Runners should consider reaching for a glass of cloudy apple juice instead of an expensive sports drink to fuel their training, new research suggests.
Scientists found that fruit juice helps fitness enthusiasts recover more quickly after an intense workout or race, as it is less irritating to the gut than added sugars found in specially formulated sports drinks.
High-carbohydrate drinks are used by athletes competing in endurance events such as marathons and triathlons. While these are essential to replenish energy, the high levels of added sugars in sports drinks can damage the gut lining, allowing bacteria to “leak” through into the bloodstream, which causes inflammation and illness.
The study examined whether a simple glass of apple juice — providing the same amount of energy as sports drinks — was more protective of the immune system and could reduce gut damage compared with other sugary drinks.
A team of German scientists looked at nearly 50 runners who completed either a one-hour intense training session or a 230km (142-mile) ultramarathon race. They were divided into three groups, and given either water, diluted cloudy apple juice or a sports drink to consume within five minutes of finishing.
Blood samples were taken before and after the exercise, to measure levels of “stress chemicals” in the blood that are markers of inflammation and how well the intestinal barrier is working.
The intestinal barrier is a critical part of the immune system that stops harmful bacteria crossing from the gut into the blood, preventing inflammation. Researchers said intense exercise — particularly running — tends to disrupt the gut barrier, causing it to leak and putting athletes at risk of getting infections or illnesses. This inflammation can harm their recovery and lead to signs of overtraining such as fatigue and aching, or complications including nausea and diarrhoea.
Apple juice contains polyphenols, which help to protect the heart and reduce inflammation
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The study, published in the journal Nutrients, found that runners who drank cloudy apple juice saw their intestinal barrier function recover more quickly after exercise than those who drank the sports drink, despite both drinks containing the same amount of sugar overall.
Levels of bacterial endotoxins and proteins linked to inflammation were lower three hours after exercise in those who drank apple juice. Apple juice also contains polyphenols — chemicals found in fruit and vegetables that help to protect the heart and reduce inflammation.
Patrick Diel from German Sport University in Cologne, who was behind the study, said: “The research comes at a timely moment for anyone inspired to get more active by the Olympic games, and these findings offer a fresh perspective how to best replenish our bodies. Simply diluting cloudy apple juice and drinking it after playing sports or exercising seems to be an easy and healthy option which supports both gut health and immune function.”
The apple juice given to the athletes was diluted with water, meaning it had the same levels of sugars — fructose, glucose and sucrose — as the sports drink it was compared with. Although sugar disrupts the intestinal lining, scientists said that because apple juice contains whole fruit pulp it irritates the gut less.
The study concluded that the “fruit juice matrix of apple juice may have beneficial effects on the immune system after exercise”, when athletes need to consume carbohydrates and sugars to recover. While water is the safest option for the gut, it does not provide any energy, and the study said that having carbohydrates in the form of fruit juice may compensate for any disruption sugary drinks have on the gut.
Carrie Ruxton, a dietitian, said: “To properly recover after exercise, our bodies need healthy carbohydrates. In light of these findings, I would encourage athletes, fitness enthusiasts and casual gym-goers to add a serving of around 150ml of cloudy apple juice to their sports bottle and top up with tap water for a low-cost and effective sports drink. Not only will this mixture keep us hydrated, it also provides energy-giving natural sugars and polyphenols to promote optimal recovery.”
Sports scientists generally recommend consuming at least 30 grams of carbohydrates per hour during exercise such as marathon running, which equates to about 500ml of sports drink or 300ml of apple juice.