What Is Bioavailability and Why It Matters for Your Supplements | TUH #252

Brecka explains that folic acid has been the default form for decades because it is cheap and chemically stable. However, after ingestion it must undergo a multi-step enzymatic transformation that depends on the MTHFR gene. If that gene is mutated — as it is in nearly half the population — the conversion efficiency plummets, meaning most of the folic acid never becomes usable folate. This not only fails to correct a deficiency but can lead to accumulation of unmetabolized folic acid, which may mask B12 deficiency and interfere with methylation pathways critical for DNA repair, detoxification, and neurotransmitter synthesis. Switching to methylfolate circumvents the genetic roadblock entirely, making the nutrient effective regardless of MTHFR status.

Brecka argues that studies showing cyanocobalamin equals methylcobalamin are misleading because they measure only serum B12, not intracellular or mitochondrial B12 activity. In individuals with impaired conversion, serum levels can be high or normal while the cells remain starved. He describes this as 'functional B12 deficiency' — the nutrient is present in the body but locked outside the cells. Methylcobalamin, as the already-active form, bypasses all conversion steps and enters the cellular machinery directly. This protocol is framed not as a luxury but as a necessity for anyone with genetic conversion inefficiencies.

Brecka sets up the contrast between forms by noting the frustration many people have with magnesium supplements that seem to do nothing but cause digestive issues. Magnesium oxide, because of its poor absorption, primarily stays in the gut, making it effective for constipation but useless for systemic goals. Magnesium glycinate, on the other hand, is designed for absorption and pairs with glycine's natural calming properties. When taken before bed, this form helps activate the parasympathetic nervous system — the 'rest-and-digest' state — easing muscle tension and promoting deeper sleep. The protocol is not just about swapping one pill for another; it's about matching the chemical form to the desired outcome.

Brecka uses creatine as a textbook example of how bioavailability changes outcomes even for a heavily researched staple. He describes the common user experience — the undissolved grit, the bloated stomach — and links it directly to the poor solubility of monohydrate. The switch to HCL is presented as a solution that is backed by a specific study where the HCL group uniquely improved body composition. The narrative underscores that even 'proven' supplements can underperform if the form restricts absorption, and that the consumer can self-diagnose by how they feel after taking it.

Brecka frames this as the foundational action that follows from understanding bioavailability. He notes that most people select supplements based on marketing claims or milligram content, assuming that 'more is better,' but the real determinant of efficacy is the chemical identity of the ingredient. By teaching listeners to spot folic acid vs methylfolate, cyanocobalamin vs methylcobalamin, and magnesium oxide vs glycinate, he empowers them to self-audit their current stack and make low-cost, high-impact swaps.

Brecka explains that cells have specific receptors and transport mechanisms that act like locks. If the supplement ingredient is the wrong shape — because it is a cheap synthetic or poorly soluble form — it cannot enter the cell and is excreted unchanged. The industry's focus on cost and long shelf life has led to widespread use of forms like folic acid, cyanocobalamin, and magnesium oxide, which are poorly absorbed by many people. The listener is left with the actionable insight that checking the form on the label is often more important than the milligram dose. He frames bioavailability not as a marketing buzzword but as a real, measurable property grounded in genetics and enzyme activity, meaning what works for one person may fail for another.

Brecka notes that creatine monohydrate requires about 500 mL of water to dissolve a single serving, and because it doesn't dissolve completely, a significant portion sits in the intestines drawing in water and causing the 'creatine bloat'. Creatine HCL’s vastly higher solubility translates to better intestinal permeability, meaning more of the creatine actually enters the bloodstream. He cites a study published in Food and Nutrition Sciences that compared the two forms in recreational weightlifters: only the HCL group saw significant body composition improvements — reduced body fat percentage and increased fat-free mass. The monohydrate group did not, likely because of water retention and poor absorption masking the benefits. The broader lesson is that the same nutrient can produce entirely different physiological outcomes depending on its chemical form.

Brecka points out that cyanocobalamin is synthetic and requires conversion to methylcobalamin, which is the form mitochondria use for energy production. Individuals with genetic variants in the MTR or MTRR genes have severely compromised conversion capacity. Even if serum B12 levels appear high on a blood test, the B12 may not be entering cells or fuelling mitochondrial processes, leading to a functional deficiency. He contrasts this with direct supplementation of methylcobalamin, which skips the conversion steps entirely. This insight shifts the diagnostic conversation from 'what's in the blood' to 'what's actually active in the tissues', and warns that relying solely on serum measurements can give a false sense of safety.

Brecka explains that magnesium oxide's poor solubility means only about 4% is absorbed; the rest remains in the gut, drawing in water and triggering peristalsis, which is why it is effective for constipation. However, when the goal is to support sleep, reduce muscle tension, or calm the parasympathetic nervous system, oxide is a poor choice. Magnesium glycinate (bisglycinate) chelates magnesium to the amino acid glycine, which naturally promotes relaxation and enhances absorption in the small intestine. Because it is highly bioavailable and does not cause digestive upset, it is ideal for taking before bed. The listener is taught to match the form of magnesium to the intended outcome, rather than assuming all magnesium is interchangeable.