Healthy gut thanks to polyphenols! Research team studies protective effects of apple juice on the intestinal barrier during exercise

In addition to digestion and nutrient absorption as well as the regulation of water balance, the human intestine has essential functions for the entire immune system. An intact intestinal barrier is of great importance for this, thanks to which pathogenic germs and their toxins are warded off. If the body is subjected to high levels of stress - such as during marathon runs - this affects the intestinal barrier and can lead to an increased transfer of bacterial toxins into the bloodstream. Similar effects have been demonstrated with high-fat as well as high-fructose diets. The increased endotoxin concentrations in the blood can result in inflammatory reactions.

Research team studies protective effects of apple juice on the intestinal barrier during exercise
© Forschungskreis der Ernährungsindustrie e.V. (FEI)
Source:  Company news

After intense exertion, sports enthusiasts like to turn to carbohydrate-containing drinks such as special sports drinks and shakes - or to natural alternatives in the form of fruit juices or fruit juice spritzers such as apple spritzer. Their consumption is described in a large number of studies as promoting regeneration and is therefore recommended. However, this positive effect is countered by the finding that carbohydrate-containing beverages and physical exertion can increase intestinal permeability; a combinatorial effect of sugar and exertion is also suspected. At the same time, there are findings from preliminary studies that fruit juice in turn exerts a positive influence on the intestinal barrier in that an increase in intestinal permeability caused by carbohydrates is reduced by the secondary plant compounds contained in juice - and here in particular polyphenols from apple juice.

But to what extent do carbohydrate-containing beverages in combination with intensive physical exercise influence the intestinal barrier? To what extent do polyphenols from apple juice counteract this? Can even the preventive intake of polyphenols from apple juice prevent the increased intestinal permeability induced by exercise or oxidative stress? Would fruit juices thus be superior to special sports drinks and shakes?

These and other questions arising from this complex process are being investigated by a research team from the German Sport University Cologne and the University of Hanover as part of a project funded by the Industrial Cooperative Research (IGF): The aim is to investigate in human intervention studies how the fruit juice matrix influences the permeability of the intestinal barrier and the resulting endotoxinemia. The studies will be conducted in subjects at rest and after intense activity. In a subproject, effects will also be investigated in athletes completing ultra-long distance runs of 160 or 230 km. In addition, the specific effects of the polyphenols contained in naturally cloudy apple juice on intestinal permeability will be investigated in vitro using an established intestinal model. The focus will be on detecting a possible preventive effect, which has already been shown for liver cells.

The proof expected as a result of the research work that fruit juices and fruit juice spritzers are superior to special sports drinks in terms of regeneration after sports activities will be able to make a decisive contribution to their positive image. The fruit juice industry, which is strongly influenced by medium-sized companies, can use the knowledge gained from the project to optimize its production processes with regard to the yield of valuable ingredients. In addition, the findings could be used for the targeted development of optimized fruit juice-based products.

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