Best Time to Drink Green Tea: Why 8 AM Backfires (Tolerance, Iron & Sleep)
I spent months drinking green tea at 7 AM, thinking I was starting my day right. Then I found the chronopharmacology research showing that timing determines whether green tea works with your body’s rhythms or against them. The difference between 8 AM and 10 AM isn’t about preference—it’s about whether you’re accelerating tolerance while sabotaging iron absorption, or maximizing benefits while preserving your natural hormonal patterns.
Disclaimer: The information on Purely Tea is for educational purposes only and is not intended as medical advice. Always consult with a healthcare professional before making changes to your diet, especially if you have underlying health conditions.
Understanding Your Body’s Natural Cortisol Rhythm
Before discussing when to drink green tea, you need to understand what’s already happening in your body without any tea at all. Cortisol, often called the stress hormone, actually serves as your body’s built-in alarm clock. It follows a predictable 24-hour rhythm with multiple peaks and valleys throughout the day.
The most dramatic cortisol event happens within 30 minutes of waking. This cortisol awakening response (CAR) produces a 50% increase in cortisol levels in healthy adults. Your body literally wakes itself up with a hormone surge that promotes alertness, increases blood pressure slightly, elevates blood sugar to provide energy, and prepares you for the day’s demands. This isn’t stress—it’s your circadian rhythm functioning exactly as designed.
Cortisol doesn’t peak just once. Throughout the day, it rises and falls in a specific pattern: primary peak occurs 8-9 AM (20-30 minutes post-wake for typical schedules), secondary peak happens around noon-1 PM, tertiary peak arrives at 5:30-6:30 PM, and lowest levels occur during early sleep phases (midnight-3 AM). The valleys between these peaks—when cortisol naturally declines—are when your body genuinely needs external stimulation.
This rhythm exists for evolutionary reasons. Morning cortisol mobilizes energy for hunting, gathering, or in modern terms, getting to work and being productive. Midday and evening peaks supported sustained activity throughout waking hours. The dramatic nighttime drop signals rest and recovery time. This pattern is so fundamental that disrupting it creates measurable health consequences including impaired glucose metabolism, weakened immune function, mood disturbances, and sleep disorders.
Understanding this rhythm is essential because caffeine—including the 25-50mg per cup in green tea—directly interacts with cortisol. The timing of this interaction determines whether you enhance your natural rhythms or fight against them. This is chronopharmacology: the study of how biological rhythms interact with drug effects. Working with your cortisol curve rather than against it produces better results with fewer negative consequences.
Why Your 8 AM Green Tea is Building Tolerance
When you wake around 7 AM, your cortisol surges naturally by 8-9 AM to approximately 50% above baseline levels. This hormone creates genuine alertness without requiring any external substances. You feel awake because your body programmed itself to be awake. Drinking green tea during this natural peak adds caffeine on top of existing maximum stimulation.
This “double peak” doesn’t make you more alert than your body already is. Instead, it creates redundant stimulation that your brain recognizes as excessive. The body’s response to repeated excessive stimulation is adaptation—it compensates by making itself less sensitive to the stimulus. This is the foundation of tolerance.
The mechanism is well-documented. Caffeine works by blocking adenosine receptors in your brain. Adenosine accumulates during waking hours and binds to receptors that signal tiredness. When caffeine blocks these receptors, adenosine can’t bind, and you don’t feel tired. However, when you consistently provide caffeine during periods when adenosine levels are naturally low (like during cortisol peaks when you’re already alert), your brain responds by creating more adenosine receptors. More receptors mean you need progressively more caffeine to achieve the same blocking effect.
Research demonstrates how quickly this happens. In a controlled study, participants consumed 300-600mg caffeine daily (equivalent to 6-12 cups of green tea or 3-6 cups of coffee). On day one, morning caffeine produced robust cortisol increases. By day five, the same dose produced virtually no cortisol response—the body had completely adapted (Lovallo et al., 2005). The caffeine wasn’t weaker. The participants’ brains had changed in just five days to require caffeine just to feel normal.
