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Your Guide to Omega-3


Omega-3 fats have hit the headlines a lot recently,  but do you know what they are, why you need them, how you get them and what they do anyway? There are so many nutritional terms used in the media, yet many are left unexplained. Let’s look at everything you need to know about this important nutrient.

Nutrition is one of the most frequently discussed topics in the media – and so many nutritional terms are being used that anyone with little knowledge in this science might be confused and feel excluded.

By the end of this article, you’ll know all you need to know about Omega-3.

What is Omega-3?

Simplistic background overview

There are many nutrients our body needs, but in nutrition, we have a tendency to group them so that we can classify them.

There are two main but broad types of nutrients: macronutrients (those nutrients we need a lot of) and micronutrients (those we need in very small amounts).

Macronutrients are divided into three further groups: protein, carbohydrate and fat. These are then split further and further.

Micronutrients are divided into two further groups: vitamins and minerals.

We will focus on the macronutrient, fat. Fat is important in our diet, we need it. Even saturated fat – it all serves a purpose to keep our body running healthily.

We make most of the fat we require ourselves; our bodies are mini chemical factories, breaking down components and building new ones. It converts some fat subtypes into others as it needs it.

But some fats our body cannot make – those fats we must get in our diet. They are called essential fats (or essential fatty acids). Any nutritional term using the word essential, simply means we must get it from the diet.

Fatty acids is just a chemistry term, and nutrition scientists will use that term rather than fat.

Essential fats

In the previous section, we stated that nutrients are grouped and then subgrouped. Fat is a great example of a nutrient that has many subgroups.

The two main subgroups are: saturated fats (those that are solid at room temperature, such as lard, butter, coconut fat) and unsaturated fats (they are liquid at room temperature – like many seed oils, olive oil and nut oils).

Unsaturated fats are further divided into monounsaturated fat and polyunsaturated fats!

All essential fats are polyunsaturated, and the two primary essential fats are omega-3  and omega-6 (linoleic acid).

So to recap, the grouping goes: macronutrient > fat > unsaturated fat > polyunsaturated fat > Omega-3.

Types of Omega-3

There are only three types of omega-3 that are well-studied:

  • Eicosapentaenoic acid (EPA)
  • Docosahexaenoic acid (DHA)
  • Alpha-linolenic acid (ALA)

Of these ALA is possibly the most important, as our bodies are able to use it to make the other two; DHA first, and then EPA.

However, research is showing that we’re not actually that efficient at it! It’s a very slow process and very little turns into either DHA or EPA, and therefore we’re probably better getting these straight from our diet [1].

As you can imagine, if the cascade goes from ALA to EPA, we’re not actually getting much EPA into our cells.

Why do I need Omega-3?

It may seem confusing to many that a fat that is so far down the list of subgrouping gets so much attention. And you’ll find that in nutrition! Things that get the most attention are things we need so little of in our diet!

One of the reasons it gets attention is that, many of us living in the age of convenience, where we get our food from the supermarket or restaurants, are starving ourselves of important nutrients.

Omega-3 is typical of this – it’s not available in as many foods as Omega-6, and they tend to appear in foods that the British don’t frequently eat.

Omega-3 is considered to be anti-inflammatory, whereas omega-6 is pro-inflammatory – although the latter is not quite so straightforward as that [2].

It’s long been thought that arachidonic acid (one of the omega-6 fats) may be behind many inflammatory diseases such as heart disease, and omega-3 keeps this in check [3].

It’s therefore important to ensure that the meals we eat on a daily basis have a good omega-3 and omega-6 balance (we need both, just more omega-3 to rein-in omega-6’s propensity to bad behaviour).

Inflammation is healthy, so we don’t want too much omega-3; just enough to ensure that inflammation is kept within a healthy boundary.

Health benefits of omega-3

Let’s now look at the number of health benefits we can achieve if we were able to successfully balance our omega-3 and omega-6 ratio.

#1 Heart disease

Omega-3 may be associated with protective effects against heart disease [4]. However, once heart disease has set in, the protective effects appears to be more with the risk of death due to heart disease rather than preventing further events [5].

