Coffee is a fruit. Fruit and vegetable consumption is unquestionably good for your health. I don't know why people find it so shocking that drinking coffee would be healthy.
In any event, in the case of coffee its consumption bears little resemblance to what would ordinarily be regarded as a fruit.
Some fruits have some compounds, along thousands of unspecified others, which seem to have a beneficial effect, most often in-vitro.
Regarding polyphenols, there is no hard, concrete evidence that any have actual positive health benefits.
One thing is for sure, the marketing surrounding these "5 a day to be healthy" is extremely strong and widespread.
This is an outdated theory, that is no longer supported by the current state of the research. The health benefits of fruits and vegetables is primarily driven by phytochemical, not fibers.[1]
Not all fruit nor vegetables are healthy, unless you consider the healthy ones only (how do you determine that scientifically?) then it's just nonsense.
Also coffee is a seed first, and seeds in general are potentially the most toxic, as evolution would prefer seeds to grow, instead of being eaten. The fact that the toxic compounds of a seed give us a nice buzz and don't kill us instead is a pretty nice coincidence.
And let's not even go into the "are fruits really healthy?" debate which is long, as reality is often more complex than quick slogans such as "eat colours and be healthy."
Find a single peer-reviewed study that finds any widely consumed vegetable or fruit has negative correlation with all-cause mortality.
> Also coffee is a seed first, and seeds in general are potentially the most toxic,
Legumes, which as a class are seeds, have a very strong inverse relationship with all-cause mortality.[1] There's zero empirical reason to believe that seeds are unhealthy, and very strong reason to believe that seeds, as with any plant-based food, are widely health-promoting.
> And let's not even go into the "are fruits really healthy?" debate which is long
No it's not. Fruit consumption is strongly associated with lower all-cause mortality. Even controlling for vegetable consumption.[2] The science is settled. Denying that fruit consumption is health-promoting is about as scientifically illiterate as denying that cigarette smoothing is unhealthy.
[1]https://www.hindawi.com/journals/bmri/2017/8450618/ [2]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5837264/
But not all seeds are good for you. Please don't eat apple seeds.