Up to 42% of American adults are deficient in vitamin D, with even higher rates among women. This "sunshine vitamin" affects far more than just your bones.
Why Vitamin D Matters
Vitamin D is actually a hormone that affects nearly every cell in your body:
- Immune function and autoimmunity
- Mood and mental health
- Bone health and calcium absorption
- Muscle strength and pain
- Fertility and pregnancy outcomes
- Cancer prevention
Who's at Risk?
- People living in northern latitudes
- Those with darker skin
- People who spend most time indoors
- Those with digestive disorders
- Women over 50
- People taking certain medications
Optimal Vitamin D Levels
Most labs list 30 ng/mL as the minimum normal, but research suggests optimal levels are 40-60 ng/mL for most health benefits.
Testing
The test you need is 25-hydroxyvitamin D (also called 25(OH)D). This measures your body's vitamin D stores.
Symptoms of Deficiency
- Fatigue and weakness
- Bone and muscle pain
- Depression and mood changes
- Frequent illness
- Slow wound healing
- Hair loss
References
- Holick, M. F. (2007). Vitamin D deficiency. New England Journal of Medicine, 357(3), 266-281.
- Forrest, K. Y., & Stuhldreher, W. L. (2011). Prevalence and correlates of vitamin D deficiency in US adults. Nutrition Research, 31(1), 48-54.
- Aranow, C. (2011). Vitamin D and the immune system. Journal of Investigative Medicine, 59(6), 881-886.
