How Maternal Nutrition During Pregnancy Affects the Child's Risk of Obesity

A study published last weekend in the journal Science sheds new light on how nutrition during pregnancy can increase the risk of diseases like extreme obesity and diabetes in the child.

In the past, it was believed that only genes determined health risks and probabilities, but today scientists understand that genes alone are not enough. This is where epigenetics comes into play: those 'switches' on genes that environmental conditions decide whether they are turned off or on. For example, studies show that babies born during wartime are at higher risk of stress and anxiety. The parents didn't pass on a new gene due to the unstable security situation, but the stress the mother experienced 'flipped the switch' of a gene related to stress and anxiety.

What happens when the environmental factor affecting the expression of the child's genes is not a security situation but the mother's nutrition during pregnancy? The child can be born at a completely normal weight, but during adolescence, they may begin to develop a tendency for extreme obesity – even if both parents are slim.

The research team, which included scientists from the University of Cambridge and King's College London, demonstrated this claim through a study conducted on pregnant mice. One group received a low-protein diet, while another group received a normal and healthy diet for a mouse. After the mouse pups were weaned, they all received a regular diet. Meanwhile, researchers began examining whether there were differences in DNA methylation – the chemical processes that determine how genes are expressed, if at all.

"At first, we found nothing, and it was a big surprise," says Professor Rakyan, a leading researcher. "But then we started looking at the ribosomal DNA data (the genetic material that produces ribosomes – protein-building mechanisms within the cell) and found enormous epigenetic changes. It turns out when these cells are under stress, such as due to inadequate nutrition, they alter the way protein is produced. Thus, in the pups of mice that received a low-protein diet during pregnancy, there was a slowdown in ribosomal DNA function. The result: these mice were 25% smaller compared to the other mice."

A low-protein diet during pregnancy is not common in the Western world. It can be found in certain underdeveloped countries among impoverished women, and the British study shows that the result may be shorter stature and lower weight of the offspring even in adulthood, even if they received proper nutrition after birth. However, the findings on mice, the researchers say, explain a reverse phenomenon among human mothers: overly rich nutrition and excessive caloric intake during pregnancy can cause genes to undergo changes that increase the offspring's risk of obesity later in life.

"This could also provide explanations for questions like the inheritance puzzle of type 2 diabetes," say the researchers. "About 20% of hereditary diabetes cases were explained by genetic research, but the rest remain unexplained. It seems we need to examine the role of epigenetic changes: a diabetic mother's diet during pregnancy can determine the child's risk of developing diabetes as they grow up."