Sandy’s Science Corner: The Adenosine Receptor Upregulation
Tolerance develops through receptor proliferation. Adenosine normally binds to A1 and A2A receptors, signaling tiredness. Caffeine’s molecular structure allows it to occupy these receptors without activating them—blocking adenosine’s effect. When you consistently introduce caffeine during high-cortisol periods (when adenosine is naturally low), your brain interprets this as abnormal receptor availability and responds by synthesizing additional receptors. This upregulation occurs within days. Now the same caffeine dose blocks the same percentage of receptors, but leaves more unblocked receptors available for adenosine. Result: you need more caffeine to achieve the same alertness. The timing accelerates this process because high-cortisol periods have low adenosine, making caffeine pharmacologically unnecessary. Your brain adapts fastest when you use drugs during periods your body doesn’t need them.
This creates a vicious cycle. Your morning tea becomes less effective. You increase the amount or frequency. Your brain adapts further. Eventually, you’re not drinking green tea to feel alert—you’re drinking it to not feel tired, which is your brain’s adapted baseline. The tea that once provided genuine benefits now just prevents withdrawal symptoms.
The solution isn’t more tea. It’s better timing. Using caffeine during cortisol valleys—when your body genuinely needs external stimulation—slows tolerance development dramatically. You maintain sensitivity because you’re filling a real alertness gap rather than adding unnecessary stimulation on top of natural peaks.
The Hidden Iron Absorption Problem
While you’re accelerating tolerance with poorly-timed green tea, you’re simultaneously creating another problem: iron deficiency. Green tea contains high concentrations of tannins—polyphenolic compounds that bind strongly to iron in your digestive tract.
The chemistry is straightforward. When tannins and iron are present together in your stomach and small intestine, they form insoluble iron-tannate complexes. These complexes cannot cross the intestinal wall. The iron bound in these complexes passes through your digestive system completely unused, excreted in feces. The inhibition is substantial: research shows tea consumption reduces non-heme iron absorption by 20-70%, depending on tea concentration and timing (Disler et al., 1975).
Non-heme iron comes from plant sources: spinach, lentils, beans, tofu, fortified cereals, and grains. This is the only iron source for vegetarians and vegans, and it constitutes a significant portion of iron intake even for omnivores. Non-heme iron is already less bioavailable than heme iron from meat—your body absorbs only 2-20% of non-heme iron under ideal conditions, compared to 15-35% of heme iron. Adding tannin binding on top of already-poor absorption creates serious deficiency risk.
Who’s most vulnerable? Women with heavy menstrual periods lose significant iron monthly, vegetarians and vegans rely entirely on non-heme sources, people with diagnosed iron deficiency or anemia, athletes with high iron turnover from training, and anyone taking iron supplements for medical reasons. These groups cannot afford 20-70% blocked absorption.
The evidence extends beyond laboratory studies. A case report documented a middle-aged man who developed severe iron-deficiency anemia traced directly to drinking over 1.5 liters of green tea daily for 20 years (Fan, 2016). His hemoglobin dropped dangerously low despite adequate dietary iron intake. When he stopped the excessive tea consumption, his iron levels recovered. This wasn’t a genetic disorder or undiagnosed bleeding—it was tea tannins systematically blocking iron absorption for two decades.
Recent research confirms tannins affect both non-heme and heme iron to varying degrees, though non-heme iron experiences much stronger inhibition (Zijp et al., 2000). The previous assumption that meat iron was completely protected has been revised—while heme iron resists tannin binding better than non-heme iron, some interaction still occurs.
The practical solution is timing separation. Tannins must be present simultaneously with iron to form binding complexes. Research confirms that consuming tea one hour before or after iron-rich meals significantly reduces inhibitory effects, allowing substantially better absorption. The tannins pass through the digestive system while iron from meals arrives separately, preventing the interaction.
