Caffeine, interactions and safety
What is actually known, and how well
Start with what you want a drink to do. Below that sits the reference material — the arithmetic you can check, the published limits with the body that set them, and interaction entries that say how strong the evidence behind each one is.
Start here
What are you drinking it for?
Pick a reason and see what the catalogue offers, and what to be careful with. These are editorial groupings built from the same filters the rest of the site uses — not medical advice.
175 drinks fit
See all 175
Uji Ceremonial Grade Matcha
70 mg · Low acidity
Argentine Traditional Yerba Maté
85 mg · Low acidity
Nitro Cascade Cold Brew Coffee
205 mg · Low acidity
Aged Fermented Shou Pu-erh Tea
60 mg · Low acidity
Shizuoka First-Flush Sencha
30 mg · Low acidity
Egyptian Golden Chamomile Blossom
Caffeine-free · Low acidity
South African Organic Red Rooibos
Caffeine-free · Low acidity
Hanoi Traditional Egg Coffee
140 mg · Low acidity
The reference material
Everything below is here in full — opened one section at a time so it can be read rather than scrolled past.
Work out your cut-off
Single-Origin Ethiopian Espresso at 15:00 is about 64 mg. By 23:00, roughly 21 mg is still in circulation.
Very little left by bedtime.
This is first-order decay — the standard textbook model. It ignores absorption time, so the first hour reads slightly high, and it cannot know your enzymes, your medication or your tolerance. Treat it as a way to compare two plans, not as a measurement of your blood.
Research & brewing science
Articles
Long-form explainers on caffeine, acidity and extraction — sourced, and honest about where the evidence runs out.
- Science & Metabolism
The Ultimate Caffeine Guide: Espresso vs. Matcha vs. Cold Brew vs. Yerba Maté
9 min read - Gastrointestinal Health
Low-Acid Coffee Guide for GERD & Acid Reflux: Temperature vs. Degradation
7 min read - Cardiovascular Health
Paper Filter vs. Metal Mesh: The Lipid Cafestol Impact on Cholesterol
7 min read - Tea Science
The Oolong Paradox: Why Half-Oxidized Tea Has the Widest Flavor Spectrum
8 min read - Gut Microbiome
Kombucha SCOBY Science: Probiotics, GABA Synthesis & Fermentation
7 min read - Origins & Rarity
World's Most Expensive Coffees: Geisha, Kopi Luwak & Blue Mountain Ranked
7 min read - Brewing Physics
The Art of Gongfu Cha: Flash Steeping Physics & Flavor Clarity
7 min read - Adaptogenic Herbs
Adaptogens in Your Cup: Ashwagandha, Tulsi, and Rhodiola Science
8 min read - Brewing Science
Coffee Water Minerals: Hardness, Alkalinity and Better Brewing
7 min read - Brewing Science
Coffee Grind Size Guide: How to Dial In Every Brewer
6 min read - Pour-Over Brewing
Coffee Bloom Guide: When It Helps and How Long to Wait
6 min read - Coffee Fundamentals
Light vs Medium vs Dark Roast Coffee: What Really Changes
6 min read - Coffee Fundamentals
Decaf Coffee Explained: Swiss Water, CO₂ and Solvent Methods
6 min read - Coffee Fundamentals
How to Store Coffee Beans: Freshness, Degassing and Freezing
6 min read - Espresso Brewing
Espresso Ratios Explained: Dose, Yield and Brew Time
6 min read - Brewing Science
Coffee Extraction Explained: Strength, Yield and Taste
6 min read - Cold Coffee
Cold Brew Coffee Ratio Guide: Concentrate vs Ready-to-Drink
6 min read - Brewing Methods
French Press Coffee Guide: Ratio, Grind and Clean Cup Technique
6 min read - Tea Brewing
Green Tea Water Temperature Guide: Avoid Bitterness Without Flat Tea
6 min read - Tea Brewing
How to Brew Black Tea: Temperature, Time and Milk
6 min read - Tea Science
Tea Caffeine Explained: Leaf, Cup Size and Steep Time
6 min read - Tea Brewing
How to Make Matcha: Ratio, Water Temperature and Whisking
6 min read - Tea Fundamentals
Pu-erh Tea Guide: Raw vs Ripe, Brewing and Storage
6 min read - Tea Fundamentals
Loose-Leaf Tea vs Tea Bags: Taste, Convenience and Value
6 min read - Tea Brewing
Best Water for Tea: Minerals, Chlorine and Temperature
6 min read - Tea Culture
Masala Chai Guide: Tea, Spices, Milk and Sweetness
6 min read - Botanical Safety
Herbal Tea Safety Guide: Ingredients, Interactions and Labels
6 min read - Tea Brewing
How to Make Iced Tea: Hot Brew, Cold Brew and Dilution
6 min read - Brewing Methods
