I was diagnosed with high blood pressure a few years back and have to take daily medication to keep it in check. One of the things pointed out to me was salt consumption (I love salt). It forces the body to retain water and it is this water retention that is the cause of many cases of high blood pressure. I believe the medication I take (although I could be wrong) is a diuretic. Oddly enough, one of the side effects of my medication is a salty taste around the lips.
This is a bit OT, but nevermind...
(Firstly I should point out that I'm a proper Doctor, not a medical one, so take this information with...a pinch of salt.
Best to remain with your GP's advice as ever!)
Yes I believe there is evidence it does raise blood pressure - this is a simple chemical idea that most high school students studying science will be getting taught as you have mentioned - however I believe that the bodies actual response to salt is much more nuanced and complicated than assuming we are a bag of salty water. Genetics for example. Some may be salt-sensitive and others will be able to remove excess salt from their bodies much more effciently* So your personal salt intake will vary from a standard guideline.
The more controversial thing is the link between heart disease and high blood pressure, i.e. one of the big reasons we are told to cut salt in the first place. Apparently there is very little actual evidence for having high blood pressure over the long term and heart disease. One assumes that GP's advice is very cautious in this case - probably better to say that it could cause heart disease, than to go 'well, it's not clear that it's the case'!
There are other things that cause high blood pressure, prolonged stress for example.
But I'm not saying would should deliberately aim for high blood pressure, there are other reasons that are demonstratably linked, increased likelyhood of strokes I believe**, just that the actual evidence is that it does provoke or be linked to certain conditions is not secure.
Intake of sodium is of course vital for your well-being of course, and the problem with demonising salt dramatically is that I've heard of people that have 'given up' salt, who are probably on course for sodium deficiency!
It's complicated. I personally do try to moderated or at least think about my salt intake and not cover all my food in a snow drift of sodium, but like you I definitely like the stuff.
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* Personally I believe exercise/activity is key here. Not only are you improving your heart health, circulation, strength with large amounts of activity which I think is the best way to cut high blood pressure - making your body more efficient in a myriad of ways that cuts the volume of blood your body actually needs etc... but you will be sweating more. Sweat contains salt and is probably our most efficient way of getting salt out of our bodies. One could also drink large amounts of water to flush salt out, but then you'd be peeing a lot, and if you are consuming very large amounts of salt then I guess your blood pressure would be spiking horribly!
** Although maybe this is just an increase in risk the same as the increase in cancer risk from red meat, I don't know!