"A lot of people don't know why they take fish oil," said Dr R. Preston Mason, a faculty member at Harvard Medical School and President of Elucida Research, a biotechnology research company. "You take fish oil for the omega-3 content. People have heard it's good for you, so they take it. It's a booming industry."
Fish oils are known to be rich in long-chained omega-3 polyunsaturated fatty acids – called docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). These are vital in coordination between cell communications, particularly in the brain.
The use of fish oils as a supplement can be traced back all the way to the 18th century, before the industry boomed the 19th century and 20th century. As its use continues to grow, research is also deepening in parallel. However, many are beginning to discover that fish oils may not live up to its claims.
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Scaling the benefits and risksFirstly, DHA and EPA are highly susceptible to oxidation, making over-the-counter fish oil supplements prone to breaking down due to light, oxygen exposure and heat during the manufacturing and delivery processes.
"Once they are broken down, certainly, they don't have their favourable benefits that we hope for," said Mason. He noted that the same thing can happen with fish, but the bad smell would give it away as not worth buying or consuming. Supplements have chemicals to cover up the rotten smell.
Mason also found that fish oil supplements were packing in more than just omega-3.
"I just wanted to ask the question: What's actually inside these capsules?” he asked. “We were quite surprised to see that in some of these widely used supplements, only a third of the product was the favourable omega-3s, and the balance of them were these other lipids, including saturated fats, which we don't associate with health benefits."
Additionally, Mr Ng Kar Foo, Consultant Dietitian at the International Medical University (IMU), highlighted that there are case reports that also demonstrate the side effects of consuming too much fish oil – e.g. bleeding or altered immune functions.
“If one is keen to consume fish oil supplements, he or she should seek advice from a doctor or a dietitian to determine the suitable dosage and to prevent drug-nutrient interaction that may cause harm to him or her,” he advised.
Oh, my cod! Is fish oil actually harmful?
Most recently, a meta-analysis of ten randomised control trials published in the Journal of American Medical Association (JAMA) Cardiology, found that fatty acids rich in omega-3 are ineffective for the prevention of cardiovascular disease.
From the 77,917 high-risk individuals who were supplemented with fish oils for roughly four years, it was discovered that there was no significant difference in reduction of heart disease. The study concluded that further recommendation of fish oils for this reason is no longer necessary.
“Carefully done trials provide no support for the hypothesis that fish oil supplements help,” said senior author, Dr Robert Clarke, a professor of epidemiology at the University of Oxford.
Similarly, another recent study showed that long-term sunflower and fish oil intake may damage the liver and give rise to non-alcoholic steatohepatitis (NASH) – a catalyst for cirrhosis and liver cancer.
“The research demonstrates that fat accumulates in the liver with age, but the most striking finding is that the type of fat accumulated differs depending on the oils consumed,” explained Jose Luis Quiles Morales, Full Professor of Physiology at the University of Granada.
“This means that regardless of this accumulation, some livers ages in a healthier way than others and with a greater or lesser predisposition to certain diseases.”
Swimming through the fishy business“The results [of the two studies] are not surprising because nutrition science does not always give clear and direct answers, especially when testing on the efficacy of a single nutrient on health,” said Mr Ng.
“Lifestyle including overall diet is the key influencing factor in most of the nutrition research and it is hard to be ruled out entirely in the research,” he added.
Nonetheless, perhaps “there are certain other things about eating fish, not just the fish oil, that are beneficial,” shared Dr Cheryl Cipriani, an infancy specialist and professor of medicine at the Texas A&M Health Science Centre in Dallas. She was commenting on two studies on fish oil consumption in pregnant women.
Mr Ng echoed in agreement, stating that the scientific evidence for a dietary source of omega-3 is stronger and more convincing.
“Those who obtain omega-3 from food sources are likely to get more health benefits because food provides a package of essential nutrients that supplements can hardly imitate,” he elaborated. "Also, food is more satisfying than consuming supplements.”
An omega-3-rich diet should suffice for many, as fatty fish such as salmon, mackerel and sardines are packed in DHA and EPA. A third fatty acid called alpha-linolenic acid (ALA) is also found in walnuts, canola, flaxseeds, chia seeds and pumpkin seeds, which can be converted into DHA and EPA.
“At the end, the old verdict will never go wrong – consuming a healthy diet (including omega-3-rich food) and practising an active lifestyle are crucial in supporting good heart and overall cardiovascular health,” concluded Mr Ng. MIMS
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