AeroPress Coffee Guide: Grind, Ratio and Pressure
3 min read - Brewing Methods
Moka Pot Coffee Guide: Heat, Grind and Ratio
3 min read - Pour-Over Brewing
V60 Pour-Over Guide: Grind, Pouring and Drawdown
3 min read - Coffee Culture
Turkish Coffee Guide: Grind, Foam and Serving
3 min read - Coffee Culture
Vietnamese Phin Coffee Guide: Grind, Dose and Drip Rate
3 min read - Coffee Processing
Washed vs Natural Process Coffee: Flavour and Brewing
3 min read - Coffee Processing
Honey Process Coffee: What It Means and How It Tastes
3 min read - Coffee Fundamentals
Arabica vs Robusta Coffee: Taste, Caffeine and Use
3 min read - Coffee Origins
Ethiopian Coffee Guide: Regions, Processing and Flavour
3 min read - Coffee Origins
Colombian Coffee Guide: Regions, Processing and Flavour
3 min read - Coffee Tasting
Coffee Cupping Guide: How to Taste Coffee Systematically
3 min read - Espresso Brewing
Espresso Crema Explained: What It Means and What It Does Not
3 min read - Tea Brewing
How to Brew White Tea: Leaf, Temperature and Time
4 min read - Tea Brewing
Oolong Tea Brewing Guide: Temperature, Steeps and Leaf
4 min read - Herbal Infusions
Rooibos Tea Guide: Brewing, Flavour and Caffeine
4 min read - South American Drinks
Yerba Maté Guide: Brewing, Caffeine and Temperature
4 min read - Herbal Infusions
Hibiscus Tea Guide: Brewing, Flavour and Safety
4 min read - Herbal Infusions
Ginger Tea Guide: Fresh Root, Brewing and Safety
4 min read - Food Pairing
Coffee and Pastry Pairing Guide: Match Flavour and Texture
3 min read - Food Pairing
Tea and Food Pairing Guide: Match Leaf, Meal and Sweetness
3 min read - Brewing Methods
Coffee Filters Guide: Paper, Metal and Cloth Compared
4 min read - Brewing Science
Coffee Agitation Guide: Stirring, Swirling and Pouring
4 min read - Cold Coffee
Flash-Chilled Coffee Guide: How to Make Better Iced Pour-Over
4 min read - Espresso Brewing
Espresso Tamping Guide: Pressure, Levelness and Consistency
4 min read - Espresso Brewing
Espresso Distribution Guide: Avoid Channeling and Uneven Shots
4 min read - Coffee Skills
How to Steam Milk: Texture, Temperature and Latte Foam
4 min read - Coffee Skills
Latte Art Guide: Milk Texture, Pouring and Practice
4 min read - Espresso Brewing
Ristretto vs Lungo: Espresso Ratio, Taste and Use
3 min read - Coffee Fundamentals
Espresso vs Filter Coffee: Taste, Caffeine and Brewing
4 min read - Coffee Tasting
Coffee Acidity Explained: Brightness, pH and Brewing
3 min read - Coffee Tasting
Coffee Bitterness Explained: Roast, Extraction and Balance
3 min read - Coffee Fundamentals
Single-Origin vs Blend Coffee: Flavour, Consistency and Choice
3 min read - Coffee Processing
Anaerobic Coffee Processing: Flavour, Fermentation and Brewing
3 min read - Coffee Processing
Coffee Fermentation Explained: Processing, Flavour and Quality
3 min read - Tea Science
Tea Oxidation Explained: Green, Oolong and Black Tea
4 min read - Tea Brewing
Tea Steeping Time Guide: How Long to Brew Every Tea
4 min read - Tea Culture
Gongfu vs Western Tea Brewing: Ratios, Steeps and Style
4 min read - Tea Fundamentals
How to Store Tea: Freshness, Light, Moisture and Odours
3 min read - Tea Fundamentals
Jasmine Tea Guide: Scenting, Brewing and Flavour
4 min read - Tea Fundamentals
Earl Grey Tea Guide: Bergamot, Brewing and Pairing
4 min read - Coffee Origins
Kenyan Coffee Guide: AA Grading, SL-28, SL-34 and Why It Tastes So Distinct
5 min read - Coffee Tasting
Coffee Flavour Wheel: How to Use It for Better Tasting and Cupping
5 min read - Espresso Brewing
Espresso Crema Chemistry: CO₂, Melanoidins and What the Foam Actually Tells You
6 min read - Espresso Brewing
Espresso Pressure Profiling: Why Fixed 9-Bar Is a Compromise and How to Use It
6 min read - Coffee Origins
Ethiopian Coffee Regions: How Yirgacheffe, Sidama, Harrar and Jimma Differ in the Cup
6 min read - Coffee Origins
Indonesian Coffee Guide: Sumatra, Java and Wet-Hulling for Earthy, Full-Body Cups
6 min read - Coffee Industry
How the Kenya Coffee Auction Works: Understanding the Nairobi Coffee Exchange
6 min read - Tea Origins
Kenya Purple Tea: The Anthocyanin-Rich Tea That Sits Between Green and Black
7 min read - Coffee Origins
Vietnamese Coffee: Why Robusta Dominates and How Phin and Condensed Milk Became Iconic
