Trendy Nutribullet blenders could make fruit juice a healthy option again, by keeping blood sugar down.
Health officials now advise drinking no more than 150ml of fruit juice a day because it is so high in sugar. Juicing removes the pulp, seeds and fibre from fruit, releasing its sugar more rapidly to cause a blood sugar spike which can contribute to type 2 diabetes over time.
But the fashionable Nutribullet, which claims to keep in the fibre, has been found to produce no more of a blood sugar surge than eating fruit normally.
In fact, when mixed fruit including bananas, kiwi and pineapple were juiced and given to a study group, the people had lower blood sugar than if they ate the fruits.
Researchers at Plymouth University, which made the findings, say this may be because eating requires more chewing, which could release sugars earlier.
‘Viable alternative to conventional fruit juice’
The researchers measured the blood sugar of 28 people after eating fruit and drinking them in juice form. They found mango produced a similar spike in blood sugar in either form, while mixed fruits actually produced a lower spike when blended into a smoothie.
The small study has been described as ‘potentially interesting’, although more research is needed.
Dr Gail Rees, deputy head of the university’s School of Biomedical and Healthcare Science, said: ‘We wanted to look at nutrient extractors because they are so popular and lots of people have one, so are preparing fruit juices differently.
‘Even though everyone seems to be using them these days, no one had looked at the effect of fruit juice prepared using a nutrient extractor on blood sugar levels.
‘The results were really surprising and we are excited that nutrient-extracted fruit could now possibly be considered a viable alternative to conventional fruit juice for the many people who find it hard to incorporate whole fruit into their diets.’
The researchers gave people 25 grams of sugar in the form of whole fruit, for example 181 grams of mango, or in a smoothie added to 125 millilitres of water.
The participants had their blood sugar measured at regular intervals after consuming the fruit.
Mango was chosen because it has a high GI (glycaemic index) value, meaning it is broken down quickly in the body, causing a rapid rise in blood sugar. In juice form, however, when prepared with a Nutribullet, it caused little more of a blood glucose rise than as solid fruit.
This is important because too many spikes in blood sugar over time increase the risk of developing type 2 diabetes.
The researchers asked 19 people to eat mixed fruits consisting of banana, mango, passion fruit, pineapple, kiwi and raspberries. They found blood sugar rose less rapidly in people who consumed the fruit in smoothie form, perhaps because less chewing was involved.
The act of chewing exposes fruit to amylase, an enzyme in saliva, which breaks down starch, so releases the sugar more quickly.
The authors also suggest the Nutribullet may break down seeds within fruit, releasing additional fibre which slows down the rate at which sugar is released.
Professor Pete Wilde, from Quadram Institute Bioscience in Norfolk, said: ‘This is potentially an interesting finding, but requires further studies to confirm the effects on pure fruit samples of different forms, together with mechanistic studies on the structural changes taking place in the starch, and its influence on the digestibility of the starch.’
Dr Alison Tedstone, chief nutritionist at Public Health England, said: ‘While interesting, a single study of this size is not sufficient evidence to review current advice.
‘We recommend eating at least five portions of a variety of fruit and vegetables a day and 150 millilitres of fruit juice counts as one portion max.
‘Due to the sugar content in fruit juice, we advise limiting intake and consuming with meals to reduce the risk of tooth decay.’