Sources and Bioavailability of Omega-3 Polyunsaturated Fatty Acids

In both sports and clinical medicine, the most significant importance lies in pharmaconutrients containing omega-3 polyunsaturated fatty acids (EPA + DHA), primarily obtained from marine sources, especially fish. In the vast majority of cases, marine-derived omega-3 polyunsaturated fatty acids are described as “fish oil.” This is primarily due to the fact that all major clinical trials, including those in sports medicine, have been conducted using omega-3 polyunsaturated fatty acids obtained from fish. This constitutes the “gold standard” evidence of effectiveness and safety, serving as a benchmark for comparison with other sources of omega-3 polyunsaturated fatty acids. The classification of the main sources of ω-3 polyunsaturated fatty acids includes the following groups (Guilliams T., 2013):

Cod Liver Oil

Cod liver oil contains a mixture of fatty acids similar in composition to non-concentrated fish oil, with much lower levels of EPA and DHA. At the same time, this source contains fat-soluble vitamins A and D.

Fish Oil

Fish oil is primarily obtained through the processing of biomass from small, fatty fish species living in the cold waters off the coasts of Chile and Peru, such as mackerel (a genus of fish in the family Scombridae), anchovies (a genus of pelagic marine fish in the family Engraulidae), and sardines (commercial name for three genera of fish in the family Clupeidae). Concentrated fish oil from these fish species is the most common form of dietary supplements in pharmaceuticals and medicine. Other fish species used for the same purpose include salmon, tuna, and herring.

Krill Oil

Krill oil is derived from small planktonic shrimp known as krill. They are processed into oil directly at sea to prevent autolysis. Krill oil (KO) contains two essential components for post-physical exercise recovery processes: omega-3 polyunsaturated fatty acids and astaxanthin (which is absent in fish oil). Although krill oil has a lower content of EPA and DHA compared to marine fish, the significant beneficial properties of this product are largely attributed to the presence of the potent natural antioxidant astaxanthin. Previous research has demonstrated the protective effect of KO in terms of both types of post-exercise muscle damage – EIMD and DOMS (1.0 g per day for 6 weeks) and immunity (2.0 g per day for 6 weeks) following intense exercise. However, no improvement in physical fitness (ergogenic effect) was observed (Skarpanska-Stejnborn A. et al., 2010; Da Boit M. et al., 2015). A recent pilot randomized controlled trial (RCT) conducted by J. Georges and colleagues (2018) on a group of well-trained men aged 18-30 showed that daily consumption of krill oil at a daily dose containing omega-3 polyunsaturated fatty acids (240 mg DHA and 393 mg EPA) and astaxanthin over an eight-week period of strength training demonstrated ergogenic effects, increasing muscle strength and improving functional performance. According to the authors, the primary potential mechanisms of action of krill oil include the activation of mTOR, an intracellular protein that is a signaling element regulating muscle fiber development and hypertrophy, and the antioxidant action of astaxanthin, as demonstrated in the study by Imai A. and colleagues (2018), which protects cells in organs and tissues from the damaging effects of oxygen-derived free radicals generated during physical exercise. Chronic activation of mTOR leads to hypertrophy (increased size) of muscle fibers and improvement in their functional characteristics (Lamas L. et al., 2010). Krill oil extract has been patented as a dietary supplement that stimulates muscle growth.

Squid Oil

As a source of omega-3 polyunsaturated fatty acids, squid oil has appeared on the market quite recently (it is obtained from the by-products of the main squid processing). Therefore, the role of squid oil as a source of omega-3 polyunsaturated fatty acids is currently quite limited.

Mollusks

Mussels are currently a minor source of commercial omega-3 polyunsaturated fatty acids. Nevertheless, market trends show positive results, and some finished forms of omega-3 polyunsaturated fatty acids from mollusks are already available (from Green-Lipped Mussels – Perna canaliculus). The omega-3 polyunsaturated fatty acid profile of mollusks includes EPA and DHA in a ratio of approximately 65:35. Research on omega-3 polyunsaturated fatty acids from this source is quite limited, and for marketing purposes, manufacturers primarily use arguments from studies on traditional fish oil concentrates, typically emphasizing anti-inflammatory properties.