Effects of Vitamin D on Skeletal Muscle Strength in Resistance Trained Adult Females

Study Overview
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Brief Summary
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The majority of vitamin D research has been done in non-athletic populations, particularly older populations, to analyze muscle weakness, pain, balance, and fractures. It has been reported that over a billion people worldwide are vitamin D deficient, including 36-70% of the young adult population. Previous literature also suggests that, even among healthy athletes, over 50% of subjects sampled had inadequate or insufficient vitamin D levels. Vitamin D deficiency can occur in young women, including pregnant women, and the risk of deficiency is even higher with advancing age in a woman's lifecycle. It is known that preserving skeletal muscle (SM) function is critical for women of all ages to prevent sarcopenia. Two factors in preserving SM are protein intake and resistance training. Relatively unknown are the actions of Vitamin D on SM function. Vitamin D deficiency can have a negative effect on SM function . However, additional research is needed to investigate the increase in SM strength when the serum concentration of vitamin D is improved. It is possible that an athlete may require an increased intake of vitamin D to assure adequate availability and storage for optimal performance; however, is known that food sources of vitamin D are limited in sufficient quantity to meet these requirements. Athletes who are insufficient will require a supplement of vitamin D3 for up to 5000 IU/day for at least eight weeks, to potentially reach optimal levels, then 1000-2000 IU/day for maintenance.

Detailed Description
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The investigators seek to determine if women with a vitamin D serum concentration lower than 50 nmol/L and who regularly resistance train will improve strength performance outcomes when taking a daily supplement of 5000 IU of vitamin D3 over an 8-week period, as compared to the same demographic of women who do not take a daily supplement of vitamin D3. The participants will receive Nature's Bounty Vitamin D3, 5,000 IU, soft gels and the PI will be providing the supplement and the placebo. A pre-intervention data collection and screening (PRE) will be performed involving blood draw, food log, a body composition test (using Dual-energy X-ray absorptiometry [DEXA]), and a BioDex testing to determine maximal muscle strength. Following PRE testing, the participants will be divided into one of two groups: 1) taking a vitamin D3 supplement (n=20) or, 2) taking a placebo. The participants will be instructed to continue their resistance training regimen. Training will be logged and turned in to the PI weekly. The participants will perform a post-intervention data collection (POST), which includes the same test from PRE. Variables of interest will include changes in: 1) blood level of vitamin D, 2) muscle and fat mass, and 3) leg strength/power during the BioDex test.

Official Title
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Effects of Vitamin D on Skeletal Muscle Strength in Resistance Trained Adult Females

Conditions
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Nutrition Status, Nutritional Requirements, Sports Nutritional Sciences

Intervention / Treatment
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* Dietary Supplement: Nature Made Vitamin D3 5,000 IU, 125mcg
* Dietary Supplement: Placebo


Participation Criteria
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Eligibility Criteria
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Inclusion criteria will include: Participant will need to answer yes to the following items: female not pregnant between the ages of 19-55 years old a non-smoker currently resistance training (i.e., lifting weights) for more than 2 days/week for a minimum of > 24 months free of any known overt cardiovascular or metabolic disease not an active user of tanning beds not consuming now or haven't consumed within the last 6 months, a vitamin D or multivitamin supplement or a form of a supplement with vitamin D added not consuming now or haven't consumed within the last 2 months, agents that affect hormones (testosterone boosters, growth hormone boosters, etc.) (does not include birth control/oral contraceptives) not allergic to rubbing alcohol Exclusion criteria will include: 1) Outside of study inclusion parameters

Ages Eligible for Study
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Minimum Age: 19 Years
Maximum Age: 55 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Parallel Assignment
Interventional Model Description: A two-arm parallel assignment; one group receives the treatment (vitamin D3 supplement 5,000IU/day) and one group receives the placebo (control).
Masking: Double


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Treatment Group<br>Participants in this group will be administered an oral Vitamin D3 supplement; 5,000 IU/ day. The participants will take the supplement themselves, orally, once per day, for 8 weeks. | Dietary Supplement: Nature Made Vitamin D3 5,000 IU, 125mcg<br>* Taking a 5,000 IU oral supplement of Vitamin D3, daily, for 8 weeks, may improve strength performance in women who have and are continuing a resistance trained workout regimen. After blood vitamin D levels have been raised to an optimal range, a lower dosage may be assigned as needed from 5,000 IU per day to 1,000-2,000 IU per day.<br>* Other names: Swanson;|
| Placebo Comparator: Control Group<br>Participants in this group will be administered an oral, soft-gel, lookalike placebo. The participants will take the supplement themselves, orally, once per day, for 8 weeks. | Dietary Supplement: Placebo<br>* Resistance trained women may not improve their strength performance with low levels of vitamin D in the blood.<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Biodex Strength performance change | Taking a daily supplement of 5,000 IU of vitamin D3 may change strength outcomes measured in newton meters (Nm). | 8 weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Serum 25(OH)D status | Taking a daily supplement of 5,000 IU of vitamin D3 may change blood levels of vitamin D. | 8 weeks | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Athlete, Nutrition, Supplement, Supplementation, Vitamin D, Strength Training, Resistance Training, Women, Female