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The Effect of Potassium Bicarbonate on Bone and Several Physiological Systems During Immobilisation (NUC)

This study has been completed.
European Space Agency
Information provided by:
DLR German Aerospace Center Identifier:
First received: July 4, 2011
Last updated: January 10, 2012
Last verified: January 2012

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 goldstandard of simulating weightlessness within earthbound conditions.

Condition Intervention
Bone Metabolism
Acid- Base Balance
Muscle Metabolism
Muscle Strenght, Muscle Power and Muscle Volume
Protein Metabolim
Body Weight and Body Composition
Cardiovascular System
Neuro- Vestibular System
Dietary Supplement: Potassium Bicarbonate

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Open Label
Primary Purpose: Basic Science
Official Title: The Effect of Potassium Bicarbonate on Bone and the Immune System During 21 Days of 6° Head- Down- Tilt Bedrest (HDT- Bedrest)

Resource links provided by NLM:

Further study details as provided by DLR German Aerospace Center:

Primary Outcome Measures:
  • The reduction of the immobilisation induced bone loss by supplementing an alkaline salt (potassium bicarbonate) [ Time Frame: 21 days of HDT- Bedrest ]
  • The influence of KHCO3 on markers of bone formation and bone resorption [ Time Frame: 21 days of HDT- Bedrest ]
  • Determination of the effects of KHCO3- supplementation on the acid base balance [ Time Frame: 21 days of HDT- Bedrest ]

Secondary Outcome Measures:
  • Influence of KHCO3 on bone mass, bone mineral density and bone strength [ Time Frame: 21 days of HDT- Bedrest ]
  • Determination of effects of KHCO3 on muscle strength, muscle power and muscle volume [ Time Frame: 21 days of HDT- Bedrest ]
  • Determine the effects of KHCO3 on body composition and body weight [ Time Frame: 21 days of HDT- Bedrest ]
  • Determine the effects of KHCO3 on the cardiovascular system [ Time Frame: 21 days of HDT- Bedrest ]
  • Determine the effects of KHCO3 on the neuro- vestibular system [ Time Frame: 21 days of HDT- Bedrest ]
  • Determination of effects of KHCO3 on protein and muscle turnover [ Time Frame: 21 days of HDT- Bedrest ]

Enrollment: 8
Study Start Date: February 2010
Study Completion Date: October 2010
Primary Completion Date: October 2010 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Active Comparator: Potassium Bicarbonate Dietary Supplement: Potassium Bicarbonate
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
No Intervention: Control Dietary Supplement: Potassium Bicarbonate
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

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 defiecient intake of calcium, energy and fluid and the abendant 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 repsect 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, mimicing 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, calciumconcentration 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 meatbolism while blood gas analysis togehter 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.


Ages Eligible for Study:   20 Years to 45 Years   (Adult)
Sexes Eligible for Study:   Male
Accepts Healthy Volunteers:   Yes

Inclusion Criteria:

  • healthy male subjects
  • age: 20- 45
  • weight 65- 85 kg
  • height: 158- 190 cm
  • BMI 20- 26 kg/m2
  • no high performance sports
  • non- smoking (minimum 6 months prior to study start)
  • willing to complete both parts of the study
  • presentation of social security and criminal record
  • successful completion of medical and psychological screening
  • signed informed consent

Exclusion Criteria:

  • drugs- and alcohol abuse
  • antiinflammatory drugs taken during the study
  • vegetarianism, veganism
  • migraine
  • psychical illness in the past Psychische Erkrankung in der Vergangenheit
  • claustrophobia
  • hiatal hernia
  • gastroesophageal reflux
  • diabetes mellitus
  • Rheumatic disease
  • muscle or joint disease
  • disc prolapse
  • orthostatic intolerance
  • Hyperlipidaemia
  • renal disease
  • thyroid dysfunction
  • hyperhomocysteinaemia
  • hyper-/hypouremia
  • hyper-/hypocalciaemia
  • anaemia
  • hypoferremia
  • Vitamin D deficiency
  • deviation of blood gases from normal values (pH 7,38 - 7,42; pO2 79 - 98 mmHg; pCO2 34 - 45 mmHg; HCO3 20 - 28 mmol/l; Base excess ± 2 mmol/l)
  • risk of thrmobosis
  • chronic back pain
  • bone fracture within one year prior to study start
  • bone mineral density 1,5 SD ≤ t-Score
  • metal implants or other osteosynthesis material
  • subject within another clinical trial within 2 months prior to study start
  • any other status which according to the apprehension of the principal investigator leads to the exclusion of the subject
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Please refer to this study by its identifier: NCT01509456

German Aerospace Centre (DLR)
Cologne, Germany, 51147
Sponsors and Collaborators
DLR German Aerospace Center
European Space Agency
Principal Investigator: Francisca May, Dr. German Aerospace Centre, Institute of Aerospace Medicine (DLR)
  More Information

Responsible Party: Institute of Aerospace Medicine, Space Physiology, DLR German Aerospace Center Identifier: NCT01509456     History of Changes
Other Study ID Numbers: AO-2004-068 (MAP) 
Study First Received: July 4, 2011
Last Updated: January 10, 2012

Keywords provided by DLR German Aerospace Center:
bone metabolism
potassium bicarbonate
alkaline salt
acid base balance
bed rest

Additional relevant MeSH terms:
Body Weight
Signs and Symptoms processed this record on February 23, 2017