Product Description
Here's something Dr. Kevin Sprouse — team physician for EF Education First Pro Cycling and one of the most respected sports medicine doctors in endurance athletics — told us when we asked about daily supplements for serious athletes: he's seen very few elite athletes with sufficient vitamin D levels. Not low. Not borderline. Straight-up insufficient.
Thorne Vitamin D is the go-to D3 supplement recommended by Dr. Sprouse as the foundation of any athlete's daily supplement protocol — and it's why it's been part of The Feed's athlete stack from the beginning.
The very habits that make you an athlete — early morning training, sunscreen on long rides, indoor workouts — are exactly what cuts off your primary vitamin D source. And the RDA wasn't set for someone logging 15-hour training weeks. Vitamin D functions more like a hormone than a standard vitamin, involved in muscle function, immune response, calcium absorption, and recovery. When your levels are low, your ceiling drops: slower recovery, more frequent illness, weaker performance when it matters most.
D3, Not D2 — The Form Matters Thorne uses D3 — the same form your skin produces from sunlight, and the form research shows is more potent and better absorbed.
NSF Certified for Sport — Clean for Tested Athletes Every batch of Thorne D-5,000 is independently tested to verify label accuracy and screened for nearly 300 banned substances. No surprises. No guessing.
Two Doses, One Decision D-5,000 (5,000 IU) is the standard daily maintenance dose for most athletes. D-10,000 (10,000 IU) is for athletes who've tested low or need to correct a confirmed deficiency. Start with bloodwork — it tells you exactly which dose you need.
For athletes, adequate vitamin D supports lean muscle mass, immune consistency, calcium absorption for high-impact bones, and cardiovascular function. Thorne's formula is pure D3 in a clean capsule — no lactose, no preservatives, nothing you don't need. A small amount of vitamin E is included to stabilize the D3 for full potency.
How to Use Thorne Vitamin D
Daily dose: Take 1 capsule daily with a meal containing fat — vitamin D is fat-soluble, so taking it with food meaningfully improves absorption.
Choosing your dose: D-5,000 IU is the standard starting point for most athletes. D-10,000 IU is better suited for correcting a confirmed deficiency or for athletes in colder climates with limited winter sun exposure. When in doubt, get bloodwork first.
Pro tip: Take it consistently in the morning with breakfast. Pair it with an omega-3 for enhanced absorption and synergistic anti-inflammatory benefits — exactly the combo Dr. Sprouse recommends as part of his Athlete Daily Protocol.
- Gluten free
- Sport Tested: NSF Certified for Sport®
Supplement Facts
D-5,000 / 60 Servings
Serving Size: 1 Capsule
Serving Per Container: 60
| Amount Per Serving | ||
|---|---|---|
| % Daily Value* | ||
| Vitamin D3 (10,000 IU) 125mcg | ** | |
* Percent Daily Values are based on a 2,000 calorie diet. Your daily values may be higher or lower depending on your calorie needs.
** Daily Value (DV) not established
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Consumable products over $40 receive a 50% store credit. This includes specialty nutrition products such as ketones or supplements/vitamins.
Thorne Vitamin D FAQ's
Everything you need to know before getting started.
Hard training dramatically increases your body's demand for vitamin D, which acts like a hormone regulating muscle function, immune response, and recovery. At the same time, athletes often train indoors, wear sunscreen, and are out before sunrise — all of which cut off natural vitamin D production. Dr. Kevin Sprouse notes that insufficient vitamin D is so common in his elite athlete patient population that he now expects it.
D-5,000 (5,000 IU) is the standard daily maintenance dose for most athletes to sustain healthy vitamin D levels year-round. D-10,000 (10,000 IU) is a higher-dose option designed for athletes who have tested low or are actively working to restore deficient levels, ideally under practitioner guidance. Bloodwork is the best way to determine which dose is right for you.
Vitamin D3 is the form naturally produced by your skin when exposed to sunlight, and research consistently shows it raises blood vitamin D levels more effectively and stays active in the body longer than vitamin D2, the form used in many cheaper supplements. Thorne uses exclusively D3 in all of its vitamin D products.
Dr. Sprouse recommends pairing vitamin D with an omega-3 supplement as part of a daily athlete protocol — the two work synergistically for immune function and anti-inflammatory support. Many athletes also pair D3 with vitamin K2 to ensure calcium is directed to bones and not arteries when vitamin D levels are elevated.