Glossary
42 terms
Psychobiotics: The Gut Bacteria That Influence Your Mood
Psychobiotics are a subset of probiotics and prebiotics with measurable effects on mental health. Through the gut-brain axis, specific strains influence anxiety, stress response, and mood. Here's what the science actually supports.
Centella Asiatica (Cica): The Three-Way Skin Repair Ingredient
Centella Asiatica is a botanical ingredient used in Asian medicine for centuries, now clinically backed for its simultaneous action on inflammation, collagen synthesis, and skin barrier repair. The science behind K-beauty's most talked-about ingredient.
What Is Polyglutamic Acid? The Natto-Derived Humectant That Outperforms Hyaluronic Acid
Polyglutamic acid (PGA) is a fermentation-derived biopolymer originally found in natto that binds moisture at four times the capacity of hyaluronic acid and simultaneously activates the skin's own hyaluronic acid synthesis enzymes. It represents a new category of humectant that both draws and builds moisture.
Skin Barrier: What It Is, Why It Breaks Down, and How to Repair It
How the stratum corneum's ceramide-lipid structure keeps moisture in and irritants out, the habits that damage it, and the evidence-based approach to restoring it.
What Is Ectoin? The Extremolyte That Rebuilds the Skin Barrier
Ectoin is a natural amino acid derivative produced by microorganisms surviving in extreme environments like salt flats and desert soils. It stabilizes the water layer around skin cells, strengthens the skin barrier, and has clinical evidence supporting its use in atopic dermatitis and sensitive skin.
What Is Ergothioneine? The Longevity Antioxidant Found in Mushrooms
Ergothioneine is a sulfur-containing amino acid found primarily in mushrooms. The human body has a dedicated transporter for it, suggesting it plays a meaningful evolutionary role in mitochondrial protection, oxidative stress defense, and cellular longevity.
Photoaging: How UV Radiation Rewrites Your Skin's Future
The biological mechanics of UV-driven collagen breakdown and pigmentation, the difference between photoaging and chronological aging, and evidence-based strategies to prevent and improve both.
What Is Inflammaging? The Silent Inflammation That Accelerates Aging
Inflammaging is the low-grade, chronic inflammation that builds in the body as the immune system ages. It leaves no obvious symptoms but quietly drives skin aging, collagen breakdown, and systemic decline.
Menopause: What Estrogen Loss Actually Does to Your Skin and Body
How the estrogen decline during perimenopause and menopause accelerates skin aging, disrupts hydration, and affects bone density, plus evidence-based strategies to manage each.
Fisetin: The Most Potent Flavonoid Senolytic, From Strawberries
Fisetin is a flavonoid in strawberries, apples, persimmons, and onions. Mayo Clinic research found it the most potent senolytic among 10 flavonoids tested. One of the few senolytic ingredients accessible without prescription.
Senolytics: The New Approach to Selectively Remove Senescent Cells
Senolytics selectively kill senescent cells, cells that accumulate with age, driving tissue aging and chronic inflammation. Through dasatinib+quercetin, fisetin, and DNA methylation clock tracking, they're opening a new frontier in late-2020s longevity medicine.
Astaxanthin: The Marine Carotenoid That Crosses Cell Membranes
Astaxanthin is the powerful antioxidant carotenoid behind the red color of salmon and shrimp. The only carotenoid spanning the entire cell membrane lipid bilayer, it acts on skin, eyes, cardiovascular, muscle, and brain simultaneously.
GHK-Cu Copper Peptide: The Tripeptide That Flips Epigenetic Switches
GHK-Cu is a complex of the glycine-histidine-lysine tripeptide and copper ions. It alters 4,000+ gene expressions to simultaneously induce collagen, elastin, and angiogenesis. A natural molecule whose blood levels decline with age.
Azelaic Acid: Dicarboxylic Acid Acting Simultaneously on Rosacea, Acne, and Pigmentation
Azelaic acid is a natural dicarboxylic acid with simultaneous anti-inflammatory, antibacterial, and melanin-inhibiting mechanisms. A rare single ingredient FDA-approved for rosacea, acne, and hyperpigmentation, and safe during pregnancy.
Vitamin K2: The Cofactor That Directs Calcium Precisely Into Bone
Vitamin K2 (MK-7, menaquinone) activates osteocalcin to direct calcium into bone and remove it from blood vessels. 3-year trials in postmenopausal women showed significantly slowed bone density decline.
Resveratrol: The Sirtuin-Activating Longevity Polyphenol
Resveratrol is the polyphenol in grape skin and red wine that activates sirtuins (SIRT1), supporting DNA repair and mitochondrial function. 2026 clinical evidence confirms skin wrinkle reduction as a single ingredient in women over 40.
Creatine: Not Just for Muscles, but a Brain Energy Coenzyme
Creatine is a naturally occurring amino acid derivative that supports ATP regeneration. Beyond strength, it acts on brain cognition and protects menopausal women's muscle and bone, repositioning as a midlife female longevity ingredient.
Exosomes: Multi-Layered Message Packages Cells Send Each Other
Exosomes are 30-150 nm extracellular vesicles cells produce to deliver proteins, growth factors, and miRNA. They signal regeneration, anti-inflammation, and barrier repair to skin cells, becoming the next-gen K-beauty core ingredient.
