The habit of ‘juicing’ is gradually growing within the population because many think that it is the perfect way of maintaining a healthy body. And there is no problem with that as long as you can rush down to the market buy fruits and prepare your own fresh juice at home.

However demand for convenience has cut down this long tape with a huge percentage of the public resorting to processed juices but what could they be missing out?

"They are missing out on the most unstable vitamins such as C. Heat processing destroys vitamin C and being an acid, processing in alkali conditions that may happened during manufacturing of bottled juices also renders the vitamin wasted,” says Joseph Uwiragiye, a nutritionist at University teaching hospital.

During fruit processing, there is bottle washing, heat treatment, sterilization, capping and addition of ingredients such as sweeteners to the products. Other additives may include flavorings or color enhancers.

Kibagabaga hospital nutritionist Isaac Bikorimana observes that since fruit juice processing sometimes involves extraction of oils, this affects the stability of fat-soluble vitamins.

"Fruits contain traces of fat soluble vitamins such as A, D, E and K but extraction of fats and oils during processing may affect their stability,” he adds.

Effect of sweeteners

Sweeteners added to process juices may be natural or artificial, but all have their effects. There is conflicting research surrounding the health benefits of artificially sweetened drinks with most studies showing that regular consumption of these beverages reduces the intake of calories and promotes weight loss or maintenance. Other research shows no effect and some even show weight gain.

A 2013 study showed that both sugar-sweetened beverages and artificially sweetened beverages were linked with an increased risk of developing type 2 diabetes despite need for more research to prove a fundamental link. 

It is against this background that Uwiragiye warns about the use of naturally occurring fructose syrup as a sweetener in processed juices. This may lead to obesity, according to the nutritionist.

"Such ingredients used during processing should be a serious concern because they affect the overall calorie intake. This is the exact reason for the increasing childhood obesity cases,” adds Uwiragiye.

The British Medical Association published similar results in support of these views. Researchers from the UK, USA and Singapore found that, in large-scale studies involving nurses, people who ate whole fruit, especially blueberries, grapes and apples, were less likely to get type 2 diabetes, which is obesity-related, but those who drank fruit processed juice were at increased risk.

Interestingly, people who swapped their fruit juice for whole fruits three times a week cut their risk by 7 per cent.

Dangers of the preservatives

Over 10 million metric tons of processed juices are consumed globally.

The World Health Organization strategy to reduce intake of free sugars to less than 10 per cent of total daily energy intake started for the first time in 1989 and was further elaborated by a joint WHO/FAO Expert Consultation in 2002.

Last year, a new updated WHO guideline called for further reduction of free sugars intake to less than 5 per cent of total energy intake at all costs.

However, Bikorimana elaborates that the problem with bottled juice sometimes arises from the added preservatives.

"Some preservatives have been associated with serious side effects that is why it is important for people to check the nutritional content of the products before buying the juices,” explains Bikorimana.

For example, Professor Peter Piper a molecular biology expert at Sheffield University found that sodium benzoate damaged the mitochondrial DNA of yeast cells. Because the damaged free-floating cell elements perform multiple functions in cells, he concludes that it may have similar effects to the human DNA thus yielding several complications.

Although our love for juicing is growing, it should be understood that much as fruit juice processing improves the microbial safety, the more processing a food undergoes, the more it becomes susceptible to nutrient loss. As such, juice concentrate contains fewer nutrients compared to fresh juice mainly because of losses from processing techniques such as evaporation and filtration.