Daily-Tea-Drinking

Quick Summary

Caffeine

  • Most tea has 15-70 mg caffeine / cup.
  • Coffee tends to have 80-135 mg caffeine / cup.
  • It is a myth that green or white teas are always lower in caffeine than black.
  • Any color of tea (black, green, white, etc.) can be high or low in caffeine.

All true teas  from the Camellia sinensis plant contain caffeine. There are a lot of debuts around this topic, so I decided to talk about it. This article outlines the caffeine levels in various teas, explores the factors influencing caffeine content, notes which teas are highest and lowest in caffeine, and dispels common myths about tea and caffeine.

Caffeine Molecule
The Caffeine Molecule

About caffeine

Caffeine is a naturally-occurring stimulant, found in several plants. Caffeine is water soluble, and is extracted into the brewed cup when preparing tea, coffee, or other caffeinated beverages.

The most well-known plants containing caffeine are tea (Camellia Sinensis), coffee, and yerba maté.

Although tea has a number of health benefits, heavy caffeine use has unpleasant effects and negative impacts on health, including anxiety and insomnia, and for this reason many tea drinkers seek to moderate their caffeine intake. The amount of caffeine in tea tends to be low, but is high enough to be a matter of concern for people drinking large quantities of tea, as well as people sensitive to caffeine for medical reasons.

How much caffeine is in tea?

Another much-repeated claim is that black tea is high in caffeine, green tea is lower, and white tea (through the naturalness of its manufacture it is implied) has next to none. While suiting the sales pitch of some tea vendors this information is so wrong as to verge on the fraudulent.

Three scientifically verifiable facts are:

1. Caffeine level varies naturally in types of tea and levels in one type may overlap with another type
2. Black and green tea manufactured from leaf from the same bushes on the same day will have virtually the same caffeine levels (within +/- 0.3%)
3. For a given bush, the finer the plucking standard, the higher the caffeine level

Actual caffeine level in tea is highest:

• when the tea is derived from buds and young first leaf tips (thus white tea has a high caffeine level)
• when the bush is assamica type rather than sinensis (can be 33% higher caffeine, thus African black tea tends to be higher than China black tea)
• when the bush is clonal VP rather than seedling (can be 100% higher caffeine, thus new plantings in Africa are higher than old seedling plantings in Asia),
• when the plant is given a lot of nitrogen fertilizer (as in Japan), and
• during fast growing seasons.

Thus tea derived from older leaf, China type seedling bush, under-fertilized husbandry and in autumn season will naturally be lowest in caffeine. Georgian and Turkish tea falls into this category: expect only 1 to 1.5% caffeine in them, compared with the usual 3% in retail teas. Tea from well-fertilized fast-growing young tips of African clonal tea can often have 5-6% caffeine. http://chadao.blogspot.it/2008/02/caffeine-and-tea-myth-and-reality.html

The caffeine content of tea varies widely from one tea to the next, and depends on how the tea is brewed, but tends to be within the range of 15-70mg per 8 ounce cup.

Caffeine can also be measured in terms of milligrams of caffeine per grams of dry tea. A teaspoon of dry tea leaves tends to weigh around 2.5 grams, the amount usually used to make a single cup, although this varies by the type of tea. One study of the caffeine content of teas (after steeping) found that the caffeine content of tea varied from about 3 mg/g to 30mg/g, which would result in a cup of tea containing between 7.5 mg and 75 mg of tea.

In most cases, tea has much less caffeine than coffee; a typical cup of coffee contains 80-135 mg of caffeine. However, it is important to note that these figures are per cup, not per serving, and in the case of large serving sizes, and also with espresso and other heavily-caffeinated drinks, the caffeine per serving can be considerably higher.

In the U.S. the standard “small” serving size is 12 ounces. A recent study of commercial coffee vendors in Australia found that roughly a quarter of espresso samples contained over 120 mg of caffeine per serving, about 1/8th contained 167 mg or more per serving, and the highest contained 214 mg per serving. The authors of this study concluded that the most often-cited figures on caffeine content of coffee tend to underestimate the actual caffeine content.

How much caffeine is safe to consume?

