From the Supplement Skeptic desk · our own database
Supplement Ingredients Deep-Dive (Bioavailability & Research Database)
Magnesium glycinate vs oxide? Vitamin B12 forms ranked? Here's the absorption science backed by studies.
Magnesium glycinate absorbs at roughly 4–15× the rate of magnesium oxide (via active dipeptide transport), while most forms of vitamin B12 absorb at similar rates regardless of form—though cyanocobalamin shows slightly higher initial absorption (~49%) than methylcobalamin (~44%). This database ranks 40+ ingredients by absorption rate, studied dose, and cost-per-absorbed-dose, so you stop buying underdosed or low-absorption forms.
- 4–15×
- Higher absorption: glycinate vs oxide
- 40+
- Supplement ingredients ranked by absorption
- 49% vs 44%
- Cyanocobalamin vs methylcobalamin absorption
- $0
- Affiliate kickback — we sell no supplements
- See exactly how much magnesium (or any ingredient) your body actually absorbs from each form.
- Match any label against the absorption rate and dose proven in clinical trials.
- Identify under-dosed ingredients hiding behind proprietary blends or low-bioavailability forms.
- Understand the cost-per-absorbed-dose — sometimes the cheapest option is actually the costliest.
- Get plain-English guidance on timing, food interactions, and form-switching protocols.
Free 60-second audit
Are you buying the low-absorption version of your supplement?
Answer 3 questions about a supplement you're considering (or already taking). We'll show you if you're getting a form that actually absorbs.
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1 What ingredient are you interested in?
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2 What form is on your label?
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3 How much are you paying per month?
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Your result
Here's what the absorption data predicts for your supplement
Get the database — $29 →Absorption rate matters as much as dose. For example, magnesium oxide — often the cheapest option — absorbs at only 4–15%, while magnesium glycinate uses an active transport pathway and absorbs significantly more. If you're paying $15/mo for low-absorption oxide, you might get better results (and better value) at a slightly higher price for a high-absorption form.
The Supplement Bioavailability Database breaks down 40+ ingredients this way: form, absorption rate, studied dose, and true cost-per-absorbed-dose. Stop guessing whether your supplement's form is worth the price.
The short version
You are buying supplement ingredients at wildly different absorption rates—often without knowing it. A $15-per-month magnesium oxide supplement absorbs at 4–15%, while a magnesium glycinate at $18 absorbs at 2–3× that rate. Same ingredient, different form, vastly different value.
This database exists so you stop paying for the low-absorption version.
Here are the facts:
- Magnesium glycinate absorbs via active transport (dipeptide pathway), achieving 4–15× the bioavailability of magnesium oxide (passive absorption only).
- Cyanocobalamin absorbs at ~49% of a 1-mcg dose, methylcobalamin at ~44%—the difference is small; form does not trump dose.
- Curcumin in plain powder absorbs poorly; liposomal or phospholipid-complexed forms absorb substantially more.
- Most supplements are under-dosed or use low-absorption forms, and your label doesn’t tell you which.
This database decodes all 40+ ingredients you’re likely buying, shows you the true cost-per-absorbed-dose, and tells you when upgrading to a high-absorption form actually saves you money.
Why form matters more than you think
Supplement shopping is trapped between two lies:
- The “form doesn’t matter” lie. Retailers say all magnesium is magnesium. It isn’t. Absorption rates vary by 10–15×.
- The “premium form is always better” lie. Some brands charge 3× more for a “proprietary blend” with zero absorption advantage.
This database cuts through both by showing you the actual absorption data from clinical trials.
The absorption gap
Take magnesium: magnesium oxide (cheapest) absorbs at ~4–15%; magnesium glycinate absorbs at ~2–3× higher rates via active transport; magnesium threonate crosses the blood-brain barrier for cognition-specific goals. If you’re paying $15/mo for oxide, you’re not saving money—you’re wasting it.
Similarly, vitamin B12: cyanocobalamin absorbs at ~49% vs methylcobalamin at ~44%—modest difference. Curcumin in plain powder absorbs poorly; liposomal forms absorb substantially more. Most supplements are under-dosed or use low-absorption forms, and your label won’t tell you which.
