Fish oil may not be as healthy as you think, new study suggests

Feb 06, 2018
  • By Jason Lemon, For The Atlanta Journal-Constitution

Fish oil has often been touted as an important part of a healthy diet, regularly praised for its numerous benefits. However, new research suggests that consistent fish oil consumption could lead to serious liver problems.

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The study, conducted by a group of international scientists and recently published in “The Journal of Nutritional Biochemistry” found that long-term intake of sunflower or fish oils damages the liver, potentially causing alterations, which give rise to liver disease. Referred to as nonalcoholic steatohepatitis, or NASH, the form of liver disease is serious and unrelated to alcohol consumption, worsening as an individual ages.

"(Our 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 and this means that, regardless of this accumulation, some livers age in a healthier way than others and with a greater or lesser predisposition to certain diseases," Dr. José Luis Quiles Morales, who co-authored the study and works as a professor of physiology at the University of Granada in Spain, told Science Daily.

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Scientists behind the study examined how the long-term consumption of different dietary fat sources such as olive, sunflower and fish oils affects the liver of rats. As part of the comprehensive study, the researchers carried out a complete analysis of the liver genome, aiming to establish how it evolved in line with a rat's consumption of different oils.

They looked at three types of oil: virgin olive oil, sunflower oil and fish oils. According to their findings, virgin olive oil proved to be the best at preserving the liver.

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Fish oil, on the other hand, increased oxidation of the liver associated with aging, reduced mitochondrial electron transport chain activity and changed the relative length of telomeres (chromosomes whose length can affect aging in cells and cause cancer). 

Sunflower oil was also demonstrated to cause negative effects.

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"The alterations caused by the long-term consumption of sunflower and fish oils make the liver susceptible to NASH," Morales told The Daily Mail. He also warned that NASH is a "very serious disease that may act as a catalyst for other liver diseases such as cirrhosis and liver cancer."

Although many nutritionists have classified fish oil as a super food and it has been previously linked to health benefits, this isn't the first time scientists have suggested it may not be so great.

Previous research has suggested taking fish oil supplements can lower the risk of death from heart disease, while others have found no benefit. A recently published review of data from 10 studies involving a total of nearly 78,000 people, revealed that patients regularly taking fish oil supplements were just as likely to experience a stroke or heart attack within a four year period of time as those who did not, according to Live Science.

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Dr. Howard LeWine, chief medical editor at Harvard Health Publishing, wrote in a 2013 blog post that he believes the evidence for fish oils' benefits and risks will be a topic of debate for the foreseeable future.

"Experts will surely remain divided on their opinions about fish oil supplements for the general population. And don't expect any clarity about what to do any time soon. I expect other studies with flip-flopping results in the future," he wrote.

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For now, Morales suggests those concerned for their liver stick to consuming virgin olive oil instead of the other alternatives.

"Virgin olive oil is the healthiest option," the researcher said, explaining that it "has already been proven in relation to diverse aspects of health."