Fish oil: warnings from a new study on a popular supplement

Pregnant women who take fish oil capsules should buy them in small batches and store them in the refrigerator, according to a group of medical researchers. By Nicky Pellegrino.

Omega 3 fatty acids are essential for
diet and particularly important for pregnant women, as there is growing evidence that consuming adequate amounts can reduce the child’s risk of developing metabolic problems, such as diabetes, later in life. Oily fish is the best source, and many pregnant women choose to take fish oil supplements. However, caution is advised, according to a group of scientists from the Liggins Institute at the University of Auckland.

Fish oil oxidizes and goes rancid more easily than other oils because it is chemically unstable. In 2015, institute researchers tested 32 products and found that more than half exceeded recommended oxidation levels. The question that remained was how much it mattered to pregnant women who might take them.

An animal-based study was conducted. Pregnant rats were given fish oil in a range of doses and oxidations. All of the animals were healthy during pregnancy and the puppies looked fine when they were born, says pediatric endocrinologist Ben Albert. But in the group that received human-relevant doses of the highly oxidized oil, 6% of the offspring died within the first two days of life.

The theory is that the rancid oil may have affected the quality or volume of breast milk, although this is not known for certain at this stage.

So how can consumers know if a fish oil supplement they are buying is fresh? “To be honest, I don’t think you can tell,” Albert said. “Oxidized oil does not necessarily smell different and often flavorings were added. In an earlier study, we investigated whether oil price, expiration date and country of origin made a difference , and it really wasn’t.”

Fish oil in capsules has a long supply chain. Much of it comes from Peruvian anchovies and is processed in China before eventually being transported to Australia or New Zealand for packaging. It’s unclear exactly where oxidation might occur along this pathway, but since heat and light speed up the process, Albert says it makes sense to be careful about how produce is stored in the home. .

“Buy a small container that you’ll finish in a short time, rather than a huge one,” he advises. “And keeping the fish oil capsules in the fridge is a really good idea.”

The natural health products industry reacted quickly to this latest research from the Liggins Institute. He said oils given to pregnant rats were artificially oxidized to higher levels than would ever be found in products on New Zealand shelves and called the study “flawed and of little value for anyone”.

But Albert supports the work and thinks the industry is missing “good news”.

The study showed that even at the maximum recommended oxidation limits, the oils were good, he explains. “We saw no signs of discomfort in any of the animals. This suggests that these recommended levels are appropriate and that the oils are safe.”

Research from the Liggins Institute has shown that even when pregnant rats are fed an unhealthy high-fat diet, consuming omega 3s in fish oil may have a protective effect on the metabolic health of their offspring. later in life. And he’ll soon be releasing the results of a study using fresh, safe fish oil in pregnant women.

“It’s important for women to try to get more omega 3s during pregnancy and I certainly wouldn’t want anyone to think that if they took fish oil they harmed their baby because it doesn’t There’s no evidence that’s the case,” Albert said. “But if you’re taking a fish oil product, you want it to be within safe oxidation limits and we should have a system that allows people to buy it with confidence.”

The Department of Health advises pregnant women to eat fish to provide essential fatty acids. He warns that increased mercury levels in long-lived and larger fish can be dangerous for the baby, but says there is little concern with canned fish like tuna, salmon and sardines.

The advantage of eating fresh or canned fish, says Albert, is that if the fish goes away, you’ll be able to tell and you won’t eat it.