To place these figures in perspective, the current consensus of the American Congress of Obstetricians and Gynecologists is that it is safe for pregnant women to consume up to 200 mg of caffeine daily.[2] For the general public, the Mayo clinic recommends that 200-300 mg of caffeine daily is safe, but that 500-600 mg daily can cause a number of health problems.[3] People with impaired liver function, and people taking medications that inhibit the CYP1A2 enzyme may have an even lower safe threshold.

If drinking a stronger tea containing 60mg caffeine / cup, 8 cups a day would be a safe amount, or 3 for pregnant women. For a weaker tea, with 30mg / cup, twice this amount would still be a safe amount of caffeine. Different people react differently to caffeine, so an amount that is safe or pleasant for one person may not be healthy for everyone.

L-theanine in tea interacts with caffeine

In addition to caffeine, tea also contains L-theanine; theanine can interact with caffeine, allowing a smaller dose of caffeine to have a stronger effect in terms of boosting concentration and alertness. This may explain why tea seems to provide a stronger boost in alertness for some people than one would expect from its caffeine content alone.

Do black, green, or white teas contain more or less caffeine?

You cannot generalize about caffeine content by tea type. Many tea companies, and even some reputable entities such as the U.S. Department of Agriculture, have made misleading generalizations about the caffeine content of broad classes of tea. It is a widespread myth that black tea contains more caffeine than green tea, and another myth that white tea contains the least caffeine of all teas.

Studies that have actually measured the caffeine content of a large number of different teas have consistently found that caffeine levels vary more among individual teas than across broad categories of tea such as black, white, green, oolong, or pu-erh. A study published in 2005 in the Journal of Food Science listed, among other things, the caffeine content of 77 different teas, and found a broad range of caffeine content among both green and black teas.[4] Surprisingly, the tea in this study that was found to contain the most caffeine was a white tea, solidly dispelling the myth about white tea’s caffeine content.

One possible exception to this observation is that matcha is known to contain high levels of caffeine, consistently much higher than other teas. This is due in part to higher caffeine levels in the leaf used to produced matcha, but it is also due to the fact that, because matcha is a powdered tea, the entire tea leaf is consumed when brewing, so a cup of prepared matcha contains 100% of the caffeine in the leaf.

 Leaves, stems, or buds/tips

Tea can be made from different parts of the tea plant, and these parts contain different quantities of caffeine. Leaf buds (tips) and younger leaves are higher in caffeine than older, mature leaves.[7] This pattern can be explained by the fact that, for the tea plant, caffeine acts a natural insecticide, serving to protect the plant against being eaten by insects. Since the tips and tender young leaves are most vulnerable to insects, these parts of the plant are highest in caffeine; the older leaves are tougher and thus lower in caffeine. “Tippy” teas such as Yunnan Gold or Silver Needle White Tea (Bai Hao Yinzhen) are thus higher in caffeine than large-leaf teas.

How you brew or prepare tea affects caffeine content

The quantity of leaf used and the length of time the leaves are steeped both directly influence the caffeine content of the final cup of tea. Using more leaves and steeping for a longer time both increase the caffeine in the resulting cup.

In 1996, Monique Hicks, Peggy Hsieh and Leonard Bell published a peer-reviewed scientific paper recording precise time related extraction of caffeine from tea using a modern detection technique (HPLC). This paper, ‘Tea preparation and its influence on methylxanthine concentration,’ appeared in Food Research International Vol 29, Nos 3-4, pp. 325-330. (FRI is copyright of the Canadian Institute of Food Science and Technology). Methylxanthines caffeine, theobromine and theophyllin all occur in tea and have similar physiological action, but in tea caffeine is the prominent methylxanthine.

In summary: Hicks et al measured the caffeine (plus theobromine) content of six different teas (three bagged and three loose-leaf, including black, oolong and green types). They measured caffeine-extraction in boiling water when steeped for 5 minutes, 10 minutes and 15 minutes. They replicated all their extractions three times to eliminate experimental error. Extrapolation of their data gives the following caffeine-extraction percentages below 5 minutes (averaged over all tea types and formats); note that while loose tea extracted marginally more slowly than tea-bag tea, it made only a couple of percentage-points’ difference:

30 seconds: 9% caffeine removal
1 minute: 18% caffeine removal
2 minutes: 34% caffeine removal
3 minutes: 48% caffeine removal
4 minutes: 60% caffeine removal
5 minutes: 69% caffeine removal
10 minutes: 92% caffeine removal
15 minutes: 100% caffeine removal

Most (but not all) herbal teas contain no caffeine

Although caffeine does occur in a number of plants, the overwhelming majority of herbal teas are caffeine free. The most notable exception is yerba mate. Other plants containing caffeine are rare as ingredients in herbal tea; these plants include guayusa, yaupon and guarana.

