Fructose and trans fatty acids implicated in 'fatty liver' and liver damage

‘Fatty liver’, as it’s name suggests, is a condition characterised by the deposition of fat in the liver. Fatty liver has for a long time know to potentially have its roots in the overconsumption of alcohol. However, increasingly doctors are seeing individuals who have fatty liver where alcohol does not appear to be the causative factor. This sort of fatty liver is often referred to as ‘non-alcoholic steatohepatitis’ or ‘NASH’ for short.

The causes of NASH are not fully elucidated, but there is at least some evidence that carbohydrate can be a factor. See here for a piece about this. This blog post focuses on a piece of research which found that high carbohydrate intake was associated with liver damage (while high consumption of protein, fat and calories was not). Carbohydrate can stimulate the production of fat in the liver. It seems that some of which can get stuck there, basically.

This week saw the publication of the effects of different diets on the liver health of mice [1]. Over the course of 16 weeks, mice were fed one of three diets:

1. regular mouse food (‘chow’)
2. a diet rich in trans-fatty acids
3. a diet rich in trans fatty acids as well as a fructose/sucrose solution

The mice eating the regular ‘chow’ were found to be of normal weight and have healthy livers at the end of the study. Not so the mice from the other groups, which became obese and also developed ‘fatty liver’. The group consuming trans fats and the sucrose/fructose solution fared worst of all: in addition to developing fatty liver, they also showed evidence of ‘fibrosis’ in the liver. Fibrosis is generally a sign of later stage liver disease, and is a precursor of full-blown cirrhosis of the liver.

This research was performed in animals (not humans) and used quite extreme test diets. Nevertheless, it does provide at least some evidence that certain elements of the diet can be specifically toxic to the liver. The fructose/sucrose solution used in the study is essentially found in the human diet in the form of ‘high-fructose corn syrup’ which has become an increasing feature in the Western diet in recent times. The same is true of trans fatty acids.

Although chemically very different, one thing that high fructose corn syrup and industrially produced trans fats have in common is they are highly processed foods which are not to be found naturally in the diet. In this sense, this latest research provides some evidence which supports the notion that the best diet for us as a species is one largely devoid of new-fangled foods and foodstuffs.

For more about the hazards of trans fatty acids see here.

For more information about the hazards associated with fructose and high-fructose corn sytrup see here and here.

References:

1. Kohli R, et al. High-fructose medium-chain-trans-fat diet induces liver fibrosis & elevates plasma coenzyme Q9 in a novel murine model of obesity and NASH. Hepatology. 6 June 2010 [epub ahead of print publication]