What’s inside
The database includes 40+ supplement ingredients (magnesium, B12, iron, zinc, curcumin, vitamin C, CoQ10, ashwagandha, and more), absorption rates by form from PubMed-indexed trials, studied doses, cost-per-dose calculators, and form-switching guidance with direct PubMed links. Also included: a “Bioavailability Decoder” cheat sheet to decode any supplement label in 60 seconds without biochemistry knowledge.
This is consumer education, not medical advice. Supplement forms and doses carry real individual variation. Review any significant changes with a licensed clinician.
What's inside
- Searchable database (instant access, PDF + web version) — 40+ ingredients with absorption rates, study citations, and bioavailability ranks.
- The Absorption Comparison Table — ingredient, form, absorption rate, studied dose, cost-per-dose, cost-per-absorbed-dose, PubMed link.
- The Bioavailability Decoder — how to read ingredient labels and spot underdosed or low-absorption forms in 60 seconds.
- The Cost-Per-Absorbed-Dose Calculator — enter your supplement cost and dose; we show you the true cost-per-studied-amount-absorbed.
- Form-Switching Guidance — magnesium types, B12 variants, iron salts, curcumin delivery systems, and when to upgrade.
Frequently asked
Does magnesium glycinate really absorb better than oxide?
Yes. Magnesium glycinate uses an active transport pathway (dipeptide absorption) in the small intestine, achieving substantially higher bioavailability than magnesium oxide, which relies on passive absorption and achieves only 4–15% absorption. Clinical research shows magnesium bisglycinate achieves the highest absorption among common forms. This is not marketing—it's documented in clinical trials.
Is methylcobalamin better absorbed than cyanocobalamin?
Not significantly. Recent clinical evidence shows cyanocobalamin absorbs at roughly 49% of a 1-mcg dose, while methylcobalamin absorbs at about 44%. The differences are modest. However, methylcobalamin may have a higher retention rate in tissues. Both forms are clinically effective; the 'better' form depends on your budget and specific health goal, not absorption alone.
What dose was actually studied in the clinical trials?
This database lists the studied dose for every ingredient. For example, magnesium glycinate efficacy is typically shown at 300–400 mg daily; curcumin bioavailability is most robust at 500–1000 mg when delivered via liposomal or other enhanced-bioavailability forms. Many retail products under-dose or substitute low-absorption forms, which is why this database exists.
Is the cost-per-absorbed-dose calculator accurate?
It uses published absorption rates from PubMed-indexed clinical trials. It is not personalized to your individual metabolism (which varies), but it gives you a realistic basis for comparing products. Two supplements at different prices and different absorption rates can have very different true costs-per-dose-absorbed.
What exactly do I get for $29?
A searchable database (PDF + web version) containing 40+ supplement ingredients ranked by form, absorption rate, studied dose, cost-per-dose, cost-per-absorbed-dose, and direct PubMed links. Plus the bioavailability decoder cheat sheet, cost calculator, and form-switching guidance. One-time payment, 30-day money-back guarantee, no subscription. We sell no supplements and take no affiliate commission.
Get Supplement Ingredients Deep-Dive (Bioavailability & Research Database) — $29
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Sources
- Bioavailability and absorption of magnesium compounds: In vitro and clinical comparison of marine magnesium salts — 2024–2025 study showing magnesium glycinate achieves higher absorption than oxide via dipeptide transport.
- Assessing Vitamin B-12 Absorption and Bioavailability: Read the Label — American Journal of Clinical Nutrition: cyanocobalamin ~49% absorption vs methylcobalamin ~44% at 1 mcg dose.
- The Oral Bioavailability of Vitamin B12 at Different Doses in Healthy Indian Adults — Dose-dependent absorption data: maximum threshold 1.5–2.5 µg per dose for B12.
- Highly Bioavailable Forms of Curcumin and Promising Avenues for Curcumin-Based Research — Liposomal, phospholipid, and nanoparticle delivery systems significantly enhance curcumin bioavailability.