Consuming sunflower and fish oils can cause liver inflammation that could lead to cancer, new research suggests.
Scientists discovered having either of the two oils each day triggers damage to the organ and made them susceptible to non-alcoholic steatohepatitis (NASH).
NASH, considered a silent killer and dubbed ‘human foie gras’, can lead to scarring of the liver, which in turn leads to cirrhosis. It can also result in cancer.
Humans often use sunflower oil while cooking, but fish oil is most often obtained through daily supplements, which make up a fifth of the £700 million market.
The oils and omega-3, shown to be beneficial for health, can also be obtained through eating trout, salmon, sardines, herring and mackerel.
But olive oil – repeatedly shown to be good for health – caused no such damage, the Spanish researchers concluded from experiments on mice.
Sunflower and fish oils could cause liver inflammation that could lead to cancer (stock)
Their analysis was made by monitoring the DNA of livers of 72 rats fed virgin olive, sunflower or fish oil from birth until they were two.
The University of Granada scientists also conducted tests investigating the ‘internal stress’ levels of animals, their overall health and telomere length.
The findings, published in the Journal of Nutritional Biochemistry, dismiss previous evidence that suggested sunflower oils could actually treat NASH.
Sunflower oil triggered thickening and scarring of liver tissue in rats, while fish oil altered the organ’s telomeres lengths.
Telomeres ‘cap’ the end of DNA strands, with longer lengths being associated with slower ageing, longer lifespans and improved wellbeing.
They were both shown to make the rats ‘susceptible to NASH’, according to study author Professor José Luis Quiles Morales.
He said: ‘The alterations caused by the long-term consumption of sunflower and fish oils make the liver susceptible to NASH.’
Professor Morales warned that it is a ‘very serious disease that may act as a catalyst for other liver diseases such as cirrhosis and liver cancer’.
NASH is caused by a build-up of fat in the liver and strikes 12 per cent of Americans and six per cent of Europeans, statistics show.
It is estimated cases of the most severe form of non-alcoholic fatty liver disease will soar in years to come due to expanding waistlines.
The Health Supplements and Food Information Service described the diets as being ‘extreme’ and more than humans would be fed.
‘Virgin olive oil is the healthiest option, which has already been proven in relation to diverse aspects of health,’ Professor Morales continued.
Out of the three, virgin olive oil is the only one to preserve liver function throughout rodents’ lives, the research revealed.
It is believed the oils have different effects on the liver because of how fat in them accumulates in rats – which are genetically similar to humans.
This leads to varying levels of inflammation and gene expression – which acts as a switch to control the amount of proteins made in the body.
Professor Morales added the study shows that the over-consumption of dietary fats, other than virgin olive oil, is ‘dangerous’.
Sunflower oil and virgin olive oil – a key ingredient of the Mediterranean diet – have both become widely available in recent years for their health claims.
But sales of fish oil have lagged behind. It is available as a liquid in some health food stores, but is most often obtained through tablet supplements.
But Case Western Reserve University scientists discovered that sunflower oils could alleviate symptoms of NASH in mice back in 2013.
The oil, high in vitamin E, allowed the rodents to avoid symptoms. Humans suffering from NASH can experience weight loss, fatigue and dull aches in their stomachs.
It comes after the MailOnline reported in June that drug giants are trying to jump on the global rise of NASH – because it could make them billions.