Fish oil

Fish oil is one of the most commonly used dietary supplements. It is rich in omega-3 fatty acids, which are very important for health. If you don't eat a lot of oily fish, then taking a fish oil supplement can help you to consume sufficient amounts of omega-3 fatty acids.

What is fish oil?

Fish oil is the fat or oil that is extracted from fish tissue. Fish oil comes from fatty fish such as salmon, herring, tuna, anchovies and mackerel. It is also sometimes made from the liver of other fish, as is the case with cod liver oil, which is made from cod liver. The World Health Organization (WHO) recommends the consumption of 1 to 2 portions of fish per week. This is because the omega-3 fatty acids contained in fish have many health benefits, including protection against many diseases. However, if you do not eat 1 to 2 portions of fish per week, then fish oil supplements can help you to get enough omega-3 fatty acids. About 30% of fish oil consists of omega-3 fatty acids, while the remaining 70% is made up of other fats. In addition, fish oil contains some vitamin A and vitamin D.

It is important to note that the types of omega-3 fatty acids found in fish oil provide greater health benefits than omega-3 fatty acids found in plant sources. The primary omega-3 fatty acids found in fish oil are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), while the omega-3 fatty acids found in plant sources are primarily alpha-linolenic acid (ALA). Although ALA is an essential fatty acid, EPA and DHA have significantly greater health benefits (1, 2).

It is also important to consume sufficient omega-3 fatty acids because in the Western diet a large proportion of omega-3 fatty acids have been replaced by other fats such as omega-6 fatty acids. This disturbed ratio of fatty acids can contribute to the development of numerous diseases (3, 4, 5, 6).

A higher intake of fish oil, which is rich in healthy omega-3 fatty acids, can provide a number of health benefits, which we will discuss in more detail below.

Fish oil can promote heart health

Heart disease is one of the leading causes of death worldwide (7). Studies show that people who eat a lot of fish have significantly lower rates of heart disease (8, 9, 10). Consuming fish or fish oil appears to reduce several risk factors for heart disease. These heart health benefits include

• Cholesterol levels: fish oil can increase levels of "good" HDL cholesterol. However, it does not appear to lower levels of "unhealthy" LDL cholesterol (11, 12, 13, 14, 15, 16).
• Triglycerides: Fish oil can reduce blood triglyceride levels by around 15 to 30% (16, 17, 18).
• Blood pressure: Even at low doses, fish oil can lower blood pressure in people with elevated blood pressure (19, 20, 21)
• Plaques: Fish oil can reduce the accumulation of plaques that can cause hardening of the arteries and also make existing plaques more stable and safer (22, 23, 24).
• Fatal cardiac arrhythmias: In people who are at increased risk, fish oil can reduce the risk of fatal cardiac arrhythmias (25). These arrhythmias can lead to heart attacks in certain cases.

The most comprehensive study on the benefits of omega-3 fatty acids for heart health was probably the highly regarded GISSI study, in which over 11,000 patients took part. After three and a half years of daily intake of 850mg of fish oil per day, overall mortality was reduced by 20% and the risk of cardiovascular death by 45%.

• Summary: Fish oil supplements may reduce some of the risk factors associated with heart disease.

Fish oil may help treat certain mental disorders

The human brain is made up of 60% fat and a large proportion of this is omega-3 fatty acids. For this reason, omega-3 fatty acids are essential for normal brain function (27, 28). In fact, some studies suggest that people suffering from certain mental disorders have lower levels of omega-3 in their blood (29, 30, 31).

Interestingly, studies suggest that fish oil supplements can prevent the development of some mental disorders or alleviate their symptoms. For example, fish oil may reduce the likelihood of developing psychotic disorders in people who are at increased risk of developing them (32, 33).

In addition, supplementation with fish oil in high doses can reduce the symptoms of schizophrenia and bipolar disorder (33, 34, 35, 36, 37, 38).

• Summary: Fish oil supplements can reduce the symptoms of certain psychiatric disorders. This effect is likely the result of an increased intake of omega-3 fatty acids.

Fish oil can support weight loss

Obesity is defined as a body mass index (BMI) above 30. Worldwide, around 39% of all adults are overweight, while 13% are obese. These figures are even higher in developed Western countries (39). Obesity can increase the risk of other diseases including heart disease, type 2 diabetes and cancer (40, 41, 42).

Fish oil supplements can improve body composition and reduce risk factors for heart disease in obese people (43, 44, 45). In addition, studies suggest that fish oil supplements in combination with diet or exercise can help with weight loss (43, 46).

