system
Given the following post, respond as if you're commenting on Reddit:
human
Why are low sodium diets suggested for high blood pressure when low sodium levels result in higher renin production and therefore higher blood pressure?

I've recently learnt at University about the renin-angiotensin system where low sodium levels result in increased renin production and therefore higher levels of angiotensin and aldosterone which result in more water conservation which ould lead to higher blood volume and therefore pressure. However, people always seem to suggest low sodium diets for those with high blood pressure issues. Why is this? Is my understanding of the renin-angiotensin system wrong or is there another mechanism in play?
gpt
The latter. The purpose of the renin-angiotensin-aldosterone system is essentially to control blood pressure, blood volume, and sodium balance. Like you mentioned, reductions in sodium stimulates renin release. However, that is just one of multiple renin-release stimuli. The more correct way to see it is: (1) decreased circulating volume (low BP)-> (2) renin release-> (3) increased sodium reabsorption/decreased sodium excretion-> (4)BP correction

The issue here is high blood pressure (aka hypertension; HTN). Water follows salt, so high sodium diets will have lots of salt in the blood vessels, which promotes water movement into blood vessels, thereby increases wall tension and inhibiting renin release. *For those w HTN, a reduction in sodium is unlikely to increase renin as the HTN is often due to high blood sodium and HTN inhibits renin release*