Bioavailability and purity: what to look for in a high-quality supplement

The quality of an Omega 3 supplement depends on several factors, among which the purity and the bioavailability of its active components stand out. Both depend on the raw material and the processes it undergoes to obtain the product that will end up on the shelves of stores and, from there, in the hands of the people who will be taking it. Which forms offer the greatest bioavailability? And how can you be sure of the purity of the finished product? Let’s find out!

It is easy to say “take Omega 3”; the proven benefits for the heart, brain, and vision are more than enough to justify the recommendation, and an increasing number of studies confirm the potential of these fats also in specific situations, such as in athletes. It is, however, more difficult to choose which product to recommend or take among the many options currently available on the market.

A first criterion may be dictated by individual needs; for example, a fish allergy may lead to choosing krill oil–based products, while the decision not to consume animal-derived products may favour microalgae oil. But there are other factors that should guide us among the shelves where supplements are displayed, and these allow everyone, regardless of specific needs, to take high-quality Omega 3. And high quality means at least three things: safety; a higher likelihood of achieving the desired benefits; and genuine economic value.

Among these factors, the bioavailability and purity of Omega 3 play a key role. What do they depend on? And how can they be assessed?

What bioavailability is and which Omega 3 are the most bioavailable

In the context of Omega 3, bioavailability can be understood both as the speed at which a substance is absorbed by the intestine and as the amount of that substance that reaches the bloodstream or the site where it exerts its action. The amount of a nutrient available to the body therefore depends on its bioavailability.

In the case of Omega 3, bioavailability is also determined by the form in which they are taken, which in turn depends on the raw material used to produce the supplements and on the processes it undergoes.

In natural fish oils, the most abundant form is represented by triglycerides; these natural fish oils also contain a fraction of Omega 3 in the form of free fatty acids.

However, many Omega 3 supplements contain concentrated fish oil, in which EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) – the two fish-derived Omega 3 – may be present in the form of ethyl esters or re-esterified triglycerides. These latter can also be accompanied by some EPA and DHA in the form of diglycerides and monoglycerides.

Finally, krill oil contains a significant proportion of Omega 3 in the form of phospholipids and variable amounts of Omega 3 in the form of triglycerides, free fatty acids, diglycerides, and monoglycerides, while microalgae oil may contain Omega 3 as free fatty acids and triglycerides or be enriched with ethyl esters, re-esterified triglycerides, and phospholipids.

Phospholipids appear to be the most bioavailable form of Omega 3. Their absorption seems to be facilitated by their ability to form mixed fat particles; in addition, the fact that they are partly water-soluble and partly fat-soluble promotes their emulsification, and their incorporation into tissues seems to be easier.

Omega 3 in re-esterified triglycerides also show good bioavailability, higher than that of natural triglycerides, which appear to be more difficult to break down. In addition to containing more EPA and DHA, re-esterified triglycerides from concentrated fish oils are believed to be better absorbed thanks to the simultaneous presence of diglycerides and monoglycerides.

Ethyl esters, on the other hand, appear to be more difficult both to process within the digestive tract – and therefore to absorb – and to utilise after absorption.

Finally, free fatty acids are more bioavailable than ethyl esters but are easily oxidised. For this reason, they can cause more gastrointestinal discomfort and are generally removed during the production of the supplement.

Omega 3 and purity: possible contaminants and how to avoid them

The purity of an Omega 3 supplement also depends on the raw material and on the production processes. In fact, fish and krill oils are at risk of contamination because of pollution in the waters where the animals from which they are extracted live; here is an overview of the health-threatening substances that can accumulate in them.

– Polychlorinated biphenyls (PCBs). These substances have numerous possible industrial and commercial applications – such as the production of paints or plastics – and are still released into the environment today from waste, old equipment, or “imperfect” production processes. They circulate between land, air, and water, eventually accumulating in marine animals. They are considered probable carcinogens and have negative effects on the immune and nervous systems, thyroid, eyes, skin, and reproduction. They are also associated with increased blood pressure and higher blood levels of triglycerides and cholesterol.

– Dioxins and furans. They can originate from waste incineration, wood and fuel combustion, volcanic eruptions, and electricity production processes; they are also present in tobacco smoke. About 90% of total exposure to these substances comes from food, including fish; once in the body, they accumulate in body fat. The tolerable level is very low (2.3 picograms per kg of body weight per day) and their adverse effects involve the skin, liver, immune, nervous and endocrine systems, reproductive functions, and development; they have also been associated with cancer.