However, not all studies have observed the same effects (47, 48). An analysis of 21 studies concluded that fish oil supplements did not significantly reduce weight in obese people, although a reduction in waist circumference and an improved waist-to-hip ratio were observed (49).

• Summary: Fish oil supplements may help reduce waist circumference and promote weight loss in combination with diet or exercise.

Fish oil can support eye health

Just like your brain, your eyes need omega-3 fatty acids. Scientific research shows that people who do not get adequate amounts of omega-3 fatty acids have a higher risk of eye disease (50, 51). In addition, eye health begins to decline with age, which can lead to age-related macular degeneration. Fish consumption has been associated with a reduced risk of macular degeneration, but results of studies using fish oil supplements are less convincing (52, 53).

One study found that consuming high doses of fish oil over a 19-week period improved vision in all subjects suffering from macular degeneration (54). However, this was only a very small study.

Two larger studies investigated the combined effect of omega-3 fatty acids and other nutrients on macular degeneration. One study showed positive effects, while the other showed no effect. The results are therefore unclear (55, 56).

• Summary: Eating fish can help prevent eye diseases. However, it is still unclear whether fish oil supplements have the same effects.

Fish oil can reduce inflammation

Inflammation is the way the immune system fights infections and treats injuries. However, chronic inflammation has been linked to numerous serious diseases including obesity, diabetes, depression and heart disease (57, 58, 59). Reducing inflammation can help reduce the symptoms of these diseases. Because fish oil has anti-inflammatory properties, it may help treat conditions that involve chronic inflammation (60). For example, in stressed and obese people, fish oil may reduce the production and gene expression of pro-inflammatory molecules called cytokines (61, 62).

In addition, fish oil supplements can significantly reduce joint pain, joint stiffness and the need for medication in people suffering from rheumatoid arthritis with accompanying joint pain (63, 64).

However, although inflammatory bowel disease is caused by inflammation, there is still no clear evidence as to whether fish oil can reduce the symptoms of these conditions (65, 66). Summary: Fish oil has strong anti-inflammatory effects and may help reduce symptoms of inflammatory diseases, particularly rheumatoid arthritis.

Fish oil can support skin health

The skin is the largest organ of the human body and contains large amounts of omega-3 fatty acids (67). Skin health declines with age, especially in older people or after too much sun exposure. Scientific research shows that a range of skin conditions including psoriasis and dermatitis may benefit from taking fish oil supplements (68, 69, 70).

• Summary: Skin can be damaged by aging or too much sun. Fish oil supplements may help keep the skin healthy.

Fish oil can support child development during pregnancy and breastfeeding

Omega-3 fatty acids are essential for early childhood growth and development (71). It is therefore important that mothers consume sufficient amounts of omega-3 fatty acids during pregnancy and breastfeeding.

Taking fish oil supplements during pregnancy and breastfeeding can improve hand-eye coordination in infants. However, it is still unclear whether they can also improve IQ (72, 73, 74, 75, 76).

Taking fish oil supplements during pregnancy and breastfeeding could also improve the child's visual development and reduce the risk of allergies (77, 78).

• Summary: Omega-3 fatty acids are vital for early childhood growth and development. The use of fish oil supplements during pregnancy and lactation may improve the child's hand-eye coordination, although effects on learning and IQ have not been adequately studied.

Fish oil could reduce liver fat

The liver processes most of the fat in the body and may play a role in weight gain. Liver disease is on the rise, particularly non-alcoholic fatty liver disease, which is characterized by fat accumulation in the liver (79). Fish oil supplements can improve liver function and reduce inflammation of the liver, which may help reduce symptoms of non-alcoholic fatty liver disease and the amount of fat stored in the liver (80, 81, 82, 83).

• Summary: Fish oil supplements may help reduce the amount of fat in the liver and the symptoms of non-alcoholic fatty liver disease.

Fish oil can reduce symptoms of depression

Depression is expected to become the second leading cause of disease by 2030 (84). Interestingly, people who suffer from severe depression have lower blood levels of omega-3 fatty acids (29, 85, 86).

Studies have shown that fish oil and omega-3 fatty acids can alleviate the symptoms of depression (87, 88, 89). In addition, studies have shown that oils rich in EPA reduce symptoms of depression more than oils richer in DHA (90, 91).

• Summary: Fish oil - especially fish oil rich in EPA - may help reduce symptoms of depression.