In addition to exploring other herbal teas, people desiring caffeine-free tea-like drinks might want to try South African rooibos and honeybush, two plants which are often described as being similar to tea in flavor, health benefits, and manner of production.

Caffeine: How much is too much?

By Mayo Clinic Staff

To place these figures in perspective, the current consensus of the American Congress of Obstetricians and Gynecologists is that it is safe for pregnant women to consume up to 200 mg of caffeine daily.[2] For the general public, the Mayo clinic recommends that 200-300 mg of caffeine daily is safe, but that 500-600 mg daily can cause a number of health problems.[3] People with impaired liver function, and people taking medications that inhibit the CYP1A2 enzyme may have an even lower safe threshold.

If drinking a stronger tea containing 60mg caffeine / cup, 8 cups a day would be a safe amount, or 3 for pregnant women. For a weaker tea, with 30mg / cup, twice this amount would still be a safe amount of caffeine. Different people react differently to caffeine, so an amount that is safe or pleasant for one person may not be healthy for everyone.

Caffeine has its perks, but it can pose problems too. Find out how much is too much and if you need to curb your consumption.

If you rely on caffeine to wake you up and keep you going, you aren’t alone. Caffeine is used by millions of people every day to increase wakefulness, alleviate fatigue, and improve concentration and focus.

How much is too much?

 Up to 400 milligrams (mg) of caffeine a day appears to be safe for most healthy adults. That’s roughly the amount of caffeine in four cups of brewed coffee, 10 cans of cola or two “energy shot” drinks.

Although caffeine use may be safe for adults, it’s not a good idea for children. And adolescents should limit themselves to no more than 100 mg of caffeine a day.

Even among adults, heavy caffeine use can cause unpleasant side effects. And caffeine may not be a good choice for people who are highly sensitive to its effects or who take certain medications.

 Heavy daily caffeine use — may cause side effects such as:

  • Insomnia
  • Nervousness
  • Restlessness
  • Irritability
  • Stomach upset
  • Fast heartbeat
  • Muscle tremors

Even a little makes you jittery

 Some people are more sensitive to caffeine than are others. If you’re susceptible to the effects of caffeine, just small amounts — even one cup of coffee or tea — may prompt unwanted effects, such as restlessness and sleep problems.

How you react to caffeine may be determined in part by how much caffeine you’re used to drinking. People who don’t regularly drink caffeine tend to be more sensitive to its negative effects. Other factors may include body mass, age, medication use and health conditions such as anxiety disorders. Research also suggests that men may be more susceptible to the effects of caffeine than are women.

References

1. Ben Desbrow et. al., An examination of consumer exposure to caffeine from retail coffee outlets, Food and Chemical Toxicology, Vol. 45, No. 9, Sep. 2007, pp. 1588-1592.
2. No Link Between Moderate Caffeine Consumption and Miscarriage, American Congress of Obstetricians and Gynecologists, Press Release, July 21, 2010.
3. Caffeine: How much is too much?, Mayo Clinic, March 24, 2009.
4. M. Friedman et. al., Distribution of catechins, theaflavins, caffeine, and theobromine in 77 teas consumed in the United States, Journal of Food Science, Vol. 70, No. 9, Nov-Dec. 2005, pp. C550-C559.
5. Jenna M. Chin et. al., Technical Note: Caffeine Content of Brewed Teas, Journal of Analytical Toxicology, Vol. 32, No. 8, Oct. 2008 , pp. 702-704(3).
6. Tea and Health – Analysis of Caffeine, Determination of caffeine by liquid chromatography – UV, in collaboration with College Centre for the Transfer of Technologies TransBIOTech, Retrieved Jul. 16, 2013.
7. Y.S. Lin et. al., Factors affecting the levels of tea polyphenols and caffeine in tea leaves, Journal of Agriculture and Food Chemistry, Vol. 51, No. 7, Mar. 26, 2003 Mar 26, pp. 1864-73.

Further Reading:

Nigel Melican, Caffeine and Tea: Myth and Reality, Cha Dao, Feb. 6, 2008.

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