This timing issue directly connects to the 8 AM green tea problem. Breakfast commonly includes iron-fortified cereals, oatmeal with nuts or seeds, tofu scrambles, whole grain toast, or other iron-containing foods. Drinking green tea with breakfast or immediately after blocks that iron. Either drink tea well before breakfast, or wait at least one hour afterward. The 10-11 AM timing recommended for cortisol reasons conveniently creates natural separation from breakfast eaten at 7-8 AM, solving both problems simultaneously.
The Sweet Spot: 10-11 AM and Why It Works
The optimal timing for green tea falls in the window between cortisol peaks—specifically, the period when your morning cortisol surge has peaked and begun declining but before the midday peak begins. For people waking around 7 AM, this window occurs approximately 10-11:30 AM.
By 10 AM, your cortisol awakening response has peaked around 8-9 AM and started its natural decline. Your body is no longer at maximum alertness from hormones alone. This is when caffeine provides meaningful benefit rather than redundant stimulation. You’re filling a genuine alertness gap as your natural stimulation wanes, not piling stimulation on top of an existing peak.
This timing slows tolerance development because you’re using caffeine when your body actually needs it. The adenosine levels that accumulated during the first hours of waking are starting to build up. Blocking these receptors now serves a real purpose. Your brain doesn’t interpret this as excessive stimulation requiring compensation through receptor upregulation—it’s appropriate stimulation matching genuine physiological need.
The iron absorption benefit comes automatically. Breakfast consumed at 7-8 AM has largely moved through your stomach by 10 AM. The critical iron absorption phase in the small intestine occurs 1-3 hours post-meal. Drinking tea at 10 AM creates sufficient separation to prevent tannin-iron binding. You get your green tea benefits without sacrificing iron absorption.
Individual variation matters. The 10-11 AM window assumes waking around 7 AM. Early risers waking at 5-6 AM experience their cortisol peak at 6-7 AM, making 9-10 AM their optimal window. Late risers waking at 9-10 AM don’t reach cortisol peak until 10-11 AM, making 11 AM-noon more appropriate for them. The principle remains constant: wait 90-120 minutes after waking to allow your natural cortisol peak to work first, then introduce caffeine as levels decline.
This is practical chronopharmacology—aligning drug intake with biological rhythms rather than arbitrary clock times. The same principles apply to other medications and supplements. Taking stimulants during natural alertness peaks wastes effectiveness and accelerates tolerance. Taking them during natural energy valleys maximizes benefit while minimizing adaptation. Green tea timing is one application of a broader principle about working with your body rather than against it.
The Pre-Workout Timing Strategy
While 10-11 AM serves general health and alertness purposes, exercise introduces a different timing opportunity based on green tea’s effects on fat metabolism. Research shows specific benefits when green tea consumption is timed 30-90 minutes before physical activity.
Green tea catechins, particularly EGCG (epigallocatechin gallate), reach peak blood concentrations approximately 1.3-1.6 hours after consumption. Aligning these peak levels with exercise maximizes the synergistic effects between catechins and exercise-induced hormone release. The mechanism centers on catechol-O-methyltransferase (COMT), an enzyme that breaks down norepinephrine and epinephrine—hormones that signal fat cells to release stored fat for energy.
EGCG inhibits COMT, preventing it from breaking down these catecholamines quickly. During exercise, your body naturally releases norepinephrine and epinephrine to mobilize energy. When COMT is inhibited by EGCG, these hormones remain active longer. The result is an extended fat-burning signal that continues beyond what exercise alone produces.
Research demonstrates measurable effects. In controlled studies, green tea consumption increased fat oxidation by 17% during moderate-intensity cycling compared to placebo (Hodgson et al., 2013). Another study found green tea extract consumed 90 minutes before interval sprinting enhanced fat oxidation both during and after exercise, with elevated norepinephrine and glycerol levels during recovery—biomarkers indicating lipolysis or stored fat breakdown (Randell et al., 2014; Roberts et al., 2015).
