Omega 3, 6, 9: What They Are and Why Fatty Acids Are Needed

On a fish oil package, "omega-3," "EPA," and "DHA" sit side by side. Let us break down what the numbers 3, 6, and 9 mean, how EPA and DHA differ from each other, and which of the label's promises are confirmed by research.

What omega 3, 6, and 9 are

The name indicates the structure: in omega-3, the carbon-carbon double bond is in the third position, that is, after the third carbon atom, counting from the methyl end of the chain. In omega-6 and omega-9, the position is different. They differ not in "benefit" but in structure and in what the body does with them.

Omega-3s are part of cell membranes and blood vessels; the body does not synthesize them in the required amounts, and they remain an essential dietary component. Omega-6s compete with them: the conversion of alpha-linolenic acid (ALA) into long-chain forms slows in their presence, and EPA and DHA accumulate more efficiently in tissues when they come directly from food.

Why the body needs omega fatty acids

Omega-3s are needed for building brain cells and for other functions. For the heart and blood vessels, they lower triglycerides, reduce the risk of rhythm disturbances, slow the formation of atherosclerotic plaque, and slightly lower blood pressure.

For outcomes, the picture is more modest. A 2018 Cochrane review of 12 randomized trials: omega-3s have no or very little effect on mortality and cardiovascular disease. A meta-analysis of nearly 78,000 people and a review of 79 randomized trials with approximately 112,000 participants gave the same result. The numbers on the bottle look more convincing than the combined result of these studies. Verdict: an essential nutrient, but not a cure for heart attack.

• Triglycerides and blood pressure: EPA and DHA lower them.
• Heart rhythm: the risk of arrhythmias is lower.
• Cardiovascular outcomes and mortality: no effect in randomized trials.
• Memory and thinking: a 2015 review found no effect on cognitive function; a 2020 review found only a small memory advantage in adults without dementia.

What EPA and DHA are

EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are long-chain omega-3s from fatty fish; both are directly beneficial for the heart. The third member of the family, ALA, is found in oils, nuts, and plants and is beneficial for the heart, but less directly. The body can assemble EPA and DHA from ALA with an efficiency of about 5% in men and slightly higher in women. DHA is a physiologically essential dietary component; the Government of Canada has recognized its importance for normal development of the brain, eyes, and nerves.

The EPA-to-DHA ratio and what the numbers on the package mean

The numbers on the package usually indicate the amount of EPA and DHA; the manufacturer specifies the units of measurement. If DHA is highlighted separately on the label, this means that its amount is stated in the composition, but it does not indicate that the product is superior.

There is no single "correct" EPA-to-DHA ratio on a package; the number on the label describes the composition of the product, not its purpose. The benchmark is different: at least two servings of omega-3-rich fish per week, with a serving being 100 g. In the absence of heart disease, experts agree that getting omega-3s from food is preferable: whole foods also carry other nutrients.

Dietary sources of omega fatty acids

Fish: salmon, mackerel, albacore tuna, trout, sardines. Plant options: ground flaxseed and flaxseed oil (the highest ALA content among plant products), walnuts, chia seeds, canola and soybean oil, soy, and tofu.

Fish have a caveat: mercury and other chemicals. Fish high in mercury (swordfish, shark, king mackerel, tilefish) is considered undesirable for pregnant women and children; variety of species reduces exposure. For middle-aged and older adults, the benefits of fish outweigh the risks.

When to discuss omega fatty acids with a doctor

The reason is existing heart disease or high triglycerides: then more omega-3s may be required than the diet provides, and the question of supplements is discussed with a doctor. The doctor assesses the diet, blood lipid profile, comorbidities, and medications being taken. A separate topic is pregnancy: a 2021 review indicates a possible favorable effect of omega-3 supplements in preeclampsia, low birth weight, preterm birth, and postpartum depression. This is not a recommendation to take anything on your own.

The mere absence of omega-3s in the diet is not a reason to call an ambulance. 103 or 112 are needed when there is a threat to life, including stroke and heart attack.

This material is for reference: it does not replace a doctor's consultation and does not turn a label into a diagnosis.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer