What are Omega-3 fatty acids?
Omega-3 fatty acids are polyunsaturated fatty acids (PUFAs). Omega-3 fatty acids are dietary fats meaning we need to acquire these from nutrition.
Our bodies can make these in low quantities. But the quantity is not enough to sustain healthy body functions (1). These omega-3 fatty acids are synonymous with fish oil because fish oil is the major source of omega-3 fatty acids in supplement form.
Omega-3’s were identified in 1929. Initial research showed that these fatty acids were important to prevent deficiency diseases (2).
The importance of omega-3 fatty acids came into prominence 1970s.
Researchers noted that Eskimos in Greenland consumed high-fat content in their diet but had a lower level of total fats including LDL and cholesterol compared to Europeans in Denmark (3).
Eskimos living in Denmark showed a similar lipid profile as Europeans. It meant that genetics was not an important factor in this regard. It had to be the diet.
The studies concluded that the Eskimo diet in Greenland was high in polyunsaturated fats (PUFAs) and low in saturated fats.
Since then numerous studies have concluded that polyunsaturated fats and not saturated fats have the potential health benefits.
Omega-3 fatty acids have been extensively studied for health benefits.
In 2004 FDA allowed products with omega-3 to state the reduced risk of coronary heart disease and hypertension with omega-3 intake (4).
The most important Omega-3 fatty acids
Three most studied omega-3 fatty acids are eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and α-linolenic acid (ALA) (5).
EPA and DHA are the nutritionally important Omega-3 fatty acids.
EPA and DHA are animal-based and ALA is plant-based. ALA is considered essential omega-3 fatty acid because it cannot be produced in the body. Therefore, it should be consumed from plant-based food sources.
EPA and DHA are considered non-essential because they are produced in small quantities from ALA by enzyme reactions. These two are also the most important Omega-3 fatty acids.
Only 2-10% of ALA is converted to EPA and DHA (6).
Since EPA and DHA can only be made in small quantities in the body, they should be supplemented from food sources for health benefits (7).
What is the recommended daily intake of Omega-3?
The health benefits of omega-3 are acknowledged by many health bodies. They have recommended daily intake of DHA and EPA to reduce the risk of heart diseases in adults.
Notably, American Heart Association recommends two servings of fatty fish which will provide approximately 250 to 500mg of EPA +DHA per day (8).
There are special guidelines for pregnant women, and mothers who breastfeed their babies.
| Organization | Population | EPA and DHA recommendation |
| Academy of Nutrition and Dietetics | Adults | ≥500 mg/day |
| American Heart Association | Adults without CHD | Fatty fish ≥2 times/week (∼500 mg/day) |
| Patients with Coronary Heart Disease | ∼1 g/day | |
| Patients with High Triglycerides | 2–4 g/day | |
| US Department of Agriculture | Adults | ≥250 mg/day |
| International Society for the Study of Fatty Acids and Lipids | Adults | ≥500 mg/day |
| Pregnant/lactating women | ≥500 mg/day (≥300 mg/day of DHA) | |
| European Food Safety Agency | Adults | ≥250 mg/day |
| Pregnant/lactating women | ≥250 mg/day (and100–200 mg/day DHA) | |
| World Health Organization | Adults | ≥250 mg/day |
In summary, the consumption of DHA+EPA between 250mg to 500mg per day is sufficient for health benefits. However, doses may vary depending on age and health status.
What are the omega-3 food sources?
The main sources of EPA and DHA are animal-based. Seafood especially, oily fish are considered primary providers of EPA and DHA.
ALA can be obtained from broccoli, cabbage, spinach, flaxseed, linseed oil, rapeseed oil, and meats.
Some ALA sources are given below (9).
Among these plant-based sources of ALA, flaxseed has the highest amount of ALA per 100g.
| Source | ALA content/100gram |
| Flaxseed oil | 53.68 g |
| Chia seeds | 17.83 g |
| Walnut oil | 10.40 g |
| Canola oil | 9.13 g |
| Hemp seed | 8.56 g |
| Soybean oil | 6.78 g |
| Mustard oil | 5.89 g |
| Hickory nut, dried | 1.04 g |
| Pistachio nuts, raw | 0.25 g |
| Pumpkin and squash seed kernels, dried | 0.12 g |
| Almonds, dried, unblanched, unroasted | 0.003 g |
Freshly caught fish has the highest amount of EPA and DHA. The canning process destroys some of omega-3.
In recent years, microalgae called Crypthecodinium cohnii has been identified as a major plant-based DHA source.
Moreover, fortified eggs by chicken raised on an omega-3 rich diet also contain a healthy amount of omega-3 (10).
