Omega-3 fatty acids are so important for health that the shortest-chain omega-3, alpha-linolenic acid (ALA), is classed as essential and must come from the diet. Longer-chain omega-3s such as EPA and DHA can be made from alpha-linolenic acid in the body, but these conversions are inefficient so that EPA and DHA are often in short-supply.

What does omega 3 do?

The long-chain omega 3, DHA, is incorporated into nerve cell membranes, helping to maintain their flexibility and speed the transmission of electrical and chemical messages. EPA plays an important role in cell communication and in suppressing inflammation. Omega 3 also has beneficial effects on the heart and circulation.

The European Commission has approved health claims that DHA is important for healthy brain function and for maintaining normal vision, while both DHA and EPA help to maintain normal blood pressure and triglyceride levels as well as contributing to the normal function of the heart.1 Many people find that omega 3 is beneficial for joints.

Omega 3 for mood

Some studies have shown people living in countries with the highest intakes of fish oil have the lowest rates of unhappiness and depression. The results from 21 studies, involving over 255,000 people, found that those who ate the most fish and obtained the most DHA and EPA were 22% less likely to develop depression than those who ate the least. The most effective intake was 1.8g of omega 3 per day.2

Anxiety often accompanies depression and in people with major depressive disorder, researchers can distinguish those that are also anxious from those that are non-anxious based on their lower blood levels of EPA and DHA. Those with the lowest omega 3 levels had the most severe anxiety.5

A similar anti-anxiety effect was found in a group of healthy medical students who took either omega 3 supplements (2.5 g per day) or placebo. Their blood was tested during low-stress periods as well as on days before an exam and those students who received omega 3 had a 20% reduction in anxiety symptoms.6

How long does omega 3 take to work for mood?

Effects are seen quite quickly. In one study involving young adults with depression, significant improvements were seen after taking omega 3 for 21 days, by which time two thirds (67%) no longer met the criteria for depression (compared with only 20% of those taking placebo).3

Omega 3 and vitamin D may work together to help regulate levels of serotonin – the so-called ‘happy’ neurotransmitter in the brain.4

Omega 3 for heart health

The results from 70 clinical trials show that people who took omega 3 fish oil supplements had blood pressure readings that were, on average, 1.52/0.99 mmHg lower than in those taking placebo - whether or not they had hypertension. When just those with untreated hypertension were assessed, taking omega 3 lowered their blood pressure by an average of 4.51/3.05 mmHg. While this may not seem like much, it is enough to avoid a diagnosis of hypertension and can significantly reduce your risk of heart attack or stroke. The researchers suggested that taking EPA and DHA was at least as effective and in some cases more effective than the usual lifestyle recommendations, such as increasing exercise and restricting alcohol and sodium.7

Where to get omega 3 in your diet

The short-chain omega 3, ALA, is found in nuts, seeds and spreads, while EPA and DHA are mainly found in oily fish such as herrings, kippers, salmon, mackerel and pilchards. A 150g serving of salmon provides around 3g omega 3, while a 150g serving of fresh tuna provides just under 2g. Tinned tuna provides hardly any omega 3 at all, as it is removed during processing. Other useful sources of omega 3 include grass-fed wild game meats, such as venison and buffalo.

The NHS suggests eating at least two portions of fish per week, of which one should be oily. Because of concerns about pollutants in sea fish, however, no-one should eat more than four portions of oily fish a week and women you are planning a pregnancy or who are pregnant or breastfeeding should have no more than two portions (140g each) of oily fish a week.8 Supplements are a great alternative as these fish oils are purified, distilled and tested to remove any toxins.

Omega-3 safety

A safety assessment by the European Food Safety Authority concluded that daily supplements providing up to 5g long-chain omega 3 raise no safety concerns for adults.9 As fish oil has a blood-thinning effect, check with your doctor before taking if you are on blood-thinning or antiplatelet medication.

Omega 3 dose

For optimal health, you need at least 450mg to 1g long-chain omega 3 (EPA and DHA) per day.

Although intakes of 1g to 1.5g omega-3 fish oils provide heart health benefits, the EU has concluded that intakes of between 2g and 4g EPA and DHA a day are needed to reach claimed effects such as the maintenance of blood pressure and triglyceride levels.10

Typically, a 1g capsule of high-strength fish oil contains around 500mg of the important long-chain EPA and DHA (check label claims). Select a pharmaceutical-grade omega 3 fish oil supplement made to GMP standards to ensure they are virtually free from marine pollutants. Omega 3 fish oil offered in the triglyceride (TG) form is most easily absorbed as they are in a ‘body-ready’ form.

For vegetarians and those who are unable to take fish products, algae is a great source of the long-chain omega 3, DHA (and is where fish originally obtain theirs). A typical capsule containing 250mg algae oil can provide as much as 100mg of DHA.

Vegetarian omega 3 from flaxseed provides the short-chain ALA essential fatty acid.

Typically, less than 5% of ALA is converted on to EPA in the body and less than 0.5% is transformed into DHA.(11) Fish oil is, therefore, the best source of these important long-chain fatty acids. A study from Norfolk, involving over 14,400 people found that total omega-3 intakes in non-fish-eaters was up to 80% lower than for fish eaters.(12)

Dr Sarah Brewer

Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn't possible, supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.



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