Tea Caffeine Headaches: 2 Types (Too Much vs Too Little) + Which Teas to Choose

You’re halfway through your afternoon when a dull ache starts creeping around your temples. By the time you notice it, the pressure is building behind your eyes, radiating across your forehead. You mentally review your day—plenty of sleep, enough water, nothing unusual. Then it hits you: you skipped your usual midday cup of tea, or maybe you had more than usual this morning. That headache? It’s probably caffeine-related, and understanding why tea causes these headaches helps you prevent them entirely.

The Two Types of Tea Caffeine Headaches

Tea caffeine triggers headaches through two opposite mechanisms, and figuring out which one affects you matters for prevention and relief.

Too much caffeine creates overstimulation headaches. When you consume more caffeine than your body tolerates, blood vessels in your brain constrict excessively, reducing blood flow. This vasoconstriction itself can trigger pain. Additionally, caffeine blocks adenosine receptors throughout your nervous system. Adenosine normally has pain-dampening properties in the brain, so when caffeine interferes with this system, pain signals may process more intensely. The combination—reduced cerebral blood flow plus altered pain signaling—creates a throbbing headache that feels different from other types.

Too little caffeine causes withdrawal headaches, which operate through the opposite mechanism. When you consume caffeine regularly, your body adapts by upregulating adenosine receptors and increasing adenosine production to compensate for caffeine’s constant blocking action. This adaptation happens remarkably quickly—as few as three days of consistent caffeine intake establishes this pattern. When you suddenly stop or significantly reduce intake, all those extra adenosine receptors become fully active. Adenosine causes vasodilation, expanding blood vessels throughout your head and neck. Research shows that adenosine concentrations in the head and neck can increase 68 percent above normal during withdrawal, causing pronounced vasodilation and pain (Echeverri et al., 2010).

How to tell which one you’re experiencing usually comes down to timing and pattern. Overstimulation headaches typically develop within an hour or two of consuming high amounts of tea—especially on an empty stomach or after a period of minimal caffeine intake. The pain feels intense, sometimes with a jittery, anxious quality. You might feel your heart racing or experience tremors alongside the headache. Withdrawal headaches, conversely, hit 12 to 24 hours after your last caffeine dose, peak around 20 to 51 hours, and can persist for 2 to 9 days. These headaches often feel duller and more constant than overstimulation ones, sometimes accompanied by fatigue, difficulty concentrating, and mood changes.

Why tea headaches feel different from coffee headaches relates to caffeine content and other compounds present. Tea delivers caffeine more gradually than coffee, and L-theanine—an amino acid abundant in tea—modulates caffeine’s effects. This combination usually prevents the sharp caffeine spike that coffee provides, which means tea-related headaches tend to develop more slowly and feel less acute. However, this gentler delivery can also make withdrawal sneakier. You might not realize you’ve developed caffeine dependence from tea until you skip a day and encounter that afternoon headache you can’t quite explain.

What Actually Happens in Your Head

The mechanisms behind caffeine headaches involve complex interactions between blood vessels, neurotransmitters, and your brain’s pain processing systems. Understanding these processes clarifies why seemingly minor changes in tea consumption can produce such pronounced head pain.

Caffeine’s effect on blood vessels is bidirectional and dose-dependent. At moderate doses, caffeine acts as a cerebral vasoconstrictor, meaning it tightens blood vessels in your brain and reduces blood flow. Research measuring cerebral blood flow with magnetic resonance imaging found that 250 milligrams of caffeine reduced blood flow by an average of 27 percent across different levels of habitual caffeine users (Addicott et al., 2009). This vasoconstriction happens because caffeine blocks adenosine A2A and A2B receptors on vascular smooth muscle. Adenosine normally causes these muscles to relax, dilating vessels and increasing blood flow. When caffeine occupies those receptors instead, the muscles contract and vessels narrow.

The rebound mechanism when caffeine wears off explains withdrawal headaches precisely. Your body compensates for chronic caffeine consumption by creating more adenosine receptors and increasing adenosine production. When caffeine levels drop, adenosine floods all these extra receptors, producing exaggerated vasodilation. Blood vessels expand beyond their normal caliber, increasing blood flow and creating pressure that registers as pain. Studies show this rebound vasodilation can normalize after two weeks of complete caffeine abstinence, which explains why withdrawal headaches eventually resolve (Chu et al., 2016).