Here is the list of animal sources of EPA+ DHA. The total EPA+DHA per 100g of each source is given in mg (milligrams) (11).
How much EPA+DHA we can get from 100g (3.5oz) of animal food sources?
Fish
| Source | EPA+DHA mg/100g (3.5oz) |
| Anchovy | 2055 |
| Catfish, farmed | 177 |
| Cod, Atlantic | 158 |
| Fish burger, fast food | 546 |
| Fish stick, frozen | 214 |
| Golden Bass (Tilefish), Gulf of Mexico | 905 |
| Golden Bass (Tilefish), Atlantic | 905 |
| Halibut | 465 |
| Herring, Atlantic | 2014 |
| Mackerel, Atlantic | 1203 |
| Mackerel, Atlantic | 401 |
| Mahimahi | 139 |
| Pollock, Alaskan | 468 |
| Salmon, Farmed | 2648 |
| Salmon, Wild | 1043 |
| Sardines | 982 |
| Shark | 689 |
| Snapper | 321 |
| Swordfish | 819 |
| Trout | 935 |
| Tuna, light (skipjack) | 270 |
| Tuna, white (Albacore) | 862 |
Shellfish
| Source | EPA+DHA mg/ 100g (3.5oz) |
| Clams | 284 |
| Crab | 413 |
| Lobster | 84 |
| Mussels | 782 |
| Oysters | 688 |
| Scallops | 365 |
| Shrimp | 315 |
Other Food Sources
| Source | EPA+DHA mg/ 100g (3.5oz) |
| Eggs fortified | 43 |
What are the major benefits of Omega-3 fatty acids?
Western and American diet is loaded with more saturated fats and less unsaturated fats.
One of the transformative trends in westerns society has been the easy access to fast food and processed food.
Fast food and processed foods contain copious amounts of saturated fats (12,13).
As a result, cases of inflammatory and metabolic diseases have sharply risen in the recent past.
The inclusion of unsaturated fats such as omega-3 polyunsaturated fatty acids (EPA and DHA) have many health benefits.
They become part of the cell membrane and provide structural integrity to our cells.
DHA is also present in the brain and retina and plays a key role in their functioning. EPA and DHA are also required for fetal development. And most importantly, omega-3 has anti-inflammatory. Antioxidants and anti-inflammation are closely related. Antioxidant activity may decrease the reduction in inflammation.
Some of the most important health benefits of omega-3 are described below.
Omega-3 benefits fetal development
Omega3 is important for the development of the fetus. DHA is of particular importance because it is required for fetal retina and brain development (14).
The presence of DHA in the retina and brain is associated with healthy eyesight and brain function.
Many studies have shown that omega-3 is beneficial for retina integrity and protection and may reduce the chance of getting retina-related diseases (15).
It is also noted that EPA and DHA omega-3 provided the best dietary intervention for Dry Eye Syndrome (16,17).
Research shows that children whose mothers took DHA and EPA during pregnancy performed better cognitively during the early months of their lives. They also had a better eye and hand coordination compared to children whose mothers did not consume DHA or EPA.
It is estimated that mothers in the USA and Canada are not consuming the necessary EPA+DHA required (18,19).
EPA and DHA provided protection against allergies in children whose mothers consumed EPA and DHA (20).
EPA+DHA consumption may also help in reducing allergies and IgE-related Eczema (21).
As mentioned above International Society for the Study of Fatty Acids and Lipids and the European Food Safety Agency recommended the consumption of more than 250mg per day of DHA for pregnant or lactating women.
The dietary guidelines in the USA by the U.S. Department of Health and Human Services recommend taking at least 8 ounces of seafood (22).
Ingesting, this much seafood will give between 300 to 900mg of EPA+DHA per day.
Omega-3 is important for fetal development and several health agencies have recommended consumption of omega-3 for pregnant women.
Omega-3 protects against cardiovascular diseases
Cardiovascular-related diseases are the main cause of death in the world. Studies have shown that chronic Inflammation is considered to be the major reason for cardiovascular diseases (23).
Research has shown that EPA and DHA are potent because of their strong anti-inflammatory properties (24).
As they become part of the cell membrane, they promote the production of eicosanoids and resolvins which have anti-inflammatory activity (25).
Due to the anti-inflammatory property of omega-3, many studies have proposed a role of omega-3 in metabolic syndrome as well (26).
Others have shown that EPA and DHA are shown to reduce inflammation by reducing the gene expression of inflammatory and atherogenic genes (27). The study identifies a number of pro-inflammatory genes.
High levels of C-reactive proteins are known for increased risk of cardiovascular disease. The treatment of EPA+DHA has been shown to reduce the sensitivity to C-reactive proteins.