Idebenone, the Smaller, Deeper-Penetrating Antioxidant That Goes Beyond CoQ10
A breakdown of idebenone's structural advantages, skin antioxidant mechanism, differences from CoQ10, concentration guidelines, and precautions.
Polynucleotides (PN·PDRN): Salmon-Derived Regenerative Molecules
PN and PDRN are highly purified DNA fragments extracted from salmon testes. They stimulate dermal fibroblast regeneration and anti-inflammation, forming the core of Rejuran and K-beauty regenerative medicine.
HMB: The Leucine Metabolite That Blocks Muscle Breakdown
HMB (beta-hydroxy-beta-methylbutyrate) is a metabolite of leucine that inhibits muscle protein breakdown. It has become a core protective strategy during GLP-1 weight loss, aging, and injury recovery.
Mandelic Acid, the AHA That Sensitive Skin Can Actually Use
How mandelic acid's larger molecular size makes it gentler than other AHAs, its clinical evidence for pigmentation and exfoliation, how it compares to glycolic acid, and how to use it safely.
Postbiotics: Microbial Metabolites That Work Without Being Alive
Postbiotics are inactivated microbial cells or metabolites that deliver biological effects without viability. Covers the difference from probiotics and prebiotics, clinical evidence for gut and skin, and how to choose products.
Telomeres, the Biological Clock at the Ends of Your Chromosomes
What telomeres are, why they shorten with age, their role as a biological age biomarker, and evidence-based strategies for preserving telomere length.
NAD+, the Coenzyme at the Crossroads of Energy and Aging
What NAD+ does in every cell, why it declines with age, the clinical evidence behind NMN and NR precursors, and practical dosing guidance.
GLP-1, the Gut Hormone Reshaping Weight Management
How GLP-1 works, the clinical evidence behind semaglutide and tirzepatide, the muscle-loss problem, and a nutrition guide for GLP-1 medication users.
Bakuchiol: The Plant-Based Retinol Alternative That Skips the Irritation
How bakuchiol works, head-to-head clinical data versus retinol, and why it matters for sensitive skin, pregnancy, and daytime routines.
Curcumin: The Anti-Inflammatory Powerhouse Inside Turmeric
Curcumin's mechanisms, the bioavailability problem and how to solve it, clinical evidence for skin, joints, and cognition.
Peptides: The Protein Fragments That Tell Your Skin to Build More Collagen
How different peptide types work, clinical evidence for Matrixyl, GHK-Cu, and Argireline, plus the right concentrations and layering order.
Ashwagandha: The Clinical Evidence Behind This Cortisol-Lowering Adaptogen
The clinical evidence for ashwagandha (KSM-66) in reducing cortisol, relieving stress, and improving sleep quality, along with appropriate dosages and safety considerations.
Rhodiola Rosea, the Adaptogen with Clinical Evidence for Fatigue and Stress
A comprehensive guide to Rhodiola Rosea — its key compounds salidroside and rosavin, clinical evidence for fatigue reduction and stress response, and practical dosage information.
Sunscreen: What SPF Numbers Actually Mean
What SPF really measures, the difference between UVA and UVB, PA ratings explained, how to choose the right sunscreen for your skin type, and how much you actually need to apply.
Nattokinase, the Fermented Enzyme with Clinical Evidence for Blood Pressure and Circulation
A complete guide to nattokinase — the enzyme derived from fermented natto — covering fibrinolytic activity, blood pressure reduction, cardiovascular benefits, dosage, and critical drug interaction warnings.
Niacinamide: One Ingredient for Barrier Repair, Pigmentation, and Pore Control
The clinical evidence behind niacinamide's barrier-strengthening, pigmentation-suppressing, and pore-refining properties, with concentration-based usage guidelines.
Hyaluronic Acid: Why Molecular Weight Changes Everything
How molecular weight determines skin penetration depth, the clinical evidence for topical and oral hyaluronic acid, and how to choose the right product for your goals.
Magnesium by Type: From Glycinate to Threonate, a Selection Guide
The eight most common magnesium forms compared by absorption, target area, and side effects. How to choose between glycinate, threonate, taurate, and citrate based on your goals.
Omega-3: Why DHA and EPA Deserve Separate Attention
The distinct roles of DHA and EPA, clinical evidence for cardiovascular and brain health, optimal dosages, and how to choose the right omega-3 product.
Vitamin D: How the Sunshine Vitamin Regulates Both Immunity and Bone Health
Vitamin D's roles in immunity, bone metabolism, and hormonal balance, along with optimal blood levels, dosage guidelines, and the risks of taking too much.
Probiotics: Different Strains, Entirely Different Effects
How probiotic effects vary by strain, the clinical evidence for gut barrier function and immune modulation, and how to choose the right one for your goals.
Retinol: The Vitamin A Derivative That Resets Your Skin's Cell Turnover
How retinol works, concentration-by-concentration effects, anti-aging clinical evidence, and the right way to use it without wrecking your barrier.
Collagen Peptides: Do They Actually Reach Your Skin When You Take Them Orally?
The clinical evidence behind oral collagen peptide supplementation, their effects on skin elasticity and joint health, optimal dosages, and how to choose the right product.
What Is Ceramide? The Lipid That Makes Up 50% of Your Skin Barrier
Ceramides account for roughly 50% of the lipids in the stratum corneum, making them the cornerstone of skin barrier function. Production drops by up to 40% in your 30s. Here's what that means and how to replenish them.