Caffeine

I was reading an old article from Bord Bia that said that tea consumption was on the rise at night-time. The reason given was that “people are at home more often and tea is a comforting affordable reliable beverage”.

There have been several papers written on the effect of caffeine on sleep disruption and even more papers written on effect of caffeine on other health issues (good and bad). A major problem in this type of research is that all the papers tend to use very different values for the caffeine content in beverages and foods.

There are plenty of reasons for the variations. Preparation plays a large role and differences in the time and temperature of steeping, the size of the tea leaf and the type of tea used will all influence the caffeine content of tea. The variety of plant, care of the plants, soil nutrients, picking season and the part of plant used will also play a role.

Caffeine Crystals under the microscope

Caffeine Crystals under the microscope (Source)

Caffeine is a white, odourless crystal that occurs naturally in coffee, tea and chocolate and is added to colas and energy drinks. After a lot of reading, here is a summary of caffeine content in tea from sources that seems reliable:

Tea (~200ml after one steeping of three minutes)

Chinese white tea – 75mg

Darjeeling white – 56mg

Indian Green – 59mg

Kenyan Green – 58 mg

Chinese Oolong (Ti Kwan Yin) – 37mg

Assam (FTGFOP) – 86mg

Darjeeling Black (SFTGFOP1) – 54mg

 

For comparison here are some for coffee and other beverages:

Coffee (~200ml)

Coffee (ground roasted) – 115mg

Coffee (instant) – 80mg

Cola – 20mg

Decaffeinated coffee – 4mg

Espresso, single shot – 75mg

Espresso, double shot – 150mg

Red Bull (250ml can) – 80mg

 

Chocolate

It seems to be generally accepted that there are 6mg of caffeine per 30g serving. But it seems to vary a lot:

70% Green and Black dark Chocolate (30g) – 4.5mg

Green and Black milk chocolate (30g) – 2mg

White chocolate (30g) – 0mg

Cadbury dairy milk (28g) – 15mg

Herbal tea

Herbal tea – 0mg

(Note: other substances like theobromine, tanninic acid, caffeol also play a role)

 

I found it surprising how high the caffeine content of green tea is. Many claim that green and white tea have less caffeine than oolong or black tea because of the minimal oxidation. It seems to be well-proven now that this is not the case. White tea in particular uses the bud of the plant which has been shown to have a higher caffeine content that the leaf. I guess most people wouldn’t have a can of coke before bed but I wonder if they know that a Chinese white tea has three times as much caffeine?

With a few exceptions, herbal tea or tisanes have no caffeine at all. That includes Rooibos so there is a huge selection of tea alternatives for night-time. I’ve been going through a rough time with sleep lately so now I only drink tea up to about 3pm and right before bed I drink hops tea. It seems to really help. And no, by hops tea I don’t mean beer though sometimes that helps too :-).

 

Main Sources:

Barone JJ, Roberts, H.R. (1996), Caffeine consumption, Food and Chemical Toxicology, Volume 34, Issue 1, January 1996, Pages 119–129.

Richardson, B. (2009), De-bunking the At-Home Decaffeination Myth Story, Fresh Cup January 2009

Chin JM, Merves ML, Goldberger BA, Sampson-Cone A, Cone EJ. (2008), Caffeine content of brewed teas. J Anal Toxicol. 2008 Oct;32(8):702-4.

 

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3 Responses to Caffeine

  1. The O'Dore says:

    Interesting and surprising data. Who would have believed it: as much caffeine in a “healthy” green tea than in a can of Red Bull. Next thing you know tea drinkers will move to extreme sports – Question is, how much caffeine in the “traditional” UK teabag in a cup? According to http://www.mayoclinic.com/health/caffeine/AN01211 14 to 61mg per 240ml. Of course some of us who leave the bag in the mug are more likely to be at the top end of this scale.
    TheO

    • admin says:

      Hi Theo, The difference between energy drinks and green tea is not just caffeine content! Green tea has antioxidants and no sugar while energy drinks have taurine or guarana combined with the caffeine plus the sugar.
      To answer your question about the teabag in a cup, there is a study here that confirms that a Lipton Black tea bag yields approximately 59mg of caffeine after 5 minutes of brewing (177ml). That’s at the higher end of the Mayo Clinic range.

  2. The O'Dore says:

    Me again, hi there.

    What I really want to know is…. is there a formula to calculate how late I can enjoy a cup of [green, black, etc.] tea without disrupting my sleep pattern? Just kept kept on waking up last night (normally sleep like a baby!)… and the prime suspect is that unusual cup of black tea I had at 9.30pm (thought it would be okay because it is was second steeping).

    Any pointers will be much appreciated,
    TheO