Whilst most people in the UK are familiar with alcohol-related liver disease as a result of heavy drinking, which is on the rise, many of us are unaware of the problems associated with another form of liver disease, non-alcoholic fatty liver disease (NAFLD) – also known as non-alcoholic steatohepatitis (NASH). A recent review of review of four human studies by a group based at the University of Edinburgh found that long-chain omega-3 fatty acids not only improve liver health and function, but also increase insulin sensitivity in people suffering from fatty liver disease.
NAFLD is a common and yet “silent” liver disease, in which individuals may present no apparent symptoms. Resembling alcoholic liver disease, NAFLD actually occurs in people who drink little or no alcohol. The major features in NAFLD are fat in the liver, with corresponding inflammation and damage that can be severe enough to lead to cirrhosis, whereby the liver is permanently damaged and scarred, thus preventing it from functioning properly and eventually leading to liver failure.
Ideally a healthy liver should have little or no fat and, for most people, carrying a little fat in the liver causes no problems. Fatty liver however, is the name given to a condition in which you have too much fat in your liver, caused by the build-up of triglycerides. Risk factors include: obesity, insulin resistance associated with diabetes, hypertension (high blood pressure) and hyperlipidaemia (too much cholesterol and triglyceride in the blood). Triglycerides are fats we consume in our diet, but they are also made by the liver and incorporated with carrier proteins called lipoproteins, which then control their release into the blood stream. If the amount of triglyceride is higher than the liver can cope with, levels within the liver increase, resulting in fatty stores. If these stores accumulate over a long period of time it may lead to inflammation, causing swelling and tenderness (hepatitis) and then to scarring (fibrosis).
Once thought to be a relatively harmless state, it appears that a fatty liver is in fact the beginnings of a serious and possibly fatal condition. Non-alcoholic fatty liver disease currently affects 10-35% of the adult population worldwide and therefore has a profound impact on public health services. Whilst consuming high fat diets increases the risk of fatty liver, not all fats have the same function and simply reducing fat intake may not be the answer. Indeed eating specific fats can even be of benefit, since a protective role has been found in certain fats, namely omega-3 fatty acids.
Whilst fish consumption has been known to have significant benefits for hyperlipidaemia and cardiovascular disease, more recently the long-chain fats typically found in oily fish have been suggested as a treatment for fatty liver (Masterton et al, 2009). But how exactly does eating fat reduce fat? Simply put, not all fats have the same function. Indeed, the omega-3 fatty acids are known to enhance hepatic fatty acid oxidation, inhibit fatty acid synthesis and reduce the secretion of very low density lipoprotein (VDLD) by regulating genes of several key enzymes, receptors and transport proteins. In simple terms this means that they switch our system from storing fat to burning fat. (Deckelbaum et al, 2006; Jump et al, 2008).
Led by Dr Gail Masterton, the results of this study were published in the December 2009 edition of the journal Alimentary Pharmacology & Therapeutics. These findings certainly suggest that moderating the diet by reducing saturated fats, depleting trans fats and increasing omega-3 fatty acids – either by increasing fish consumption or more simply by consuming a highly concentrated fish oil supplement – offers a highly protective role against potentially fatal NAFLD.
Deckelbaum RJ, Worgall TS, Seo T. (2006) n-3 fatty acids and gene expression. American Journal of Clinical Nutrition. 83: 1520S-1525S.
Jump DB, Botolin D, Wang Y, Xu J, Demeure O, Christian B (2008). Docosahhexaenoic acid (DHA) and hepatic gene transcription. Chemistry and Physics of Lipids, 153: 3-13.
Masterton GS, Plevris JN, Hayes PC. (2009) Review article: omega-3 fatty acids – a promising novel therapy for non-alcoholic fatty liver disease. Alimentary Pharmacology & Therapeutics. [Epub ahead of print].