Fish oil supplements are widely used for their health and wellness benefits. Fish oil is sold at local drug stores and can also be found in supplement stores. In certain cases, high-dose fish oil can be prescribed by your doctor.
In this blog, we’ll cover the components of fish oil supplementation, how they affect your physiology, the potential health benefits, the amount of fish oil you need to take, how to check the quality of your fish oil supplement, and if fish oil has any side effects you need to worry about.
What Is in Fish Oil Supplements?
Fish oil supplements contain omega-3 fatty acids. Omega-3 consists of polyunsaturated fatty acids (PUFAs) with more than one carbon-carbon double bond in their backbone. They are polyunsaturated because their chain comprises several double bonds.
The way we name fatty acids is by the location of the first double bond, counted from the tail, that is, the omega (ω-) or the n- end. Thus, in omega-3 fatty acids, the first double bond is between the third and fourth carbon atoms from the tail end. You can see the differences between the structures of the omega-3, 6, and 9 fatty acids below. Notice where the first double bond is in each fatty acid type (denoted by two parallel lines).
Figure 1. Structural differences in Omega fatty acids.
What Type of Foods Contain Omega-3 Fatty Acids?
Omega-3s can be found in fish such as sardines, salmon, tuna, halibut, along with some plants, and nut oils. Within the Omega-3s, there are five fatty acids which include: α-linolenic acid (ALA), docosahexaenoic acid (DHA), docosapentaenoic acid (DPA), eicosapentaenoic acid (EPA), and stearidonic acid (SDA).
Fish oil supplements generally consist of two Omega-3s: EPA AND DHA. The industry standard for fish oil intended for human consumption is that it should contain 30% of EPA plus DHA, and an 18:12 ratio (EPA:DHA) is the most preferred and valuable profile.
Compared to EPA, DHA contains a longer carbon chain (22 vs 20) and an additional double bond (6 vs 5) per molecule, which is deemed to be the reason for the different metabolic effects between the two molecules.
How Does Fish Oil Work?
Fish oil supplements work by increasing the amount of EPA and DHA in your diet. In a perfect world, we would consume a diet rich in nutrients so that we don’t have to use supplements. However, that’s difficult to accomplish so sometimes we need to supplement our diet.
The fatty acids from fish oil are stored in membrane phospholipids within the cells of our body. They are responsible for several cellular functions including the maintenance of the cell membrane structure, fluidity, signaling, and cell-to-cell interaction.
What Are the Benefits of Fish Oil?
Fish oil has a long history with cardiovascular disease. In 1985, a seminal study found an inverse-dose relationship (more fish, less chance of cardiovascular disease) in Greenland Eskimos over a 20 year period.
The study found that the risk of coronary heart disease was 50% lower in people who ate 30 grams of fish per day compared to those who did not eat any fish at all. This study is part of the reason why it’s recommended to consume one or two meals with fish per week.
Jumping forward a few decades, these findings are controversial and the translation of consuming fish as a meal compared to supplementing your diet with fish oil to improve cardiovascular health has not been consistent. For example, a 2012 meta-analysis on the role of fish oil supplementation on major cardiovascular events found that fish oil supplementation was not associated with a lower risk of death, heart attack, or stroke based on relative and absolute measures of association.
Recent large-scale randomized controlled trials (RCTs) have also found that supplementation with fish oil did not result in a lower incidence of major cardiovascular events or cancer compared to a placebo.
Another recent RCT found no benefit for elederly people consuming 1.8g of fish oil per day after a heart attack. Finally, a Cochrane Review and meta-analysis on fish oil for prevention of cardiovascular disease indicates that increasing EPA and DHA has little or no effect on mortality or cardiovascular health, which comes mainly from trials using fish oil supplements.
The one caveat to all of these studies is the dose of fish oil used. Some studies use very low doses (0.5g/day) of fish oil and some use very high doses of fish oil (4g/day).
In a recent study on patients with elevated triglyceride levels, the risk of cardiovascular events was significantly lower among those who received 4 grams of a fish oil supplement (icosapent ethyl) per day compared to those who received the placebo. Therefore, given the inverse-dose relationship with fish you saw earlier, there might be a benefit to higher doses of fish oil, but more research is needed to figure out who would benefit most and how that might work.
Fish oil may also help improve other health metrics like insulin sensitivity, which could translate to improvements in body composition. However, a recent meta-analysis found no significant overall effect of fish oil on insulin resistance. Another meta-analysis found no evidence that fish oil supplementation can decrease body weight in overweight or obese adults. In combination, these reviews indicate that fish oil (alone) probably doesn’t improve insulin sensitivity or body composition.
Lastly, there is a mountain of evidence to support fish oil for improving triglyceride levels and a fair amount of evidence that fish oil can be used for treating depression. There is also some evidence that fish oil can modestly decrease blood pressure in people with high blood pressure.
