I think saying there is zero reason to limit caffeine consumption is a bit of a stretch since we're talking about a drug which causes dependence, reduces motor control and increases anxiety.
I say this as a huge coffee fan. Grind my own single origin beans, brew them in my Hario pour over or Aeropress etc.
But I'm not going to pretend it's this wonderful health drink when it clearly has negative side effects.
I think what you're picking up on is a distrust by analogy. In the past we thought some things were safe, but they weren't (smoking etc). But the opposite of being ignorant about the effects of chemicals we ingest isn't to suddenly say everything is unsafe. It's to test everything. And we have tested caffeine, and it's safe.
caffeine is a neurotoxin produced by the coffee bean to repel insects
Were you thinking of nicotine instead? It certainly serves that role against insects for the tobacco plant.
Does it? I remember reading that it increased reflexes, improves stamina, and increases physical strength.
If that's all true (I might have read an outdated/bad study), then what counts as motor control?
(Gonna lump all my responses to the various comments here, so apologies if I come across as a bit strong.)
Here's what I found regarding motor control:
> There is also some evidence that fine motor control may be impaired as a function of the increase in anxiety
http://www.ncbi.nlm.nih.gov/pubmed/12204388
From the aforementioned Wikipedia article:
> Caffeine in plants acts as a natural pesticide: it can paralyze and kill predator insects feeding on the plant
Regarding my comment on it being a neurotoxin. Caffeine is a central nervous system stimulant. You're basically ingesting plant insecticide which in turn stimulates the nervous system, causes the adrenals to release adrenaline and causes a heightened alert response as well as many other positive AND negative effects. Hence my remark.
Source: http://brown.edu/Student_Services/Health_Services/Health_Edu...
Most of the research I've seen promotes its health benefits in narrow isolation on one particular facet of human physiology. I haven't seen any evidence that could conclusively sway me towards going from 1 cup a day of coffee to say 4-6 which apparently is the amount a lot of people drink.
My own feeling on coffee is that like anything which has pros and cons it should be drunk in moderation.
http://arstechnica.com/science/2015/11/coffee-drinking-linke...