Caprylic acid (octanoic acid, C8) is a medium-chain saturated fatty acid — one of the four fatty acids that make up medium-chain triglycerides (MCTs). Unlike long-chain fatty acids (which require bile acids and chylomicron packaging to enter the lymphatic system), caprylic acid is absorbed directly into the portal vein, transported straight to the liver and rapidly converted to ketone bodies — an alternative fuel source to glucose used by the brain, heart and muscles. This metabolic shortcut is what makes C8 genuinely unique.
What Are MCTs and How Does Caprylic Acid Fit In?
Medium-chain triglycerides are triglycerides containing fatty acids with 6–12 carbon chains. Four MCTs occur in nature:
- C6 — Caproic acid: Rarely supplemented; causes GI discomfort at supplemental doses
- C8 — Caprylic acid: Fastest conversion to ketones; most rapidly absorbed MCT; most studied for cognitive effects
- C10 — Capric acid: Slightly slower conversion than C8; both are often combined in C8:C10 MCT products
- C12 — Lauric acid: Often classified as MCT but behaves more like a long-chain fatty acid metabolically; makes up approximately 50% of coconut oil
Standard “MCT oil” derived from coconut oil typically contains a mix of C8 and C10 (and sometimes C12). Pure C8 caprylic acid products are more concentrated — and more expensive — but produce ketones more rapidly than mixed MCT oil.
What Does Caprylic Acid / MCT Actually Do?
Brain fuel via ketones — strong evidence in specific populations
Ketone bodies (acetoacetate, beta-hydroxybutyrate, acetone) are an alternative fuel to glucose that the brain uses efficiently. MCT consumption significantly raises blood ketone levels even without dietary carbohydrate restriction — unlike achieving ketosis through diet alone, which takes days. Research has shown meaningful cognitive benefits specifically in people with early Alzheimer’s disease and mild cognitive impairment (where glucose metabolism in neurons is impaired but ketone utilisation is preserved). In healthy adults, the cognitive effect of MCTs is less dramatic but real: some trials show improved working memory and processing speed, proposed to relate to the mild ketosis produced.
Energy and exercise performance — moderate evidence
MCTs are used as an energy source during endurance exercise. Several trials confirm MCT supplementation spares muscle glycogen during exercise, potentially extending endurance performance. However, large doses (above 30g) cause GI distress during exercise — limiting practical use.
Antifungal activity — good evidence for caprylic acid specifically
Caprylic acid has documented antifungal activity against Candida albicans and other Candida species in vitro and in some clinical contexts. The mechanism involves disrupting the fungal cell membrane. This is used in integrative medicine for gut Candida overgrowth — though large-scale RCTs in humans are limited.
Weight management — weak evidence
MCTs have a higher thermogenic effect than long-chain fats and may slightly reduce energy intake via ketone-mediated satiety signals. Effects on body weight are modest in clinical trials and not clinically meaningful as a standalone intervention without dietary changes.
How to Use MCT/Caprylic Acid
- Start low — 5–10ml per day and increase gradually. GI distress (nausea, loose stools) is common when starting at full dose
- Add to coffee, smoothies or take in capsule form
- For cognitive effects: take in the morning on an empty stomach or with minimal carbohydrate to maximise ketone production
- For exercise: consume 30–60 minutes before training — but start at very low doses (5ml) to assess GI tolerance during exercise
CapryBio by BioBodyBoost — caprylic acid (C8) in convenient capsule format, halal certified, vegan, UK GMP. Capsule format eliminates the GI distress risk associated with large liquid MCT doses. Browse the full range.