Ashley’s Personal Experience: Pre-Workout Discovery
I tested three timing windows over six weeks: 30 minutes, 60 minutes, and 90 minutes pre-workout. At 30 minutes, I felt slightly nauseous during intense intervals—too close to consumption. At 90 minutes, the energy boost felt subtle. The 60-75 minute window hit perfectly—clean, sustained energy through my entire HIIT session with no jitters like pre-workout supplements gave me. My endurance improved noticeably in week three. I could maintain higher intensity longer without feeling depleted. The difference between caffeinated supplements and green tea is night and day—supplements spike then crash, green tea sustains. Now I brew two cups at 8:30 AM for my 9:45 AM training sessions, and it’s become as essential as my warm-up.
The optimal dose based on research is 125-375 mg EGCG, equivalent to approximately 2-3 cups of brewed green tea or one standardized extract capsule. The timing sweet spot is 60-90 minutes before exercise starts, allowing catechin absorption and distribution to peak during your workout.
However, there’s an important caveat: habitual caffeine consumption diminishes these effects. Research shows individuals with low habitual caffeine intake (under 300 mg daily) experience significantly greater fat oxidation benefits than high consumers. If you’re already drinking 3-4 cups of coffee daily (300-400 mg caffeine), adding green tea produces minimal additional metabolic benefit—your body has already adapted to regular caffeine. The pre-workout strategy works best for people who maintain low baseline caffeine consumption and use green tea strategically around training.
The thermogenic effect extends beyond workouts. Studies show green tea catechins increase 24-hour energy expenditure by approximately 4% compared to placebo—an additional 75-100 calories daily burned at rest. This comes from enhanced thermogenesis, the production of heat through metabolic activity.
For morning exercisers, this creates a timing conflict with the cortisol tolerance principle. If you train at 7 AM, drinking green tea at 5:30-6 AM for pre-workout benefit means consuming during or before your cortisol awakening response. In this case, the exercise benefit likely outweighs the tolerance concern—you’re using the caffeine for a specific performance purpose, not just habitual consumption during natural alertness. However, limiting this to training days rather than daily morning tea helps minimize tolerance development.
The Afternoon Window: 2-3 PM
Beyond the morning sweet spot, afternoon presents a second optimal window. Cortisol’s secondary peak occurs around noon-1 PM, then declines through early afternoon. The valley between noon and evening peaks falls roughly between 2-3 PM—another period when caffeine provides genuine benefit rather than redundant stimulation.
This timing serves as an alternative to afternoon coffee that many people use to combat post-lunch energy dips. The advantage of green tea over coffee in this window relates to L-theanine, an amino acid found almost exclusively in tea. L-theanine creates calm focus without jitters—it promotes alpha brain wave activity associated with relaxed alertness while moderating caffeine’s stimulating effects.
Afternoon green tea provides mental clarity without the overstimulation that often accompanies afternoon coffee. The theanine-caffeine combination produces sustained focus for several hours without the crash that follows coffee’s higher caffeine dose. This makes the 2-3 PM window particularly suitable for afternoon work that requires concentration without anxiety or jitteriness.
However, this afternoon consumption must respect the evening cutoff discussed in the next section. A 2-3 PM cup leaves sufficient time for caffeine metabolism before sleep, but pushing toward 4-5 PM starts encroaching on the period where caffeine interferes with sleep quality. The afternoon window works specifically because it falls between cortisol peaks while still maintaining adequate separation from bedtime.
The Evening Cutoff: Why 6 Hours Before Sleep Matters
Green tea’s relatively modest caffeine content—25-50mg per cup compared to coffee’s 95-200mg—creates a false sense of security about evening consumption. However, caffeine’s half-life means even these moderate doses interfere with sleep when consumed too late.
Caffeine’s half-life in most adults is 5-6 hours. This means that 5-6 hours after consumption, half the caffeine remains active in your system. If you drink green tea at 4 PM, approximately 13-25mg caffeine is still circulating at 10 PM. While this seems minor, it’s enough to interfere with sleep quality in caffeine-sensitive individuals.
