What are the health benefits of omega 3 fatty acids? Can omega 3 really improve your brain health, reduce your cholesterol and help your general heart health? What is the evidence and does it matter if you choose to supplement instead of eating sufficient omega 3 in your diet? How can you optimise your diet to include natural sources?
What Are Omega Fatty Acids?
There are two types of fats or fatty acids that are essential and can’t be produced in our bodies. These are omega 3 and omega 6. Omega 3 can be broken down into three main forms: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).
Where Are Omega Fatty Acids Found?
Omega 3 are found in a number of different foods. ALA is found in plant oils, such as flaxseed, soybean, and canola oils. DHA and EPA are found in oily fish, fish oils, and krill oils. DHA and EPA are actually synthesised by microalgae, not by the fish, but accumulate in the tissue when they are eaten by fish and shellfish further up the food chain.
Beef is very low in omega-3s, but beef from grass-fed cows contains somewhat higher levels of omega-3s, (mainly as ALA), than that from grain-fed cows1. However, consumption of red meat is associated with an increased risk of bowel cancer, so it would be better to get your omega 3 fatty acids from plants and oily fish instead.
Sources of omega 6 are meat, eggs, walnuts, sunflower seeds and dairy.
The Whole Food Effect
It is really hard to distinguish the benefits of consuming omega 3 in the diet, compared with supplementing. Many of the meta-analyses have grouped together people randomised to eat more oily fish with those taking omega 3 supplements. Other studies have found a whole food effect, where supplementation does not seem to confer the same benefits as oily fish, possibly because the omega 3 fatty acids aren’t taken in isolation, but with other compounds found in seafood.
Why Are Omega Fatty Acids So Important?
Omega 3 and 6 fatty acids have an important structural role, needed for cell membranes. Omega 3 are antioxidants and anti-inflammatory, while omega 6 are more pro-inflammatory. Together they are also energy sources, and are used to form signalling molecules called eicosanoids, comprised of prostaglandins, thromboxanes, and leukotrienes. Additionally, the importance of DHA in the development of brain and retina is well established2.
There are many different prostaglandins with wide ranging roles such as the sensation of pain, inflammation, regulation of pregnancy and birth, control of blood pressure, secretion of stomach acid, contraction and relaxation of smooth muscle.
Thromboxanes regulate blood clotting by causing constriction of blood vessels, and the aggregation of platelets (so they stick together), which are early steps in blood clotting.
Leukotrienes are involved in immune function by attracting immune cells such as neutrophils to sites of inflammation. They also constrict bronchioles in the lungs and make capillary walls permeable.
Omega 3:6 Ratio
You might have heard about the omega 3:6 ratio and how it is important to cut down omega 6 intake. This is thought to be because the metabolic products of omega 3 fatty acids are less inflammatory than those produced from omega 6 fatty acids.
Western diets are associated with an imbalance of omega 3/6 such that instead of levels of omega 3 being higher than 6, the reverse is more commonly seen. This is associated with an increased risk of chronic inflammation3. This may be one of the reasons why western diets are associated with increased inflammation and chronic disease.
A higher ratio of omega 3 than omega 6 fatty acids tip the balance to less inflammation rather than more. The exact ratio has yet to be defined, but it now appears that it is preferential to increase omega 3 rather than decrease omega 6.
What Are The Health Benefits of Omega 3?
Omega 3 has been associated with a number of different health benefits but what are the health benefits of omega 3 that are supported by evidence?
Omega 3 and Hypertension
Evidence of benefit of omega 3 fatty acids is mixed with large scale studies showing either no effect 4, or a small reduction in risk of hypertension5. Omega 3 fats do have other health benefits though, are unlikely to do harm, and are easily incorporated into your diet by eating oily fish twice a week and seeds such as chia seeds, flaxseeds and nuts.
Omega 3 and Heart Disease
In a systematic review and meta-analysis of 13 trials, totalling over 127,000 participants with omega 3 supplementation for an average of 5 years, found a reduction in risk of myocardial infarction, coronary heart disease, death, total coronary heart disease, death from cardiovascular disease (CVD), and total CVD6. They found a dose-dependent relationship, meaning that higher doses of omega 3 supplements were associated with great beneficial effects6.
Another large review of 86 trials combined, totalling over 162,000 people looked to see what the effect of increased omega 3 had on cardiovascular risk7. This was provided mostly by omega 3 supplements, while a few trials gave oily fish.
Increasing ALA, made no significant difference to blood clots of the coronary arteries supplying the heart (coronary events), but slightly reduced cardiovascular events (diseases related to blood vessels such as clots and rhythm problems).
While EPA and DHA decreased triglycerides (a type of fat) by about 15%, and reduced the risk of coronary artery death and coronary events, which are illness of arteries supplying the heart. They did not, however, have an effect on cardiovascular events (for example strokes, heart irregularities).
Increasing ALA, made no significant difference to coronary events, but slightly reduced cardiovascular events.
In summary these two large meta-analyses suggest that together omega 3 (ALA, EPA and DHA combined), is associated with decreased triglyceride levels, and may reduce the risk of coronary and CVD, but these effects are smaller and dose-related.