Fish oil may improve attention in hyperactive children

A number of behavioral disorders in children, such as attention deficit hyperactivity disorder (ADHD), involve hyperactivity and inattention. Considering that omega-3 fatty acids make up a significant part of the brain, adequate intake may be important in preventing the development of behavioral disorders in the early years of life (92).

Fish oil supplements may reduce perceived hyperactivity, inattention, impulsivity and aggression in children. This may promote early childhood learning (93, 94, 95, 96). Summary: Fish oil supplements have been shown to help reduce hyperactivity, inattention and other negative behavior patterns.

Fish oil may help prevent symptoms of age-related mental decline As we age, brain function declines and the risk of Alzheimer's disease increases. People who eat more fish tend to experience a slower decline in mental ability as they age (97, 98, 99).

However, studies of fish oil supplements conducted with older adults have not provided clear evidence that these supplements can slow a decline in brain function (100, 101). However, some very small studies have shown that fish oil may improve memory performance in healthy older adults (102, 103).

• Summary: People who eat more fish experience a slower decline in mental function as they age. However, it is still unclear whether fish oil can prevent a decline in mental function in older adults.

Fish oil could reduce asthma symptoms and the risk of allergies

Asthma, a condition characterized by swelling of the airways and shortness of breath, is becoming an increasingly common disease.

A number of studies have shown that fish oil may reduce asthma symptoms, which appears to be particularly the case during the early years of life (104, 105, 106, 107). In a review of almost 100,000 people, it was found that fish oil or omega-3 consumption by the mother reduced the risk of asthma in children by 24 to 29% (108). In addition, the consumption of fish oil supplements by pregnant women could reduce the risk of allergies in infants (109).

• Summary: A higher consumption of fish and fish oil during pregnancy could reduce the risk of asthma and allergies in infants.

Fish oil can improve bone health

As we age, bones begin to lose their essential minerals, increasing the risk of fractures. This can lead to conditions such as osteoporosis and osteoarthritis. Calcium and vitamin D are very important for bone health, but some studies suggest that omega-3 fatty acids may also be beneficial.

People with higher omega-3 intakes and higher omega-3 blood levels appear to have higher bone mineral density (110, 111, 112). However, it is still unclear whether fish oil supplements improve bone mineral density (113, 114).

A number of small studies suggest that fish oil supplements may reduce markers of bone loss, which could reduce bone disease (115).

• Summary: Higher omega-3 intake is associated with higher bone density. However, it is still unclear whether fish oil supplements can increase bone density.

How should you supplement fish oil?

If you don't eat 1 to 2 portions of fish per week, then it may make sense to consider taking a fish oil supplement. There are a few things you should bear in mind:

Dosage

EPA and DHA dosage recommendations depend on age and health status. The WHO recommends a daily intake of 200 to 500 mg of a combination of EPA and DHA. However, it may be necessary to increase this dosage if you are pregnant, breastfeeding or at increased risk of heart disease (116).

You should choose a fish oil supplement that contains at least 300 mg of EPA and DHA per serving.

Dosage form

Fish oil supplements are available in a variety of forms, including ethyl esters, triglycerides, free fatty acids and phospholipids. As your body cannot absorb ethyl esters as well, you should use one of the other forms listed (117).

Concentration

Many supplements contain up to 1,000 mg of fish oil per serving - but only 300 mg of EPA and DHA. On the other hand, supplements containing over 60% EPA and DHA are also available.

Fresh

Omega-3 fatty acids are susceptible to oxidation, which makes them rancid. To avoid this, you can choose a product that contains an antioxidant such as vitamin E. You should also store your supplements away from light and in a cool place - ideally in the fridge. Do not use fish oil if it smells rancid or has passed its best-before date.

Timing

Other dietary fats can help your body absorb omega-3 fatty acids better. For this reason, it is best to take your fish oil supplement with a meal that contains fat (119).

Safety and side effects

Fish oil is likely to be safe for most people, including pregnant and breastfeeding women, when taken in small amounts (3 grams per day or less). There are some safety concerns when fish oil is taken in high doses. Taking more than 3 grams could interfere with blood clotting and increase the risk of bleeding. High doses of fish oil could also reduce the activity of the immune system and therefore the body's ability to fight infection. This is a particular concern for people taking medication to reduce the activity of the immune system (e.g. organ donation recipients) and the elderly. High doses of fish oil should only be used under medical supervision. Fish oil can cause side effects including belching, bad breath, heartburn, nausea, loose stools, skin rashes and nosebleeds. Taking fish oil with meals or freezing it can often reduce these side effects. Also, consuming large amounts of fish oil through some food sources may not be safe and harmless. Some fish (particularly shark, king mackerel and farmed salmon) may be contaminated with mercury and other industrial and environmental chemicals, whereas fish oil supplements do not usually contain these contaminants.