The mechanism extends beyond simple wakefulness. Cortisol naturally declines through evening, reaching its lowest levels during early sleep phases. This decline signals rest time to your entire endocrine system. Evening caffeine disrupts this natural cortisol curve, creating conflicting signals—your circadian clock says sleep, but caffeine promotes alertness. This conflict degrades sleep quality even when you manage to fall asleep, reducing time spent in deep sleep stages and increasing nighttime awakenings.
Poor sleep creates cascading health consequences that directly undermine the reasons many people drink green tea. Sleep disruption impairs metabolic health, reduces insulin sensitivity (relevant for blood sugar regulation similar to how green tea and Ceylon tea improve glucose metabolism), elevates hunger hormones ghrelin and reduces satiety hormone leptin, decreases next-day fat oxidation and thermogenesis, and impairs exercise recovery and performance.
Here’s the irony: if you’re drinking green tea for metabolic benefits or weight management, evening consumption that undermines sleep actually sabotages your goals. The modest metabolic boost from catechins doesn’t offset the metabolic harm from poor sleep. One night of poor sleep can reduce insulin sensitivity by 20-30%—far more than green tea’s positive metabolic effects could compensate for.
The practical cutoff is 6 hours before your intended bedtime. If you sleep at 11 PM, stop green tea by 5 PM. Earlier sleeper targeting 10 PM? Cutoff at 4 PM. This 6-hour window accounts for caffeine’s half-life plus additional time for the remaining caffeine to drop to levels that don’t interfere with sleep onset or quality.
Individual variation exists based on caffeine metabolism. Genetic variants in the CYP1A2 enzyme affect caffeine breakdown speed. Fast metabolizers clear caffeine quickly and can drink it later without sleep effects. Slow metabolizers experience prolonged caffeine presence and need earlier cutoffs, sometimes 8-10 hours. If you follow the 6-hour rule but still experience sleep problems, extend the cutoff and monitor whether sleep quality improves.
Decaffeinated green tea offers an evening alternative for people who enjoy tea’s taste and ritual without wanting stimulation. Decaffeination removes 97-99% of caffeine while retaining some catechins. However, the metabolic benefits—fat oxidation enhancement, thermogenesis increase—require caffeine’s synergistic contribution. Decaf works for relaxation and hydration but shouldn’t be expected to provide the metabolic effects that research documents for caffeinated green tea.
Meal Timing Specifics: The Iron Absorption Strategy
Understanding the general principle that tannins block iron is one thing. Implementing practical meal timing strategies is another. The specifics depend on what you eat and when throughout the day.
Breakfast presents the most common timing conflict. Many breakfast foods contain significant non-heme iron: iron-fortified cereals (common in many commercial cereals), oatmeal with nuts or seeds, tofu scrambles or tempeh breakfast dishes, whole grain toast or bagels, smoothies with leafy greens and seeds. Drinking green tea with any of these meals or immediately after blocks a substantial portion of that iron—20-70% depending on tea strength and individual factors.
The solution requires either drinking tea before breakfast with sufficient time gap (at least 30 minutes, preferably 60 minutes), or waiting after breakfast (minimum 1 hour, preferably 90 minutes). For most people, the after-breakfast strategy works better. Eating breakfast at 7-8 AM and drinking tea at 10-11 AM creates the natural separation that solves both the iron problem and the cortisol timing issue simultaneously.
Lunch and dinner bring similar considerations. Lunch with lentil soup, bean salad, or a spinach-heavy meal, and dinner with tofu stir-fry, chickpea curry, or fortified grains all contain non-heme iron that tannins can bind. The one-hour separation rule applies: finish your meal, wait 60 minutes minimum before drinking tea. Or drink tea an hour before meals.
The timing becomes critical for anyone concerned about iron absorption and anemia risk, particularly those with diagnosed deficiency or high iron needs. Iron supplements require even more separation—90 minutes to 2 hours. Iron supplements provide concentrated doses that tannins can bind to efficiently. Don’t take iron supplements with tea or even within an hour of tea consumption.
