Quick Verdict
Whey Protein
Fast-digesting complete protein derived from milk. Richest natural source of BCAAs, especially leucine (key mTOR activat
Evidence: strong (800+ studies)
Vitamin D3
Actually a steroid hormone precursor. Critical for calcium absorption, immune function, hormone production. Widespread d
Evidence: strong (1000+ studies)
Side-by-Side Comparison
| Whey Protein | Vitamin D3 | |
|---|---|---|
| Category | protein | vitamins |
| Evidence Level | strong | strong |
| Studies | 800+ | 1000+ |
| Dosage | 20-40 g | 1000-5000 IU |
Stack Compatibility
Whey Protein: Creatine, Casein (before bed), Dextrose (post-workout insulin spike)
Vitamin D3: Magnesium (essential cofactor), Vitamin K2 (MK-7), Calcium (if dietary intake low), Zinc
Which Should You Choose?
Both serve different purposes. Choose based on your priority.