Precautions and warnings

Liver disease: Fish oil may increase the risk of bleeding. Fish or seafood allergy: Some people who are allergic to seafood such as fish may also be allergic to fish oil supplements. There is no reliable information on the likelihood that people who suffer from an allergy to seafood are also allergic to fish oil. Until more is known about this, people who are allergic to seafood should avoid fish oil supplements or use them with caution.

Bipolar disorders: Taking fish oil could worsen the symptoms of this disorder.

Depression: Taking fish oil could worsen some symptoms of this disorder. Diabetes: There are concerns that taking fish oil in high doses could make it more difficult to control blood sugar.

High blood pressure: Fish oil can lower blood pressure and cause blood pressure to drop too much in people on antihypertensive medication. HIV/AIDS and other conditions where the immune system response is reduced: Higher doses of fish oil may reduce the immune system response. This could be a problem for people with a previously weakened immune system.

Pacemakers: Some, but not all, research suggests that fish oil may increase the risk of an irregular heartbeat in patients with a pacemaker. For this reason, people with a pacemaker should avoid fish oil supplements to be on the safe side.

Familial adenomatous polyposis: There are concerns that fish oil may further increase the risk of cancer in people suffering from this condition.

Interactions

Care should be taken when combining fish oil supplements with the following medications:

Hormonal contraceptives (birth control pills):

Fish oil appears to help lower some fat levels in the blood. These fats are called triglycerides. Hormonal contraceptives may reduce the effectiveness of fish oil in reducing these blood fat levels.

Medication for high blood pressure

Fish oil could lower blood pressure. Taking fish oil in combination with medication for high blood pressure could result in an excessive drop in blood pressure.

Orlistat (Alli)

Orlistat (Alli) is used to support weight loss. Orlistat prevents absorption of dietary fats in the intestine. There are concerns that orlistat may also reduce the absorption of fish oil when taken together. To prevent this potential interaction, orlistat and fish oil supplements should be taken at least 2 hours apart.

Care should be taken when combining fish oil supplements with the following medications:

Medications that slow down blood clotting

Fish oil could slow down blood clotting. Taking fish oil in combination with medications that also slow blood clotting could increase the risk of bleeding and the tendency to bruise.

Some medications that can slow blood clotting include aspirin, diclofenac (Voltaren), ibuprofen, naproxen and others.

Conclusion

Omega-3 fatty acids contribute to normal brain and eye development. They fight inflammation and can help prevent heart disease and declining brain function. Because fish oil contains a lot of omega-3 fatty acids, people who are at increased risk of one of these disorders may benefit from using it. Of course, eating whole foods is always better than using supplements and eating two portions of oily fish a week can provide your body with sufficient amounts of omega-3 fatty acids. However, supplements can be a good alternative if you don't like eating fish.

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Further studies

1. Simopoulos AP. The importance of the ratio of omega-6/omega-3 essential fatty acids. Biomed Pharmacother. 2002 Oct;56(8):365-79
2. Crawford MA, Bloom M, Broadhurst CL, Schmidt WF, Cunnane SC, Galli C, Gehbremeskel K, Linseisen F, Lloyd-Smith J, Parkington J. Evidence for the unique function of docosahexaenoic acid during the evolution of the modern hominid brain. Lipids. 1999;34 Suppl:S39-47
3. Simopoulos AP. Human requirement for N-3 polyunsaturated fatty acids. Poult Sci. 2000 Jul;79(7):961-70
4. Morris DH. Methodologic challenges in designing clinical studies to measure differences in the bioequivalence of n-3 fatty acids. Mol Cell Biochem. 2003 Apr;246(1-2):83-90
5. Visioli F, Rise P, Barassi MC, Marangoni F, Galli C. Lipids. Dietary intake of fish vs. formulations leads to higher plasma concentrations of n-3 fatty acids. 2003 Apr;38(4):415-8
6. Tsuboyama-Kasaoka N, Takahashi M, Kim H, Ezaki O. Up-regulation of liver uncoupling protein-2 mRNA by either fish oil feeding or fibrate administration in mice. Biochem Biophys Res Commun. 1999 Apr 21;257(3):879-85