Can fish oil in pregnancy prevent diabetes in children?

New Zealand researchers are investigating whether fish oil supplements taken during pregnancy could help prevent children from developing weight problems in later life. Photo / Supplied

New Zealand researchers are investigating whether fish oil supplements taken during pregnancy could help prevent children from developing weight problems in later life.

The study is being led by a team of scientists at the University of Auckland-based Liggins Institute, who have published several major papers on the popular supplements over recent years.

The team is seeking women who are less than 16 weeks pregnant, aged between 18 and 40, and have a body mass index (BMI) of 30 to 45, with a goal for a third of the participants to be Maori and another third to be Pacific women.

Half of the 160 women in the trial would take fish oil capsules during pregnancy and for three months after birth, while the rest take placebo olive oil-based capsules.

"We already know that if you carry extra weight while you are pregnant, your child is more likely to develop weight problems and diabetes as they grow up," study leader Dr Ben Albert said.

"Women who are pregnant try incredibly hard to improve their health to give their baby the best start.

"But what should they do? Is there something simple they could take?

"Our previous work suggests fish oil may be protective for the developing baby."

Albert said it was important Maori and Pacific women were included in the study as it was known the ethnicities were likely to be affected by weight problems more than others.

The new trial comes after a study in rats, led by Albert and published last year, which suggested fresh fish oil may prevent children of overweight pregnant women from later developing diabetes.

Other evidence has suggested omega 3 fatty acids in fresh fish oil improve the way insulin works, which protected against diabetes and related diseases.

Children of overweight women had nearly twice the risk of developing problems like diabetes later in life, and at least three in 10 pregnant women in New Zealand were overweight.

Up to one in five New Zealand women currently take fish oil supplements during pregnancy, according to the latest estimate.

But it was not known if supplements sold here contain fresh fish oil, as it's not stated on the label, or oil that has gone off by becoming oxidised.

Albert was not advising mothers-to-be to take fish oil supplements until they could be confident the supplements they buy were fresh.

Earlier Liggins research showed how most tested samples of 36 fish oil capsule brands sold in New Zealand were rancid, oxidised beyond international recommended levels.

How "off" they were had nothing to do with best-before date, price, or the country they came from.

"If we find in our clinical trial that taking fresh fish oil during pregnancy has the same protective effect in humans it does in rats, that would further strengthen the case for some kind of independent, regular testing of fish oil supplements," says Dr Ben Albert. Photo / Supplied

And when the researchers fed highly oxidised fish oil to pregnant rats in a later experiment, a third of their pups died.

Those findings were met with criticism by the natural health products sector, which argued that study's "negative conclusions" were based on scenarios that could not occur in real life.

"If we find in our clinical trial that taking fresh fish oil during pregnancy has the same protective effect in humans it does in rats, that would further strengthen the case for some kind of independent, regular testing of fish oil supplements," Albert said.

"Until then, our best advice is for pregnant women to eat fresh fish. We can assure the women in our study that the fish oil supplements will be fresh."

The wider challenge – of breaking the intergenerational cycle of weight-related health problems – was tough and will require multiple long-term strategies across our society, he said.

"But improving the health of mothers while they are pregnant is one really powerful approach because the unborn baby's environment in the womb has lifelong effects on how their bodies work.

"I am increasingly seeing children in my clinic with serious weight problems, many of them with complications like diabetes that we used to see only in adults.

"If we could reduce this with a safe, accessible, food-based supplement, it could make a real difference for thousands of families."

The new trial was funded by the Health Research Council and collaboration between Cure Kids and government-funded National Science Challenge A Better Start.

Results were expected in 2020.

• Women wishing to take part in the trial can contact the researchers at fishoilpreg@auckland.ac.nz