Middle-aged adults born at the height of China’s famine in the 1950s and 60s may have a greater risk of abnormally high blood sugar than those born just a few years earlier or later, a new study finds.

The findings, reported in the journal Diabetes, support the theory that nutrition and growth during fetal development may affect the odds of developing type 2 diabetes later in life.

Previous studies, for example, have found a relationship between low birth weight and higher diabetes risk in adulthood in both developed and developing countries, said Dr. Frank B. Hu, of the Harvard School of Public Health in Boston, the senior researcher on the study.

Adults born at a low weight have also been found to have higher risks of heart and kidney disease than those born within the normal range.

These latest findings, Hu told Reuters Health in an email, give further support to the “developmental origins” hypothesis. According to that theory, poor nutrition during pregnancy may alter fetal development in a way that affects lifelong metabolism and disease risks.

For example, Hu noted, animal research suggests that poor fetal nutrition may affect the structure and function of cells in the pancreas that produce insulin, the hormone that regulates blood sugar.

In humans, problems in the body’s response to insulin precede the development of type 2 diabetes.

For their study, Hu and his colleagues looked at blood sugar levels among 7,874 Chinese adults born between 1954 and 1964. Those born between October 1, 1959 and September 30, 1961 were considered to have been exposed to the nation’s famine during fetal development. Those born earlier were categorized as exposed during early-, mid- or late-childhood; those born later were considered “unexposed.”

Overall, roughly 6 percent of the fetal-exposed group had hyperglycemia - blood sugar that was abnormally high but not yet high enough for a diagnosis of type 2 diabetes. That compared with just over 2 percent of the group unexposed to the famine.

Adults exposed to the famine during late-childhood also had a 6-percent rate of hyperglycemia. But when the researchers considered other factors - such as study participants’ age, exercise levels and smoking habits - they found that fetal exposure to the famine, especially in the regions of China most severely affected, was linked to an increased risk of hyperglycemia.

Of fetal-exposed adults from the most severely affected areas, just over 7 percent had hyperglycemia, versus 2 percent of the unexposed group, and anywhere from 2 percent to 5 percent of those exposed during childhood.

With other factors taken into account, adults in the group exposed during fetal development were four times more likely than their unexposed counterparts to have hyperglycemia.

What’s more, the researchers found a particularly strong link between fetal exposure to the famine and hyperglycemia among adults who currently had an “affluent” Western-style diet rather than a traditional Chinese diet. This group had the highest prevalence of hyperglycemia, at 19 percent.

According to Hu, this suggests that a “rich” diet later in life may worsen any effects of fetal undernourishment on the long-term risk of hyperglycemia.

The researchers found no clear association, however, between famine exposure of any kind and the risk of type 2 diabetes in adulthood. But that, they say, may be because there too few diabetes cases; at the time of the study, those in the fetal-exposed group were in their early 40s, and type 2 diabetes is most common after the age of 45.

None of the findings prove that fetal nutrition, itself, affects the long-term risk of hyperglycemia - or, by extension, type 2 diabetes. But they add to evidence of an association between nutrition in the womb and adult disease risks, according to the researchers.

The bottom line, Hu said, is that adequate nutrition during pregnancy is “critical” for both mom and baby.

According to the American College of Obstetricians and Gynecologists (ACOG), normal-weight women should get, on average, an extra 300 calories per day during pregnancy, and gain about 25 to 35 pounds by the end. Overweight and obese women should be more careful about their calories since their weight-gain recommendations are lower: 15 to 25 pounds for overweight women, and 11 to 20 pounds for those who are obese.

All pregnant women, according to ACOG, should eat a well-balanced diet and, in most cases, use prenatal vitamins to ensure that they are getting enough nutrients. During pregnancy, women need extra amounts of certain nutrients, like iron, folic acid and vitamins B6 and B12.

SOURCE:  Diabetes, online July 9, 2010.