Finally, there is a bit of evidence that fish oil is anti inflammatory, and can reduce the risk of low-grade systemic inflammation. These are all huge health benefits, especially in those who have health issues that are generally treated with other drugs (e.g., statins)
What Are the Performance Benefits of Fish Oil?
People use dietary supplements to improve their workouts or increase their recovery. Fish oil supplements could bring some benefits to people who exercise by lowering the amount of oxidative stress and improving performance or immune responses and overall function.
For example, one study on rugby players found that 551 milligrams (mg) of EPA combined with 551 mg of DHA consumed twice per day had a moderate beneficial effect when combined with a protein supplement on muscle soreness and explosive power.
Another study investigated the influence of 8 weeks of fish oil supplementation (5g/day) on the response of muscle protein synthesis to ingesting 30 g of whey protein with and without resistance exercise in resistance-trained young men, but found no differences in anabolic signaling between fish oil and placebo (coconut oil). Thus, fish oil supplementation did not provide an additional stimulus for muscle protein synthesis.
Fish oil has also been studied with endurance exercise. There are some beneficial effects including reduction of oxygen consumption, lower heart rate, and lower perceived exertion during exercise. Yet, the mechanism that causes these changes is unclear and these benefits don’t seem to translate to long-term effects.
For example, in a study on trained cyclists with low habitual fatty acid intake, eight weeks of high or low dose DHA-rich fish oil supplementation resulted in a reduced oxygen cost during a cycling time trial compared to a placebo condition (soybean oil), but this improvement did not translate into a performance advantage, with no improvements in time trial completion time, mean power during the time trial and quadriceps strength.
In older adults (>60ish), fish oil does seem to have some benefits. For example, one meta-analysis found fish oil supplementation was associated with an increase in muscle mass by ~0.33 kg for the elderly, especially when more than 2 g/day of fish oil was given. In terms of muscle strength.
For muscle performance, fish oil administration slightly enhanced performance in the timed up and go test compared to that for the controls and facilitated a faster walking speed when administered for more than 24 weeks. On the other hand, the authors found that fish oil supplementation did not cause greater handgrip strength or one-repetition maximum strength of the leg.
Overall, most of the studies on fish oil that find positive effects for performance outcomes (strength, muscle size, etc) are in older adults, rodents, or cell culture studies. So don’t expect your fish oil supplement to give you a magic boost in your strength or physique if you’re healthy.
How Much Fish Oil Should I Take?
The Food and Agriculture Organization of the United Nations recommends a dose of 250 mg/day of EPA plus DHA for adult males and non-pregnant/non-lactating adult females. The American Heart Association recommends about 1 g/day of EPA plus DHA for patients with known coronary heart disease, and 2 to 4 g/day for patients trying to lower their triacylglycerol levels.
Given the evidence cited above, it seems that there may be a benefit for larger doses in the 2-4g/day range to treat some health issues. However, more research is needed to determine how much we need to consume to benefit performance.
Does the Quality of Fish Oil Matter?
In short — yes. Oxidation can change the amount of EPA and DHA in your fish oil supplement. For example, a 2015 article stated that fish oil supplements in New Zealand are highly oxidised and do not meet their label content. Other studies have also shown that a large percent of fish oil is oxidized.
Ideally, if you choose to consume fish oil it should come from a company that uses Good Manufacturing Practice (GMP) standards and has long-term stability testing relative to a set quality standard for oxidation and also meeting label claims on EPA and DHA content.
If you plan to use fish oil supplements, it should be stored in the fridge and not exposed to light. If you’re brave you can even taste the oil to see if it changes over time or if it’s oxidized. It’s also best not to buy large bottles of fish oil and make sure to consume and check the expiration date on your fish oil container.
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Does Fish Oil Have Side Effects?
The side effects of omega-3 supplements are usually mild. They include bad taste or breath, occasionally bad-smelling sweat, headache, and gastrointestinal symptoms such as heartburn, nausea, and/or diarrhea. These symptoms are mild and not very common, but no one likes fish oil burps.
The FDA claims that omega-3 supplements containing EPA and DHA are safe if doses don’t exceed 5,000 mg per day, which aligns with the European Food Safety Authority regulations. However, if you’re consuming more than 2-3g/day you should consult with your physician.
The Take-home on Fish Oil
Fish oil is one of the most studied supplements because people do not routinely eat enough fish to reach the recommended 250-500mg of EPA and DHA per day.
Ideally, we would consume fatty fish at least twice per week. If that’s not possible then supplementing with fish oil (1-3 g/day) might be a good idea. However, don’t expect any performance or body composition benefits because of fish oil supplementation.
The strongest scientific rationale for fish oil consumption is to reduce blood lipids (triglycerides). There is also some evidence that fish oil can help with depression and slightly lower blood pressure in those with high blood pressure. The benefits of fish oil on heart health are mixed and are likely seen with higher doses.
Omega-3 fatty acids can potentially make a positive difference in your overall health and wellbeing when consumed correctly. Consider this information, as well as medical advice from a professional, as you make changes to your dietary habits and lifestyle.