Vasoconstriction versus vasodilation explained simply: Imagine your brain’s blood vessels like water hoses. Caffeine tightens the hose, reducing flow (vasoconstriction). This reduced pressure can actually feel good initially—it’s why caffeine helps some headaches. But when caffeine wears off suddenly, the hose expands dramatically (vasodilation), creating a pressure surge that triggers pain signals. The vessels push against surrounding tissues and nerves, generating that characteristic throbbing sensation.

Why some people get headaches and others don’t involves multiple factors. Genetic variations affect how quickly you metabolize caffeine and how many adenosine receptors you naturally produce. People who metabolize caffeine slowly experience prolonged effects from each dose, making them more susceptible to overstimulation headaches. Those with naturally lower adenosine receptor density may develop less pronounced rebound when caffeine wears off. Individual pain sensitivity thresholds vary enormously too—what one person experiences as mild pressure, another perceives as debilitating pain. Hydration status, sleep quality, stress levels, and even hormonal cycles (for women) all modulate headache susceptibility in ways that interact with caffeine’s vascular effects.

High-Caffeine Teas That Trigger Headaches

Not all teas pose equal headache risk. Caffeine content varies dramatically based on tea type, processing method, and brewing technique, making some varieties more problematic for headache-prone individuals.

Matcha represents the concentrated culprit in the tea world. Because you consume the entire powdered tea leaf rather than steeping and discarding leaves, matcha delivers all the caffeine that leaf contains. A standard serving using 2 grams of matcha powder contains approximately 60 to 70 milligrams of caffeine—comparable to a small coffee. However, many people use more powder or consume multiple servings daily, quickly escalating intake. Two teaspoons of matcha (around 4 grams for thick koicha-style preparation) delivers roughly 140 milligrams—more than most cups of coffee. The rapid absorption of powdered tea also means caffeine hits your system faster than with steeped tea, increasing overstimulation risk for sensitive individuals.

Gyokuro stands as the hidden high-caffeine tea that surprises people expecting typical green tea moderation. This premium Japanese green tea undergoes extended shading before harvest—up to three weeks under shade cloths. This deliberate stress response triggers the plant to produce more caffeine as a natural insect defense. A properly brewed cup of gyokuro contains 120 to 140 milligrams of caffeine, exceeding most small coffees. The sweet, umami-rich flavor disguises this high content, and people accustomed to thinking of green tea as “low caffeine” may consume gyokuro liberally without realizing they’re approaching coffee-level stimulation.

Yerba mate, while not technically from the Camellia sinensis plant, deserves mention as a popular tea-like beverage with significant headache potential. Traditional preparation involves filling a gourd two-thirds full with mate leaves and adding hot water, creating an extremely high leaf-to-water ratio. The resulting infusion can contain 80 to 180 milligrams of caffeine depending on preparation strength. Many people also re-steep mate multiple times throughout the day, accumulating caffeine doses that rival or exceed coffee consumption.

Strong breakfast blends and their caffeine loads create headache triggers through sheer concentration. English Breakfast, Irish Breakfast, and similar blends typically combine multiple bold black teas—often including high-caffeine Assam—and are designed for robust brewing. A standard 8-ounce cup of breakfast blend contains approximately 40 to 70 milligrams of caffeine, but many people brew these teas strong, use more tea, steep longer, and drink multiple cups throughout morning. This can easily result in consuming 150 to 250 milligrams of caffeine just from breakfast tea, especially when combined with a morning matcha latte or afternoon green tea.

How much is too much for headache-prone people varies individually, but patterns emerge. Most studies identify 400 milligrams daily as the general upper limit for adults, but headache-sensitive individuals often encounter problems well below this threshold. For some people, exceeding 200 milligrams daily triggers overstimulation headaches. Others develop withdrawal symptoms when daily intake exceeds 100 milligrams—equivalent to just two or three cups of moderate-strength tea. The key indicator: if you experience headaches either when consuming your usual amount or when you skip it, your intake has likely exceeded your personal tolerance.

Brewing Methods That Increase Headache Risk

How you prepare tea dramatically affects its caffeine content and, consequently, headache risk. Understanding extraction variables helps you control caffeine intake more precisely than simply choosing tea types.

