Swallowing the Probiotic Dose
A capsule of live organisms begins its journey to the gut.
- 1–10 B: Typical dose (CFU per capsule)
- ~10 s: Mouth-to-stomach transit (via esophagus)
- Lacto/Bifido: Common genera (most used strains)
- $70B+: Global market size (probiotic industry)
What is a probiotic dose
Live microorganisms packaged for a therapeutic health benefit.
Billions of live cells must survive to matter clinically.
Capsule composition
Freeze-dried organisms suspended in a protective carrier matrix.
The journey ahead
Next stop: the stomach, the harshest barrier in the gut.
Entering the Gastric Environment
Stomach acid creates one of the body's harshest microbial barriers.
- 1.5–3.5: Stomach pH range (fasting conditions)
- 1–4 h: Gastric emptying time (liquid to solid meals)
- ~2.0: Pepsin optimum pH (protein digestion enzyme)
- ~1.5 L: Daily HCl secreted (gastric parietal cells)
Why the stomach is hostile
Hydrochloric acid denatures proteins and kills most bacteria.
Few ingested microbes survive gastric transit unprotected.
pH as a barrier
Lower pH means faster, more lethal organism inactivation.
Residence time matters
Longer stomach dwell time increases cumulative acid exposure.
Strain-Dependent Population Loss
Some strains tolerate acid far better than others.
- <10%: Low-resistance survival (uncoated, sensitive strain)
- ~60%: High-resistance survival (uncoated, hardy strain)
- Moderate: Lactobacillus tolerance (generally acid-tolerant)
- Low: Bifidobacterium tolerance (generally acid-sensitive)
Strain-to-strain variation
Acid resistance differs widely across probiotic species.
Strain selection alone can shift survival many-fold.
Mechanisms of tolerance
Proton pumps and stress proteins buffer internal pH.
Consequence for dosing
Sensitive strains need much higher starting doses.
Enteric Coating Shields the Payload
A pH-sensitive shell keeps acid away from the organisms.
- >90%: Coated survival rate (across resistance levels)
- pH 6–7: Coating dissolves at (intestinal environment)
- Methacrylate: Common material (polymer copolymer)
- Improved: Shelf stability (vs uncoated capsules)
How enteric coating works
The shell resists acid but dissolves in alkaline intestine.
Coating decouples survival from strain acid resistance.
Formulation trade-offs
Coating adds cost and manufacturing complexity.
When coating is skipped
Uncoated formulas rely entirely on strain hardiness.
Arrival at the Small Intestine
Surviving organisms reach their intended site of action.
- Small intestine: Target zone (duodenum to ileum)
- ~6–7: Duodenal pH (near neutral)
- Hours: Colonization window (transient residence)
- ~10⁹ CFU: Effective dose needed (for measurable benefit)
Why delivery matters
Only surviving organisms can exert any health benefit.
Formulation and strain choice together decide final dose.
Beyond the stomach
Bile and pancreatic enzymes pose further downstream challenges.
Measuring success
Viable delivered count predicts likely clinical effect.