You know all about fish oil and heart health, but that’s just the tip of the iceberg for these healthful fats. Omega-3s are critical to the function of the immune system. In this article, we look at the relationship between omega-3 fatty acids and immunity from a developmental and cellular approach.

‌‌‌‌Omega-3s, Pregnancy, and Development 

The importance of omega-3 fatty acids during pregnancy and early childhood development has focused on the role of docosahexaenoic acid (DHA) in brain health, but it is important to note that they also are critical to proper immune system function. 

This critical role was shown in a 2011 study. Women who supplemented with 400 mg of DHA during pregnancy showed a decreased number of colds contracted by their babies early in life. Cold symptoms occurred 24% less often at one month of age among babies whose mothers took DHA. At 3 months, infants in the DHA group spent 14% less time ill. At 6 months, infants in the DHA group experienced shorter duration of fever, nasal secretion, difficulty breathing, rash, and “other illness.” The time spent with difficult breathing was reduced by 54%.¹ 

These results aren’t surprising. They’re just another addition to the growing body of evidence that highlights the critical roles long-chain omega-3 fatty acids EPA and DHA play in human health and proper development of children.

The significance of this 2011 study was that it indicated the potential of omega-3 fatty acids in the development of the immune system of the respiratory tract. Along with an increased risk for upper respiratory infections, altered immune function in the airways could also lead to asthma. With childhood asthma rates skyrocketing, several studies have explored the link between the levels of omega-3 fatty acids during pregnancy and the risk for childhood asthma. 

In a 2016 study researchers in Denmark assessed the effect of fish oil supplementation for pregnant women on the risk of persistent wheeze and asthma in their children. A total of 736 pregnant women in their third trimester of pregnancy were given either 2.4 g of omega-3 fatty acids from fish oil (55% EPA and 37% DHA) or a placebo (olive oil) daily. A total of 695 children from these women were followed for five years. The risk of persistent wheeze or asthma in the fish oil group was 31% less in the fish oil group versus the olive oil placebo after five years. Fish oil supplementation was also associated with a 25% reduced risk of infections of respiratory tract infections.

A follow-up analysis of these children in 2020 showed some interesting results. Researchers had expected to see differences in the microbiomes of the infants and their mothers with fish oil supplementation. The microbiome refers to the collection of microbial DNA from these samples and is known to greatly influence the immune system. Researchers did not find changes in the intestinal microbiome between the two groups, but they did find changes in the overall diversity of the respiratory tract microbiome that may play a role in helping the immune system protect against asthma and infection.³ 

‌‌‌‌Omega-3s and Cell Membranes

The most significant aspect of how omega-3s improve immune function may be through their effects on cell membranes, including white blood cells. 

Every cell in the body needs homeostasis—a constant internal environment. And a healthy cell membrane, the wall between the internal cell and the outside, is key. Without this membrane, cells lose their ability to hold water and vital nutrients, as well as the ability to communicate.

Cell membranes are composed chiefly of fatty acids derived from the diet. As a result, the composition of cell membranes—and the resulting structure, function, and integrity—can be influenced by dietary changes. A diet composed mostly of saturated fat, cholesterol, and trans-fatty acids produces cell membranes that are much less fluid in nature than the membranes of people who eat optimum levels of monounsaturated fat and EPA and DHA from fish oils.

‌‌‌‌Omega-3s and White Blood Cells

In addition to their critical role in cell membrane health, omega-3 fatty acids have also been shown to impact immune function by:

• Regulating gene expression of white blood cells, which helps regulate proper immune function.
• Reducing the production of inflammatory compounds that can damage the immune system.
• Improving the manner in which immune cells communicate with each other, leading to improved immune system function.

‌‌‌‌Omega-3s and Prostaglandin Production

The body also transforms EPA and DHA from omega-3 fatty acids into compounds known as prostaglandins, which act as important mediators in carrying out many bodily functions including regulating inflammation.⁴ These prostaglandins also help maintain blood pressure and regulate heart, digestive, and kidney function.

Because of these effects of prostaglandins and related compounds, omega-3s can mediate many physiological processes, making them useful in promoting health in every tissue in the body. 

As it relates to immune function, omega-3 fatty acids are very important in controlling the immune system against becoming overactive, as occurs in what is known as a “cytokine storm.” EPA and DHA are part of the body’s toolbox to resolve excessive inflammation and tissue damage quickly. At sites of inflammation, EPA and DHA are enzymatically converted to specialized pro-resolving mediators (SPMs) known as resolvins and protectins.⁵ 

These molecules resolve inflammation and protect cells from damage. Nutritional supplements containing antioxidants and EPA and DHA have been used in several human trials for improving lung function in hospitalized patients with severe respiratory tract distress. A 2019 Cochrane review of all of these trials identified a significant clinical improvement in lung function and blood oxygenation with this nutritional approach.⁶ 

These results reflect the important role of omega-3s in protecting against inflammation and lung injury through their conversion to resolvins.

‌‌‌‌Fish Oil Supplement Recommendations

One of the major advances in nutritional medicine has been the development of fish oil supplements that contain highly concentrated forms of omega-3s while being free of lipid peroxides, heavy metals, and environmental contaminants. These “pharmaceutical grade” supplements are revolutionizing nutritional medicine.

For general health and during pregnancy, the recommended dosage is 1,000 mg of EPA and DHA daily. Read the label carefully: You want to get 1,000 mg of EPA and DHA, not 1,000 mg of fish oil. When the body is challenged with inflammation or elevated blood lipids, the dosage recommendation is usually 3,000 mg of EPA and DHA daily

Learn more about omega-3 fatty acids.

References:

1. Imhoff-Kunsch B, Stein AD, Martorell R, et al. Prenatal docosahexaenoic acid supplementation and infant morbidity: randomized controlled trial. Pediatrics. 2011;128(3):e505-e512. 
2. Bisgaard H, Stokholm J, Chawes BL, et al. Fish Oil-Derived Fatty Acids in Pregnancy and Wheeze and Asthma in Offspring. N Engl J Med. 2016 Dec 29;375(26):2530-9. 
3. Hjelmsø MH, Shah SA, Thorsen J, et al. Prenatal dietary supplements influence the infant airway microbiota in a randomized factorial clinical trial. Nat Commun. 2020 Jan 22;11(1):426.
4. Innes JK, Calder PC. Omega-6 fatty acids and inflammation. Prostaglandins Leukot Essent Fatty Acids. 2018 May;132:41-48. 
5. Chiang N, Serhan CN. Specialized pro-resolving mediator network: an update on production and actions. Essays Biochem. 2020 Sep 23;64(3):443-462. 
6. Dushianthan A, Cusack R, Burgess VA, Grocott MP, Calder PC. Immunonutrition for acute respiratory distress syndrome (ARDS) in adults. Cochrane Database Syst Rev. 2019;1(1):CD012041.