The Effect of Potassium Bicarbonate on Bone and Several Physiological Systems During Immobilisation
Condition: Bone Diseases, Metabolic; Acid-Base Imbalance; Muscular Atrophy; Sprains and Strains; Protein Metabolism; Body Weight Changes; Cardiovascular Abnormalities
MeSH terms: Bone Diseases; Bone Diseases, Metabolic; Muscular Atrophy; Cardiovascular Abnormalities; Metabolic Diseases; Acid-Base Imbalance; Body Weight; Body Weight Changes; Sprains and Strains
Study type: Interventional

Summary: 
      Mainly due to the absence of gravitational forces in weightlessness, astronauts suffer from
      an increased bone loss- negatively affecting health and vitality during a mission. The
      development of effective countermeasures to this loss includes many different aspects like
      sports but also nutrition.

      Alkaline salts, abundant in fruits and vegetables, have shown to have positive effects on
      markers of bone turnover of postmenopausal women but also men and younger adults. With the
      current study the effects of a potassium bicarbonate supplementation added to a standardised,
      strictly controlled, definite diet of healthy, young men, should be verified within 21 days
      of 6°- HDT- Bedrest- the gold standard of simulating weightlessness within earthbound
      conditions.
    

Detailed description: 
      Astronauts in space suffer from an increased bone loss which is mainly related to the absence
      of gravitational forces. This increased bone reduction is accompanied by an higher
      concentration of calcium in urine and in this respect enhancing the risk of renal stones. Due
      to the fact, that bones´ regeneration does not occur rapidly even after returning to earth,
      astronauts face an increased risk of osteoporosis.

      Nutritional factors such as a deficient intake of calcium, energy and fluid and the abundant
      intake of table salt exhibit additional negative effects on bone. Results of several studies
      consistently show the negative effects of acids on bone (increased bone loss). With respect
      to space missions of longer duration one big challenge is the development of countermeasures
      for the negative consequences of weightlessness on bone.

      As not all needed experiments for the development of countermeasures can be conducted in
      space, simulation models of weightlessness such as 6° Head- Down- Tilt- Bedrest (HDT-
      Bedrest) have been implemented on earth, miming some physiological conditions of
      weightlessness such as unloading and immobilisation of the lower parts of the body and the
      fluid shift.

      Alkaline salts, such as potassium bicarbonate (KHCO3), demonstrate positive effects on bone
      when being supplemented to postmenopausal women. Apart from the positive effects on markers
      of bone turnover, calcium concentration in urine could be reduced. Thus, the main aim of the
      present study was to reduce the immobilization induced bone resorption through an alkalizing
      effect of the alkaline salt KHCO3's supplementation during Head- Down- Tilt- Bedrest (HDT-
      Bedrest)-a leading simulation model of weightlessness.

      The crossover designed study consisted of two parts of equal length (36 days)- 7 days of
      adaptation, 21 days of HDT- Bedrest, 6 days recovery and 2 days of long- term follow- up.
      Both study parts only differed in the HDT- period, where one group of the 8 healthy, young,
      male participating subjects was supplemented with 90 mmol KHCO3 daily (3 times a day 30 mmol
      KHCO3 diluted in 200 ml tab water, supplemented together with the main meals), while the
      other group only received 200 ml of tab water without any supplementation (Control group).

      The measurements of bone formation markers as well as bone resorption markers in blood and
      urine supply insight into the influences of the supplementation on bone metabolism while
      blood gas analysis together with the pH- values of the 24h- urine point out the alkalising
      effects of KHCO3. Further physiological systems like protein and muscle metabolism, body
      weight and body composition, circulation and the neuro- vestibular system are simultaneously
      under investigation.
    

Intervention name(s): Potassium Bicarbonate
Intervention type(s): Dietary Supplement
Intervention description(s): 90 mmol daily, effervescent tablets 30 mmol diluted in 200 ml tab water supplemented three times a day together with the main meals for 21 days of HDT- bedrest
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: bone metabolism; potassium bicarbonate; alkaline salt; acid base balance; bed rest