Omega-3 supplements, and what the evidence shows

What omega-3 fats are

Omega-3 fats are a family of fats the body needs from food. The two found in oily fish and fish oil are EPA and DHA, and plants provide another, called ALA [1].

In Great Britain, a label may say that EPA and DHA contribute to the normal function of the heart, and only if the product is a real source of them, with the effect obtained at 250 mg a day [2]. No food or supplement may claim that omega-3 prevents or improves heart disease [3].

What the large trials show

For most people, extra omega-3 makes little or no difference to deaths or heart events. A Cochrane review of 86 trials and 162,796 people found little or no effect on death from any cause, heart and circulation events or stroke, with a possible small fall in coronary heart disease events, about 1 fewer for every 167 people treated [1].

In the VITAL trial of 25,871 healthy older adults, 1 g a day of omega-3 for a median of 5.3 years did not lower major heart events or cancer [4].

What omega-3 does change

The clearest effect of omega-3 is on triglycerides, a type of fat in the blood. The Cochrane review found that EPA and DHA lowered triglycerides by about 15%, more so at higher doses [1]. The Great Britain register allows a label to say that EPA and DHA contribute to the maintenance of normal blood triglyceride levels at 2 g a day, and of normal blood pressure at 3 g a day [2].

If you do choose a supplement, read the label for the amount of EPA and DHA in each daily dose, which is often far less than the total weight of oil in the capsule. In VITAL, 1 g a day caused no excess bleeding or other serious side effects [4].

The prescription exception

One trial stands apart from the rest. REDUCE-IT gave 4 g a day of icosapent ethyl, a purified prescription form of EPA, to 8,179 people on statins who had raised triglycerides and either heart disease or diabetes with other risks [5]. Heart events fell from 22.0% in the placebo group to 17.2% over a median of 4.9 years [5].

NICE recommends this medicine only for adults at high risk who take statins, with fasting triglycerides of 1.7 mmol/litre or above and LDL cholesterol above 1.04 and up to 2.60 mmol/litre [6]. A trial of a different high dose omega-3 mix, compared with corn oil in 13,078 similar patients, was stopped early when it showed little chance of benefit [7]. NICE advises that there is no evidence other omega-3 products help prevent heart disease [8].

Who it is not for, and the risks

NICE advises doctors not to offer omega-3 supplements to prevent heart disease, and to tell people there is no evidence they help, apart from the prescription exception above [8].

Omega-3 supplements have been linked to a higher risk of atrial fibrillation, an irregular heart rhythm. A review of 7 trials and 81,210 people found a 25% higher risk overall, and a greater risk at doses above 1 g a day [9]. In REDUCE-IT, more people on the medicine were admitted to hospital with atrial fibrillation or flutter, 3.1% against 2.1% [5].

Speak to a doctor before taking omega-3 if you take a blood thinner or have an irregular heartbeat. If you have chest pain, or a racing, irregular heartbeat with dizziness or breathlessness, call 999 in the UK or the local emergency number.

Questions to ask your doctor

Knowing your own risk first is what decides whether omega-3 has any role for you. A blood test that measures ApoB and Lp(a) with your lipids, read beside your blood pressure and family history, gives a doctor that picture.

• What is my own risk of heart disease, and what would lower it most?
• Are my triglycerides raised, and is a prescription option relevant to me?
• Could omega-3 affect my heart rhythm or interact with my medicines?
• If I take it, what dose, and for how long?

How The Wellness can help

The Longevity+ blood test measures ApoB and Lp(a) alongside a full profile, and a doctor turns the results into a plan for your heart health. A GP appointment is the place to decide whether omega-3 or a prescription belongs in that plan.

Every doctor is GMC registered, and samples go to accredited laboratories. Our clinics are on Baker Street in Marylebone and Eccleston Street in Belgravia.