Over the last 30 years, various studies have tried to find if omega-3 fish oils help alleviate allergy and asthma symptoms. As with most nutrients and food supplements, the conclusions vary drastically from trial to trial.
So, I wrote a very detailed article on how to interpret results from such clinical trials of nutrients. Read on this website: How to understand the evidence from clinical trials of nutrients. Here are the summary points of what differentiates nutrients from pharmaceuticals:
- Nutrients come from varied sources, differing in nature;
- Nutrients work together, with some other nutrient affecting the action of one under investigation;
- Our bodies have non–zero starting levels of nutrients, with benefits possibly coming for most deficient people;
- Triage theory for nutrients, with our bodies overriding our need for a nutrient’s targeted use in a trial;
- Sample size and trial duration, with nutrient trials needing much larger sample sizes and trial durations
- Side benefits, with nutrients have multi–system use, money is never wasted, and side effects are rare.
Using the reference of various points raised in that article, let us evaluate the results of various clinical trials about asthma.
Various trials, results and published articles
Here is a 2002 paper from the Cochrane Database of Systematic Reviews. It analyses 9 clinical trials conducted between 1986 and 2001.
The authors did not find any evidence to recommend omega-3 fish oil supplements in asthma control. On the other hand, they did not find any proof of harm, either.
So, no benefit, no harm.
Cochrane Database is the Gold standard for meta-analysis (combined analysis of multiple articles) on any topic. It strictly follows evidence–based medicine methodology. It looks for the evidence, its strength (how conclusive the evidence is), the trial quality (was the trial designed properly), etc.
On the downside, it does not go into the logical aspects of why a trial worked or not worked. If it did not show results, the subject is closed, etc.
Personally, I feel that evidence–based medicine is a great approach for pharmaceutical research. However, when it comes to nutrition based research, for the reasons mentioned above, the science can never be so black and white. One should delve deeper into why certain trials gave certain results, etc.
This is an invited review article in the journal Allergology International that discusses the role of omega-3 fatty acids in asthma and allergic diseases. It is a fairly comprehensive paper, full of technical words.
It focuses on the mechanisms of action of omega–3 oils in the body, describing various chemical cascades that take place. It shows how omega–3 oils reduce inflammatory markers found in the allergies and asthma.
It gives a long list of epidemiological and observational studies showing how omega–3 oils prevent or reduce asthma and allergies. It also gives more than 100 references. Read at leisure.
It claims that bioactive metabolites of omega–3 oils possess anti–inflammatory properties, showing benefits in allergy and asthma.
The article concludes by saying that in asthma and other allergic conditions, fatty acid metabolism is ‘dysregulated’.
In other words, it is saying that in normal people, omega–3 and other fatty acids keep the inflammation in check.
On the other hand, in patients with asthma and other allergies, this mechanism is impaired and that is the cause of high inflammation. Effectively, the pathway through which additional omega–3 oils could help in asthma and other allergies is itself severely hampered.
While that is not the main conclusion, it is still very interesting!
A study published in the New England Journal of Medicine in 2016 showed that fish oil taken by pregnant ladies during the third trimester of pregnancy reduced the risk of wheezing, asthma and infections in their infants.
For a primer on immune system, written for the benefit of parents, read: Our immune system.
This shows that the omega–3 oil benefits transmit from the mother to the baby in the womb, too.
The study authors cautioned that they used a high quality fish oil preparation, indirectly hinting that a cheap–quality fish oil may not be good enough.
This is important because many people do not even know that there are qualities, or grades, in fish oils. In the quest for cheapest prices, they may end up buying the cheapest product on the shelf, and get no results.
A University of Rochester Medical Centre study was published in 2017 in the Journal of Clinical Investigation—Insight. It found that fish oil can reduce the production of antibodies that cause allergic reactions and asthma symptoms.
Fish oil reduced the levels of Immunoglobin E antibodies, that cause allergic reactions and asthma symptoms.
Patients who took high doses of corticosteroids benefited less because corticosteroids block the beneficial effects of fish oil.
In some people who were taking oral steroids regularly, their body had a reduced ability to fight asthma–related inflammation.
For more details in simple English, read: Fish oil may help patients fight asthma.