Heme iron from meat sources is less affected by tannins than non-heme iron, but recent research shows some interaction still occurs. Omnivores who eat meat regularly face less risk than vegetarians, but shouldn’t assume complete protection. The safest approach for anyone concerned about iron is maintaining timing separation regardless of iron source.
For vegetarians and vegans who rely entirely on non-heme iron, tea timing becomes non-negotiable. Every meal contains the only iron you’ll get. Blocking 20-70% of that iron through poor timing creates real deficiency risk over months and years. These individuals should treat the one-hour separation as mandatory, not optional.
Pregnancy and menstruation create additional iron demands. Pregnant women need substantially more iron for fetal development and increased blood volume. Women with heavy periods lose significant iron monthly. Both groups should be particularly careful about tea timing around meals and iron supplementation.
Individual Factors That Change Optimal Timing
While general recommendations provide useful starting points, individual variations mean optimal timing differs somewhat between people based on chronotype, caffeine sensitivity, habitual consumption patterns, and iron status.
Chronotype—whether you’re naturally a morning lark or night owl—shifts your entire cortisol curve by hours. Morning larks naturally wake early (5-7 AM) and feel most alert in early morning. Their cortisol awakening response peaks around 6-8 AM, earlier than average. For larks, the optimal green tea window shifts earlier to approximately 9-10 AM instead of the standard 10-11 AM recommendation. Their natural cortisol decline happens sooner.
Night owls naturally wake later (8-10 AM or beyond) and peak alertness occurs in late morning or afternoon. Their cortisol awakening response is delayed, possibly not peaking until 10-11 AM or even noon. The standard 10-11 AM timing places green tea consumption right during their cortisol peak—exactly what to avoid. Night owls should shift to 11 AM-1 PM consumption, or align green tea timing with workout schedules if that provides better results.
Most people fall between these extremes as intermediate chronotypes and do well with standard 10-11 AM timing. If you’re uncertain about your chronotype, observe when you naturally wake without alarms and when you feel most alert during the day. Morning people who bound out of bed at 6 AM are likely larks. People who struggle before 9 AM and hit their stride after noon are likely owls.
Caffeine sensitivity varies dramatically between individuals due to genetic differences in caffeine metabolism. The CYP1A2 enzyme in the liver breaks down caffeine. Genetic variants create fast metabolizers who clear caffeine rapidly and slow metabolizers who experience prolonged effects.
Fast metabolizers process caffeine efficiently and often can drink coffee in late afternoon without sleep disruption. They may need shorter cutoff times before bed (4-5 hours instead of 6) and may experience less pronounced tolerance development because the caffeine doesn’t stay in their system as long.
Slow metabolizers feel caffeine effects for many hours. They may need 8-10 hour cutoffs before sleep. They’re more prone to jitteriness at standard doses. They build tolerance faster because caffeine remains present longer, giving more time for receptor adaptation.
Genetic testing can identify CYP1A2 variants, but practical observation works just as well. If you can’t sleep after drinking tea at 3 PM, you’re likely a slow metabolizer. If afternoon tea never affects your sleep, you’re probably a fast metabolizer. Adjust timing and cutoffs based on how your body actually responds rather than strict rules.
Habitual caffeine consumption dramatically affects how much additional benefit you get from green tea. Research consistently shows low habitual caffeine consumers (under 300 mg daily, roughly equivalent to less than 3 cups of coffee) experience significantly better fat oxidation, thermogenesis, and metabolic effects from green tea than high consumers.
If you already drink 3-4 cups of coffee daily (300-400mg caffeine), your body has adapted to regular high-dose caffeine. Adding green tea on top produces minimal additional benefit. The metabolic effects largely depend on caffeine’s contribution, and you’ve already saturated those pathways. For high caffeine consumers, green tea’s benefits reduce primarily to catechin antioxidant effects, which are valuable but don’t include the thermogenic and fat oxidation effects that attract many people to green tea.
