Several sports-related studies including omega-3 fatty acids stress the importance of an adequate intake for athletes, notes Lena Burri, Director of Scientific Writing, Aker BioMarine
The sports nutrition market grew 8% last year, according to Nutrition Business Journal (NBJ), reaching nearly $5 billion in sales. And the future looks even brighter, as the market research firm predicts a compound annual growth rate (CAGR) of almost 16% through 2020.
During the past several years, the sports nutrition market has played host to a variety of products and ingredients, such as protein powders and amino acid combinations; but, recently, researchers have been quietly looking into how omega-3s — eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) — might also play a role in areas such as athletic performance, endurance and recovery. Alongside that trend, although omega-3s have struggled recently, they too will return to positive growth by 2020, according to NBJ.
The human immune system is a complex interplay of cells, tissues and organs that support, repair and prevent invasion of the body by bacteria, parasites, viruses and fungi. Omega-3 fatty acids enhance the immune function by mixing into immune cell membranes, which reduces the amount of the pro-inflammatory fatty acid, arachidonic acid. The incorporation of omega-3 fatty acids, instead, promotes the formation of the less potent EPA and DHA-derived inflammatory mediators.
The immune-enhancing properties of omega-3 fatty acids might play a key role in situations when the immune system function is reduced. Such a compromised immune system can occur after heavy training and sports competitions, when the risk of infection is increased, especially for upper respiratory tract infections.
It has been recommended by Simopoulos, et al. that non-professional athletes or those participating in leisurely active pursuits should eat up to 2g of fish oil per day in a 2:1 ratio of EPA to DHA.1
Competitive athletes, however, should probably consume even more omega-3 fatty acids to fully benefit from the immunomodulatory effects. In a recent study of 106 German winter elite endurance athletes, only one was within the optimal omega-3 target range to lower the risk of cardiovascular events and suboptimal brain function (reaction time and executive function).2
These surprisingly low omega-3 levels, which were even lower than in heart disease patients, may be explained by the high energy needs of athletes using these fatty acids as an energy source.3 Omega-3 supplementation might therefore be crucial to help athletes optimize their physical and mental performance, while also decreasing heart rate and oxygen consumption during exercise.4
Krill oil contains EPA and DHA, which are mostly bound to phospholipids. The way these omega-3s are digested and delivered throughout the body differs completely from other marine source omega-3s, such as fish oil. It is this difference, researchers say, which dictates how omega-3s from krill oil perform in various clinical trials.
The potential of Superba Krill to strengthen immune function after a simulated cycling time trial has been tested in both male and female participants (unpublished data). The study was conducted at the University of Aberdeen under the supervision of Dr Stuart Gray, Senior Lecturer in Exercise Physiology. The Omega-3 Index, a measure of the percentage of EPA and DHA in red blood cell fatty acids, was measured after 6 weeks of either 2g of Superba Krill oil (daily) or placebo supplementation. The results showed that those participants administered with krill oil significantly increased their Omega-3 Index.
Further, after 6 weeks, the volunteers performed an incremental maximal exercise test on a cycle ergometer. Participants cycled at 70 revolutions per minute with the workload increasing by 30 Watts every minute for males, and 20 Watts every minute for females, until volitional exhaustion. Immune function parameters such as cell signalling molecule production (IL-2, IL-4, IL-10, IL-17 and IFN-gamma) and the ability to destroy target cells by natural killer (NK) cells were measured at baseline and in the recovery period after exercise (post exercise, 1 hour and 3 hours).
The results demonstrated that supplementation of the diet with 2g per day of krill oil for 6 weeks can significantly increase the production of IL-2 and increase the toxic effect of NK cells on other cells in the recovery period after exercise. The effect was gender-independent.
Study co-ordinator, Dr Stuart Gray, commented: 'Our study is in agreement with our previous work with fish oil, in which we observed similar results. However, the krill oil EPA and DHA dose used was only a quarter from the dose given in the earlier fish oil study. It remains to be proven whether the different structural forms (omega-3 phospholipids from krill oil versus omega-3 triglycerides from fish oil) can explain this difference.'
The ability of krill oil to positively influence oxidative stress and immune function shows that the regular consumption of omega-3 phospholipids from krill oil might be an effective nutritional strategy to support athletes in the post-exercise recovery phase.
Philip C. Calder, Professor of Nutritional Immunology, University of Southampton, UK, and Aker BioMarine Science Board member, explains: 'In comparison with a sedentary lifestyle, engaging in moderate exercise improves immune function and lowers the risk of upper respiratory tract infections (URTI). However, high intensive exercise can have immune system modulating effects that weaken the defence mechanisms of a recovering body.5 The resulting U-shaped relationship between exercise intensity and risk of URTI was nicely shown by Professor David Nieman (Figure 1).'6
Figure 1: The relationship between exercise intensity and upper respiratory tract infections (URTIs)
'The immune system changes after heavy exercise include a decrease of interleukin 2 (IL-2) and interferon gamma (IFN-gamma) molecules, which regulate the activity of immune cells. Likewise, natural killer (NK) cell function was shown to be decreased after heavy exercise. NK cells are a first line of defence, which react quickly to threats such as bacteria and viruses to keep them under control until the antigen-specific immune system responds.'
'Their activity can be decreased by up to 60% for several hours after extended exercise.7 This has led to the view that, after intense training or a sports competition, there is an open window of 1–9 hours of lowered host defence, which increases the likelihood of an infection. To address this issue, omega-3 supplementation has been shown to increase IL-2 and INF-gamma production, as well as NK cell function, which might therefore help to increase host protection after exercise.'
1. A.P. Simopoulos, 'Omega-3 Fatty Acids and Athletics,' Current Sports Medicine Reports 6, 230–236 (2007).
2. C. von Schacky, et al., 'Low Omega-3 Index in 106 German Elite Winter Endurance Athletes: A Pilot Study,' Int. J. Sport Nutr. Exerc. Metab. 24, 559–564 (2014).
3. C von Schacky, 'The Omega-3 Index as a Risk Factor for Cardiovascular Diseases,' Prostaglandins Other Lipid Mediat. 96(1–4), 94–98 (2011).
4. G.E. Peoples, et al., 'Fish Oil Reduces Heart Rate and Oxygen Consumption During Exercise,' J. Cardiovasc. Pharmacol. 52, 540–547 (2008).
5. A. Skarpanska-Stejnborn, et al., 'Effects of Supplementation with Neptune Krill Oil (Euphasia superba) on Selected Redox Parameters and Pro-Inflammatory Markers in Athletes During Exhaustive Exercise,' J. Human Kinetics 25, 49–57 (2010).
6. D.C. Nieman, 'Upper Respiratory Tract Infections and Exercise,' Thorax 50, 1229–1231 (1995).
7. D.C. Nieman, et al., 'Indomethacin Does Not Alter Natural Killer Cell Response to 2.5 h of Running,' J. Appl. Physiol. (1985) 79, 748–755 (1995).