Over-steeping increases caffeine extraction significantly. Caffeine is highly water-soluble and extracts continuously as long as tea leaves remain in contact with water. Research measuring caffeine extraction over time found that after 30 seconds, only about 9 percent of caffeine had entered the water. At one minute, roughly 18 percent. Three minutes reached 48 percent, and five minutes extracted 69 percent (Hicks et al., 1996). Steeping for 10 or 15 minutes—something people do when they get distracted or intentionally brew strong tea—can extract nearly all available caffeine, potentially doubling or tripling what a standard 3-minute steep would provide.

Water temperature effects on caffeine release follow predictable patterns. Hotter water extracts caffeine more efficiently. Boiling water (100°C) pulls caffeine from leaves much faster than water at 70 or 80°C. This matters particularly for green and white teas, which are often brewed at lower temperatures to prevent bitterness. If you brew these delicate teas with boiling water—either because you prefer stronger flavor or don’t control temperature carefully—you extract significantly more caffeine than traditional preparation methods would.

Multiple quick steeps versus one long steep creates interesting caffeine dynamics. The gongfu brewing method, popular with oolong and pu-erh teas, involves many short infusions of 15 to 30 seconds each using a high leaf-to-water ratio. Counter-intuitively, this often extracts less total caffeine than one long Western-style steep. The first gongfu infusion pulls surface caffeine quickly, but subsequent steeps extract progressively less since the highly soluble caffeine depletes first. The cumulative caffeine from six 20-second gongfu steeps may be less than one 5-minute Western steep of the same leaves.

The “strong tea” mistake that backfires happens when people try to maximize tea’s benefits by brewing aggressively. They use more leaves, hotter water, and longer steeping, thinking they’re extracting more beneficial compounds. While this does increase antioxidant extraction, it also dramatically elevates caffeine content—often to levels that trigger headaches, jitters, or sleep disruption. A “double-strength” brew doesn’t just double the good stuff; it doubles the caffeine too, potentially pushing sensitive individuals past their threshold.

The Withdrawal Headache Timeline

Understanding withdrawal’s predictable pattern helps you identify whether headaches stem from missing your usual tea rather than from consuming too much.

When withdrawal headaches typically hit follows a consistent schedule. Symptoms begin 12 to 24 hours after your last caffeine intake. For regular morning tea drinkers, this means afternoon or evening on the first day without tea, or the following morning if they had evening tea. The headache doesn’t usually arrive suddenly—it builds gradually as adenosine increasingly occupies those upregulated receptors.

Why skipping your usual tea causes pain connects directly to those compensatory changes your body made. Research shows that caffeine consumption creates physiological dependence through adenosine receptor upregulation, increased adenosine production, and heightened receptor affinity. These changes happen quickly—just three days of regular caffeine intake suffices to establish dependence patterns. When you miss your usual dose, you’re not simply returning to baseline; you’re experiencing an exaggerated adenosine effect due to your body’s compensatory adaptations. The withdrawal headache reported by up to 50 percent of regular caffeine users represents this system imbalance.

The difference between daily tea drinkers and occasional sippers is stark. Someone who drinks two cups of tea every day for months has thoroughly adapted their adenosine system. Missing a day triggers pronounced withdrawal symptoms—headache, fatigue, irritability, difficulty concentrating. An occasional tea drinker who has three cups one day and none the next typically experiences no withdrawal because their system hasn’t adapted. The consistency of intake matters more than the amount for withdrawal development, though higher intake generally produces more severe withdrawal when stopped.

How long withdrawal headaches last depends on individual factors but follows general patterns. Peak intensity occurs 20 to 51 hours after cessation—roughly the second day without caffeine. Most people experience substantial improvement by days 3 to 5, with complete resolution within 2 to 9 days. However, some individuals report lingering subtle effects for two weeks. The duration correlates with habitual intake level and duration of regular use. Someone drinking five cups daily for years may experience longer, more intense withdrawal than someone drinking two cups daily for months.

Teas That Are Safer for Headache-Prone People

If caffeine-related headaches plague you, strategic tea selection minimizes risk while maintaining the pleasure and ritual of tea drinking.

White tea offers naturally lower caffeine content due to its minimal processing and use of young buds and leaves. Despite the common myth that young buds contain more caffeine (which has some truth), white tea’s gentle processing and traditional light steeping produce infusions with relatively modest caffeine—typically 15 to 30 milligrams per cup. Silver Needle, made from buds only, and White Peony both provide delicate, slightly sweet flavors without the caffeine load of black or green teas. However, steeping method matters—brewing white tea Western-style for 2 to 3 minutes yields far less caffeine than multiple gongfu-style infusions.