Large population-based studies have described lower heart disease and failure in people who consume fish regularly (28,29).
Population studies in northern Quebec, Canada revealed that high fish consumption is favorably associated with lower cardiovascular disease (CVD) risk (30).
Similarly, large population-based comprehensive studies such as the Diet and Reinfarction Trial (DART) and The Lyon Diet Heart Study showed similar results with a diet rich in omega-3 fatty acids (31,32).
High blood pressure is one of the major risk factors of cardiovascular disease (33).
Omega-3 also has a blood pressure-lowering effect. Therefore, an omega-3 diet rich could reduce the risk of hypertension in healthy individuals (34).
Arterial stiff is another risk factor for cardiovascular disease. Several studies have found that omega-3 is beneficial in reducing arterial stiffness in the older population (35,36).
It is important to note that frying may reduce the nutritional benefits. Therefore, boiling or baking is the recommended method of cooking.
1-2 servings per week of fish with high EPA and DHA is associated with a lower risk of coronary heart-related death and total mortality (37).
The studies so far have shown that omega-3 has a cardioprotective effect, and population studies are favorable in the role of omega-3 and reduced incidence of cardiovascular disease.
Omega-3 importance in Alzheimer’s Disease and Dementia
Alzheimer’s disease is a debilitating disease with no cure at the moment. In 2006, there were 26.6 million worldwide. It is estimated that by 2050, this number will quadruple (106.2 million)(38).
Alzheimer’s is manifested by progressive loss of memory that leads to a reduction in quality of life. Therefore, brain health is an important factor in the prevention of Alzheimer’s disease.
Omega-3 is studied for brain health because the DHA is present in the neuron cell membranes where it performs vital neural functions.
25% of the cell membrane phospholipid in grey matter is DHA, which is important for learning and brain function (39).
Research showed that Alzheimer’s Patients had lower serum levels of EPA and DHA compared to the control group (40).
Numerous studies have been conducted in mice to see the effects of omega-3 in Alzheimer’s disease model mice.
beta-Amyloid plaques (the misfolded proteins) in the brain are thought to be the primary reason for Alzheimer’s disease.
Mice fed a diet high in DHA had a lower plaque burden compared to the control group (41).
In humans, the research shows that eating food high in omega-3 e.g. fish, green vegetables, nuts, and fruits, and reducing the intake of foods lower in omega-3 such as dairy, red meat, and processed fats, decreases the risk of Alzheimer’s (42).
Certain inflammatory biomarkers such as IL-1B, IL-6, and TNF α are produced by brain cells.
These are thought to be important for Alzheimer’s disease progression.
Patients treated with EPA and DHA had lower levels of this inflammatory biomarker inducing that EPA and DHA can reduce the release of these inflammatory biomarkers (43).
Some studies did not find a significant positive effect of omega-3 in Alzheimer’s patients but patients with low to mild Alzheimer’s disease had the positive effects of the omega-3 supplementation (44).
Other research has found similar results with DHA supplementation (45).
In summary, EPA and DHA may have a positive effect on Alzheimer’s disease progression. However, the supplement EPA and DHA may not provide the cure for the disease. Including EPA and DHA-rich food in diet from an early age is a good dietary habit to develop.
Omega-3 promotes strength and muscle mass
The natural process of aging causes the loss of muscle mass and ultimately leads to morbidity.
Omega-3, along with other micronutrients (vitamin C and E) can improve muscle mass and strength by reducing inflammation (46).
Muscle increase and protein synthesis are noted in healthy young and old individuals who took daily omega-3 supplements for 2 months (47).
Omega-3 supplementation also improves athletic performance and recovery in people doing resistance training (48).
Research also shows that omega-3 intake can help reduce muscle soreness and stiffness and improve joint mobility in athletic and non-athletic people. These effects were noted in both women and men (49,50,51)
Due to EPA and DHA’s role in recovery and muscle strength, fish oil is being regularly consumed by bodybuilder and athletes.
Omega-3 supplementation improves athletic performance, muscle mass increase, and recovery.
Omega-3 and Diabetes
The role of omega-3 in improving diabetes is controversial.
There are studies where no or negative effects are observed with the use of omega-3 while other studies have shown positive effects.
Some studies show that omega-3 intake may increase the risk of diabetes at higher doses of consumption (more than 2 fish servings/week) (52).
Other studies have shown a beneficial effect of omega-3 supplements in diabetes (53).
It may also improve insulin sensitivity and decrease inflammatory markers (54).
Meta-analysis of omega-3 research has shown that there is little or less favorable data to suggest that omega-3 has a direct role in mitigating diabetes (55, 56).
