Soy Protein Isolate vs Vitamin C
Protein vs Vitamin · evidence-backed comparison
- • Vitamin C has the stronger evidence base (strong (multiple rcts / meta-analyses)).
- • Soy Protein Isolate has the broader effect profile across the 9 effect categories.
- • Vitamin C is cheaper per serving ($0.06 vs $0.60).
Side-by-side traits
| Trait | Soy Protein Isolate | Vitamin C |
|---|---|---|
Category | Protein | Vitamin |
Active compound | Soy isoflavones + amino acid blend | L-ascorbic acid |
Form available | Powder | Capsule, Tablet, Powder, Liquid, Gummy |
Source | plant | synthetic |
Typical dose | 25–40 g per serving | 500–2000 mg daily |
Dose range | 25–40 g | 500–2000 mg |
Loading protocol | — | — |
Best taken with | water or plant milk | split doses, with food |
Best time of day | post-workout | any |
Bioavailability How efficiently the body absorbs and utilizes the compound. | High (4/5) | High (4/5) |
Onset time | Acute: 45–75 min | Acute and cumulative |
Half-life | — | ~30 min (plasma) |
Evidence level Quality and quantity of human research. | Moderate (some RCTs) | Strong (multiple RCTs / meta-analyses) |
Overall effect Subjective effect magnitude. | Moderate (3/5) | Low (2/5) |
Muscle / strength | High (4/5) | Low (2/5) |
Physical energy | Low (2/5) | Low (2/5) |
Focus / cognition | Very Low (1/5) | Very Low (1/5) |
Mood / stress | Low (2/5) | Low (2/5) |
Sleep quality | Low (2/5) | Very Low (1/5) |
Immunity | Low (2/5) | High (4/5) |
Recovery Post-exercise recovery support. | High (4/5) | Moderate (3/5) |
Longevity / healthspan | High (4/5) | Moderate (3/5) |
Safety rating 5 = exceptionally well-tolerated; 1 = significant risk profile. | High (4/5) | High (4/5) |
Price per serving Approximate USD per typical daily dose. | $0.60 | $0.06 |
Vegan friendly | Yes | Yes |
Gluten free | Yes | Yes |
3rd-party tested | Yes | Yes |
About Soy Protein Isolate
Complete plant protein with all 9 EAAs. Equivalent muscle-building to whey in older adults; mild cardio-protective effects from isoflavones.
About Vitamin C
Essential antioxidant and collagen cofactor. Doesn't prevent colds but shortens duration; chronically high doses may blunt training adaptations.
Vetted brands, third-party testing, ships worldwide.
Vetted brands, third-party testing, ships worldwide.
Soy Protein Isolate safety
Common side effects:
- • Mild estrogen-mimicking (debated, minor)
Avoid if:
- • Soy allergy
- • Hormone-sensitive cancers (consult MD)
Drug interactions:
- • Thyroid meds (levothyroxine)
Vitamin C safety
Common side effects:
- • GI upset (high doses)
- • Diarrhea (>2000 mg)
- • Kidney stones (predisposed)
Avoid if:
- • Hemochromatosis
- • G6PD deficiency
- • Kidney stones
Drug interactions:
- • Iron (boosts absorption)
- • Chemotherapy
Common uses
- • Vegan muscle gain
- • Heart health
- • Menopause support
Stacks well with: Creatine Monohydrate
Common uses
- • Immune support
- • Collagen synthesis
- • Antioxidant
- • Iron absorption
Stacks well with: Zinc, Collagen Peptides
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Medical disclaimer
SupplementDuel is for educational purposes only and is not medical advice. Consult a physician before starting, stopping, or combining supplements — especially if you are pregnant, breastfeeding, take prescription medication, or have a chronic condition.