According to a study published in Lancet, 80% of people from mainland China consume more than 12.5 gm of salt /day whereas 84% of people from other countries have salt intake of 7.5 ~12.5 gm/ day. When we look at cardiovascular [CV] events (eg. Stroke or heart attacks), positive association is seen only in mainland China, which means higher salt intake is associated with stroke. In other countries, those in the highest tertile (one third) of salt intake (more than 12.5g/ day) have non-significant association with CV events. There was no association between salt intake and CV events in the middle tertile (salt intake 10 ~12.5 g/ day). In the lowest tertile (ie. Salt intake less than 10 g/ day), there is inverse association meaning less salt intake is associated with more CV events. One important finding is CV events decreased with increasing potassium intake (K in chemistry) in all countries. Therefore, those in countries other than mainland China, following WHO recommendation of low sodium intake might lead to more CV events.
I will cite another study from Lancet which analyzed data from 4 studies and followed people for a mean period of 4 years. N = 133118 (63559 with hypertension & 69559 without hypertension), so a very large study with huge statistical power. Findings: in those people with hypertension, salt intake of more than 17.5 g/day AND less than 7.5 g/ day were both associated with increased risk of death or CV events (stroke or heart attack). Please note, this is the case in hypertensive patients. Those with normal blood pressure have another story: higher salt intake (NaCl more than 17.5 g/day) was NOT associated with risk of death or CV events. Read carefully please, in these people WITHOUT hypertension, salt intake < 7.5g/ day was associated with a significantly increased risk of death or CV events! What all these mean is: following WHO recommendation (salt intake < 5g/day) is likely to increase your risk of death or CV events whether or not you have hypertension. Luckily, only less than 1% of the world population complies to their darn suggestion.
This brings up the issue of “salt sensitivity” which is found only in a small % of the population. In these salt-sensitive people, higher salt intake might increase blood pressure, but not in those insensitive to salt. There is also evidence that this salt sensitivity is related to sugar intake, so if you quit sugar or reduce its intake, your sensitivity to salt might improve, so blood pressure may not go up with increased salt intake.