Could how much sugar you consumed before your second birthday shape your health decades later – even into your 70s?

A new study that my colleagues and I conducted suggests the answer could be yes. People who had less sugar exposure during the first few years of life were much less likely to develop several different cancers later in life, and they also showed signs of slower biological ageing. We also found that even in adulthood, they continued to consume less sugar and had healthier diets overall.

This is not an easy question to study in real life. Researchers obviously can’t run that experiment on real babies – split them into groups, feed one group sugar, then wait 70 years to see what happens.

Britain’s postwar sugar rationing offered a rare alternative. After the second world war, sugar remained rationed in Britain for several years. But in September 1953, rationing ended and people started eating a lot more sugar. Consumption nearly doubled. This meant that children born just a few months apart had very different levels of sugar exposure both in the womb and during early childhood.

For our study, we used data from over 64,000 people born in Britain between 1951 and 1956. Those born earlier spent a larger share of their first 1,000 days under sugar rationing, while those born later experienced progressively less of it.

By the first 1,000 days, we mean the period from conception to a child’s second birthday. This is a critical stage because the body is developing very rapidly. Organs are growing, metabolism is taking shape, and the immune system is maturing.

Food and taste preferences also begin to form during this period. Although 1,000 days is a relatively short period, the effects of the food environment during this stage can last throughout a person’s life.

To track cancer cases, we used the UK Biobank – a huge health database that follows participants for decades and records, among other things, who develops cancer and when.

We found that people who experienced longer periods of sugar rationing during their first 1,000 days had a lower incidence of five types of cancer: breast, prostate, liver, rectal and lung cancer. The effect was strongest for liver cancer, where rates were around 69% lower, and weakest – though still substantial – for breast cancer, at 36% lower. Importantly, these differences only began to appear decades after sugar rationing had ended.

We also found that exposure to sugar rationing is related to biological ageing. Biological age is not the same as chronological age. Two people may both be 70 years old, while their cells and immune systems show different levels of ageing.

One way we measure biological ageing is through telomere length. Telomeres are protective structures located at the ends of chromosomes. As cells age, telomeres usually become shorter.

We found that people who experienced longer periods of sugar rationing during their first 1,000 days had longer telomeres. Based on our estimates, this difference is equivalent to about 2.2 years of slower biological ageing.

We also found lower levels of a protein called granzyme B, which rises when the immune system has been working overtime for years – another sign of slower ageing at a cellular level. Taken together, these results suggest that lower sugar exposure early in life may be related to slower ageing at the cellular level.

What is most surprising, however, is not the cancer results or the biological markers of ageing. It’s how early-life sugar exposure continued to affect people’s diets even 50 years later.

We found that people who experienced sugar rationing early in life still consumed less sugar in adulthood, around age 50. They also ate less overall, and their diets were healthier and more diverse. This suggests that the level of sweetness people are exposed to very early in life may shape their taste preferences for a long time.

There appear to be two mechanisms at work. One is biological – early nutrition may shape how the metabolism, organs and immune system develop. The other is behavioural – a taste for less sweetness, formed early, seems to stick.

Other research using the end of Britain’s sugar rationing has also found that people who experienced more sugar rationing early in life had lower risks of type 2 diabetes and hypertension. A recent study using the same end of Britain’s sugar rationing found lower risks of dementia and Alzheimer’s disease, while another study reported lower risks of heart disease and stroke.

This does not mean that children should not eat sugar at all, and it certainly does not mean that postwar sugar rationing is a desirable policy. What this historical evidence shows is that, during a critical period of development, even relatively small differences in sugar exposure over a short period may leave effects that are still observable half a century later.

Children may not remember what they ate before age two. But their later health, their bodies and even their taste preferences may still carry the imprint of those very early-life experiences.