Having said that, the REDUCE_IT trial showed that patients with known cardiovascular disease or diabetes and are at risk of events (such as a heart attack) benefitted from purified fish oil and reduced their risk by 25 percent [6].

Similarly, people with peripheral vascular disease may not get any additional protection from omega-3 [7]. However, it is possible that this is dependent upon how you get your omega-3 as shown by the REDUCE_IT trial above.

It seems that omega-3, whether from the diet or supplementation, could prevent us from developing heart disease in the first place.

Omega-3 appears to be successful in reducing the risk factors for heart disease, including:

  • Blood pressure and vascular function [8]
  • Glucose control in diabetics [9]
  • Triglyceride blood fats [10,11]
  • HDL cholesterol [12]

#2 Mood

People who have a lot of omega-3 in their diet tend to have happier moods. In fact, omega-3 is associated with less symptoms in people with major depressive disorders [13] and people that live in countries with higher omega-3 intake tend to have less depression [14].

However, whilst omega-3 has been associated with improved symptoms with anxiety, there is still a need for more consistent studies so that we can understand what mechanisms are behind this [15].

#3 Cancer

Diets rich in fish oil could slow the spread and growth of breast cancer – although this has only been found in animal studies [16].

However, other studies have shown that there may not be a link between omega-3 and cancers in general [17] – although studies are ongoing all the time, and different studies show different results.

For example, ALA omega-3 found in seeds and nuts might protect against prostate cancer, but omega-3 EPA found in fish oils do the opposite  [18].

Omega-3 from fish consumption could be protective against colorectal (bowel) cancer [19].

#4 Better cognition

Omega-3 may protect against dementia and cognitive decline [20], and may even help the brain work more efficiently [21,22].

The brain relies on DHA omega-3 because it is an essential component of brain cells, and this leads to the belief that omega-3 may influence cognition and cognitive decline.

However, studies to date show mixed results regarding omega-3 preventing the onset of Alzheimer’s disease [23,24, 25].

Most of the papers do suggest better and more studies are required around the use of omega-3 and cognitive impairment.

#5 Rheumatoid arthritis

If you suffer from rheumatoid arthritis, there is some evidence that omega-3 can help reduce the amount of medication required.

Although omega-3 itself does not improve symptoms in everyone, it appears to keep symptoms at a similar level to those experienced whilst on medication [26,27,28].

This is great if medication is giving you unwanted side effects, but never self-medicate – speak to your rheumatologist if you’re interested in pursuing dietary measures.

#6 Fatty liver

Omega-3 may also reduce fat in the liver [29,30]. Fatty liver can be a subsequence of carrying too much body weight, drinking excess alcohol or from type 2 diabetes.

Fatty liver has no current treatment option other than lifestyle changes, such as diet and exercise. Omega-3 may also help reduce inflammation in the liver caused by excess fat.

Fatty liver runs the risk of the liver becoming inflamed, scarred and then hardened – which ultimately leads to the death of liver cells.

#7 Muscle mass

Omega-3 may help preserve muscle mass [31]. This is important as we age, as muscle mass loss leads to frailty in elderly people [32].

It’s also important for sportspeople or those who need to preserve their muscle mass, particularly when trying to reduce their fat mass.

#8 Fertility

Globally, fertility rates are decreasing [33]- largely caused by lifestyle factors such as stress, obesity, poor nutrition and excess alcohol consumption.

Catalan researchers have recently published a systematic review (scientific collation of clinical studies) that suggest that men who supplement with omega-3 oils and co-enzyme Q10 had better sperm quality.

Adding other minerals such as zinc and selenium, and compounds like carnitines appear to have an all-round beneficial impact on sperm.

Obviously, this is only one half of the battle to help combat the problem of infertility.

Where do I get it?

The best source of omega-3 is oily fish. There are limited amounts of it in white fish, and some chicken eggs will also contain omega-3, depending upon the grain given to the chickens as feed.

Oily fish include:

  • Salmon
  • Herring
  • Sardine
  • Mackerel
  • Trout
  • Sprats
  • Anchovy
  • Whitebait
  • *Swordfish
  • *Marlin

You can also get omega-3 from crab, shrimp, oysters and a number of dairy products have been enriched with it – particularly milk and yoghurt.

