Pregnant women should cut their intake of sugar if they want to protect their children against Type 2 diabetes and high blood pressure, research suggests.

The conclusion came after experts found babies conceived during sugar rationing in the Second World War were protected against chronic disease.

Experts from the University of Southern California looked at the health records of 38,155 Britons who had been exposed to rationing, and compared them with 22,028 who had not.

They found that those whose sugar was limited while in the womb and in early childhood were 35 per cent less likely to have developed Type 2 diabetes in their lifetimes. They also had 20 per cent less chance of being diagnosed with high blood pressure.

The researchers said that early sugar may impact physiological programming in the womb as well as creating “a lifelong preference for sweetness” that could damage future health.

They added that “action to reduce the sugar content of foods and drinks aimed at or attractive to children is needed”.

Writing in the journal Science, the researchers warned: “Infancy and toddlerhood in particular are critical periods for developing a taste for sweets that can elevate sugar consumption throughout life.

“Over 70 per cent of foods marketed to infants or toddlers contain added sugars in formula, foods, or beverages. By age two, many children consume the adult-recommended seven teaspoons of sugar daily, nearly tripling it by their teens.

“Limiting exposure to sugar in utero and in early life can protect against Type 2 diabetes and hypertension.”

Sugar was rationed in Britain from 1940 until 1953, as imports fell during the war and production in Europe dropped. Sweets were also rationed from 1942.

Dieticians have argued that wartime rationing provided the healthiest diet the country has ever eaten, with the population encouraged to eat more eggs, milk, fruit, vegetables and fish.

Child height increased in most regions in England and Wales during the war, while life expectancy increased dramatically after 1946.

However, the end of rationing led to a nearly twofold increase in sugar consumption almost overnight.

For the new study, the team used data from the UK Biobank, which has been gathering data from tens of thousands of Britons since 2007.

As well as finding that sugar rationing had reduced the overall risk, it also delayed the onset of diabetes by four years and high blood pressure by two years.

Commenting on the findings, Dr Hilda Mulrooney, a reader in nutrition and health at London Metropolitan University, said: “The message is clear – exposure to high intakes of added sugar in utero and early childhood is a significant risk factor for chronic disease.

“This suggests that action to reduce the sugar content of foods and drinks aimed at or attractive to children is needed.”

Evidence already suggests that early exposure to sugar during pregnancy and early life may impact metabolism, obesity risk and taste perception, which can later influence food choices and the risk of other chronic diseases.

However Amanda Adler, a professor of diabetic medicine and health policy at the University of Oxford, said other factors may have influenced the findings.

She said: “It may be that at the same time rationing ended and people consumed more sugar, they also changed other habits becoming, for example, less physically active.

“So, this may have influenced in part their risk for diabetes later in life.

“It’s intriguing and entirely possible that a lower exposure to sugar in utero via the mother would lead to life-long benefits.

“This study is an open invitation to clinical trialists to clarify the ‘right’ levels of sugar to add to the diet for pregnant or lactating women, and for their infants.”