> For healthy adults, the FDA says 400 mg a day is OK. But consuming much more than that can have dangerous, negative effects. And the milligrams add up quickly. A medium-size coffeehouse coffee can contain more than 300 mg, and most 16-ounce energy drinks contain between 160 and 240 mg of caffeine…

3-4 cups might be on the high end of the safe spectrum, depending on what your idea of a "cup" is. (For the record, 3 half-litre beer steins of coffee a day turned out to be a spectacularly bad idea, even if hearing colours was briefly entertaining.)

> (For the record, 3 half-litre beer steins of coffee a day turned out to be a spectacularly bad idea, even if hearing colours was briefly entertaining.)

I've consumed caffeine to the point of serious gastric distress and very mild heart palpitations and I've never experienced synesthesia. I'm unwilling to push beyond that to higher doses, but two or three 12-cup pots a day of light roast filtered black coffee is about average for me, so what the Hell? Is there just that much individual variation here?

IIRC, the only well documented case of synesthesia is https://en.wikipedia.org/wiki/Grapheme_%E2%86%92_color_synes... . It's an interesting case because the color and letter recognizing parts of the brain are very close, so it's logic that some info may leak and get correlated.

Perhaps someone can design an (safe) experiment to measure the effect of caffeine in synesthesia ...

There must be. At a previous job, I regularly drank 2L of coffee a day (in ~10oz increments), and never experienced anything other than unpleasant slight jitteriness occasionally.

I think my cups are closer to 200 ml, which apparently is approaching 100 mg caffeine per cup, so I guess you're right.

A "medium-size coffeehouse coffee" (at Starbucks) is 16 fl.oz. Here in Europe, that's not really a normal cup of coffee.

America! What's a normal-sized coffee there, to compare? Large at Starbucks ("venti") is 20oz (~591ml). The caffeine levels at $ seem to be similar between USA and EU: http://www.caffeineinformer.com/the-complete-guide-to-starbu... but I'm guessing that that's more due to it being such a touristy place. From what I've seen, they use less espresso than "real" coffee shops: http://www.starbucks.co.uk/blog/introducing-our-new-standard... if you've paid attention to espresso machines for whatever reason, you know that most machines make two shots per pull, so typically higher-end places will use either 2 or 4 shots (since that's either 1 or 2 times they need to make espresso for the drink). If they have a large size (16-20oz), I've found that it's common to use 4 shots in that, which is going to be more caffeine than $, possibly by a wide margin.

If you're in the Bay Area and really want to go nuts with your caffeine for whatever reason, Dutch Bros in North Bay / East Bay (usually go there when I'm by Sac) has drinks on their menu with 6 shots: http://dutchbros.com/AboutUs/OurMenu and they're atypically strong per-shot.

> I'll drink my 3-4 cups of black filtered coffee a day with a good conscience.

Sounds similar to what I used to drink. I now drink similar amounts of decaf black coffee a day and sleep a whole lot better. This is partly why I quit and definitely why I won't go back to regularly drinking normal coffee (it's been 6 years or so).

(Yes, I know decaf still contains ~10% of the caffeine of normal coffee, this just means I'm down to the equivalent of half a cup of coffee a day, which is below dependency levels as I get no withdrawal effects if I stop this for a few days.)

> Excessive use of anything tends to be bad.

Many of those 'alarming' articles are mainly studying the point from where the use of anything is dangerous for our health. It is easy to get the numbers and to publish, and the website gets a clickbait.

It's widely knew that too much coffee is dangerous. But a normal dose has plenty of benefits, and a lot of research supports both points.

> It's widely knew that too much coffee is dangerous. But a normal dose has plenty of benefits

I'd be interested in reliable cites for either of those.

Here's what Cochrane Collaboration says. http://www.evidentlycochrane.net/caffeine-and-health-evidenc...

It's a short list.

Here's a round-up: http://www.nytimes.com/2015/05/12/upshot/more-consensus-on-c...

Cool, thanks. Some of those studies seem to find protective benefits with decaf. Or there wasn't enough data to know if the same effects are present with decaf.

> Most studies did not include data on decaffeinated coffee, either because too few people drank it or because data were not available. The few studies that did, though, had differing results. With respect to cardiovascular disease, decaffeinated coffee did not seem to have the same protective effects as regular coffee. With respect to the one stroke meta-analysis, it seemed to be just as protective as regular coffee. In two breast cancer analyses, decaffeinated had the same nonrelationship as regular coffee. Decaffeinated coffee was also protective against lung cancer, not as protective against Parkinson’s disease, and protective against diabetes and overall mortality, but perhaps to a lesser extent than regular coffee.

> But for most studies, there just aren’t data available. The conclusion to take away: There’s less evidence overall for a potential benefit, but still, there’s no evidence of harmful associations.