A lot of athletes and members of the general population take fish oil supplements in the belief that these assist in the maintenance of a number of bodily functions. Fish oil supplements have been linked to improved heart health, joint health, brain health. Additionally, in the case of athletes benefits include increased endurance, recovery, supercompensation and maximising lean body mass. But can you expect these highly valued supplements to increase your heart rate variability (HRV), and if so, why?
Fat supplements and physical performance
In their 2013 review paper of the research studies on fish oil supplements and sports performance, Macaluso et al  propose a new role for these supplements increasing testosterone synthesis which (in case you didn’t know) is one of the key hormones responsible for anabolic development of physical performance in men and women.
Fish oil contains both DHA, and EPA which are both omega-3 polyunsaturated fatty acids. There is research evidence that DHA and EPA reduce the incidence of cardiovascular disease and importantly for athletes, reduce the release of inflammatory acute-phase proteins, leading perhaps to reduced delayed onset muscle soreness (DOMS).
As an interesting aside, I met team Sky nutrition maestro Nigel Mitchell last year and asked him how much supermarket salmon I would have to eat to equal the amount of these omega-3s found in the supplements. He replied that farmed salmon has little if any of these ingredients because they originate farther down the food chain, in krill and the plankton that krill feed on. Wild salmon and tuna are apparently good sources though.
A very interesting hypothesis of this review paper is that fish oil may assist in the natural biosynthesis of testosterone from cholesterol via the intermediate hormone progesterone. The evidence comes mainly from animal studies at this point, but increased concentrations of testosterone were found in both testes and ovaries of the subjects. Exogenous testosterone (applied from outside the body) increases muscle mass and sprinting performance, though the jury is still out as to whether it also increases steady state endurance performance. Finally, the authors did identify a role for testosterone on regeneration & maintenance of the heart muscle, the myocardium.
Fish oil benefits to athletes:
|1. Controlling inflammatory response to tissue repair, remodelling and adaptation||2. Preserving health in multiple organs: heart & blood vessels; brain & mood; joints; nervous system.|
|3. Preventing muscle breakdown & enabling repair||4. Metabolic wellness: body composition and insulin sensitivity|
Who, what, why?
Physiologists in South Australia  decided to investigate whether fish oil could increase the HRV in a population of obese adults at risk of future heart attacks for whom increases in HRV would be beneficial by offering protection against lethal heart arrythmias.
They decided to compare the increases in HRV with those conferred by exercise in 46 subjects during a 12 week supervised program. Sub groups took either 6g / day of fish oil or 3days / week of 45 minutes aerobic exercise. Controls took no exercise or an equivalent dose of sunflower oil. The researchers wisely ensured that the subjects enrolled for the study were not already taking fish oil supplements, eating oily fish or exercising more than once a week.
What did they find?
For the group taking fish oil supplements, they found a significant positive impact on parasympathetic HRV (HFP) during the 12 week course of the study. They found this consistent with other studies on low HRV populations. They also found an increase in LFP HRV, which is partly parasympathetic, partly sympathetic and reflects the ability of the body to regulate blood pressure effectively in the group performing aerobic exercise 3 times per week. This finding was in contrast to the decrease in LFP HRV in the group that took no exercise.
What they also found was a decrease in resting heart rate of about 3% in both groups having fish oil supplements and those doing exercise. Not only resting, but heart rates during exercise at a constant load also fell significantly and progressively during the program in participants who took supplements, but did not exercise, as well as in those who did.
Conclusion and implications
In this study, fish oil supplements, which delivered 1.5g DHA per day and 0.36g EPA per day increased parasympathetic HRV and lowered both resting heart rate and the HR response to exercise.
The authors stated that the ‘lower HR at sub-maximal workloads, without any effect on peak HR, indicates that fish oil improves cardiac efficiency without negatively impacting on the ability to maximise HR responses’.
I have to thank Mike T. Nelson of www.miketnelson.com who is an expert on sports nutrition and metabolic flexibility, for pointing me to other studies, such as this one by well respected HRV researcher George Billman .
After finding increased HRV in dogs taking fish oil supplements, Billman analysed the data carefully and concluded that: ‘ these data suggest that perhaps, rather than altering cardiac autonomic regulation, these lipids exert their actions via changes in the intrinsic pacemaker rate.’ In other words, fish oils may act to reduce the normal rate at which the heart contracts in the absence of specific control inputs from the nervous system. Mike Nelson himself says that “Perhaps n-3 PUFAs exert multiple effects on the cardiac system that are potentially performance enhancing.”
In total though, this all sounds like good news for athletes, and considering that Macaluso et al found no documented evidence of side effects from taking these supplements in their review, it seems one of those rare occasions where not making use of fish oil supplements (or eating the oily fish themselves of course) could be a missed opportunity.
 Ninio DM, Hill AM, Howe PR, Buckley JD, Saint DA. “Docosahexaenoic acid-rich fish oil improves heart rate variability and heart rate responses to exercise in overweight adults.” Br J Nutr. 2008 Nov;100(5):1097-103.
 Billman GE, Harris WS. “Effect of dietary omega-3 fatty acids on the heart rate and the heart rate variability responses to myocardial ischemia or submaximal exercise” Am J Physiol Heart Circ Physiol. 2011 Jun;300(6):H2288-99.