1057 GMT July 15, 2019
But they are less successful in treating patients with severe asthma who use high doses of oral steroids, according to express.co.uk.
Prescribed in preventer inhalers, as tablets or in a liquid medicine, the fish oil is less effective because the corticosteroids block the beneficial effects.
Steroids help to calm and prevent inflammation in the airways by blocking the effects of certain chemicals in the immune system uses to ‘kick-start' inflammation.
They relieve symptoms, but do not cure the underlying disease.
Around 5.4 million people are currently receiving treatment for asthma in the UK — one in every 12 adults and one in every 11 children.
The study by researchers at the University of Rochester Medical Center used cell cultures from local asthma patients.
Previous work by lead author Professor Richard Phipps found certain fatty acids contained in fish oil regulate the function of immune cells (B cells).
Asthmatics have an imbalance between molecules that dampen inflammation and those that increase inflammation.
The new study collected blood samples of 17 asthma patients and isolated their B immune cells in the laboratory to explore the impact of pure omega-3-derived products on IgE and other molecules that fuel the disease.
Most of the patients were taking corticosteroids in either pill form or by inhaler, depending upon severity of their asthma.
Results showed that all responded to the omega-3 fatty acids to some degree, as evidenced by a reduction in the levels of IgE antibodies.
But Phipps said that unexpectedly the cells from a small subset of patients who were taking oral steroids were less sensitive to the omega-3 treatment.
He said: "Steroids are usually a very effective treatment for asthma.
"However, although the science is in the early stages, it appears that when corticosteroids are used steadily, in some cases the steroids reduce some of the body's natural ability to fight asthma-related inflammation."
The study confirms research published in the New England Journal of Medicine in December that showed prenatal exposure to fish oil reduced the risk of wheeze and asthma in children.
He said, “In that study, the fish oil used as a dietary supplement was a special high-quality preparation and consumers should use caution when buying fish oil because not all fish oil is the same.
"You really need high-quality, standardized material that's been processed and stored correctly before comparing results from one study to another study
"Our study used the pure, biologically active products in fish oil, known as 17-HDHA, and we've provided a clear line of evidence for why intake of high-quality fish oil is good."
Omega-3 polyunsaturated fatty acids have been shown to have many health benefits.
Once ingested, they convert to special pro-resolving mediators that halt inflammation without also suppressing the immune system.
They can be found in foods such as flax seed oil, salmon, tuna, anchovies, and walnuts.