Supplementation and Sports: Krill Oil Boosts the Immune System After Physical Exercise

Sport supplementation with krill oil for six weeks enhances the immune system during the recovery phase after physical effort, increasing the activity of specific cells called Natural Killers, which play an important role in the body’s defense. Krill-based supplements, rich in omega 3 and antioxidants, can therefore protect the athlete’s health immediately after intense physical activity, precisely when the activity of Natural Killer cells and other immune components decreases for several hours.

These are some of the results obtained by researchers from the University of Glasgow (Scotland), who tested the effects of sports supplementation with oil extracted from krill, the group of small crustaceans living in the Atlantic. The data were published in the prestigious journal PloS One.

Sports and Immune Defenses: What’s the Relationship?

The immune system is a complex network of cells and molecules capable of recognizing and reacting to exposure to foreign and harmful substances. Physical exercise can have both positive and negative effects on immune function. In particular, moderate physical activity leads to a boost in immune defenses and consequently reduces infection risk compared to sedentary individuals. Other studies show that intense and prolonged physical activity, such as that performed by marathon runners or cyclists, suppresses the immune system, making athletes more susceptible to infections. The decrease in immune system activity after prolonged, high-intensity exercise is called the “Open Window” and lasts several hours; during this phase, the athlete is more vulnerable to infections, especially respiratory tract infections. 

Specifically, this protection deficiency seems due to decreased IgA antibodies in the mucous membranes of the airways, a reduction in type 1 T lymphocytes, and lowered Natural Killer cells, which have a crucial role in protecting the body against harmful microorganisms. Using specially formulated dietary supplements is a good strategy to boost the body’s natural defenses and thus protect the athlete without compromising sports performance. Fish oil supplements rich in omega-3 are recommended for athletes for their anti-inflammatory, antithrombotic, antiarrhythmic, and lipid-lowering capacities. Several studies suggest that most athletes, including amateurs, should consume EPA and DHA to prevent joint inflammation. Over time, these substances may also improve sports performance, as reported by recent studies (read here).

Krill Omega-3s Boost the Immune System During the “Open Window”

Experiments by Scottish researchers demonstrated that, in both men and women, supplementation with krill oil induces significant immune changes during the recovery period after physical exercise. Specifically, the researchers observed that subjects following supplementation showed increased production of IL-2, a signaling molecule belonging to the cytokine family that regulates immune cell activity, and increased activity of Natural Killer cells. As explained by the study coordinator, Dr. Stuart Gray, this last finding is very important because under normal conditions Natural Killer activity can decrease by up to 60% for several hours after prolonged exercise. These results confirm those obtained in a previous study by the same scientists, where fish oil supplementation appeared to increase IL-2 and Natural Killer activity during the same recovery period. However, in the current study, krill oil was administered at a dose about one quarter that of the fish oil used in the previous research, suggesting a greater potential of krill oil in sports nutrition to increase athlete protection after intense exercise.

Some Details of the Study

The researchers recruited 37 healthy male and female volunteers with an average age of about 26 years. Each subject was randomly assigned to take either two grams per day of krill oil or a placebo for six weeks. All participants performed a time trial cycling simulation before and after the treatment. Analyses at the start and after six weeks showed that those who received the supplement had increased EPA and DHA levels in red blood cells by 75% and 21% respectively, while the Omega-3 Index rose by 27%. Conversely, concentrations of omega-6 fatty acids, arachidonic acid, and docosatetraenoic acid decreased by 7% and 17% respectively. 

Regarding the immune system, the krill oil group showed a significant increase in IL-2 production, and no changes were observed in other cytokine production during the recovery period. Additionally, no effects on physical performance, heart rate, or oxygen consumption were detected. As noted by the scientists, this work is the first to study the effects of krill oil supplementation on immune function marker cells and molecules and demonstrated that this supplement can enhance certain immune system elements about three hours after exercise without affecting physical performance. 

It remains to be understood whether this immune system effect is sufficient to reduce respiratory infections, warranting further studies to clarify the role of krill oil. 

Source: M. Da Boit, I. Mastalurova, G. Brazaite, N. McGovern, K. Thompson, S.R. Gray “The Effect of Krill Oil Supplementation on Exercise Performance and Markers of Immune Function” PLoS One; 2015; Volume 10, Number 9: e0139174.