Houjicha represents roasted and reduced caffeine content through processing. This Japanese green tea undergoes roasting at high temperatures, which degrades some caffeine molecules and drives off volatile compounds. The result contains significantly less caffeine than unroasted sencha—often 50 percent less, putting most houjicha around 7 to 15 milligrams per cup. The nutty, toasty flavor appeals to people who find green tea too grassy, and the low caffeine makes it appropriate for evening consumption without headache or sleep concerns.

Kukicha, the twig tea solution, derives from tea plant stems and twigs rather than leaves. Since caffeine concentrates in leaves (particularly young ones), twigs contain minimal caffeine—typically 10 milligrams or less per cup. Kukicha offers a subtle, slightly sweet, creamy flavor that’s refreshing without being boring. In Japan, it’s considered suitable for children and elderly people precisely because of its low stimulant content.

Decaf options actually work when processed properly. Modern CO2 decaffeination can remove 96 to 99 percent of caffeine while retaining most flavor and beneficial compounds. Quality decaf green tea contains roughly 2 to 5 milligrams of caffeine per cup—essentially negligible even for highly sensitive individuals. The taste differs slightly from regular tea (slightly flatter, less astringent), but premium decaf from Japanese producers can be surprisingly good. Decaf Earl Grey, using the bergamot oil to mask any processing flavor, often succeeds better than plain decaf black tea.

Herbal alternatives provide zero caffeine when you need complete avoidance. Rooibos, chamomile, peppermint, hibiscus, and countless other tisanes offer diverse flavors and their own beneficial compounds without any caffeine. These aren’t technically tea (not from Camellia sinensis), but they fill the same niche—hot, flavorful beverages for any time of day. For people whose headaches stem from any caffeine whatsoever, herbals represent the safest choice.

The Dehydration Factor

Caffeine’s relationship with hydration contributes to headaches in ways people often overlook, particularly with tea consumed throughout the day without adequate water intake.

How tea’s mild diuretic effect contributes deserves nuanced understanding. Caffeine does increase urine production through multiple mechanisms—it inhibits sodium reabsorption in the kidneys and may directly stimulate bladder smooth muscle. However, the diuretic effect is modest, especially for regular caffeine consumers whose bodies have adapted. Research shows that moderate caffeine intake (up to 400 milligrams daily) doesn’t cause significant dehydration in habitual users. The fluid you consume in tea largely compensates for any increased urination.

Why drinking tea without water causes problems emerges from two factors. First, even modest fluid losses matter when you’re starting from an inadequately hydrated baseline. Many people chronically exist in mild dehydration without realizing it. Adding tea’s diuretic effect—even a gentle one—can tip them into symptomatic dehydration, with headache as a primary indicator. Second, some people psychologically substitute tea for water. They drink six cups of tea daily but minimal plain water, assuming tea hydrates equivalently. While tea does provide hydration, the optimal approach includes both tea and water to ensure sufficient fluid intake without excessive caffeine.

The hydration-headache connection operates through blood volume and brain positioning. Even mild dehydration reduces blood volume, which can lower blood pressure and reduce blood flow to the brain. Dehydration also causes slight brain tissue shrinkage, allowing the brain to pull away minutely from the skull. This creates traction on pain-sensitive structures—meninges, blood vessels, and nerves—triggering headache. The combination of reduced cerebral blood flow plus mechanical pain from tissue traction creates dehydration headaches that feel similar to caffeine withdrawal headaches, making it difficult to distinguish causes.

How much water you actually need alongside tea depends on individual factors—body size, activity level, climate, overall diet. A reasonable baseline: drink at least one glass of plain water for every two cups of tea. If you consume high-caffeine teas like matcha or gyokuro, increase this ratio. Monitor urine color as a practical hydration indicator—pale yellow suggests adequate hydration, while dark yellow or amber indicates you need more water. If you’re experiencing headaches and unsure whether caffeine or dehydration is the culprit, try drinking an extra 16 to 24 ounces of water and waiting 30 minutes. If the headache eases, dehydration was likely contributing.

