Fish oil is recommended for a healthy diet because it contains the omega-3 fatty acids eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), precursors to eicosanoids that reduce inflammation throughout the body. Fish do not actually produce omega-3 fatty acids, but instead accumulate them from either consuming microalgae that produce these fatty acids, as is the case with fish like herring and sardines, or, as is the case with fatty predatory fish, by eating prey fish that have accumulated omega-3 fatty acids from microalgae. Such fatty predatory fish like mackerel, lake trout, flounder, albacore tuna and salmon may be high in omega-3 fatty acids, but due to their position at the top of the food chain, these species can accumulate toxic substances (See biomagnification). For this reason, the FDA recommends limiting consumption of certain (predatory) fish species (e.g. albacore tuna, shark, and swordfish) due to high levels of toxic contaminants such as mercury, dioxin, PCBs and chlordane. There are vegetarian, DHA Omega-3 products made from algae available if toxic contaminants are of concern.
Many people have turned to fish oil supplements to get adequate omega-3 fatty acids.
Fish oil supplements have sometimes come under scrutiny in recent years. In early 2006, government agencies such as the Food Standards Agency in the UK and the Food Safety Authority of Ireland reported PCB levels that exceeded the strict new European maximum limits in several fish oil brands, which required temporary withdrawal of these brands. To address the growing concern over contaminated fish oil supplements, the International Fish Oil Standards program, a voluntary review process, was created at University of Guelph.
Patented production purification processes do however exist in order to remove pollutants and dioxins from fish oil to levels far below the EU limits. This is called stripping technology.
Most of the fish oils used for Omega purposes are originating from Peru, Chile and Morocco because the Omega 3 levels in the fish caught in these areas are higher (around 30%) than in Scandinavian and other fish oils (around 20%). Fish oils are being used in the Omega 3 industry to produce nutraceuticals and pharmaceuticals. However, the largest off-takers of the Omega 3 fish oils are still the leading buyers with the big fish feed companies such as Ewos, Skretting and Biomar in the lead.
In 2005, fish oil production declined in all main producing countries with the exception of Iceland. The 2005 production estimate is about 570 000 tonnes in the five main exporting countries (Peru, Denmark, Chile, Iceland and Norway), a 12% decline from the 650 000 tonnes produced in 2004.
Peru continues to be the main fish oil producer worldwide, with about one fourth of total fish oil production. Though Peruvian catches of fish destined for reduction in 2005 were more or less in line with the 2004 result, fish oil production declined from 350 000 tonnes to 290 000 tonnes, due to lower fat content of the fish. In the recent summer months, the fat content was as low as 2% which compares to 4% in 2004. Despite an 18% decline in production, Peruvian earnings from fish oil exports reached 156 million US$ in 2005, exceeding the 2004 income by 6 million US$. This was due to the impressive increase in fish oil prices.
Some experts believe that taking fish oil (in any form) can help regulate cholesterol in the body, because fish oil has high levels of omega-3 fatty acids. The regulation occurs through effects of the EPA and DHA constituents on Peroxisome proliferator-activated receptor alpha (PPARα). Besides cholesterol regulation, benefits include anti-inflammatory properties and positive effects on body composition. However, the preferred source of Omega 3 should be from the fish's body, not the liver. The liver and liver products (such as cod liver oil) of fish and many animals (such as seals and whales) contain Omega-3, but also the active form of vitamin A. At high levels, this form of the vitamin can be dangerous. Early explorers to the land of the Inuit were given raw liver by the natives, which contained a toxic overdose of vitamin A for the white explorers; however, the same amount was harmless to the Inuit, who had no other source of Vitamin A except animal livers.
Studies were conducted on prisoners in England where the inmates were fed seafood which contains Omega-3 Fatty acids. The higher consumption of these fatty acids corresponded with a drop in the assault rates. Another Finnish study found that prisoners who were convicted of violence had lower levels of omega–3 fatty acids than prisoners convicted of nonviolent offenses. It was suggested that these kinds of fatty acids are responsible for the neuronal growth of the frontal cortex of the brain which, it is further alleged, is the seat of personal behavior.
Recent studies have suggested that fish oil may affect depression, and importantly, suicide risk. One such study, took blood samples of 100 suicide-attempt patients and compared the blood samples to those of controls and found that levels of Eicosapentaenoic acid were significantly lower in the washed red blood cells of the suicide-attempt patients.
A study examining whether omega-3 exerts neuroprotective action in Parkinson's disease found that it did, using an experimental model, exhibit a protective effect (much like it did for Alzheimer's disease as well). The scientists exposed mice to either a control or a high omega-3 diet from two to twelve months of age and then treated them with a neurotoxin commonly used as an experimental model for Parkinson's. The scientists found that high doses of omega-3 given to the experimental group completely prevented the neurotoxin-induced decrease of dopamine that ordinarily occurs. Since Parkinson's is a disease caused by disruption of the dopamine system, this protective effect exhibited could show promise for future research in the prevention of Parkinson's disease.
A study from the Orygen Research Centre in Melbourne suggests that omega-3 fatty acids could also help delay or prevent the onset of schizophrenia. The researchers enlisted 81 'high risk' young people aged 13 to 24 who had previously suffered brief hallucinations or delusions and gave half of them capsules of fish oil while the other half received fish-tasting dummy subtitute. One year on, only three percent of those on fish oil had developed schizophrenia compared to 28 percent from those on the substitute - a very impressive result, but not yet published in a peer reviewed journal.
The American Heart Association recommends the consumption of 1g of fish oil daily, preferably by eating fish, for patients with coronary heart disease. Note that optimal dosage relates to body weight.
The US National Institutes of Health lists three conditions for which fish oil and other omega-3 sources are most highly recommended: hypertriglyceridemia, secondary cardiovascular disease prevention and high blood pressure. It then lists 27 other conditions for which there is less evidence. It also lists possible safety concerns: "Intake of 3 grams per day or greater of omega-3 fatty acids may increase the risk of bleeding, although there is little evidence of significant bleeding risk at lower doses. Very large intakes of fish oil/omega-3 fatty acids ("Eskimo" amounts) may increase the risk of hemorrhagic (bleeding) stroke."
Fish oil feeding delays influenza virus clearance and impairs production of (interferon-gamma) and virus-specific immunoglobulin A in the lungs of mice
Feb 01, 1999; Fish Oil Feeding Delays Influenza Virus Clearance and Impairs Production of Interferon-gamma and Virus-Specific Immunoglobulin A...