– Dioxin-like PCBs. These are polychlorinated biphenyls with toxic properties similar to those of dioxins and are particularly dangerous for children. They have been associated with effects on development, the immune system, thyroid and steroid hormones, and reproductive functions.

– Mercury. It is released into the environment as a result of human activities such as pesticide use, mining, and industrial waste production. The main form ingested with food is the organic form, methylmercury; it is produced by aquatic microbes, accumulates in the muscles and liver of fish, is easily absorbed by the intestine, and is highly toxic. It is a cumulative neurotoxic agent that readily enters nervous tissue, to which it binds strongly and whose development and functioning it affects; it also has adverse cardiovascular, haematological, pulmonary, renal, immunological, endocrine, and reproductive effects. It can cross the placenta and accumulate in the foetus, increasing the risk of miscarriage, preterm birth, congenital disabilities, and developmental abnormalities. The fish species most at risk of contamination are large carnivorous predators occupying high levels of the food chain and living longer, especially those closer to the seabed in contaminated geographical areas.

– Lead. It originates from both natural sources (rocks, soil, water) and human activities (industry and the use of fossil fuels, through which it reaches the atmosphere and, from there, seas and oceans). As with mercury, the most toxic form is the organic one, which accounts for between 50% and 70% of the lead present in the oceans. Its adverse effects include reduced nervous system function, foetal developmental abnormalities, and an increased risk of miscarriage.

– Arsenic. Its sources include industrial activities (glass production, animal feed), pesticides, herbicides, fungicides, and pharmaceuticals. It is associated with cancer, skin lesions, cardiovascular disease, diabetes, and, in the case of exposure during pregnancy or early childhood, adverse effects on cognitive development and increased mortality among young adults. Fortunately, in fish it is present mainly in the organic, less toxic form.

– Cadmium. It derives from natural (such as volcanic eruptions) and human activities (such as the use of fertilisers) and causes adverse effects at renal, neurological, bone, and cardiovascular levels; it is also associated with lung cancer. In fish, it forms stable complexes (for example, with muscle proteins); high salinity reduces its accumulation in aquatic organisms.

Microalgae cultivated in controlled environments do not present the same contamination risk as other marine-derived oils. However, oils obtained from fish and krill can also be safe; in fact, both these and other health-threatening substances that may be present in the raw material can be removed through sophisticated and meticulous purification processes.

Today, the high quality of Omega 3 supplements is certified by specific labels, in particular the one issued by the International Fish Oil Standards (IFOS), a programme run by an independent Canadian company that uses the parameters established by the Global Organization for EPA and DHA Omega-3s (GOED) as a reference.

By analysing each batch, the laboratories that authorise the use of the IFOS logo assess the levels of total and dioxin-like PCBs, dioxins, furans, mercury, lead, arsenic, and cadmium. They also verify the absence of oxidised Omega 3 (which, in addition to reducing the concentration of active Omega 3, themselves represent a form of impurity) and ensure that the concentration of EPA and DHA declared on the label matches that actually present in the product purchased.

How to choose a supplement based on quality

To choose an Omega 3 supplement that guarantees high bioavailability and purity, it is therefore useful to look for information on the chemical form in which EPA and DHA are present, favouring phospholipids and re-esterified triglycerides, and to select products bearing the IFOS logo, remembering that the highest quality corresponds to the 5-Star certification, with each star corresponding to a specific criterion among:

– match with the concentration of active ingredients declared on the label;
– oxidation < 75% of the CRN (Council for Responsible Nutrition) standard;
– PCBs < 50% of the CRN standard;
– dioxins < 50% of the WHO standard;
– positive evaluations in all tests to which the product has been subjected.

References:

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García-Maldonado E, Alcorta A, Zapatera B, Vaquero MP. Changes in fatty acid levels after consumption of a novel docosahexaenoic supplement from algae: a crossover randomized controlled trial in omnivorous, lacto-ovo vegetarians and vegans. Eur J Nutr. 2023 Jun;62(4):1691-1705. doi: 10.1007/s00394-022-03050-3

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Kim MG, Yang I, Lee HS, Lee JY, Kim K. Lipid-modifying effects of krill oil vs fish oil: a network meta-analysis. Nutr Rev. 2020 Sep 1;78(9):699-708. doi: 10.1093/nutrit/nuz102

Schuchardt JP, Hahn A. Bioavailability of long-chain omega-3 fatty acids. Prostaglandins Leukot Essent Fatty Acids. 2013 Jul;89(1):1-8. doi: 10.1016/j.plefa.2013.03.010

U.S. Environmental Protection Agency. epa.gov

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