Children whose parents keep them off sugar during their first two years of life have lower rates of diabetes and high blood pressure for the rest of their lives, a new study has found.

That protection remains even if the children begin eating more sugar after age 2, according to findings published on Thursday in Science.

Processed sugar begins to be harmful to children while they are still fetuses in utero, the scientists found.

Despite recommendations by public health authorities that children avoid added sugars in food — or foods that have been sweetened in addition to their natural ingredients — about 85 percent of U.S. children eat added sugars every day, according to 2020 findings in the Journal of the Academy of Nutrition and Dietetics.

For infants, that mostly meant sweetened yogurts, baby foods and pastries, while for toddlers it meant candy, pastries and fruit drinks.

Although most children exceed World Health Organization recommendations for sugar intake, the consequences of that excessive consumption have not been entirely clear. A 2021 Canadian study of the physical impacts of sugar consumption found no correlation between sugar intake and children’s waistlines — though those results said little about longer-term impacts sugar consumption might have on those children’s metabolisms.

To uncover such hidden, lifelong impacts of early-life sugar intake, researchers took advantage of a natural experiment: the strict sugar rationing in the United Kingdom after World War II, which effectively enforced levels of sugar consumption analogous to what modern-day U.S. public health authorities prescribe.

When those restrictions ended in 1953, however, U.K. sugar consumption almost immediately doubled.

That policy change created a rare bright line in the historical record, allowing scientists to see the long-term difference between the slightly older children who had had less access to sugar and their younger counterparts — even as both groups, after 1953, began to eat a lot more sugar than had been possible before.

The results were stark. Over their lifetime, children who didn’t consume much sugar during the first 1000 days of their lives — a period extending from their conception until their second birthday — lowered their risk of developing diabetes by 35 percent and hypertension by 20 percent.

The low-sugar diet also postponed the onset of those diseases by four and two years, respectively — with outsized effects seen in children who didn’t eat much sugar after six months, which is around the time that infants begin eating solid food.

Reduction of sugar intake by pregnant women accounted for about one-third of the reduction in risk, the researchers found.