Cholesterol and Triglycerides
A meta-analysis combining 58 trials together, found a dose-response relationship between lower-dose dietary and supplemental omega-3 intakes and triglyceride levels8. This means that an increased intake of omega 3, led to a decrease in triglycerides, and that higher doses led to a greater effect8. This effect was also stronger in people with a raised baseline level of triglycerides8.
One of the ways of decreasing your risk of cardiovascular disease is by lowering your cholesterol. Reducing saturated fats in your diet, and eating instead omega 3 for example from walnuts9 and oily fish may help instead.
Omega 3 and brain health
DHA is an essential component of cell membranes within the brain, and so researchers have hypothesized that omega 3 might protect cognitive function. Patients with Alzheimer’s disease have lower levels of DHA than healthy people10. Lower DHA levels are also associated with higher levels of amyloid protein deposits in healthy adults, while higher DHA levels are correlated with preservation of brain volume (loss of function leads to loss of brain tissue, and therefore loss of brain volume)11.
In a meta-analysis of 14 randomised controlled trials analysed together, people who hadn’t taken omega 3 supplements before were given them12. Ten out of the 14 trials showed a positive outcome on at least one domain of brain function such as working memory, executive function, verbal memory, short-term memory, perceptual speed, etc12.
However, several other meta-analyses, including a Cochrane review, have not found a beneficial effect. They assessed the effects of omega-3 supplementation on cognitive function and dementia in healthy older adults and those with Alzheimer’s disease or cognitive impairment 13–16. In summary, omega-3 supplementation was not found to affect cognitive function in healthy older adults or in people with Alzheimer’s disease. Another study found that for people with mild cognitive impairment, omega-3s may improve certain aspects of cognitive function, including attention, processing speed, and immediate recall, but more research is needed16.
In the same way that atherosclerosis (cholesterol deposits and inflammation in the arteries) leads to strokes, cardiovascular and coronary events, and high blood pressure, it leads to vascular disease in the brain. The risk of atherosclerosis and neurodegeneration is established, particularly with vascular cognitive impairment and dementia (VCID). A grouped meta-analysis has not found there to be a link between omega 3 and VCID, but more information is needed to see if omega 3 can prevent cognitive decline.
Omega 3 and fertility
Omega 3 appears to have a role in healthy gamete formation17,18 with consumption associated with increased probability of pregnancy17, and live birth rate19. Read more about what to eat to improve fertility.
Omega 3 and Arthritis
Omega 3 supplements have been found to benefit clinical outcome of rheumatoid arthritis20 and may even delay the need for medications21. There is also limited evidence that omega 3 supplementation may benefit people with other types of autoimmune arthropathies such as systemic lupus erythematosus (SLE) as well, but more research is needed20.
Due to the potential of Omega 3 to reduce cell growth and act as an anti-inflammatory, the role of supplementation in the prevention cancer has been investigated. There have been a few small scale trails with mixed results, some reducing the risks of specific cancers such as breast and colorectal, but others finding an increase in risk of prostate cancer.
The first large-scale clinical trial (VITAL trial) to examine the effects of omega-3s on the primary prevention of cancer in the general population looked at the effects of omega-3 fish oil supplementation (1 g/day containing 460 mg EPA and 380 mg DHA) with or without 2,000 IU/day vitamin D for a median of 5.3 years22. The study included 25,871 men aged more than 49 years and women aged greater than 54, with no previous cancer, heart attacks, or strokes. Compared with placebo, the omega-3 supplement had no significant effect on cancer incidence, cancer mortality rates, or the development of breast, prostate, or colorectal cancers22.
Omega 3 in Your Diet
Now I’ve talked through what are the health benefits of omega 3, how can you optimise your diet? Aim to have oily fish twice a week if you aren’t pregnant, or once a week if you are, as the benefits of omega 3 have to be offset by risk of contamination with heavy metals.
Vegan sources of omega 3 are chia seeds, linseed, hemp seeds, walnuts and vegetable oils such as rapeseed. To meet the current guidance, you would need to eat about a tablespoon of chia or ground linseeds, or two tablespoons of hemp seeds or six walnut halves a day.
Algae oil is an alternative to fish oil which makes it an attractive option for vegetarians. But while algae oils do contain large amounts of DHA, most don’t contain any EPA fatty acids at all. Algae and seaweed are the only plant-based source of EPA and DHA, but ALA can be converted in your body into EPA and DHA. Only about 10-15% of ALA is converted into EPA and DHA, so you do need to eat more ALA. Interestingly women are more able to convert ALA and this is thought to be related to ensuring the foetus gets enough EPA and DHA during pregnancy.
I hope this article has clarified what are the health benefits of omega 3. There are lots of potential benefits of eating a diet that contains omega 3, especially if oily fish replaces less healthy options. Therefore, try to change your diet by:
- Swap fish for red meat, and aim to eat oily fish twice a week
- Enjoy mixed nuts
- Eat more seeds, especially chia and flaxseed that are high in omega 3.
Although some of these studies suggest the more omega 3 the better, there is a limit to the recommended dose of supplements of 2g, unless prescribed by your doctor.
Omega 3 supplements may interfere with warfarin, due to it’s anti-platelet role in clotting, so best to check with your doctor before starting a supplement.
Find out more about cod liver oil, krill oil and fish oil supplements here.
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