Tea and Coffee Strength?

hsline80n0

Hello!

The entries for "Tea, Brewed, Unsweetened" and "Coffee, Prepared from Grounds" give no indication of how strongly brewed the beverage is. Is there some default assumption going into the entry that I can use to extrapolate the difference when I make it? When I make it at home, I have a feeling I make it weaker than normal, so I'd like to try to adjust for that off some known standard.

I normally wouldn't try to get that picky about it, but varying the ratio of water to tea/coffee has a non-trivial impact to my caffeine intake, which I'm trying to improve but not eliminate.

Susan_RD_101

I believe the reference for a standard, 8 oz. cup of coffee is 100 mg caffeine (with tea being slightly less). But I'm not 100% sure if this is correct.

watson

The caffeine content of coffee / tea depends on so many factors, it's not easy to apply "standard" values to your diary.
For coffee I would say the biggest factor is the type of coffee bean, typically you will have either Arabica, Robusta or a mix of both. In general you can assume, that Robusta has about double coffeine content compared to Arabica. So stick to 100% Arabica coffees if you want to keep caffeine intake down.
The way the coffee is prepared also plays a role in how high the "extraction" rate of the coffee components is and therefore how much caffeine will land in your cup. This is a very complicated topic - I have given up on trying to research correct caffeine values for my diary. In my opinion the only way to get correct values would be to have your cup of coffee analysed by a laboratory, but who does that? And then you would have to stick to that particular type of coffee bean and brewing method... I found a youtube video where they had a laboratory analyse different cups of coffee from coffee chains (starbucks,...) and they even got different results for USA east vs. west coast for the same coffee chain...
I seem to remember, that the entries here on Cronometer match with a survey that was performed by the USDA to get an average for coffee nutrition for different types of coffee prepared a certain way.
For tea: If you drink tea from one of the bigger brands (Twinings / Lipton,...) you can find caffeine content for the unprepared tea (per weight), and these should be pretty accurate since the product is always a blend of tea leafes to keep the same "quality" for the end-product. How much of that caffeine is extracted is then depending on the brewing time (assuming you use boiling water). Take a look at this research paper to get an idea: https://www.researchgate.net/publication/23471909_Caffeine_Content_of_Brewed_Teas

As you can see, it will be almost impossible to get correct caffeine values for your diary. Since the caffeine content depends on so many factors, you will not find a standardized value. I just use the entries from the database and call it a day...