Physical exercise increases the permeability of the gut for particular proteins, Wageningen researchers have discovered. The search for sustainable sources of protein raises questions about their potential health implications. It is therefore important to learn more about the absorption and digestion of proteins. ‘It has been known for some time that physical exertion can lead to an increased permeability for sugars, says PhD researcher Lonneke Janssen Duijghuijsen. ‘The same thing was suspected for proteins, but had not been proven.’
In the study, which is part of the IPOP Customized Nutrition programme, researchers studied the effects of exertion on absorption of proteins. This was done using the allergen Ara h 6, a peanut protein that can cause severe allergic reactions. Ten healthy test subjects had to eat 100 grams of peanuts – about three handfuls – and wash them down with a sugar solution. Then they were allowed to read or use the computer. The test was repeated one week later but this time the test subjects had to cycle for an hour after eating the peanuts.
Blood samples were taken at intervals during both tests. The researchers ascertained the levels of peanut allergen and sugar solution in the blood. The solution contained two sugars: lactulose and L-rhamnosus. The proportions of these two in the blood, the L/R ration, is a measure of gut permeability. Finally, the level of FABP2, a protein released when the gut is damaged, was also measured.
After exercise, more peanut allergen was found in the blood of nearly all the test subjects. Big individual differences were found, ranging from no increase at all to an increase to 150 times the amount. Janssen Duijghuijsen: ‘We found a clear link between the gut permeability and the level of peanut allergen in the blood. There were also signs of damage to the gut.’
Why the gut becomes more permeable after exercise is not yet understood, says Janssen Duijghuijsen. ‘We think it is because less blood flows to the gut. This causes damage to the gut and reduces the amount of energy that goes to the gut. This can cause the connections between intestinal cells to be broken, so that larger molecules can get through.’ According to the researcher, this mechanism could also play a role in exercise-induced anaphylaxis, an extremely serious allergic reaction triggered by exercise.