Vitamin D: The Overlooked Key to Performance, Recovery, Sleep, and Longevity

Why Vitamin D Matters More Than You Think

In the world of performance, recovery, and longevity, few nutrients are as impactful yet often overlooked as vitamin D. Once thought to be just a bone-health regulator, research now shows it plays a foundational role in sleep, muscle function, hormone balance, and immune resilience. Athletes, high performers, and anyone optimizing for long-term health should pay close attention to their vitamin D levels.

Vitamin D’s Multi-System Impact

Vitamin D acts as a steroid hormone, improving athletic performance.

Vitamin D isn’t just a vitamin; it functions as a steroid hormone that influences gene expression across nearly every major system in the body. The vitamin D receptor (VDR) is found in muscle, the brain, the immune system, and even the cardiovascular system. This means vitamin D affects everything from strength and endurance to stress resilience and recovery.

• Muscle & Performance: Boosts muscle strength, power, and endurance while reducing injury risk.

• Sleep Optimization: Regulates the sleep-wake cycle via melatonin and circadian rhythm support.

• Hormonal Balance: Influences testosterone, cortisol, insulin, and thyroid function.

• Recovery & Longevity: Reduces inflammation, supports immune function, and protects against chronic disease.

Vitamin D and Physical Performance: Strength, Endurance & Recovery

Vitamin D is crucial for muscle contraction, protein synthesis, and neuromuscular coordination. Athletes with sufficient vitamin D levels consistently show higher strength, power, and aerobic capacity, while those deficient experience fatigue, slower reaction times, and increased injury risk.

Strength & Power

Higher serum 25(OH)D levels are associated with greater muscle strength improvements, especially in individuals who start with a deficiency.

• Professional soccer players with low vitamin D had significantly lower muscle torque compared to those with sufficient levels.

• Supplementing vitamin D improved grip strength, sprint speed, and vertical jump height in elite athletes.

• Fast-twitch muscle fibers (responsible for explosive power) require vitamin D for optimal function.

Endurance & VO₂max

• Vitamin D enhances mitochondrial efficiency and oxygen utilization, which supports endurance.

• One study showed a 20% increase in VO₂max after 8 weeks of supplementation.

• Athletes with higher vitamin D levels consistently perform better in aerobic capacity tests.

Recovery & Injury Prevention

Athletes with lower vitamin D levels experience a higher incidence of injuries, reinforcing the importance of maintaining adequate 25(OH)D levels for musculoskeletal health.

• Vitamin D reduces muscle inflammation and enhances muscle regeneration.

• Athletes with vitamin D deficiency (<20 ng/mL) are at a 2-5x greater risk of stress fractures and muscle strains.

• It lowers inflammation markers (e.g., IL-6, TNF-alpha), which accelerates post-exercise recovery.

For peak performance, aim for a serum 25(OH)D level of 40–50 ng/mL. If deficient, supplementation can improve muscle function, endurance, and injury resilience.

Vitamin D and Sleep: Optimizing Recovery & Circadian Rhythms

Sleep quality scores improve with increasing vitamin D levels, highlighting its role in melatonin regulation and circadian rhythm balance.

Sleep is a biological superpower for recovery and longevity, and vitamin D plays a bigger role in sleep regulation than most realize.

How Vitamin D Affects Sleep

Vitamin D deficiency is linked to poor sleep quality.

• Regulates Melatonin: Vitamin D receptors in the brain help control melatonin production, which regulates sleep-wake cycles.

• Reduces Sleep Disorders: Deficiency is linked to higher rates of insomnia, restless legs syndrome, and sleep apnea.

• Improves Sleep Quality: Trials show supplementation improves sleep latency (falling asleep faster) and sleep duration.

Key Findings

• A 2018 meta-analysis found that individuals with low vitamin D levels had a 50% higher risk of sleep disorders.

• Supplementation improved sleep quality scores, increased total sleep time, and reduced nighttime awakenings.

• Vitamin D deficiency disrupts circadian rhythms, leading to fatigue and poor recovery.

Maintaining vitamin D levels above 30 ng/mL helps optimize melatonin production, circadian rhythm stability, and sleep efficiency.

Vitamin D and Hormonal Balance: Testosterone, Cortisol, and Metabolism

Vitamin D supplementation is linked to an increase in testosterone and a decrease in cortisol, supporting a favorable hormonal environment for performance and recovery.

