Soy Protein Isolate
90.0gprotein / 100g375 cal · 1.0g fat · $$ · Quality 0.9
Whey Protein Isolate (WPI)
90.0gprotein / 100g370 cal · 1.0g fat · $$$ · Quality 1.0
Soy Protein Isolate edges out Whey Protein Isolate (WPI) by less than half a gram of protein per 100g (90.0g vs 90.0g) — statistically a wash for practical meal planning.
Quality flips the other way, though: Whey Protein Isolate (WPI) has the stronger amino acid profile (highest DIAAS of any common protein source) versus Soy Protein Isolate's one of the highest-quality plant proteins, near-complete on its own.
Budget-wise, Soy Protein Isolate runs meaningfully cheaper per typical serving ($$) than Whey Protein Isolate (WPI) ($$$).
The dietary-restriction question settles this for a lot of people before the macros even matter: Soy Protein Isolate is vegan, Whey Protein Isolate (WPI) isn't.
Whey Protein Isolate (WPI)'s typical serving also delivers more leucine (2700mg vs Soy Protein Isolate's 2450mg) — relevant if the goal is maximizing the muscle-protein-synthesis trigger per meal, not just total grams.
The real deciding factor is dietary fit, not macros: choose Soy Protein Isolate if you need it to be plant-based, choose Whey Protein Isolate (WPI) otherwise — the protein numbers are close enough that diet compatibility should lead.
Full nutrition comparison
| Per 100g | Soy Protein Isolate | Whey Protein Isolate (WPI) |
|---|---|---|
| Protein | 90.0g | 90.0g |
| Calories | 375 | 370 |
| Fat | 1.0g | 1.0g |
| Carbs | 2.0g | 1.5g |
| Fiber | 1.5g | 0.0g |
| Quality score | 0.9 | 1.0 |
| Relative cost | $$ | $$$ |
| Prep time | 1 min | 1 min |
Frequently asked
Which has more protein, soy protein isolate or whey protein isolate (wpi)?
Soy Protein Isolate has 90.0g of protein per 100g compared to Whey Protein Isolate (WPI)'s 90.0g.
Which is lower in calories?
Whey Protein Isolate (WPI) is lower in calories per 100g, at 370 vs the other's 375.