Vitamin D: The Sunshine Vitamin

Vitamin D also known as the “Sunshine Vitamin” is needed for calcium absorption and maintance of adequate serum calcium levels. It also aids in normal mineralization of the bone, bone growth, and bone remodeling, along with numerous other key functions. Currently, research is focused on the benefits to the muscle from Vitamin D. For example, Vitamin D binds to receptors in the muscle which then promote growth and strength. This is a key component to staying active for a lifetime.

How much can I get from sun exposure?
It has been suggested by some vitamin D researchers, for example, that approximately 5-30 minutes of sun exposure between 10 AM and 3 PM at least twice a week to the face, arms, legs, or back without sunscreen usually lead to sufficient vitamin D synthesis.

Individuals with limited sun exposure need to include good sources of vitamin D in their diet or take a supplement to achieve recommended levels of intake. (2011, NIH, Office of Dietary Supplements)

How much do I need per day?
Adequate Intake Level

  • birth to 50 years, 5 µg (200 IU)
  • 51–70 years, 10 µg (400 IU)
  • 71+ years, 15 µg (600 IU)

How much is too much?
Tolerable Upper Intake Level (UL)

  • birth to 12 months 25 µg (1,000 IU/day)
  • children and adults 50 µg (2,000 IU/day)

“Furthermore, a consistent literature indicates physical and athletic performance is seasonal; it peaks when 25-hydroxy-vitamin D [25(OH)D] levels peak, declines as they decline, and reaches its nadir when 25(OH)D levels are at their lowest. Vitamin D also increases the size and number of Type II (fast twitch) muscle fibers.” (2009 Cannell, Athetic Performance and Vitamin D, Offical Journal of the American College of Sports Medicine, 1102-1110)

A 2009 study on adolescent girls found that individuals with higher levels of Vitamin D exhibited more muscle power and force. This was tested by measuring jump height, velocity, and power. (The Journal of Clinical Endocrinology & Metabolism Vol. 94, No. 2 559-563, 2009)