The solution for high consumers is reducing baseline caffeine to make room for strategic green tea use. Replace one or two cups of coffee with green tea, or cycle off caffeine entirely for 2-4 weeks to reset sensitivity. After a reset period, green tea produces much more noticeable effects.
Iron status determines how strict you need to be about meal separation timing. Diagnosed iron deficiency or anemia requires strict 2-hour separation between tea and meals or supplements. Normal iron status allows the standard 1-hour separation. Athletes with high iron turnover from training should err on the side of longer separation. Anyone taking iron supplements should separate by 90 minutes to 2 hours minimum.
Conclusion
The difference between drinking green tea at 8 AM and 10 AM determines whether you’re accelerating caffeine tolerance while blocking up to 70% of iron absorption, or aligning with your natural cortisol rhythm while preserving nutrient absorption. The research is unambiguous: early morning consumption during cortisol peaks creates tolerance within five days, tannins block iron when consumed with meals, and evening caffeine disrupts the sleep that’s essential for the metabolic health you’re trying to support. Wait until 10-11 AM when cortisol naturally declines, creating genuine alertness need rather than redundant stimulation. Time pre-workout consumption 60-90 minutes before exercise for the 17% fat oxidation boost. Stop consumption 6 hours before sleep to protect sleep quality. Maintain one-hour separation from iron-rich meals, especially if you’re plant-based or have low iron status. Green tea’s benefits are substantial and well-documented—but only when timing works with your body’s circadian rhythms rather than fighting against them.
Disler, P. B., Lynch, S. R., Charlton, R. W., Torrance, J. D., Bothwell, T. H., Walker, R. B., & Mayet, F. (1975). The effect of tea on iron absorption. Gut, 16(3), 193-200. https://pubmed.ncbi.nlm.nih.gov/1168162/
Fan, F. S. (2016). Iron deficiency anemia due to excessive green tea drinking. Clinical Case Reports, 4(11), 1053-1056. https://pmc.ncbi.nlm.nih.gov/articles/PMC5093162/
Hodgson, A. B., Randell, R. K., & Jeukendrup, A. E. (2013). The effect of green tea extract on fat oxidation at rest and during exercise: Evidence of efficacy and proposed mechanisms. Advances in Nutrition, 4(2), 129-140. https://pubmed.ncbi.nlm.nih.gov/23493529/
Lovallo, W. R., Whitsett, T. L., al’Absi, M., Sung, B. H., Vincent, A. S., & Wilson, M. F. (2005). Caffeine stimulation of cortisol secretion across the waking hours in relation to caffeine intake levels. Psychosomatic Medicine, 67(5), 734-739. https://pubmed.ncbi.nlm.nih.gov/16204431/
Randell, R. K., Hodgson, A. B., Lotito, S. B., Jacobs, D. M., Rowson, M., Mela, D. J., & Jeukendrup, A. E. (2014). The combined effect of green tea and acute interval sprinting exercise on fat oxidation of trained and untrained males. Journal of the International Society of Sports Nutrition, 11(1), 54. https://pubmed.ncbi.nlm.nih.gov/27298806/
Richards, J. C., Lonac, M. C., Johnson, T. K., Schweder, M. M., & Bell, C. (2010). Epigallocatechin-3-gallate increases maximal oxygen uptake in adult humans. Medicine and Science in Sports and Exercise, 42(4), 739-744. https://pubmed.ncbi.nlm.nih.gov/19952844/
Roberts, J. D., Roberts, M. G., Tarpey, M. D., Weekes, J. C., & Thomas, C. H. (2015). Green tea, intermittent sprinting exercise, and fat oxidation. Journal of Dietary Supplements, 12(4), 331-348. https://pmc.ncbi.nlm.nih.gov/articles/PMC4517022/
Zijp, I. M., Korver, O., & Tijburg, L. B. (2000). Effect of tea and other dietary factors on iron absorption. Critical Reviews in Food Science and Nutrition, 40(5), 371-398. https://pubmed.ncbi.nlm.nih.gov/11029010/
