Omega-3 in Community Pharmacy: Triglycerides & Brain Health

Omega-3 supplements are among the most requested products at the pharmacy counter, and they usually arrive with expectations about the heart and memory that the evidence does not support equally. This is what the trials and the regulators say, indication by indication, and where the line runs between a supplement and a medicine.

EPA and DHA: what each one is and what to check on the label

The long-chain omega-3 fatty acids are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). They come from oily fish, krill oil and microalgae, which are the option for people who do not eat fish. DHA is a structural component of the membranes of the nervous system and the retina. EPA modulates eicosanoid synthesis and has a modest antiplatelet effect that only matters at high doses.

The first question at the counter is about the label: "1,000 mg of fish oil" is not 1,000 mg of EPA plus DHA. What counts is the milligrams of EPA and DHA per dose, and that is also what the health claims authorised in the EU are based on:

• DHA contributes to the maintenance of normal brain function and normal vision, with 250 mg a day.
• EPA and DHA contribute to the normal function of the heart, with 250 mg a day.
• EPA and DHA contribute to the maintenance of normal blood triglyceride levels, with 2 g a day.

These are claims about normal function, not about preventing or treating any disease: a supplement cannot be marketed for that.

Triglycerides: the indication with the strongest support

As a medicine, omega-3 acid ethyl esters are authorised for endogenous hypertriglyceridaemia, as an addition to diet when diet alone is not enough, at 2 to 4 g a day. They lower triglycerides by reducing hepatic VLDL synthesis. It is a prescription indication: high triglycerides are assessed by the doctor, who decides whether treatment is needed and which one.

Cardiovascular prevention: the result depends on what is given

Here the evidence is mixed, and it is worth explaining it that way:

• In 2019 the European Medicines Agency (EMA) concluded that omega-3 acid ethyl esters at 1 g a day are not effective in preventing further events after a heart attack, and that indication was removed from the product information. Check your own national regulator for local status.
• The REDUCE-IT trial, with 4 g a day of icosapent ethyl (purified EPA) in high-risk patients already on a statin, reduced cardiovascular events by 25 % in relative terms. It has been argued that its placebo, mineral oil, may have worsened the control group and widened the difference.
• The STRENGTH trial, with a high-dose combination of EPA and DHA, was stopped early for lack of benefit.

In other words: the result of a specific drug, at a specific dose and in a specific population, does not carry over to a fish oil supplement. And there is a safety signal worth knowing: several high-dose trials (1 g a day or more) have observed more atrial fibrillation. Megadoses should not be offered without a medical indication.

Cognitive function: less than the box promises

DHA is needed by the brain, which is where its authorised claim comes from. But needing something does not mean that taking more improves memory. Systematic reviews, including Cochrane reviews, have not found a clear benefit of supplementation on cognitive function in healthy older adults or in established dementia. When someone complains about their memory, the right step is to refer them to a doctor, not to offer a capsule.

To check an omega-3 against the rest of a patient's treatment you can use the drug interactions checker.

What to ask before recommending it

• How much oily fish they eat. Guidelines put diet first: two or three portions a week. The supplement covers what the diet does not.
• Whether they take anticoagulants or antiplatelet drugs. At usual supplement doses no adjustment is needed, but at high doses (more than 3 g a day) it can add an antiplatelet effect: with a vitamin K antagonist the INR and minor bleeding need watching, and the doctor has to know.
• Whether they are allergic to fish or shellfish. Check where the oil comes from and ask first. Algal oil is an alternative.
• How much they plan to take. More than 5 g a day of supplemental EPA plus DHA is not recommended.

In pregnancy and breastfeeding, the product information and the pregnancy and breastfeeding tool are the starting point, and a specific regimen is for the doctor or midwife to decide.