The researchers pulled data from UK Biobank, focusing on adults conceived just before and after the 1953 end of wartime sugar rationing in the United Kingdom.

The study, published in Science, indicated that children exposed to sugar restrictions during their first 1,000 days, including pregnancy in utero, had up to a 35-per-cent-lower risk of developing Type 2 diabetes and up to 20-per-cent-lower risk of hypertension as adults. Surprisingly to the researchers, in-utero exposure alone was enough to lower risks.

The study – led by the University of Southern California in collaboration with the University of California Berkeley and McGill – provides some of the first compelling human evidence of the lifelong effects of early sugar intake.

Yesterday’s ration, today’s guideline

While rationing was in effect during the Second World War and several years afterward, sugar intake was less than 40 grams per day for adults and none for children under two. When rationing ended, consumption skyrocketed. The stark contrast gave researchers a clear snapshot of sugar’s effects.

“What’s fascinating is that sugar levels allowed during rationing mirror today’s guidelines. Our study suggests that if parents followed these recommendations, it could lead to significant health benefits for their children," said co-author of the study, Claire Boone, Assistant Professor in McGill’s Department of Economics and the Department of Equity, Ethics, and Policy.

Health Canada recommends little to no added sugars for children under two. There are strict limits on sodium and food additives for infants, but there are no regulations on sugars.

‘Natural experiment’ shows long-term effects

Boone said studying nutrition is notoriously difficult because it’s hard to control diets over long periods of time and track outcomes accurately.

“That’s why there is so much conflicting dietary research out there,” she said.

“This natural experiment allows us to see the long-term effects of sugar intake in a real-world setting, providing the public with a much clearer picture.”

She noted that as public debates continue about measures like sugar taxes and tougher regulations on sugary foods marketed to infants and toddlers, the study’s findings add to mounting evidence showing how important early diet is for lifelong health.

Boone added that the next phase of research will explore how sugar early in life could affect inflammation and cancer risk.

The study was supported by the U.S. National Institute on Aging.