In our bodies, there are certain white blood cells, called B–cells, that do the job of identifying body invaders, such as bacteria and toxins. B–cells produce chemicals called antibodies, which tell some other white blood cells, called T–cells, to attack and destroy the specific invaders.
A crude example would be that of a group of terrorists (bacteria or toxins) entering a building or a mall. The local police (B–cells) secure the surrounding area, tagging it as the crime scene. They may put yellow tape (antibodies) all around the place. Special teams (T–cells) arrive with their weapons to take on and eliminate the terrorists. Sorry for the gross example, but that is exactly how our body’s immune system works.
Asthma is a chronic inflammatory disease of the lungs. In case of asthma and certain allergies, B–cells produce certain antibodies called Immunoglobin E (IgE). Most individuals with asthma and certain other allergies have high blood levels of IgE.
I like this trial because it did not try to find the effects of fish oils on asthma or other allergies. For the reasons mentioned at the start of this article, we may not have found any clear–cut effects on the symptoms.
The trial, instead, tried to see the effect on the IgE antibodies in the asthmatic patients. It found the levels of IgE reduced with fish oil use.
In some cases, where the patients were using heavy dose of oral steroids, the fish oils had less effect on IgE. Oral steroids are used to reduce the inflammation and mucus production in the lung. The steroids seemed to block the effect of fish oils on inflammation, reducing their effect on IgE.
Interestingly, the study mentioned another important thing (such things get missed when you look only at the results):
This is very significant because it is not my opinion, but the opinion of the University of Rochester team, who had evaluated various fish oil options for their trial.
A study was published in 2019 in the Annals of the American Thoracic Society about obese adolescents. The study gave 3000 mg of fish oil daily for 6 months to 98 obese youngsters of 12 to 25 years of age. The study found no improvement in asthma control with fish oil in such individuals.
The title of the article said, “fish oil…does not improve asthma in teens”. It did not mention obese teens. Obesity is also an inflammatory condition, which, perhaps, slows down the anti-inflammatory properties of fish oils.
The authors say that larger doses for longer periods may show different results. But they still conclude: “there is insufficient evidence for clinicians to suggest to patients with uncontrolled asthma that they should take daily fish oil supplements to help their asthma.”
Now, how did they extend their conclusions from ‘insufficient evidence in obese youngsters’ to ‘insufficient evidence in all individuals’?
Johns Hopkins Medicine researchers published a study in 2019 in the American Journal of Respiratory and Critical Care Medicine. They studied effects of omega–3 and omega–6 oils on childhood asthma symptoms triggered by indoor air pollution.
The researchers measured PM2.5 and PM10, two indoor air pollution numbers. They found that omega–3 oil intake reduced the effects of indoor pollution on asthma severity, while omega–6 oils increased the same effect.
This is an observational study, which involved the adolescents filling up a questionnaire to analyse their dietary habits. So it cannot be used to claim any cause and effect relation.
Also, the study tries to find the effects on the symptoms (which are the effects of the inflammation), and not what is happening to the inflammation itself. Not an ideal way to study nutrients, as explained earlier.
The only interesting thing is the inflammatory effects of air pollution are somewhat quenched by omega–3 oils. So perhaps, the air pollution triggers inflammation through the same pathway that omega–3 reduces it.
Here is a very comprehensive article on essential fatty acids, their sources, safety, preventive ability, curative ability, evidence, and hundreds of references.
I am giving it at the end because that website wants me to add a statement: “This link leads to a website provided by the Linus Pauling Institute at Oregon State University. Health Sachet is not affiliated with or endorsed by the Linus Pauling Institute or Oregon State University.”
People with allergies and asthma should consider fish oil as a part of their regular diet and/or supplementation. They should be prepared to see lesser effect of fish oils than their normal counterparts, because their body’s inflammation control mechanism seems to be somewhat hampered.
Omega–3 fish oils are relatively expensive, and high quality fish oils will be even so, if one can find them. Depending on one’s financial ability, one can consider buying high quality fish oils.
In none of the trials, fish oils has been shown to cause any negative effect. So there is no harm in taking fish oil for asthma and allergies, independent of one’s opinions about the trial results above.