Tannin Headaches vs Caffeine Headaches

Sometimes what appears to be a caffeine headache actually stems from tea’s tannins—astringent compounds that can trigger headaches through different mechanisms than caffeine.

How to identify if tannins are the real problem involves careful observation. Tannin headaches typically develop during or shortly after drinking tea, rather than hours later like withdrawal headaches. They often accompany stomach irritation or nausea, since tannins can increase stomach acid production and irritate the gastric lining. If you experience headaches specifically from drinking tea on an empty stomach, but not when consuming the same tea with food, tannins likely play a role. Additionally, if low-caffeine black tea triggers headaches but higher-caffeine green tea doesn’t, suspect tannins rather than caffeine.

Which teas are highest in tannins follows processing patterns. Black tea contains the most—between 11 to 15 percent by weight—because the oxidation process converts catechins into tannins. Strong breakfast blends, Assam, and heavily oxidized oolongs pack particularly high tannin loads. Green tea contains significantly less, around 2 to 3 percent. White tea usually has the least among true teas. Interestingly, some herbal teas like hibiscus contain substantial tannins despite being caffeine-free, which is why hibiscus sometimes triggers headaches in sensitive individuals.

Why black tea might cause headaches independent of caffeine relates to multiple tannin effects. Beyond stomach irritation, tannins can trigger histamine release in sensitive individuals, potentially causing vasodilation and headache. Some research suggests tannins may affect blood pressure regulation and vascular tone independent of their caffeine content. The combination of tannins’ astringency, potential for gastric upset, and vascular effects creates a headache profile distinct from pure caffeine headaches.

Testing whether tannins affect you requires systematic experimentation. Try drinking the same amount of caffeine from different sources—green tea versus black tea, or tea versus coffee. If black tea triggers headaches but equal-caffeine green tea doesn’t, tannins probably contribute. Alternatively, drink your usual tea with milk or cream—these bind to tannins and neutralize their astringency. If adding milk eliminates headaches, you’ve identified tannin sensitivity. Finally, try matching your tea consumption with food rather than drinking on an empty stomach. If this prevents headaches, tannins affecting your stomach likely triggered the pain.

Personal Tolerance and Timing Issues

Individual factors dramatically influence whether tea causes headaches, making universal recommendations impossible. Understanding your personal patterns helps you prevent caffeine-related head pain effectively.

Why afternoon tea hits different than morning tea involves your body’s natural cortisol rhythms and accumulated caffeine. Cortisol peaks naturally in the morning, providing natural alertness that works synergistically with caffeine. Afternoon cortisol levels are lower, so the same dose of tea caffeine produces relatively stronger effects. Additionally, if you consumed morning tea, afternoon consumption adds to already-elevated caffeine levels since caffeine’s half-life is 4 to 6 hours. What felt like a moderate morning dose becomes an excessive afternoon total.

Empty stomach tea drinking triggers headaches through multiple pathways. Without food buffering, caffeine absorbs faster, creating a sharper blood concentration spike that’s more likely to cause overstimulation symptoms. The rapid absorption also means blood levels drop more precipitously, potentially triggering earlier withdrawal. Tannins in tea stimulate stomach acid production, which on an empty stomach can cause irritation, nausea, and headaches. Finally, low blood sugar combined with caffeine’s metabolic effects can produce or worsen headaches in sensitive individuals.

Sleep deprivation amplifies caffeine effects substantially. When you’re sleep-deprived, your baseline adenosine levels are already elevated—adenosine accumulates during waking hours and clears during sleep. If you didn’t sleep well, you start the day with excess adenosine. The same caffeine dose that normally feels pleasant may over-stimulate when competing with high adenosine levels, or may produce a more dramatic rebound when it wears off because those baseline adenosine levels were already problematic.

Hormonal cycles and caffeine sensitivity create predictable patterns for women. During the late luteal phase of the menstrual cycle (the week before menstruation), many women experience increased caffeine sensitivity. Estrogen and progesterone fluctuations affect how quickly the liver metabolizes caffeine. Some research suggests caffeine clearance slows during certain cycle phases, meaning the same tea dose produces higher blood caffeine levels and longer-lasting effects. Women often report that tea they tolerate fine during most of the month triggers headaches, jitters, or sleep disruption during premenstrual days. Tracking these patterns helps you adjust consumption proactively.

