Iron Bisglycinate vs L-Tryptophan
Mineral vs Sleep · evidence-backed comparison
- • Iron Bisglycinate has the stronger evidence base (strong (multiple rcts / meta-analyses)).
- • Iron Bisglycinate has the broader effect profile across the 9 effect categories.
- • Iron Bisglycinate is cheaper per serving ($0.18 vs $0.35).
- • L-Tryptophan has a slightly cleaner safety profile.
- • Iron Bisglycinate has higher bioavailability (better absorption).
Side-by-side traits
| Trait | Iron Bisglycinate | L-Tryptophan |
|---|---|---|
Category | Mineral | Sleep |
Active compound | Ferrous bisglycinate | L-tryptophan |
Form available | Capsule, Tablet | Capsule, Powder |
Source | synthetic | microbial |
Typical dose | 18–25 mg elemental iron | 500–1500 mg |
Dose range | 18–25 mg | 500–1500 mg |
Loading protocol | — | — |
Best taken with | vitamin C, empty stomach (or with food if GI sensitive) | carbs (improves CNS uptake), empty stomach |
Best time of day | morning | evening |
Bioavailability How efficiently the body absorbs and utilizes the compound. | Very High (5/5) | Moderate (3/5) |
Onset time | Cumulative: 4–12 weeks | Acute: 60 min |
Half-life | — | ~2 hours |
Evidence level Quality and quantity of human research. | Strong (multiple RCTs / meta-analyses) | Moderate (some RCTs) |
Overall effect Subjective effect magnitude. | Moderate (3/5) | Moderate (3/5) |
Muscle / strength | Low (2/5) | Very Low (1/5) |
Physical energy | High (4/5) | Very Low (1/5) |
Focus / cognition | Moderate (3/5) | Very Low (1/5) |
Mood / stress | Moderate (3/5) | High (4/5) |
Sleep quality | Low (2/5) | High (4/5) |
Immunity | Low (2/5) | Very Low (1/5) |
Recovery Post-exercise recovery support. | Moderate (3/5) | Very Low (1/5) |
Longevity / healthspan | Very Low (1/5) | Very Low (1/5) |
Safety rating 5 = exceptionally well-tolerated; 1 = significant risk profile. | Moderate (3/5) | High (4/5) |
Price per serving Approximate USD per typical daily dose. | $0.18 | $0.35 |
Vegan friendly | Yes | Yes |
Gluten free | Yes | Yes |
3rd-party tested | Yes | Yes |
About Iron Bisglycinate
Best-tolerated iron form for treating deficiency anemia. Don't supplement without a confirmed low ferritin / low Hgb test.
About L-Tryptophan
Serotonin and melatonin precursor. Generally safer than 5-HTP for daily use, with strong sleep-onset and mood support.
Vetted brands, third-party testing, ships worldwide.
Vetted brands, third-party testing, ships worldwide.
Iron Bisglycinate safety
Common side effects:
- • Constipation (less than ferrous sulfate)
- • Dark stools
Avoid if:
- • Hemochromatosis
- • Iron overload
- • Untested males without deficiency
Drug interactions:
- • Levothyroxine
- • Calcium
- • PPIs
L-Tryptophan safety
Common side effects:
- • Drowsiness
- • GI upset
- • Dry mouth
Avoid if:
- • SSRI use (serotonin syndrome)
- • Liver disease
Drug interactions:
- • SSRIs
- • MAOIs
- • Sedatives
Common uses
- • Anemia treatment
- • Heavy menstruation
- • Endurance athletes
Stacks well with: Vitamin C
Common uses
- • Sleep onset
- • Mood
- • Carb cravings
Stacks well with: Magnesium Glycinate
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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.