Plain English Summary
Vitamin D deficiency is a public health problem. There are many consequences of vitamin D deficiency. Many studies have investigated the effects of vitamin D supplementation on muscle strength, but the results remain controversial. There is also contradictory data about which administration route is healthier. We aimed to compare the effects and safety of single high-dose with daily low-dose oral colecalciferol on 25(OH)D levels and muscle strength in postmenopausal women with vitamin D deﬁciency or insufﬁciency.
Background and study aims
Vitamin D is involved in calcium absorption, immune function and protecting bone, muscle and heart health. Vitamin D deficiency is a common health problem. Vitamin D supplements are used to improve vitamin D status; however, there is contradictory information on what doses to give and how often they should be given. Many studies have investigated the effects of vitamin D supplementation on muscle strength, but the results remain controversial. We aimed to compare the effects and safety of a single high dose with daily low doses of oral colecalciferol (vitamin D3) on vitamin D levels and muscle strength in postmenopausal women with vitamin D deficiency or insufficiency.
Who can participate?
Postmenopausal women who had low vitamin D levels in their blood
What does the study involve?
One group received a low dose of vitamin D3 once a day by mouth and the second group received a single high dose of vitamin D3 by mouth. Blood vitamin D levels and muscle strengths were measured at before the women took the vitamin D3 and at the 4th and 12th weeks.
What are the possible benefits and risks of participating?
Participants will receive treatment for their vitamin D deficiency. Side effects from vitamin D supplements are not common and occur almost exclusively in people who take long-term, high-dose supplements without monitoring blood levels. Elevated calcium levels, nausea, vomiting, poor appetite, stomach pain, constipation or diarrhea, kidney injury are potential side effects of excessive vitamin D intake.
Where is the study run from?
The Endocrinology and Metabolism Clinic of Ankara Diskapi Training and Research Hospital
When is the study starting and how long is it expected to run for?
November 2014 to February 2016
Who is funding the study?
There is no funding source for the study. The study coordinators will cover all expenses and participants will not be responsible for any expenses.
Who is the main contact?
Dr Mahmut Apaydin, firstname.lastname@example.org
Dr Mahmut Apaydin
Diskapi Training and Research Hospital
The effects of single high-dose or daily low-dosage oral colecalciferol treatment on vitamin D levels and muscle strength in postmenopausal women
Many studies have investigated the effects of vitamin D supplementation on muscle strength, but the results remain controversial. We aimed to compare the effects and safety of single high-dose with daily low-dose oral colecalciferol on 25(OH)D levels and muscle strength in postmenopausal women with vitamin D deﬁciency or insufﬁciency
Medical Ethics Committee of Ankara Diskapi Training and Research Hospital, 26/01/2015, 19/36
Non-randomised parallel-arm study
Primary study design
Secondary study design
Non randomised study
Patient information sheet
Not available in web format, please use contact details to request a participant information sheet
Effect on muscle strength of vitamin D supplementation
60 healthy postmenopausal women who had serum vitamin D levels <20 ng/ml (50 nmol/l) were enrolled in the study. Group 1 (n=32) was given daily oral dosages of 800 IU vitamin D3, and group 2 (n=28) was given a single oral dose of 300,000 IU vitamin D3. Serum vitamin D levels and muscle strengths were measured at baseline, week 4 and week 12.
Primary outcome measure
25OH vitamin D levels 3 months after treatment
Secondary outcome measures
Muscle strength 3 months after treatment. Muscle strength tests were performed at 60° using a Biodex system 3 isokinetic dynamometer.
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
3. Aged 50-68 years
4. Vitamin D level <20 ng/ml (50 nmol/l)
Target number of participants
Participant exclusion criteria
1. Individuals who had granulomatous conditions, thyroid disease, malabsorption syndromes, liver disease, kidney disease, diabetes or postural instability (cerebellar disease, vestibular disease, vitamin B12 deficiency, drugs)
2. Individuals taking anticonvulsants, calcium or vitamin D supplements, barbiturates, or steroids in any form
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Diskapi Training and Research Hospital
İrfan Bastug Cad. 06110, Altındag/ Ankara, Turkey
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
We are planning to publish it in BMC Endocrine Disorders
IPD sharing statement
The datasets generated during and/or analysed during the current study will be available upon request from Dr Mahmut Apaydin.
Intention to publish date
Participant level data
Available on request
Basic results (scientific)
Pretreatment vitamin D levels did not differ between the two groups (10.2±4.4 ng/mL (25,4±10,9 nmol/L); 9.7±4.4 ng/mL (24,2±10,9 nmol/L), p>0.05). A significant increase in vitamin D levels was observed in both groups at 4 and 12 weeks after vitamin D3 treatment. The increase in the single-dose group was significantly higher than the daily low-dosage group at the 4th week (35.9±9.6 ng/mL (89,6±23,9 nmol/L), 16.9±5.8 ng/mL (42,1±14,4 nmol/L), p=0.01). The increase in the single-dose group was significantly higher than in the daily low dosage group at the 12th week (23.4±4.7 ng/mL (58,4±11,7 nmol/L), 19.8±7.2 ng/mL (49,4±17,9 nmol/L), p=0.049). The quadriceps muscle strength score increased significantly in the daily group at the 4th week (p=0.038). The hamstring muscle strength score increased significantly in the daily group at the 12th week (p=0.037).