Effect of Vitamin D on Body Composition and Functionality of Older Adults

This randomized controlled study investigated the effects of vitamin D3 supplementation on muscle strength, body composition, and functional performance in older adults with obesity. Vitamin D deficiency is highly prevalent in this population and has been associated with reduced skeletal muscle mass, decreased physical performance, increased fat accumulation, and progression toward frailty. Improving vitamin D status may contribute to better musculoskeletal health and improved physical function.

Participants received 10,000 International Units (IU) per day of vitamin D3 for a total period of 12 weeks. All assessments were conducted at baseline and at week 12. Handgrip strength was measured using a Jamar hand dynamometer as an indicator of muscle strength. Skeletal muscle mass, body fat percentage, visceral fat index, metabolic age, and related measures were obtained via Bioelectrical Impedance Analysis (BIA). Anthropometric variables including weight, body mass index (BMI), waist circumference, abdominal volume index (AVI), and body adiposity index (BAI) were also recorded.

Functional status was assessed using the Short Physical Performance Battery (SPPB), a validated tool consisting of balance, gait speed, and chair stand tests. The SPPB ranges from 0 to 12 points, with higher scores indicating better physical performance.

Serum concentrations of 25-hydroxyvitamin D [25(OH)D] were evaluated using standardized laboratory techniques to determine changes in vitamin D status associated with supplementation.

This study seeks to clarify whether vitamin D3 supplementation can improve muscle strength, muscle mass, functional performance, and body composition among older adults with obesity, and to better understand the role of vitamin D in age-related musculoskeletal decline.

Inclusion criteria

• Adults aged 60 years or older.
• Diagnosis of obesity (BMI ≥ 30 kg/m²).
• Patients attending the outpatient clinic of IMSS No. 24 in Miahuatlán de Porfirio Díaz, Oaxaca.
• Able to perform physical and functional tests (handgrip, SPPB).
• Capable of providing informed consent.
• Willing to comply with the intervention and attend baseline and 12-week evaluations.

Exclusion criteria

• Known diagnosis of hypercalcemia or disorders of calcium metabolism.
• Current use of high-dose vitamin D supplementation or medications affecting vitamin D metabolism.
• Severe renal or hepatic disease.
• Active cancer treatment.
• Neurological or musculoskeletal conditions that impair mobility or functional testing (e.g., recent fractures, severe osteoarthritis, stroke with major disability).
• Cognitive impairment preventing the understanding of instructions or informed consent.
• Any medical condition that, in the judgment of investigators, would interfere with participation or pose additional risk.
• Participation in another clinical trial during the study period.