Fish Oil for Athletes? Fish for Everyone? Not for Ergogenic Benefits | Summary of Latest Metas + Umbrella Review

An illustrated synthesis of the most recent evidence.

There are two fishy articles in the latest issue of Advances in Nutrition, two articles worth taking a closer look at, as I've found. Paper 1 and probably the more SuppVersity-ish paper comes from the University of Bath and is, as the authors themselves highlight, the first systematic review of fish oil supplements (#FS) in athletes that has ever been conducted in the 25-years+ history of fish oil supplements 😮 (the "fish-eating" umbrella review is addressed in the infobox).

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Impossible? Everybody knows that fish oil is rather a vitamin than a supplement, right? So why wouldn't athletes benefit? Ahh... Wrong question: The right question would read "In which domains of health and performance will athletes benefit?" and the answer is both exciting and disappointing:

No performance benefits (no benefits in any of the reviewed studies), but overall beneficial trends in  central nervous system (#CNS), cardiovascular system (#CVS), proinflammatory cytokines, and certain aspects of skeletal muscle physiology.

The N=32 RCTs that made the cut were all rather small-scale studies, averaging only 27 participants (ranging from 15-81 athletes per study). That's 32 out of 137 papers the researchers identified and eliminated the 115 papers that "failed to report fully the methodology and statistical approach were excluded, [and] studies where the participants were not classified as athletes (i.e., recreationally or physically active, or resistance-trained were excluded)" (Lewis 2020).

Bias? "Sponsorship and research funding by the fish oil industry was clearly reported in 7 RCTs," the authors report. When this came in combination with a lack of blinding on part of the authors, this is an issue to consider. With the share of single-blind studies being only 20%, it's yet not surprising that excluding those won't generally change the results.

What the scientists generously overlooked were studies in which the fish oil came as part of an (antioxidant) supplement stack, and that few studies actually tested the n–3 fatty acid status. Moreover, they included studies in a diverse group of athletes (sport, sex of participants), didn't pre-specify the fish oil dose, or the duration of the study, and whether supplements were EPA or DHA only.

"We are not aware of any RCTs that have demonstrated a negative effect of FS on performance"

Figure 1: There was no evidence of performance benefits in 2016 (Peoples 2016) and there are non, today (Lewis 2020). But does this make supplementation 'useless'? Not really.

This is good news! But performance benefits were not confirmed, either. As previously hinted at, that doesn't mean the products are totally useless, they're just not acutely ergogenic - and that's something we have known for several years (Peoples 2016). 

Figure 1 illustrates the proven benefits and underlines the lack of ergogenic effects in athletes in form of either maximal aerobic power or sports-specific exercise performance ... with the list of sports in Lewis 2020 including cycling, judo, soccer, basketball, swimming, paddling, marathoning, track and field, rugby, wrestling, football, etc.

Will fish work just as well? As the authors of the meta-analysis point out, the majority of studies used dosages of DHA and EPA that are "achievable through the consumption of oily fish" (Lewis 2020). Good sources are Mackerels (5,134 mg/100g), Salmon (2,260 mg/100g) or Herring (2,366 mg/100g | total n-3 content).  Plus: All of those contain plenty of protein, and other essential nutrients while having negligible on your levels of unwanted heavy metals (learn more about the 'healthiest' fish).

Risk reduction per additional 100g of fish/day (Jayedi 2020). 

According to the latest umbrella meta-analysis "[e]very 20 g/d increment could decrease 2%–7% risk of various health outcomes" (Li 2020); a result that is in line with the significant evidence from another 2020 meta-analysis that demonstrated that every 100-g/d increment in fish consumption was associated with a 8% lower risk of all-cause mortality, 25% reduced cardiovascular mortality, 22% risk reduction of coronary heart disease, and more in the figure to the left based on data from Jayedi 2020. 

The benefits the latest meta-analysis confirmed were a general reduction in inflammation was the most frequently studied variable in athletes, with doses of EPA ranging from 300 to 2400 mg/d, and of DHA from 400 to 1500 mg/d. In that,  different markers of inflammation reacted differently with particularly significant effects (4/5 studies) for TNF-α for which we have no evidence that it could make an important (positive) contribution to training-induced adaptation. But wait, there's more:

• insufficient evidence for reduced incidence of upper respiratory tract illness (URTI),
• muscle recovery in 4/7 RCTs, as measured in form of muscle soreness, countermovement jump, creatine kinase activity 
• positive effects of EPA and DHA at various doses were observed on cardiovascular and oxygen kinetics in all studies of cyclists [cycling efficiency, maximal oxygen uptake (VO2max)]

Great? Well, even though Lewis et al. al didn't find evidence of ergolytic (performance impairing) effects, I would like to note that the increased (unwanted) oxidation of fatty acid you may have heard about is real:

"Three RCTs with various doses of EPA and DHA showed that FS increased biomarkers of lipid peroxidation (i.e., malondialdehyde, F2-isoprostanes) at rest, and 4 RCTs reported this postexercise" (Lewis 2020).

With albeit few studies detecting cognitive benefits and positive effects of DHA on biomarkers of neuronal injury it still seems to be a (literally) smart move to eat the generally recommended two servings of fish per week - that will also help you to avoid the rancid supplements. 

Bio-advantage of krill may not be relevant in the long run | Plus: What we learned about krill oil in 2018 | Archive

Two servings of fatty fish a week? Yes, you can... eat that much fish conveniently and cheaply, even. After all, it can be canned (no pun intended) fish, too: as Tenore et al. (2014) highlight, canned bluefin tuna s not just a "cardioprotective functional food" but also "potentially safer than commercial fish oil". With more than 1g of DHA and EPA, each 50g serving of canned tuna also contains slightly more long-chain n3s than your average fish oil cap. Plus: The main nutrient loss/deterioration occurs way before canning during chilling, freezing, cooking which you'll do w/ "fresh" fish as well (Aubourg 2001) | Comment!

References:

• Aubourg, Santiago P. "Loss of quality during the manufacture of canned fish products." Food Science and Technology International 7.3 (2001): 199-215.
• Jayedi, Ahmad, and Sakineh Shab-Bidar. "Fish Consumption and the Risk of Chronic Disease: An Umbrella Review of Meta-Analyses of Prospective Cohort Studies." Advances in Nutrition (2020).
• Lewis, Nathan A., et al. "Are there benefits from the use of fish oil supplements in athletes? A systematic review." Advances in Nutrition (2020).
• Li, Ni, et al. "Fish consumption and multiple health outcomes: Umbrella review." Trends in Food Science & Technology (2020).
• Peoples, Gregory E., and Peter L. McLennan. "Fish oil for physical performance in athletes." Fish and Fish Oil in Health and Disease Prevention. Academic Press, 2016. 119-136.
• Tenore, Gian Carlo, et al. "Canned bluefin tuna, an in vitro cardioprotective functional food potentially safer than commercial fish oil based pharmaceutical formulations." Food and chemical toxicology 71 (2014): 231-235.