Organic/grass fed ruminant animals like beef will also have higher levels of omega-3.

*These are large predatory fish and may contain high levels of marine pollutants that are toxic if eaten in high amounts. Older fish will also have had more time to accumulate pollutants than younger fish.

Vegan/vegetarian sources

There are vegan sources of omega-3 oil, but they tend to be high in ALA rather than DHA and/or EPA. They include:

  • Flax or linseeds
  • Chia seeds
  • Rapeseed (canola) oil
  • Soya and soya products (such as tofu, tempeh and soya milk)
  • Walnuts
  • Wholewheat grains
  • Pumpkin seeds
  • Beans

Vegans need to remember that ALA is not well absorbed and we don’t convert enough into DHA and then EPA! Supplementing might be the only option.


You can supplement with Omega-3. Typically cod liver oil is the easiest to find, but not necessarily the best. Fish oil or omega-3 oil is the better option, although the smell can be extremely off-putting to some and is neither vegetarian nor vegan friendly.

The best option [34] is considered the most unethical by some pressure groups [35], and that’s krill oil. Krill are tiny ocean crustaceans that are favoured meal by many Antartic-living animals such as whales, penguins and seals.

By fishing for these to make krill oil is potentially ecologically damaging, so do be aware of this before buying it.

There are drawbacks of taking fish oils every day – they can cause:

  • Bad breath
  • Bad smelling sweat
  • Diarrhoea
  • Heartburn and belching
  • Headaches

Fish oils should not be taken with anti-blood clotting or blood pressure tablets. Always ensure your physician knows what supplements you’re taking before taking prescription drugs

Today, obtaining non-fish sources of omega-3 oil has become a lot easier, thanks to the farming of ocean algae. However, ensure you get supplements made from a sustainable source.

Small fish eat plankton which themselves feed off algae. Algae is the only ocean source of omega-3, it simply travels up the food chain as each creature is eaten by another larger than itself.

One other thing, sources of omega-3 are often rich sources of vitamins A & D – this needs to be considered if using supplementation – particularly multivitamins and cod liver oils together (the liver stores both vitamins A and D).

Vitamin A warning

Omega-3 oils may also contain vitamin A, and so if you’re into taking supplements and take vitamin A or a multivitamin too – check that you’re not inadvertently overdosing!

The recommended dosage is 1.5mg (1500ug) daily – so always look at the labels to ensure you’re not exceeding this. Remember – vitamin A is easily obtained in the diet too, particularly from yellow and orange vegetables like squash, sweet potato and carrots.

If you’re unsure about what you’re doing with supplements, never guess – talk to your pharmacist first or a registered dietitian/nutritionist.

How much do I need?

For those who eat fish (omnivores and pescatarians), it is recommended that men, women over child-bearing age or women who cannot/do not want children should aim to consume two portions of fish weekly, one should be oily.

COMA however think that this is too low and we should be increasing our consumption due to the associated health benefits [36].

They suggest at least 1.5g of omega-3 daily, either by supplement or by consuming fish, but this is not an official recommendation.

One portion of white fish and one portion of oily fish gives us around 0.45g of omega-3 oil daily.

Age One portion size
18 months to three years ¼ – ¾ small fillet or 1-3 tablespoons
Four to six years ½ – 1 small fillet or 2 – 4 tablespoons
seven to eleven years 1 – 1 ½ small fillets or 3 – 5 tablespoons
12 years to adult 140g (5 oz) fresh fish or 1 small can oily

This means you’d need to eat 3 portions of white fish and 3 portions of oily fish weekly – this is not practical, so a supplement for most would be beneficial.

Women who are pregnant, or within child-bearing years and wish to have children should not exceed the one portion per week [37].

This is due to potential toxicities in the fish and the risks this could have on unborn children. However, the biggest risk is with larger predatory fish higher up the food chain. It’s therefore better to consume smaller fish.

Omega-3 is very important to the development of the child, both unborn and during the early infant years – however, there is no current scientific evidence to support supplementation in pregnant mothers or children [38,39,40].

Image Credit
Akshar Dave –

Further Reading for Background Science
National Institutes of Health – Omega-3 Fatty Acids

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