Mars-500
«Mars-500» project
Simulation of a manned flight to Mars
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The experiment “Long-term control of total body Na+ and K+ content and body fluid homeostasis in humans”

Cardiovascular disease is the major cause of death worldwide and is a dramatic socio-economic challenge. In industiralized countries, 55% of all deaths are cardiovascular deaths. Besides diabetes and obesity, arterial hypertension is the major risk factor for cardiovascular disease. Therefore, the pathogenesis of arterial hypertension has been an intensive area of research. Despite tremendous intellectual and material efforts ≈90% of patients suffering from elevated blood pressure are still diagnosed with essential hypertension, which means that the underlying pathophysiology and the molecular mechanisms are unclear.

Salt intake has been implicated in blood pressure regulation and hypertension for over 5000 years but it is still an open question whether high dietary salt intake affects total body water and consequently blood pressure.

Highslide JS
The average daily ration of one crew member on a diet Dr. Tize. From left to right - breakfast, lunch and dinner. In the background bite (can be eaten throughout the day between meals) .
photo: IBMP

The unique opportunity that the environment of a simulated flight to Mars provides, namely the constancy of external parameters, restricted basic life resources, compliance of specifically selected trained subjects may help to unravel the relationship between different dietary salt intake levels, total body water and blood pressure in healthy individuals.

The diets for the Mars500 volunteers have been designed in such a way that salt content is reduced in three steps from daily 12 g to 9 g to 6 g NaCl, while all other nutrients are maintained at a certain level. 24-hour urine samples are collected and blood pressure is monitored on a daily basis. Bioimpedance analyses to control total body water are performed weekly. This day-to-day experimental approach allows us to investigate changes in total body sodium content in the subjects in conjunction with the effects of dietary salt restriction on blood pressure.

Therefore, the Mars500 experimental approach for the first time allows investigation of physiological regulatory patterns of salt and water homeostasis and their linkage with salt-sensitive hypertension on the long-term in humans.

Jens Titze, University of Erlangen, Germany.

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