New Study Shows Harmful Effects of ‘Healthy’ Fruit Juices on the Liver


A new study has shed light on how high quantities of fructose found in fruit juices and smoothies affect the body – countering previous beliefs and aiding our understanding of how sugar consumption can lead to chronic diseases.

Researchers had previously believed that fructose in our food and drinks is processed by our liver, however the findings from a study at Princeton University in New Jersey, suggests that it is infact the small intestine that mainly processes manageable quantities of fructose – but that this can vary according to the nature and amount consumed.

In the study published in the Journal Cell Metabolism, the researchers examined how fructose travels through the digestive system in mice. They found that low doses of fructose are largely broken down in the small intestine where they are absorbed into the blood as glucose. However high quantities of fructose such as those in processed foods and drinks overwhelm the small intestine and are unable to be broken down so some are transferred to the liver and colon – coming into contact with the microbiome.

Too Much Fructose May Harm the Liver and Microbiome

The team found that fructose that wasn’t absorbed into the small intestine is passed to both the liver and to the colon, where it comes into contact with the microbiome – where the team believe it may cause disease by affecting the liver function or microbial composition

Although the findings do not show that fructose influences the make up of the microbiome, the team believes that “an effect is likely” and that this link should be investigated further.

Many studies has shown how consuming too much sugar can harm the liver, increase insulin resistance,  and can lead to metabolic syndrome and conditions such as diabetes and obesity.
Other studies have also shown how drinks containing high levels of fructose such as fruit juices can increase the risk of non-alcoholic fatty liver disease, and lead to cirrhosis or liver cancer.

In the study, the small intestine was found to clear fructose more efficiently after a meal. The team now believe that the small intestine protects the liver from otherwise toxic fructose exposure and the findings add to a body of scientific evidence on the effects of too much fructose on the body.

The team suggest that consuming processed fructose in foods and drinks on an empty stomach or between meals, such as in the morning or mid-afternoon, the small intestine is overwhelmed and has a limited ability to process it.

“We can offer some reassurance that fructose from moderate amounts of fruits will not reach the liver”

However the author of the study, Joshua D. Rabinowitz, of the Lewis-Sigler Institute for Integrative Genomics at Princeton University, explains,
“We can offer some reassurance [based on these studies]that fructose from moderate amounts of fruits will not reach the liver.  We saw that feeding of the mice prior to the sugar exposure enhanced the small intestine’s ability to process fructose,” Rabinowitz continues. “And that protected the liver and the microbiome from sugar exposure.”

Rabinowitz says that the results support “the most old-fashioned advice in the world,” which is to “limit sweets to moderate quantities after meals” and avoid sugary drinks outside of meal times. The full publication of the study can be read here.


How to Avoid  Sugar in Fruit Juices and Soft Drinks

The findings of the study add to a large amount of evidence of the perils of high sugar intake and that even the natural sugars found in fruit juices are harmful for us when consumed in a processed or concentrated form and in excess.  More worrying is the fact that most fruit juices also contain added sugars and sweeteners – often as much sugar and calories as a sugary soft drinks.

While fruit juices may contain vitamins, nutrients and antioxidants – the lack of fibre and the damaging effects of large quantities of sugar should be of more concern than any nutritional benefits.

So how best to avoid fruit juices and sugar sweetened soft drinks? Our suggestion where ever possible is to drink water.

While not a substitute for sugar, here are some great recipes ideas to add flavour to water

10 Great Ways to Add Flavour to Water

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