How to Prevent Tea Headaches

Prevention beats treatment for caffeine-related headaches. Strategic approaches minimize risk while maintaining the enjoyment and benefits of tea drinking.

Consistent caffeine timing strategy prevents withdrawal headaches effectively. If you drink tea daily, consume it at roughly the same times each day. Your body adapts to predictable caffeine schedules, maintaining stable adenosine receptor activity and neurotransmitter balance. Weekend variations—sleeping in and having your first tea two hours later than usual—can trigger withdrawal headaches. If you typically drink morning tea, try to maintain that schedule even on days off. Similarly, if afternoon tea is part of your routine, skipping it unpredictably creates the conditions for withdrawal headache development.

Gradual reduction methods work far better than sudden cessation if you’re cutting back. Reduce daily caffeine by approximately 10 to 25 percent every three to four days. For example, if you drink four cups of black tea daily, drop to three and a half cups (slightly weaker brewing or smaller portions) for several days, then to three cups, and so forth. This gentle tapering allows your adenosine system to downregulate gradually without the dramatic rebound that causes withdrawal headaches. Some people mix regular and decaf tea during reduction periods, progressively shifting the ratio toward decaf.

Hydration rules to follow include drinking water proactively throughout the day rather than reactively when thirsty. Thirst indicates you’re already mildly dehydrated. Drink a glass of water before your first tea of the day, between tea sessions, and with any high-caffeine teas. The rough guideline of one cup of water per two cups of tea provides a starting point, adjustable based on your activity level, climate, and how you feel.

Food pairing helps buffer both caffeine absorption and tannin effects. Having tea with or after meals slows caffeine absorption, preventing the sharp spike that triggers overstimulation headaches. Food in your stomach also neutralizes some tannin astringency and reduces their irritating effects on the gastric lining. Protein and fat particularly slow caffeine absorption—having tea with breakfast, lunch, or a substantial snack creates more stable, gradual caffeine levels than drinking it alone.

When to switch tea types throughout the day follows a logical pattern. Higher-caffeine options work best earlier in the day when cortisol levels naturally support alertness and when you have more time before sleep for caffeine to clear your system. Reserve matcha, gyokuro, and strong black teas for morning and early afternoon. Transition to moderate-caffeine options like standard green tea or lighter oolongs in mid-afternoon. After 3 or 4 PM, switch to low-caffeine alternatives like white tea, houjicha, or kukicha. In the evening, choose either decaf or herbal options entirely. This graduated approach provides stimulation when you want it while minimizing sleep disruption and withdrawal risk.

Conclusion

Tea caffeine headaches stem from two opposite mechanisms—consuming too much creates overstimulation through excessive vasoconstriction and altered pain processing, while consuming too little (after your body has adapted to regular intake) causes withdrawal through rebound vasodilation. Understanding which mechanism affects you clarifies prevention strategies. High-caffeine teas like matcha, gyokuro, and strong breakfast blends pose the greatest risk for overstimulation, while suddenly skipping your usual tea triggers withdrawal regardless of type. Headache-prone individuals should focus on consistent timing of moderate-caffeine intake, adequate hydration, strategic food pairing, and transitioning to lower-caffeine options later in the day. Quality over quantity, consistency over intensity, and mindful consumption prevents most tea-related headaches while preserving the pleasure and benefits of this ancient beverage.

References

• Addicott, M. A., Yang, L. L., Peiffer, A. M., Burnett, L. R., Burdette, J. H., Chen, M. Y., Hayasaka, S., Kraft, R. A., Maldjian, J. A., & Laurienti, P. J. (2009). The effect of daily caffeine use on cerebral blood flow: How much caffeine can we tolerate? Human Brain Mapping, 30(10), 3102-3114.
• Chu, C. S., Lai, J. Y., Chen, C. Y., Wang, Y. L., Wang, C. L., & Yang, C. H. (2016). Caffeine discontinuation improves acute migraine treatment: a prospective clinic-based study. The Journal of Headache and Pain, 17(1), 69.
• Echeverri, D., Montes, F. R., Cabrera, M., Galán, A., & Prieto, A. (2010). Caffeine’s vascular mechanisms of action. International Journal of Vascular Medicine, 2010, 834060.
• Hicks, M. B., Hsieh, Y. H. P., & Bell, L. N. (1996). Tea preparation and its influence on methylxanthine concentration. Food Research International, 29(3-4), 325-330.