that UK Biobank participants are not a perfect representation of the entire British population. Dementia develops through a complicated combination of aging, genes, cardiovascular health, lifestyle and environmental factors. Early sugar exposure should therefore be viewed as one possible influence among many rather than a single cause.
Still, the unusual timing of Britain’s rationing system gives the study an important strength. Comparing people born close to the same historical cutoff can reduce some of the differences that normally make nutrition studies difficult to interpret. The large number of participants and the use of dementia records, brain imaging and thinking tests also provide several forms of supporting evidence.
Overall, the study offers intriguing evidence that nutrition very early in life may have consequences that stretch across decades. The findings are not a reason for extreme sugar restriction during pregnancy or childhood, when adequate nutrition is essential.
Instead, they support further research into whether avoiding excessive added sugar during the first 1,000 days could contribute to healthier aging and a lower risk of dementia later in life.
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Source: The Hong Kong University of Science and Technology.