Vitamin D interacts with several endocrine systems, impacting energy, muscle growth, stress resilience, and fat metabolism.

Testosterone & Androgens

• Men with higher vitamin D levels tend to have higher total and free testosterone.

• A 2024 meta-analysis of 17 trials found significant increases in testosterone after vitamin D supplementation, particularly in those deficient.

Cortisol & Stress Resilience

• Vitamin D receptors are present in adrenal glands, which regulate cortisol output.

• A study in Norway found vitamin D supplementation improved heart rate variability and stress responses.

Metabolic Health & Insulin Sensitivity

• Vitamin D is crucial for insulin function—deficiency is linked to higher rates of insulin resistance and type 2 diabetes.

• A meta-analysis of 28 RCTs found vitamin D significantly reduced fasting glucose and HbA1c levels, improving metabolic health.

Maintaining optimal vitamin D levels supports hormone balance, enhances resilience to stress, and improves metabolic health—all crucial for longevity and performance.

How to Optimize Vitamin D Levels

Both sunlight exposure and supplementation effectively raise serum 25(OH)D levels, with higher doses of supplementation providing the most significant increases.

What’s the Ideal Blood Level?

For performance, recovery, and longevity, research suggests a sweet spot of 40–50 ng/mL. Levels below 20 ng/mL are considered deficient and impair health.

How Much to Supplement?

• General maintenance: 1,000–2,000 IU/day

• If insufficient (20–30 ng/mL): 2,000–5,000 IU/day

• If deficient (<20 ng/mL): 5,000–10,000 IU/day for 8 weeks, then retest.

Best Time to Take It?

• Morning or midday is ideal (mimics natural sun exposure).

• Take with fat-containing food for better absorption.

Sun Exposure: The Best Source

• 10–20 minutes of midday sun (w/o sunscreen) on arms and legs can provide 5,000+ IU.

• However, winter, high latitudes, and indoor lifestyles limit sun exposure, making supplementation necessary.

Vitamin D-Rich Foods

• Fatty fish (salmon, sardines, mackerel)

• Egg yolks

• UV-exposed mushrooms

• Fortified dairy & plant-based milks

Avoiding Toxicity

• Upper limit: 4,000 IU/day is considered safe for long-term use.

• Toxicity is rare but occurs at >150 ng/mL, leading to hypercalcemia (high blood calcium levels).

Action Plan

1️⃣ Test your levels (25(OH)D blood test).

2️⃣ Target 40–50 ng/mL for optimal performance & longevity.

3️⃣ Supplement strategically (2,000–5,000 IU/day as needed).

4️⃣ Combine with sunlight exposure and whole foods.

5️⃣ Monitor & adjust seasonally (increase intake in winter).

Optimizing vitamin D is a simple, science-backed strategy to improve physical performance, recovery, sleep, and longevity. Don’t let deficiency hold you back—make vitamin D a non-negotiable part of your routine.

Want some expert guidance on how to create a curated supplement stack for your recovery and performance needs?

Book a call with Evans Performance today.

Sources:

1. Holick, M. F. (2017). The vitamin D deficiency pandemic: Approaches for diagnosis, treatment, and prevention. Reviews in Endocrine and Metabolic Disorders, 18(2), 153–165. https://doi.org/10.1007/s11154-017-9424-1

2. Owens, D. J., Allison, R., Close, G. L., & Fraser, W. D. (2018). Vitamin D and the athlete: Current perspectives and new challenges. Sports Medicine, 48(1), 3–16. https://doi.org/10.1007/s40279-017-0854-x

3. Forbes, S. C., Holowatyj, E., Masternak, M. M., Booth, F. W., & Roberts, M. D. (2020). The effects of vitamin D on skeletal muscle function and athletic performance: A review. Journal of the International Society of Sports Nutrition, 17, 57. https://doi.org/10.1186/s12970-020-00383-5

4. Martens, P. J., Gysemans, C., Verstuyf, A., & Mathieu, C. (2020). Vitamin D’s effect on immune function. Nutrients, 12(5), 1248. https://doi.org/10.3390/nu12051248

5. McClung, J. P., Gaffney-Stomberg, E., & Lee, J. J. (2014). Vitamin D and muscle mass: Understanding potential mechanisms and changes with aging. Nutrition Reviews, 72(2), 104–112. https://doi.org/10.1111/nure.12099