What Is Bioavailability?
Bioavailability refers to the proportion of a nutrient that is absorbed and available for use by the body. It's arguably the most important factor in supplement effectiveness — yet most consumers focus only on the dose listed on the label. A 500mg magnesium oxide capsule delivers only about 20mg of absorbable magnesium (4% bioavailability), while a 200mg magnesium glycinate capsule delivers about 160mg (80% bioavailability). The cheaper, higher-dose product is actually far less effective. Understanding bioavailability can save you money and dramatically improve results.
Key Takeaways
- Bioavailability is the proportion of a nutrient actually absorbed by the body
- Magnesium oxide has only 4% bioavailability vs 80% for glycinate
- A cheaper high-dose product can be far less effective than a pricier low-dose one
Magnesium Forms Compared
Magnesium is the poster child for bioavailability differences: Magnesium Glycinate/Bisglycinate — 80% absorption, gentle on stomach, calming (glycine is a relaxing amino acid). Best for sleep, anxiety, general supplementation. Magnesium Citrate — 25-30% absorption, good all-around form, mild laxative effect. Best for constipation and general use. Magnesium Threonate (Magtein) — crosses blood-brain barrier, specifically studied for cognitive benefits. Best for brain health and memory. Magnesium Taurate — combined with taurine for cardiovascular benefits. Best for heart health and blood pressure. Magnesium Oxide — only 4% absorption, primarily acts as a laxative. Best avoided for supplementation. Magnesium Malate — good absorption, combined with malic acid for energy production. Best for fatigue and fibromyalgia.
Key Takeaways
- Glycinate has 80% absorption and is calming — best all-around form
- Threonate crosses the blood-brain barrier — best for cognitive health
- Oxide has only 4% absorption — avoid for supplementation
Vitamin and Mineral Form Guide
Key form differences across common supplements: Vitamin B12 — Methylcobalamin (active, no conversion needed) is superior to Hydroxocobalamin (long-acting) which is superior to Cyanocobalamin (synthetic, requires conversion, contains trace cyanide). Folate — L-Methylfolate (5-MTHF, active form) is preferred because 40% of the population has MTHFR mutations reducing folic acid conversion. Iron — Iron bisglycinate (gentle, well-absorbed) is superior to Ferrous sulfate (common but causes GI issues) which is superior to Ferric forms (poorly absorbed). Zinc — Zinc picolinate and Zinc bisglycinate are the best absorbed forms, followed by Zinc citrate, then Zinc gluconate, with Zinc oxide being poorly absorbed. Calcium — Calcium citrate (absorbed with or without food) is more versatile than Calcium carbonate (requires stomach acid).
Key Takeaways
- Methylcobalamin is the active form of B12 — no conversion needed
- 40% of people have MTHFR mutations that impair folic acid conversion
- Iron bisglycinate causes far fewer GI side effects than ferrous sulfate
Absorption Enhancers
Certain compounds dramatically increase the absorption of specific nutrients: Black Pepper Extract (Piperine/BioPerine) — increases curcumin absorption by 2,000%, also enhances CoQ10, resveratrol, and many other compounds by inhibiting liver metabolism. Fat with fat-soluble vitamins — vitamins A, D, E, K, CoQ10, curcumin, and astaxanthin absorb 3-6x better when taken with dietary fat (even a small amount like a tablespoon of olive oil). Vitamin C with Iron — vitamin C converts ferric iron to ferrous iron and chelates it, increasing absorption by 2-6x. Always pair iron supplements with vitamin C. Phospholipid delivery (liposomal) — wrapping nutrients in phospholipid bubbles can increase absorption 5-10x for certain compounds like vitamin C, glutathione, and curcumin.
Key Takeaways
- Piperine increases curcumin absorption by 2,000%
- Fat-soluble vitamins absorb 3-6x better with dietary fat
- Vitamin C increases iron absorption by 2-6x
Absorption Blockers to Avoid
These common substances reduce nutrient absorption: Coffee and Tea (tannins) — reduce iron absorption by 60-90%. Separate iron supplements from coffee/tea by at least 1 hour. Phytic Acid (grains, legumes, nuts) — binds minerals (iron, zinc, calcium, magnesium) and reduces absorption by 50-80%. Soaking, sprouting, or fermenting reduces phytic acid. Calcium — competes with iron, zinc, and magnesium for absorption. Don't take calcium at the same time as these minerals. Fiber supplements — can bind fat-soluble vitamins and minerals, reducing absorption. Separate by 2 hours. Antacids and PPIs — reduce stomach acid, which is needed to absorb many minerals (iron, calcium, magnesium, B12). Long-term PPI use is associated with multiple nutrient deficiencies.
Key Takeaways
- Coffee/tea tannins reduce iron absorption by 60-90%
- Phytic acid in grains binds minerals and reduces absorption by 50-80%
- Long-term PPI/antacid use causes multiple nutrient deficiencies
Patented vs Generic Ingredients
Many supplements use patented, branded ingredients. Are they worth the premium? Often yes: KSM-66 Ashwagandha — full-spectrum root extract, standardized to 5% withanolides, used in most clinical trials. Generic ashwagandha extracts vary wildly in quality. Cognizin (CDP-Choline) — patented citicoline with consistent quality and clinical evidence. Generic citicoline may have variable purity. Albion Minerals (TRAACS) — chelated minerals with verified bioavailability. Generic 'chelated' minerals may not be truly chelated. CarnoSyn (Beta-Alanine) — the only beta-alanine with New Dietary Ingredient (NDI) status and extensive clinical testing. MenaQ7 (Vitamin K2 MK-7) — most clinically studied MK-7 with guaranteed trans-isomer content (the active form). The premium for patented ingredients is typically 20-50% more, but the guaranteed quality and clinical backing often justify the cost.
Key Takeaways
- KSM-66 is the gold standard ashwagandha — used in most clinical trials
- Albion TRAACS minerals have verified bioavailability
- Patented ingredients cost 20-50% more but offer guaranteed quality