For a long time, dietary fats were treated as uniformly harmful — something to be reduced or avoided at all costs. Today, the science tells a very different story. High-quality fats play a substantial role in preventing many chronic diseases, and omega-3 fatty acids in particular have become one of the most studied areas in nutritional research. The classification of fatty acids can seem complicated at first glance, but understanding a few key concepts — including what DHA and EPA are, and what the Totox index measures — makes it much easier to evaluate quality and choose wisely.
Fats and Fatty Acids: The Basics
Fats are a large and chemically diverse group of compounds, but they share a common structure: each molecule consists of glycerol and one or more fatty acids. It is the fatty acid component that determines both the physical properties and the health effects of any given fat. Beyond being the body's most energy-dense fuel, fats serve as carriers for the fat-soluble vitamins — A, D, E, and K — and form an indispensable part of every cell membrane in the body.
What Are Fatty Acids?
Fatty acids are organic compounds containing a carboxyl group. In nature, they commonly occur as esters bound with glycerol. They are structural components of the brain, nervous system, and cell membranes, and their influence extends across virtually every aspect of human health — physical and psychological alike. The nutritional value of any fat depends primarily on the type and degree of saturation of the fatty acids it contains.
Types of Fatty Acids: Saturation and Health Effects
Fatty acids are classified into three main groups based on the number of double bonds in their carbon chain — in other words, their degree of saturation. This structural difference is what makes some fats actively health-promoting and others potentially harmful.
Saturated Fatty Acids
Saturated fatty acids are found primarily in animal products such as butter, cured meats, and red meat. The body uses them mainly as a concentrated energy source, but excess intake is associated with elevated cholesterol levels and increased risk of cardiovascular disease. Crucially, the body can synthesise them internally, so they do not need to be obtained from food — making overconsumption easy to achieve and worth monitoring.
Monounsaturated Fatty Acids
Monounsaturated fats, of which omega-9 is the primary representative, help maintain healthy cholesterol levels and support cardiovascular function when consumed in moderation. The body can produce omega-9 on its own — given an adequate intake of omega-3 and omega-6 — so it is not considered an essential fatty acid in the strict sense.
Polyunsaturated Fatty Acids (PUFAs): The Essentials
Polyunsaturated fatty acids — also known as Essential Fatty Acids (EFAs) — are the most important group from a nutritional perspective. The human body cannot synthesise them independently, which means they must be obtained from food or supplementation. They regulate physiological processes, contribute to cell structure, and may help prevent or reduce the severity of serious conditions including coronary artery disease, stroke, and autoimmune disorders.
Two sub-groups dominate the clinical conversation:
- Omega-3 fatty acids — influence hormonal and lipid metabolism, protect the brain, contribute to cardiovascular health, and help moderate chronic inflammation. The key members are ALA (alpha-linolenic acid), EPA (eicosapentaenoic acid), and DHA (docosahexaenoic acid).
- Omega-6 fatty acids — exhibit anti-inflammatory and immunostimulating properties, and help lower LDL cholesterol and blood pressure. The most clinically significant representative is linoleic acid (LA).
DHA and EPA: What They Are and Why They Matter
DHA and EPA are two long-chain omega-3 fatty acids with distinct but complementary roles. Together, they represent the most biologically active forms of omega-3 and are found primarily in marine sources — cold-water fish, certain seafood, and high-quality fish oil.
DHA (docosahexaenoic acid) is a critical component of brain tissue and the retina. Research has linked low DHA levels to an increased risk of cardiovascular disease, immune dysfunction, and psychological disorders including depression. It is also indispensable during pregnancy and early childhood for the development of the central nervous system.
EPA (eicosapentaenoic acid) is involved in nerve signal transmission between fibres, supports cognitive function and concentration, and has demonstrated benefits across a wide range of inflammatory conditions. Interestingly, EPA can serve as a biochemical precursor to DHA — the body is capable of converting it, though the conversion rate is limited.
The Gap Between Recommendations and Reality
Data from large-scale dietary surveys consistently show that intake of DHA and EPA falls significantly short of expert-recommended levels across all age groups. The primary dietary sources are marine fish, select seafood, and pure fish oil — foods that are simply not consumed in sufficient quantities by most people. For those who do not eat oily fish regularly, supplementation is often the most practical route to adequate intake. Our Fish Oil & Omegas (EPA/DHA) range covers a broad spectrum of options, from standard fish oil capsules to high-concentration liquid formats and vegan algae-based alternatives.
The Totox Index: The Quality Marker You Should Know About
EPA and DHA content tells you what is in a fish oil. The Totox index tells you whether that content is still intact — and whether the oil is safe to consume.
Fatty acids, and omega-3s in particular, are prone to oxidation. When fish oil oxidises, it generates peroxides and reactive radicals — compounds that not only degrade the oil's nutritional value, but also pose a genuine health risk through cumulative oxidative damage to tissues and organs.
The Totox value is calculated by combining two oxidation measurements: the peroxide value (PV) and the anisidine value (AV), using the formula: Totox = 2×PV + AV. According to EFSA (the European Food Safety Authority), a Totox value below 25 is required for fish oil to be considered acceptable. The lower the value, the fresher and more stable the oil.
[warning:Not all fish oil supplements display a Totox value — this parameter is only relevant for pure, unflavoured fish oils of the highest quality. If you are investing in a concentrated omega-3 supplement, checking whether the manufacturer publishes oxidation data is a reasonable quality check.]High Totox values indicate a large burden of free radicals — molecules associated with progressive, cumulative damage to cells and organs. In short: high-quality fish oil is fresh, low-oxidation fish oil, and the Totox index is how that freshness is measured. Products from brands such as Nordic Naturals, Green Pasture, Carlson Labs, Rosita, and Zinzino are known for their transparency around oxidation testing and third-party quality standards. You can explore these and many more options in our omega-3 collection.
Choosing the Right Omega-3 Supplement
Beyond the Totox index, a few other factors are worth considering when selecting an omega-3 supplement. The triglyceride form is generally considered to offer better bioavailability than the ethyl ester form. Concentration matters — the combined EPA+DHA content per serving is more informative than the total fish oil content. And for those following a vegan or plant-based diet, algae-based omega-3 supplements provide DHA and EPA directly from the original marine source, without the fish.
For cardiovascular and brain support specifically, our Brain & Cognitive and Cardiovascular categories include omega-3 supplements alongside other complementary nutrients.
[products:nordic-naturals-ultimate-omega-lemon-flavour-60-softgels, green-pasture-fermented-cod-liver-oil-unflavored-120-capsules, now-foods-ultra-omega-3-500-epa-250-dha-90-softgels, zinzino-balanceoil-lemon-300-ml, rosita-extra-virgin-cod-liver-oil-evclo-150-ml, aliness-krill-oil-nko-omega-3-with-astaxanthin-500-mg-60-capsules]For plant-based options and everyday supplementation at a more accessible price point, the following are worth exploring:
[products:aliness-vegan-omega-3-forte-dha-500-mg-60-veg-capsules, dr-jacobs-dha-epa-algae-oil-60-capsules, vitaler-s-omega-3-forte-1000-mg-120-capsules, aliness-fish-omega-3-forte-triglycerides-500-250-mg-60-capsules, now-foods-omega-3-180-epa-120-dha-100-softgels, solgar-triple-strength-omega-3-950-mg-50-softgels] [note:All products at Medpak are shipped from within the European Union — fast delivery, no customs fees, to customers across Europe.]
