Vitamin D Supplementation and Muscle Characteristics in Trained Subjects

Effects of 12 Weeks of Vitamin D Supplementation on Muscle Characteristics in Trained Subjects

This study evaluates the effect of vitamin D supplementation on outcomes muscle performance and characteristics in 70 trained healthy individuals (18-40 years of age). Subjects will be allocated to ingest either vitamin D (35) or placebo (35) in a double-blinded fashion

Study Overview

• Status: Completed
• Conditions: Healthy Subjects, Trained
• Intervention / Treatment: Dietary supplement: Vitamin D3; Dietary supplement: Placebo

Detailed Description

Vitamin D insufficiency compromises muscle functionality, leading to changes in muscle mass and strength, manifested at the cellular level. While this is increasingly recognized as a problem for individuals with vitamin D deficiency (typically 25(OH)D < 25 nmol/l), there is no general consensus for the remainder of the vitamin D-spectra. This lack of knowledge is probably linked to the variation in protocols of studies that have investigated the physiological role of vitamin D. These variations vary from aspects such as interventional vs observational studies to aspects related to subject characteristics such as age, health and training status. In this project, we will evaluate the effects of 12 weeks of vitamin D supplementation (2000 IU/day) on muscle performance and characteristics in 70 trained healthy individuals (18-40 years of age). Subjects will be allocated to either a vitamin D (35) or a placebo group (35) in a double-blinded manner. They will be instructed to continue their ordinary modes and frequency of training.

We anticipate baseline vitamin D levels in blood (and hence changes in vitamin D obtained through supplementation), measured as 25(OH)D, to be a major determinant of the efficacy of the intervention. This means that we expect individuals with low baseline levels of 25(OH)D to display more pronounced changes in functional and biological outcome measures than those with high baseline values. Such a scenario could be related to an inability of our protocol to increase blood levels of 25(OH)D in individuals with higher physiological levels of vitamin D (which essentially means that ingestion of vitamin D3 is leveled out or exceeded by elimination of vitamin D derivatives). Alternatively, it may be related to inabilities of tissues to respond to the resulting elevation in vitamin D levels. To study the individual variation in vitamin D responses, data on both functional and biological variables will be divided into quartiles based on baseline 25(OH)D-levels, whereupon comparisons will be made between the low-end and high-end quartile. Individual variation will also be assessed using a mixed model approach.

• Study Type: Interventional
• Enrollment (Actual): 71
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Norway
  • Lillehammer, Norway
    • Lillehammer University College

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 40 years (Adult)
• Accepts Healthy Volunteers: Yes
• Genders Eligible for Study: All

Description

Inclusion Criteria:

- Individuals that have performed strength and / or endurance exercise training at least 3 X week for at least 6 months prior to the study

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Vitamin D3; Vitamin D3 capsules for 12 weeks (2000 IU daily, equivalent to 50 ug)	Dietary supplement: Vitamin D3; Vitamin D3 dissolved in olive oil, encapsuled; Other Names: cholecalciferol
Placebo Comparator: Placebo; Placebo capsules for 12 weeks (the number of daily capsules will match that of the vitamin D-group)	Dietary supplement: Placebo; Olive oil, encapsuled

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Lower body maximal dynamic strength	Changes in the ability of lower body muscles to exert maximal force during a dynamic movement	wk 0, wk12
Muscle fiber composition	Changes of the muscle fiber composition of musculus vastus lateralis in a 2X to 2A direction, measured using mRNA profiling	wk0, wk12

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Gene expression in muscle	Changes in RNA abundances in musculus vastus lateralis, measured at the level of single genes	wk0, wk12
Vitamin D in blood	Changes in levels of 25(OH)D in blood	wk0, wk12
Steroid hormones in blood	Changes in levels of steroid hormones in blood	wk0, wk12
Muscular endurance	Changes in the ability of muscles to perform repeated dynamic contractions at submaximal loads (50% of 1 repetition maximum)	wk0, wk12
Upper body maximal dynamic strength	Changes in the ability of upper body muscles to exert maximal force during dynamic movements	wk0, wk12

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Training diary	Diary that includes information on type of training, duration and intensity performed	From 1 month prior to study to post test (w12)
Vitamin D-intake diary	Diary withthat includes information on approximate intake of vitamin D from sources other than the study-specific supplement, including ingestion of fish, seafood and vitamin D-supplement	From 1 month prior to study to post test (w12)
Sun exposure diary	Diary that includes information on exposure to solarium or sun in countries south of Norway	From 1 month prior to study to post test (w12)

Collaborators and Investigators

• Sponsor: Inland Norway University of Applied Sciences
• Collaborators: Sykehuset Innlandet HF
• Investigators: Principal Investigator: Håvard Nygaard, MSc, Inland Norway University of Applied Sciences

Study record dates

Study Major Dates

• Study Start: November 1, 2015
• Primary Completion (Actual): February 28, 2017
• Study Completion (Actual): February 28, 2017

Study Registration Dates

• First Submitted: November 5, 2015
• First Submitted That Met QC Criteria: November 5, 2015
• First Posted (Estimate): November 6, 2015

Study Record Updates

• Last Update Posted (Actual): September 8, 2017
• Last Update Submitted That Met QC Criteria: September 7, 2017
• Last Verified: March 1, 2017

More Information

Terms related to this study

• Keywords: Vitamin D; Strength; Endurance; Muscle; Muscle fiber
• Additional Relevant MeSH Terms: Physiological Effects of Drugs; Micronutrients; Vitamins; Bone Density Conservation Agents; Calcium-Regulating Hormones and Agents; Vitamin D; Cholecalciferol
• Other Study ID Numbers: Trainsome 2015#006