Blending fruit and veges retains vitamins and minerals that you lose with juicing. But neither is a bad way to boost your intake.
ANSWER: Given how few fruit and vegetables we eat as a nation, whether it’s juicing or smoothies, nutrition scientist Tim Crowe says it’s a step in the right direction. “You’ll be having more of the beneficial nutrients from these foods, so that’s a good thing.”
But overall, there is a clear winner when it comes to the juicing-versus-smoothie battle, says Crowe. “Smoothies come out on top, because they contain additional nutrients. You get the fibre, plus you get some of the additional liquid that you’ll lose in the pulp when you juice, and you get a lot more of the nutrients that are present in the skin of food, which you lose in juicing. So, you actually get more vitamins and minerals overall.”
And although that fibre is blended into a smooth mixture, it’s still useful, says Crowe. “We can’t digest that fibre, so doing mechanical blending doesn’t change that. And our gut microbiome can deal with it just as beneficially.”
On the plus side, says Crowe, when you blend food, you break more of the cell walls open and that releases extra nutrients.
One small negative is that the presence of the fibre slows the absorp-tion of some fat-soluble vitamins. But overall, you’re getting more nutrients with blending.
When it comes to the digestion and absorption of the fruit sugars into our circulation, there isn’t a lot of difference between fruit juices and smoothies, says Crowe.
“The effect on blood sugars of juice versus the fruit, for a similar amount of carbohydrate, is not a big difference.
“What matters for blood glucose response is not just the form of carbohydrate, but also the amount. With a [glass of] juice or a smoothie, you can have a lot of carbohydrate and sugar at one time, whereas in one serving of fruit you’ll have a smaller amount. So, a smoothie or juice can be a bigger load; that’s probably more the issue.”
Fructose, one of the main sugars found in fruit, is absorbed quite slowly into the body, says Crowe. So, the fruit sugars have a slower effect on blood-sugar responses.
Surprisingly, a lot of fruit and fruit juices have a low glycaemic index – the relative ranking of carbohydrate in foods showing how they affect blood-glucose levels. Those that are more slowly digested, absorbed and metabolised cause a lower and slower rise in blood glucose and therefore insulin levels.
Low GI foods have a GI index below 55. Apples, for example, have a GI of between 34 and 44, and, even with much of the fibre removed, apple juice has a ranking of between 39 and 44.
Still, everyone’s glucose response to food is different, says Crowe. “It could be fine for me, but for someone else it may cause a high blood-sugar spike.”
From a dental perspective, whole fruit is a safer bet – with the chewing process limiting fruit contact to the bite surfaces of the teeth only. If you’re going to drink juice or a smoothie, use a reusable straw to limit contact with your teeth.
“Of course, it all comes down to what you’re putting in them, too. We’re talking about juices and smoothies as if it’s only fruit, and that’s going to have the sugar.
“But if you’re putting in carrots and celery and [other] vegetables, well, knock yourself out,” says Crowe.
That’s because vegetables don’t have the acidity or high sugar content of fruits.
This article was first published in the January 18, 2020 issue of the New Zealand Listener.