Absorption Kinetics: From Ingestion to Circulation

by Jason J. Duke - Owner/Artisan

Fresh Content: December 11, 2025 14:23

You are not what you eat; you are what you absorb. The journey from the mouth to the blood is treacherous. We map the mechanisms of the intestinal wall, rejecting the "more is better" myth in favor of Transport Kinetics. Understand the difference between ingestion (putting it in your mouth) and bioavailability (getting it into the cell).

Macro visualization of intestinal villi using active transport proteins to selectively absorb glowing nutrient particles into the bloodstream
Figure 1: The Selective Gate. (Click to Enlarge) The Villi do not just "soak up" nutrition; they actively select and transport resources via protein carriers.

The Audit: Transport Mechanisms

Mechanism Description Energy Cost Examples
Passive Diffusion Substance flows from high concentration to low concentration. No carrier needed. Zero (Gravity). Water, Small Lipids, Some Gases.
Active Transport Requires a specific protein carrier to move substance across the membrane. High (Requires ATP). Amino Acids, Glucose, Most B-Vitamins.
Facilitated Diffusion Uses a carrier protein but follows the concentration gradient. Low. Fructose.

1. The Universal Machine: Biology is a Mandate

We must reject the notion that digestion is a "lifestyle choice." Your body is a machine governed by the laws of physics and biochemistry. It is not unique in its mechanism, only in its status. Every human requires the same transport vehicles to move nutrients across the intestinal border.

When you consume a supplement, it drops into the "acid bath" of the stomach (pH 1.5–3.5). If the casing (capsule/tablet) does not dissolve here, the nutrient remains locked. Once released, it moves to the small intestine, where the Villi (finger-like projections) act as the border patrol. This is where the battle for bioavailability is won or lost.

2. The Rate-Limiting Gate

Why does taking 5,000mg of Vitamin C often result in nothing more than digestive distress? Because of Saturation Kinetics. Active transport relies on specific carrier proteins (like the SVCT1 transporter for Vitamin C).

Think of these proteins as shuttle buses. There are a finite number of buses. Once every seat is taken (Saturation), the remaining passengers (nutrients) are left at the curb. They remain in the gut, attracting water via osmosis (causing loose bowels) and eventually exiting the body. "Megadosing" often ignores the capacity of the transport fleet.

3. Solubility Dynamics: Fat vs. Water

Physics dictates entry. Hydrophilic (water-loving) compounds dissolve in the blood but struggle to cross the lipid (fat) membrane of the cell without a carrier. Lipophilic (fat-loving) compounds can slide through the cell membrane but require dietary fat to be emulsified by bile in the gut first.

Taking Vitamin D (Lipophilic) with a fat-free breakfast is a wasted act. Without the signal of dietary fat, the gallbladder does not release bile, the vitamin is not emulsified, and it passes through the system unabsorbed. We cultivate absorption by pairing the nutrient with its necessary solvent.

The Sovereign Reframe: Do not throw resources at a closed gate. Understand the mechanism of entry to ensure the offering is received.

Codex III: The Mechanics of Vitality

You understand how nutrients enter. Now, learn what happens when they arrive: