The occasional sweet treat likely won’t ruin your health. But too much added sugar at a young age could increase the risk of health complications later in life.

Limiting added sugars during the first 1,000 days after conception — so during pregnancy and a baby’s first two years — reduces the risk of a child developing diabetes and hypertension in adulthood, researchers report October 31 in Science.

“In the first 1,000 days of life, the brain and body are gearing up to finish developing,” says Sue-Ellen Anderson-Haynes, a registered dietician in Boston and a spokesperson for the Academy of Nutrition and Dietetics. Nutrition during that timeframe is particularly important, she says, because “everything the mother eats gets transformed into nutrients for the fetus.”

Current nutritional guidelines recommend that adults consume less than 40 grams of added sugars per day and that children under age 2 consume no added sugars. But by age 2, the average American child consumes about 29 grams of added sugars a day; the average adult consumes nearly 80 grams per day.

To study the effects of excess added sugars early in life, economist Tadeja Gracner of the University of Southern California in Los Angeles and colleagues took advantage of a natural experiment: the end of sugar rationing in the United Kingdom after World War II. While rationing was in effect, each person was allotted about 8 ounces (about 227 grams) of sugar per week. Once sugar rationing ended in September 1953, daily sugar consumption for adults jumped to around 80 grams per day.

Even though other foods were rationed during and after WWII, sugar intake increased the most after rationing was lifted. Consumption of other rationed foods, such as cheese, milk and fresh fruits remained relatively constant once rationing ended. Similarly, the end of butter rationing caused many families to switch from margarine, with its unsaturated fats, back to butter, so overall fat consumption did not increase significantly.

Gracner and her colleagues collected data from the U.K. Biobank for more than 60,000 participants born from October 1951 to March 1956. They divided participants into two cohorts: Individuals born before July 1954, who experienced sugar rationing in utero and in early life, and those born from July 1954 onward, who did not experience any rationing.

People who experienced sugar rationing early in life were less likely to develop type 2 diabetes or high blood pressure in adulthood than people who did not experience sugar rationing, the team found. The risk of developing diabetes among people who rationed early in life was about 62 percent of the risk experienced by those whose sugar intake was not rationed; the risk developing hypertension among those who experienced rationing was about 79 percent of the risk of those who did not.

Kids who experienced sugar rationing early weren’t immune to developing these chronic conditions, but it tended to happen later in life: four years later on average for diabetes than the nonrationed cohort, and two years later on average for high blood pressure. Participants were also less likely to develop diabetes and hypertension if they experienced sugar rationing in utero, even if the participant did not experience rationing after birth.

Avoiding added sugars can be challenging, Gracner says, especially when so many foods for both adults and young children contain them. “I don’t want parents to be feeling guilty for giving their toddlers sugar sometimes,” she says. More nutritional education and regulations on the marketing and pricing of sugary foods could help parents choose less sugar-laden options for their kids and themselves, she says (SN: 4/16/19).

“I think we all want to improve our health and give our children the best starting life,” Gracner says. “The takeaway is that reducing added sugar early is one of the powerful steps in that direction.”