Omega-3 may have a positive effect on diabetes because of its anti-inflammatory properties but a robust evidence is lacking at the moment.
Omega-3 is good for Joint Health
Anti-inflammatory activity may also help in fighting joint and bone-related diseases. Many bone and joint diseases originate as a result of prolonged inflammation.
Research has shown that consuming moderate doses of omega-3 by rheumatoid arthritis patients shows positive effects on joint tenderness and morning joint stiffness (57).
Other studies have shown that the use of omega-3 especially EPA, results in decreased use of non-steroidal anti-inflammatory drugs (NSAID) in patients with rheumatoid arthritis (58, 59).
Omega-3 may protect joints and bones and reduce the effects of rheumatoid arthritis by anti-inflammatory activity.
Omega-3 could help alleviate depression and anxiety
It is well known that omega-3 fatty acids are an integral part of brain cells. Therefore, they are predicted to play a tremendous role in mental health.
Depression and anxiety are major causes of disability worldwide.
Animal research shows that deficiency in omega-3 is associated with anxiety and depression-like symptom in addition to abnormal social behavior in rodent offspring (60,61).
Studies in humans show that low levels of polyunsaturated fatty acids omega-3 and higher omega-6 to omega-3 ratios are associated with a higher risk of depression, schizophrenia, and anxiety (62, 63).
In comprehensive population research, high levels of plasma omega-3 are correlated with the reduction in symptoms of depression.
Moreover, low DHA correlates with low levels of a serotonin marker called CSF 5-HIAA in healthy individuals. CSF 5-HIAA low levels are associated with depression and suicide (64).
Interestingly, the use of supplemental omega-3 is shown to reduce anxiety and inflammation. Thus, omega-3 supplementation may provide improvement in anxiety symptoms (65).
Omega-3 fatty low levels in the body are associated with depression and anxiety. Thus, symptoms of depression and anxiety can be improved with the consumption of omega-3
Omega-3 risks
The FDA has included omega-fatty acids, EPA, and DHA in the General Recognized As Safe (GRAS) list (66).
Up to 3g per day of omega-3 consumption is considered safe as per FDA.
Also, mostly recommended intake of 250mg to 500mg for healthy individuals is well below the safe dosage of 3g/day.
Thus, consuming omega-3 at moderate levels is not harmful to the human body.
Omega-3 fatty acids are obtained mostly from fish. Many fish contain high levels of mercury, polychlorinated biphenyls (PCBs), and dioxins (67).
Old, at the top of the food chain fish, seem to accumulate the highest amount of mercury and toxins. Limiting the consumption of sharks, swordfish, Mackrel family, and tilefish family should reduce the intake of these toxins.
It is also important to source the fish from trusted sources.
Children, pregnant women, and lactating mothers are considered high-risk groups.
FDA recommends limiting the consumption of fish to 12 Oz. per week for pregnant women and nursing mothers.
Due to the toxins in the fish, consuming omega-3 supplements is becoming popular. Omega-3 Supplements are mercury and toxin-free.
The most reported side effect is fishy aftertaste (68).
Similarly, with the advancement in our knowledge of food, new ways to obtain omega-3 are being developed.
Marine microalgae provide an alternative to fish. They are rich in EPA and DHA (69).
Different types of microalgae are being studied. They are well tolerated and have no toxic effects. And they are also suitable for individuals who follow a vegan or vegetarian diet (70,71).
Omega-3 reduces platelets aggregation which is thought to increase bleeding after an injury. But the studies have shown little to no effect on bleeding during or after surgery in patients who consume fish oil (72,73)
Similarly, people using warfarin, a blood-thinning agent to mitigate atrial fibrillation (AF) and deep vein thrombosis (DVT) may not be at risk of adverse effects of fish or krill oil (74).
Common supplement side effects are given below (75).
| Gastro-Intestinal upset | Clinical bleeding | Fishy aftertaste | Worsening glycemia | Rise in LDL | |
| Up to 1g/day | Very low | Very low | Low | Very low | Very low |
| 1 to 3g/day | Moderate | Very low | Moderate | Low | Moderate |
| More than 3g/day | Moderate | Low | Likely | Moderate | Likely |
In summary, omega-3 fatty acids are safe for human consumption. Although, fish consumption is associated with toxins.
Food supplements and microalgae can provide toxin-free suitable alternatives.
The Gist
Omega-3 fatty acids (EPA+DHA) have many benefits. Omega-3 are considered essential fatty acids meaning they need to be consumed from food.
Major sources of omega-3 are marine seafood, especially oily fish. An alternative, sources of omega-3 are fish oil supplements. They are cheap and easily available
