Fruit juice shows that not all plant-based diets are healthy

by Jennifer Bowden / 10 December, 2017

Photo/Getty Images

If you believe fruit fibre floating in a glass of fresh juice makes it any less sugary, you’re mistaken.

QUESTIONIn a past column on sugar in fruit versus juice, you noted that the sugar in fruit is encapsulated by the cell wall. I presume in the process of making juice, the cells are broken. So if fruit juice contains pulp, does this mean the integrity of the cells is maintained? Or is the act of squeezing an orange sufficient to disrupt the cell walls?

ANSWER: It’s a modern conundrum – although plant-based diets are recommended for good health, not all plant-based foods are healthy. A recent study found that a diet that emphasises less-healthy plant foods is associated with a higher risk of coronary heart disease. So, which plant foods are dodgy?

In a major US study, researchers tracked 200,000 adults over 20 years and found those who stuck to a diet rich in such foods as whole grains, fruits, vegetables, nuts and legumes had a significantly lower heart disease risk than people who consumed less-wholesome plant foods. The less-healthy foods included fruit juices, refined grains, potatoes, fries and sweets, reported the Journal of the American College of Cardiology.

Fries and refined grains are well known to be less than healthy, but it’s a surprise to many people that juice squeezed from a fresh, wholesome piece of fruit could be bad for us.

All fruit contains sugars, along with vitamins, minerals and dietary fibre. So why is the sugar in fruit okay but the sugar in fruit juice a problem?

In fruit’s natural state, the sugars are neatly contained within the cells of the fruit pulp. Studies suggest the fibre in whole fruits may slow emptying of the stomach and therefore how quickly the sugars are absorbed into the circulation.

A slower, more gradual rise in blood-sugar levels is preferable as that is linked to a reduced risk of developing type 2 diabetes and heart disease; it may also help with healthy weight maintenance.

Chewing a piece of fruit releases the sugars in the juice from the cellular structure. In contrast, when the fruit is squeezed, the pulp structure is broken to release the fruit juice containing the sugars. Even if juice contains some pulp, its removal from the fruit indicates cells have been disrupted. The sugars in the resulting juice are then absorbed more quickly.

On top of that, several pieces of fruit typically go into a glass of juice, providing a much bigger sugar hit than eating a single orange, say.

Fruit is best enjoyed just the way nature intended – whole from the plant.

This article was first published in the November 4, 2017 issue of the New Zealand Listener.

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