Fruit juice made with nutrient extractors would add less glucose to the blood

A team at the University of Plymouth believes that preparing fruit juice with a commercial nutrient extractor may reduce the spike in blood glucose levels that occurs after consumption. The study, which was published last year in the journal Nature, notes that juice prepared with an extractor called “Nutribullet 600” resulted in a 50% reduction in blood sugar levels compared with eating whole fruit.

Although everyone seems to be using them these days, nobody had observed the effect of fruit juice prepared with a nutrient extractor on blood sugar levels, say the scientists from the university's Faculty of Medicine and Biomedical Sciences. They did so because they were curious to see how it would compare with eating whole fruit.

The new extractors homogenise, juicers remove

The growing popularity of “nutrient extractor” style blenders suggests that the public, as well as patients who already exhibit risk factors for type 2 diabetes, are consuming fruit in a new way for which the health risks are unclear. Unlike traditional juicers, which remove the pulp and leave only the juice, these blenders homogenise the whole fruit without removing elements such as the fibre-rich skin.

In the crossover study, each participant served as their own control; participants were placed in one of two study groups;

• The control drinks were prepared on the morning of the test and consisted of 25 g of glucose dissolved in 125 ml of water.
• The nutrient-extracted portions were processed with 125 millilitres (ml) of water.
• The mango juice consumed was made from mango alone (181 g).
• The mixed fruit juice consumed consisted of banana (25 g), mango (25 g), mburucuyá/passion fruit (50 g), pineapple (50 g), kiwi (50 g) and raspberries (50 g).
• For each group, the two test meals contained 25 grams (g) of total sugar per portion.
• The group that consumed mixed fruit and the group that consumed mango (a fruit with a high glycaemic index (GI)).

Participants consumed each test drink, with a minimum washout period of three days between test days.

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When using the extractor;

• In the case of high-GI mango, there were no differences between juice made with a nutrient extractor and eating the whole fruit, indicating that even for a high-GI fruit, the effect of nutrient extraction does not increase the GI compared with whole fruit.
• Nutrient extraction to make mixed fruit juice (with pulp and skins) resulted in a drink with a significantly reduced GI (32.7) compared with eating the same mixed fruit as a salad (GI: 66.2).

The results were truly surprising and, according to the researchers, they are excited that nutrient extraction to make fruit juice could now possibly be considered a viable alternative to conventional fruit juice for the many people who find it difficult to incorporate whole fruit into their diets. Of course, this is only an initial study and will require further research before we know whether this should change nutritional guidelines; the mechanism is also important.

Just 150 ml of fruit juice a day?

Current public health advice in many parts of the world recommends limiting fruit juice consumption to just 150 ml per day. The reasoning behind this advice comes from the theory that juicing releases sugars from cells, removing insoluble fibre, which in turn increases the postprandial glucose response.

In the case of nutrient extractor-based homogenisation, no fruit is removed, so both insoluble and soluble fibre remain in the solution that forms the juice. The scientists called for more research time to understand how nutrient-extracted samples in a mixed fruit juice show this remarkable drop in glycaemic index (GI) compared with eating mixed whole fruit, and why this did not happen when it involved a single fruit with a high glycaemic index.

The authors suggest that when chewing whole fruit, it is exposed to salivary amylase for longer than the nutrient extract, which is presumably drunk more quickly. The suggestion is therefore that less starch is converted into glucose in the nutrient extract, which may lead to slower digestion of starch in the duodenum, but this would require further experiments to clarify.

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Source

• Nutrition and Diabetes: Nutrient-extraction blender preparation reduces postprandial glucose responses from fruit juice consumption