Changes in Acid Base Status During High Salt Intake

Study Overview
=================
Brief Summary
-----------------
The study aimed to examine the effects of an alkalinisation of a NaCl (sodium chloride, salt)-rich diet on acid base status, bone metabolism, protein turnover and other influenced physiological systems. Due to increased urinary calcium excretion and bone resorption a high NaCl-intake is considered as a risk factor for osteoporosis. On the contrary an alkaline diet is known to have a beneficial influence on bone metabolism. Therefore the investigators hypothesized that an alkaline diet can reduce NaCl-induced bone resorption. 8 healthy male volunteers took part in a stationary study carried out in the metabolic ward of the German Aerospace Center. The study consisted of 2 campaigns, each lasting 16 days. Both campaigns were divided into 5 days of adaptation, 10 days of intervention and 1.5 days of stationary recovery. During the intervention period the volunteers diet was NaCl-rich (7.7 mmol Na/kg body weight/day) and supplemented in one campaign by 90 mmol potassium bicarbonate (KHCO3) in a randomized cross-over design. The other campaign served as control. Bone metabolism was studied by bone formation markers in the fasting morning blood and 24h-urinary bone resorption markers. Acid base status was assessed by blood gas analyses in the fasted and the postprandial state as well as urinary markers. Protein turnover was studied with stable isotopes. Further physiological systems like energy metabolism and the cardiovascular system are also under investigation.

Conditions
-----------------
Low Grade Metabolic Acidosis

Intervention / Treatment
-----------------
* Dietary Supplement: High NaCl + KHCO3
* Other: Control: high NaCl


Participation Criteria
=================
Eligibility Criteria
-----------------
Inclusion Criteria: healthy males 19 - 35 years 65 - 85kg 170 - 190 cm successfully completed psychological and medical screening Exclusion Criteria: athletes smoking drug- or alcohol abuse hyperlipidemia renal diseases obesity anemia bone diseases diabetes rheumatism blood donation within three month prior to study start participation in another clinical investigation three month prior to study start

Ages Eligible for Study
-----------------
Minimum Age: 19 Years
Maximum Age: 35 Years

Sexes Eligible for Study
-----------------
Male

Accepts Healthy Volunteers
-----------------
Accepts Healthy Volunteers

Study Plan
=================
How is the study designed?
-----------------

Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Campaign 1<br> | Dietary Supplement: High NaCl + KHCO3<br>* 7.7 mmol Na/kgBW/d + 90 mmol KHCO3<br>Other: Control: high NaCl<br>* 7.7 mmol Na/kgBW/d<br>|
| Experimental: Campaign 2<br> | Dietary Supplement: High NaCl + KHCO3<br>* 7.7 mmol Na/kgBW/d + 90 mmol KHCO3<br>Other: Control: high NaCl<br>* 7.7 mmol Na/kgBW/d<br>|

What is the study measuring?
-----------------
Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in daily urinary C- and N-terminal bone collagen telopeptides (mmol/d) |  | Daily for a duration of 16 days | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Serum concentration of bone specific alkaline phosphatase (microg/L) |  | Baseline, after 3, 6, 8, 10 days of intervention, 2 days after finishing the intervention | 
| Daily Nitrogen balance (g/d) |  | Daily for a duration of 16 days | 
| Free cortisol excretion in 24h urine (microg/d) |  | Baseline, after 3, 6, 10 days of intervention | 
| Phenylalanine hydroxylation (micromol/min) |  | Baseline, end of intervention | 
| Systolic blood pressure (bpm) |  | Daily for a duration of 16 days | 
| 24h urinary net acid excretion (mEq/d) |  | Baseline, end of intervention | 
| Serum concentration of N-terminal propeptide Type I (mmol/L) |  | Baseline, after 3, 6, 8, 10 days of intervention, 2 days after finishing intervention | 
| Free cortisone excretion in 24h urine (microg/d) |  | Baseline, after 3, 6, 10 days of intervention | 
| Protein synthesis (micromol/min) |  | Baseline, end of intervention | 
| Protein degradation (micromol/min) |  | Baseline, end of intervention | 
| Diastolic blood pressure (bpm) |  | Daily for a duration of 16 days | 
| Capillary pH |  | Baseline, after 3, 6, 8, 10 days of intervention, 2 days after finishing intervention | 
| Capillary HCO3- Concentration (mmol/L) |  | Baseline, after 3, 6, 8, 10 days of intervention, 2 days after finishing intervention | 
| Capillary Base excess (mmol/L) |  | Baseline, after 3, 6, 8, 10 days of intervention, 2 days after finishing intervention | 
| Capillary pCO2 (mmHg) |  | Baseline, after 3, 6, 8, 10 days of intervention, 2 days after finishing intervention | 
| Capillary pO2 (mmHg) |  | Baseline, after 3, 6, 8, 10 days of intervention, 2 days after finishing intervention |