By Nutritionist Hazel Grassie
Where the hype began
In the 1970’s, two Danish scientists travelled to the isolated Inuit villages of Northwest Greenland. Here, the local diet was made up of mainly whale, seal and fish. Contrary to belief at the time that animal fat increased the risk of heart disease; in these villages heart attacks were rarely reported. Blood analysis of the local people revealed low levels of cholesterol and triglycerides. Eventually, the scientists postulated that low levels of heart disease in these communities were down to the Omega 3 rich diet. To test this hypothesis, the DART study was conducted involving 2000 welsh men with a history of heart attack. Of these men, those who were told to eat more oily fish had a 29% decrease in mortality risk. The publication of these results in combination with support from the influential American Heart Association (AHA) caused a massive increase in the awareness of Omega 3 health benefits and a consequent soar in fish oil sales. NB. Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA) are both long-chain polyunsaturated fatty acids (LC-PUFAs), known as Omega 3 fats.
An Inuit hunting for fish. Image source: http://www.alaskannature.com/inuit.htm
Fresh fish consumption
Epidemiological studies show that regular consumption of oily fish (3-4 times per week) lowers the risk of heart disease. Currently, we are advised to eat at least 2 portions (140g) of fish per week, including one of oily fish. As oily fish can contain low levels of contaminants such as heavy metals, dioxin and PCBs, there also exist maximum advised intakes. The guideline is no more than 4 portions per week for the general population and no more than 2 portions for women who are pregnant or planning pregnancy. Unfortunately, most people do not eat enough fish. The UK population eats well below the recommended 1 portion of oily fish per week. This is where we encounter support for the fish oil supplement.
Fresh oily fish. Image source: http://vkool.com/healthy-foods-for-men/
We cannot fault the reasoning that given a great body of evidence supporting the cardiac benefits of fresh oily fish, surely the extracted oil will have similar effects. Initially health institutes encouraged this concept, stating that it was “likely” supplements had beneficial effects on health. Unfortunately, it is quite common in the field of nutritional research that a dietary claim can persist even in the face of strong contradictory evidence. Researchers are possibly too hasty in their advocation of certain foods as health superstars.
This may be true in the case of fish oil supplementation. Authors A. Grey and M. Bolland carried out a systemic review of randomized trials that investigated the effects of fish oil consumption. They found that 22 of 24 studies showed no health benefit of fish oil supplements. We must note however, that the majority of trials are carried out on people with a history of cardiac problems. It is difficult therefore to detect a benefit of fish oils amongst an array of other medicines. Whether fish oil supplements can help healthy people to reduce their risk of developing heart disease remains an open scientific question.
The efficacy of supplements against the real thing
Despite the conflicting claims of fish oil effectiveness, the idea persists. Many people choose to take fish oil supplements. This may be for financial or locational limitations to buying fresh fish or a general disliking for fish yet an awareness of its benefits. Others take fish oils to treat inflammatory conditions like arthritis or simply to increase their Omega 3 levels in combination with dietary sources. What I want to know is where exactly the differences lie between fish and fish oil supplements to give rise to such the counterintuitive research results.
Fish oil supplements. Image source: http://top10supplements.com/best-fish-oil-supplement/
Whole fish contains EPA and DHA but also protein, selenium, vitamin D and a complete profile of fatty acids. Vitamin D serves to assist the body in reducing the risk of many common diseases such as arthritis and osteoporosis. Oily fish is one of the best dietary sources of vitamin D. Most fish oil supplements on the other hand contain only EPA and DHA, which have been extracted from the original source and concentrated.
Although the concentrations of DHA and EPA in supplements are at levels otherwise unobtainable through daily diet, research shows that other fats present in whole fish assist the body’s absorption of EPA and DHA. In fact, one study found that blood levels of DHA were 9 times higher in subjects consuming salmon compared to subjects taking fish oil supplements. The authors concluded that the molecular shape of the fatty acid in fresh fish is more recognizable to the body and thus, more readily absorbed. Another study found that taking olive oil alongside fish oil supplements dramatically increased Omega 3 absorption. Evidence is inconclusive as to whether supplements combined with a high-fat meal can deliver amounts of LC-PUFA comparable to those of whole fish.
It is greatly important that people are not deficient in omega 3 fats and for that reason I would encourage people to be aware of their oily fish consumption and supplement this if necessary. If you are going to take a fish oil supplement it is important keep in mind that not all supplements are equal. The best product in terms of bioavailability is perhaps ethyl ester oil. This oil retains a semi natural state, is partly purified and has double concentration of EPA and DHA. Avoid supplements of origin from a species under threat. You can check these on the Marine Stewardship Council website.
Conclusively, there is a great body of evidence that refutes initial promises for cardiac benefits from fish oil supplements. However, research shows that taking other fats in conjunction can improve absorption, which may enable health benefits. I would advise anyone who is not meeting the recommended 1 portion of oily fish per week to increase their intake if possible. In cases where there is inadequate fish consumption or inflammatory conditions, I would advise use of a quality fish oil supplement in combination with a nutritionally balanced meal.