Iodine (Potassium Iodide) vs L-Tryptophan
Mineral vs Sleep · evidence-backed comparison
- • Iodine (Potassium Iodide) has the stronger evidence base (strong (multiple rcts / meta-analyses)).
- • L-Tryptophan has the broader effect profile across the 9 effect categories.
- • Iodine (Potassium Iodide) is cheaper per serving ($0.05 vs $0.35).
- • L-Tryptophan has a slightly cleaner safety profile.
- • Iodine (Potassium Iodide) has higher bioavailability (better absorption).
Side-by-side traits
| Trait | Iodine (Potassium Iodide) | L-Tryptophan |
|---|---|---|
Category | Mineral | Sleep |
Active compound | Potassium iodide | L-tryptophan |
Form available | Capsule, Tablet, Liquid | Capsule, Powder |
Source | mineral | microbial |
Typical dose | 150 mcg daily | 500–1500 mg |
Dose range | 150–300 mcg | 500–1500 mg |
Loading protocol | — | — |
Best taken with | with food | 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: 2–8 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. | Low (2/5) | Moderate (3/5) |
Muscle / strength | Very Low (1/5) | Very Low (1/5) |
Physical energy | Low (2/5) | Very Low (1/5) |
Focus / cognition | Very Low (1/5) | Very Low (1/5) |
Mood / stress | Low (2/5) | High (4/5) |
Sleep quality | Very Low (1/5) | High (4/5) |
Immunity | Low (2/5) | Very Low (1/5) |
Recovery Post-exercise recovery support. | Very Low (1/5) | Very Low (1/5) |
Longevity / healthspan | Low (2/5) | 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. | $0.05 | $0.35 |
Vegan friendly | Yes | Yes |
Gluten free | Yes | Yes |
3rd-party tested | Yes | Yes |
About Iodine (Potassium Iodide)
Essential for thyroid hormone synthesis. Iodized salt usually covers needs; supplement only if confirmed deficient.
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.
Iodine (Potassium Iodide) safety
Common side effects:
- • Acne
- • Hyperthyroidism (high doses)
- • Goitre (paradox)
Avoid if:
- • Hyperthyroid
- • Graves' disease
- • Hashimoto's (caution)
Drug interactions:
- • Lithium
- • Anti-thyroid drugs
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
- • Thyroid support
- • Pregnancy
- • Iodine deficiency
Stacks well with: Selenium (Selenomethionine)
Common uses
- • Sleep onset
- • Mood
- • Carb cravings
Stacks well with: Magnesium Glycinate
Related comparisons
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.