Nitrate and sucrose: GI function

The gastrointestinal (GI) tract plays an important role in the human body. The GI wall regulates the uptake of nutrients, and also has a very important function as a barrier between the internal and external environment. The penetration of harmful substances and microbiota from the GI lumen (external environment) into the systemic circulation (internal environment) depends on this barrier.

During high-intensity exercise, GI complaints and intestinal injury frequently occur, thereby hampering exercise performance. Splanchnic hypoperfusion, resulting in intestinal damage, has been postulated as one of the key underlying mechanisms for exercise associated GI symptoms. Attenuating such hypoperfusion therefore appears a promising strategy to reduce GI injury and its negative effects on performance. During episodes of splanchnic hypoperfusion, the synthesis of nitric oxide (NO) is suppressed. A previous study of our group found that supplementation with L-citrulline as a donor of the endogenous NOS dependent pathway lead to improved splanchnic blood flow and reduced intestinal damage during high intensity exercise. By acting as a local NO donor, through the nitrate-nitrite-NO pathway, dietary nitrate may also increase microcirculatory blood flow in the splanchnic area. Alternatively, the ingestion of carbohydrates will directly stimulate an increase in splanchnic microcirculatory blood flow, simply through the normal digestive processes taking place. Thus, both strategies may effectively reduce intestinal damage, and as such prove valuable in reducing the negative effects of exercise on the gut.



The aim of this study is to investigate the effects of both dietary nitrate and sucrose ingestion on splanchnic perfusion and intestinal (enterocyte) damage during high intensity exercise.

We hypothesize that both nitrate and sucrose will reduce GI damage and improve GI blood flow during high-intensity exercise compared with placebo.

Screening: 1 hour (inclusive Wmax test)

3 test days: each 5 hours, baseline blood sample + 3 hours of blood sampling and tonometry measurements every 20 min (total 9 samples); 1 hour prior to cycling, 1 hour during cycling and 1 hour post cycling.

On each test day the subjects will perform 60 min of cycling at 70% Wmax, were the effect of each intervention on GI parameters will be investigated:

NIT: 1.1 g of NaNO3 (sodium nitrate) dissolved in 200 mL water 2.5 h prior to exercise. 200 mL water provided both 15 min prior and 30 min into exercise.

SUC: 1.1 g of NaCl (placebo) dissolved in 200 mL water 2.5 h prior to exercise. 20 g sucrose dissolved in 200 mL water provided both 15 min prior and 30 min into exercise.

PLA: 1.1 g of NaCl (placebo) dissolved in 200 mL water 2.5 h prior to exercise. 200 mL water provided both 15 min prior and 30 min into exercise.