All About Vitamin D

When it comes to sports nutrition, there are often questions about specific micronutrients and supplements. Vitamin D happens to be included a lot in these conversations simply because of its many benefits and roles in the body. However, it is always important to get your blood work done to see what your levels are to proceed with the next steps. Always ask your doctor about supplementation before taking anything.

What does vitamin D do? It helps with:

• Calcium regulation (aids in absorption)

  • Increases efficiency of calcium binding sites for muscle contraction

• Improves muscle strength by helping increase size and amount of type II (fast twitch) muscle fibers

• Bone health (growth, density, and remodeling)

  • Prevents stress fractures

• Signaling gene response

• Protein synthesis

• Hormone synthesis

• Immune response

• Cell turnover and regeneration

Deficiency Guidelines:

*More than 77% of the general population are insufficient in vitamin D

• Deficiency = <20 ng/mL (50 nmol/L)

• Insufficiency = 20-32 ng/mL (50-80 nmol/L)

• Optimal = >40 ng/mL (100 mol/L)

Symptoms of deficiency can include…

• Muscle weakness

• Frequent stress fractures

• Decreased reaction time

• Poor balance

• High frequency of infectious illness

Recommended Intake:

*Body requires 3000-5000 IU/day

The Endocrine Society recommends…

• Children (0-18yrs) = 400-1000 IU/day

• Adults (19-70) = 1500-2000 IU/day

• Older adults (>70) = 1500-2000 IU/day

• Pregnancy/lactation =

  • (14-18 yrs) 600-1000 IU/day

  • (19-50 yrs) 1500-2000 IU/day

*Athletes may require up to 5000 IU per day for 8 weeks, then 1000-2000 IU/day for maintenance 

Upper Limit:

• Children (0-18yrs) = 2000-4000 IU/day

• Adults (19-70) = 10,000 IU/day

• Older adults (>70) = 10,000 IU/day

Sources of Vitamin D:

*Vitamin D from these food sources are only ~50% efficient in the body

• Fatty fish (salmon, mackerel, sardines, tuna)

• Egg yolks

• Fortified products (ie: milk, orange juice, cereal)

*Vitamin D from sun exposure with the guidelines below produces 10,000-20,000 IU

• Sun exposure (optimal from 10am-3pm)

  • 5-15 minutes unprotected (light skinned individuals)

  • ~30 minutes unprotected (darker skinned individuals)

• Sun is a major risk factor for developing deficiency

This information comes from: Ogan, D., & Pritchett, K. (2013). Vitamin D and the athlete: risks, recommendations, and benefits. Nutrients, 5(6), 1856–1868. https://doi.org/10.3390/nu5061856

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