Thanks for the link, that's a very thorough meta-analysis. My thoughts are:
what the hell do I know? :)
The meta-analysis results are very confusing: low salt intake is associated
with a relative risk of cardiac death, but moderate and high salt intake is
associated with a relative risk of stroke death. Now what?
Some of the studies analysed controlled for various groups, e.g. with high
BMI, or, indeed, with previous CVD. Some followed patients up for 10 or more
years, some had 10,000 or more subjects, some had more or less than 60% male
subjects- and all these factors seem to have afffected outcomes.
So perhaps a tentative conclusion should be that salt intake doesn't have a
significant effect on healthy individuals, but it does seem to affect those
with underlying conditions.
The question is- how do you know what underlying conditions you have, given
that our interest in the study is probably to decide how much we should cut
back on our salt consumption as individuals, according to dietary advice from
basically all major health bodies, etc.
Well, I have a single data point on this. A relative of mine recently found
out she has kidney disease. The news came out of the blue. She had a blood
test for something unrelated and there was a worying signal. She was referred
to a nephrologist, had an ultrasound to check the state of her kidney and
discovered that she's missing one kidney from birth. It turns out that people
with a single kidney from birth have an increased risk to develop kidney
disease, higher than people who lose a kidney later in life, who in turn have
a higher risk than the general population. It seems also that my relative's
liberal salt consumption (until now) has played a role in her developing
kidney disease, because the most likely course of events is that her blood
pressure was elevated, which damaged her kidney, which raised her blood
pressure, which further damaged her kidney, etc.
Like I say, this came out of the blue. Kidney disease is like that: it sneaks
up on you, when you don't expect it. My relative was lucky to find out before
she found herself on a hospital bed, strapped to a dialysis machine, but
others have not been so lucky.
This whole affair made me realise I have no idea what might be going on in my
body, that may affect me very suddendly a few years down the line. Perhaps I
have some underlying condition I don't know of, myself. Maybe I'll find, when
I'm older, that I have a high blood pressure and that I need to take
medication, and cut back on salt, to control it.
Current guidelines are to limit salt intake and those are based on numerous
studies carried out over many years, and, I think, clinical experience.
Perhaps there were confounding factors not controlled for, in those studies-
like high BMI, previous CVD, smoking (!) etc etc. But, if those confounding
factors caused a significant jump in the relative risk for things that can
easily kill anyone, then maybe the message is that there are many things that
can increase the risk from high salt intake- and that many people are affected
by those things. In which case the wise thing is to not assume that you can
eat as much salt as you want, and that you have to be a little bit careful
with it, now, so you that don't have to make huge, very difficult changes,
later.
My relative has had to cut back entirely on the salt that she eats: no
cheese, no cured meats, no eating out unless she can be entirely sure the food
she eats is unsalted (which means steak and fries pretty much every time,
because there's nothing else that most restaurants can guarantee is
salt-free). That is a big pain in the ass, and she might have been able to
avoid it if she had been more careful earlier on.
For the record- I'm suggesting everyone should do as I say, not as I do. I
salt my food liberally, still. Incorrigible :)
Edit: On the other hand, you can always monitor your blood pressure. If you're eating "too much salt" that's how you'd find out. But, who monitors their blood pressure when without a good reason?