6 min read - Coffee Science
Coffee Roasting Chemistry: The Maillard Reaction, Pyrolysis and What Each Phase Does
6 min read - Tea Brewing
Sencha Brewing Guide: How to Match Water Temperature to Leaf Grade
7 min read - Tea Origins
Genmaicha Guide: Toasted Rice, Sencha and Why It Became the People's Tea
6 min read - Tea Brewing
Gyokuro Brewing: The 20-Day Shade, L-Theanine Peak and How to Brew It Right
6 min read - Tea Origins
Hojicha: The Roasted Green Tea That Became Japan's Evening Drink
6 min read - Tea Origins
Chinese Green Tea Guide: Longjing, Bi Luo Chun and the Pan-Fired Tradition
6 min read - Tea Origins
Darjeeling First Flush vs Second Flush: How Flush Affects Flavour
6 min read - Tea Origins
Assam Tea Guide: CTC Processing, Brisk Character and Breakfast Blends
6 min read - Tea Culture
Japanese vs Chinese Green Tea: Processing, Flavour and Brewing Philosophy
6 min read - Tea Origins
Tieguanyin Guide: The Heritage Oolong with Roast and Floral Complexity
5 min read - Tea Origins
Ceylon Tea Guide: Sri Lankan Black Tea by Region, from Nuwara Eliya to Ruhuna
5 min read - Coffee Processing
Carbonic Maceration Coffee: How Anaerobic Fermentation Changed Specialty Coffee
5 min read - Coffee Science
Coffee Terroir: How Altitude, Soil and Climate Make Single Origins Taste Different
6 min read - Coffee Tasting
Coffee Taints and Defects: How to Identify Off-Flavours in the Cup
5 min read - Coffee Industry
Specialty Coffee Pricing: What Drives the Cost of $50/lb Coffees
5 min read - Coffee Science
Coffee Freshness Chemistry: Why Stale Coffee Tastes Like Cardboard
5 min read - Coffee Industry
Direct Trade vs Fair Trade vs Specialty: Three Different Models, Different Claims
5 min read - Coffee Processing
Anaerobic Coffee Processing Variations: Thermal Shock, Yeast Inoculation and More
5 min read - Coffee Fundamentals
Coffee Storage: When Freezing Works, Why Degassing Matters and What Actually Helps
5 min read - Pour-Over Brewing
Chemex Coffee: Why the Thick Filter Produces a Different Cup than V60
5 min read - Pour-Over Brewing
Kalita Wave: Why the Flat-Bottom Brewer Is More Forgiving than the V60
5 min read - Pour-Over Brewing
Siphon Coffee: The Vacuum Brewer and Why It Produces a Different Cup
5 min read - Brewing Science
Coffee Extraction Physics: Solubility, Diffusion and How Concentration Develops
5 min read - Cold Coffee
Cold Brew Extraction: The Chemistry of Long, Low-Temperature Brewing
6 min read - Espresso Brewing
Espresso Physics: Pressure, Flow and Why Channeling Ruins Shots
5 min read - Pour-Over Brewing
Pour-Over Variables: Why Your Recipe Sometimes Fails and How to Fix It
5 min read - Brewing Science
Immersion Brewing: Why Steeping Is More Forgiving than Pour-Over
6 min read - Equipment
Burr Grinder Guide: Why Conical and Flat Burrs Produce Different Particles
5 min read - Equipment
Home Espresso Machines: What E61, Decent and Breville Actually Do Differently
5 min read - Equipment
Home Water Filtration for Coffee: TDS, Hardness and Why Magnesium Matters
5 min read - Equipment
Coffee Scales: Why 0.1g Resolution Matters and What Auto-Timing Does
5 min read - Equipment
Espresso Machine Maintenance: Descaling, Backflushing and Gasket Care
5 min read - Equipment
Pour-Over Kettles: Why Gooseneck and Variable Temperature Matter
5 min read - Equipment
Home Coffee Roasting: Popcorn Poppers, Drum Roasters and How to Start
5 min read - Espresso Brewing
Espresso Tampers, Distribution Tools and WDT: What Each Actually Does
5 min read - Coffee Tasting
Coffee Cupping Protocol: How to Cup Like a Specialty Coffee Professional
5 min read - Coffee Tasting
Coffee and Food Pairing: How Acidity, Body and Roast Affect Combinations
4 min read - Coffee Tasting
Coffee Tasting Vocabulary: How to Build a Personal Lexicon
4 min read - Coffee Tasting
Coffee Acidity vs Bitterness: Finding the Balance Between Bright and Harsh
4 min read - Coffee Skills
Latte Art: How to Pour Heart, Rosetta and Tulip Patterns
5 min read - Brewing Science
Coffee Brewing Ratios: From Ristretto to Long Brew, How Ratio Affects Cup
5 min read - Coffee Tasting
Coffee Service Temperature: How Drinking Temperature Affects Flavour Perception
4 min read
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