Sodium and potassium in hypertension

​the Agency for Healthcare Research and Quality just published their Comparative Effectiveness Review on sodium and potassium intake: effects on chronic disease outcomes and risk (see https://effectivehealthcare.ahrq.gov/topics/sodium-potassium/final-report-2018 for full report, and https://effectivehealthcare.ahrq.gov/sites/default/files/cer-206-evidence-summary-sodium-potassium.pdf for shorter evidence summary).

Details:
-- this report highlights the results of 257 publications, reviewing the following key questions

** Link between dietary sodium intake and blood pressure:

    -- prospective observational studies confirm that sodium intake may be associated with systolic blood pressure as well as the risk of incident hypertension​

** benefits and harms of reducing dietary sodium intake on blood pressure:
    -- sodium reduction decreases blood pressure on average 3.23/2.24 mmHg in adults, with mean difference in sodium intake being 42 mmol/d (966 mg/d), in both men and women
    -- reductions in systolic blood pressure for those with hypertension was 4.14 mmHg, vs 1.51 mmHg for those who are normotensive
    -- the results are less clear in children

** effect of reducing sodium intake on cardiovascular and kidney disease morbidity and mortality, as well as total mortality
    -- sodium reduction may significantly decrease the risk of combined cardiovascular morbidity and mortality, as well as the risk for a composite measure of cardiovascular outcomes
    -- evidence from a small number of RCTs is less clear for stroke
    -- evidence is insufficient to assess the actual sodium intake level and the associated risk for cardiovascular outcomes

** Link between high potassium intake and blood pressure:
    -- increased potassium intake from dietary supplements reduces blood pressure in adults, though results are apparently limited to those who had pre-hypertension or hypertension
    -- higher potassium intake appears to be associated with lower risk of kidney stones
    -- evidence is insufficient for other minerals modifying the effects of potassium such as sodium, calcium, magnesium
    -- insufficient evidence linking potassium intake with long-term chronic disease outcomes, “primarily due to the limitations in the potassium intake assessments”  

Commentary:

-- the relationship between sodium and hypertension is a bit complex. There seem to be differences in salt sensitivity: some patients being more salt sensitive than others. Studies have shown, for example, that African-American individuals are more salt sensitive vs white. Those who have medication-resistant hypertension are more salt-sensitive. Those who are on low potassium diets tend to be more salt-sensitive. And there are new studies (confirming and extending some of the older ones) finding that there seems to be identified genetic predisposition to salt sensitivity.

-- despite differences in individual sodium sensitivity, on a population basis sodium is a major risk factor for hypertension. the decreases in blood pressure noted above are therefore an average of those who are salt-sensitive and those salt-resistant (ie, the blood pressure reductions in those who are salt-sensitive is actually much more than the numbers above).

-- studies have been clear over the last several decades that dietary potassium decreases blood pressure in those with hypertension. For reasons unclear to me, the negative relationship between sodium and hypertension has achieved more sway in the medical and popular communities than the positive relationship with potassium

-- the issue of non-pharmacologic therapy for hypertension has been elevated by the new American heart Association guidelines defining hypertension as greater than 130/ 80 mmHg, see: http://gmodestmedblogs.blogspot.com/2017/11/new-aha-hypertension-guidelines.html . This document also encourages sodium restriction and high potassium diets​

Relevant prior blogs: 
** http://gmodestmedblogs.blogspot.com/2013/11/dietary-sodium-and-disease.html / reviews the Institute of Medicine’s 2013 critique of the studies done on sodium/hypertension, noting that there needs to be several 24-hour urinary sodium measurements to reflect the actual sodium intake (several studies used dietary recall, which is likely inaccurate). They also note that there are no compelling data and maybe harm in decreasing daily sodium below 2300 mg/d 
** http://gmodestmedblogs.blogspot.com/2015/02/new-nutrition-draft-guidelines.html  has the US Dept of HHS nutrition guidelines, plus comments on a systematic review from the BMJ summarizing the data on potassium intake and blood pressure response/clinical outcomes (see htn potassium lowers BP bmj 2013 in dropbox, or doi: 10.1136/bmj.f1378), noting that potassium intake has decreased dramatically in modern society. this study reviews the data on blood pressure and stroke (both seem to be better with potassium)​

so, I bring up this article as an affirmation of the negative role of sodium in hypertension and its complications. But, especially because of the positive role of potassium in decreasing blood pressure (though, the data to date suggest this is confined to those who are either pre-hypertensive or hypertensive). And also to reiterate that the (largely unachievable) prior sodium intake goal of 1500 mg/d may be harmful, reinforcing the more achievable but still difficult goal of 2300 mg/d
--and there is the 2-birds-with-one-stone approach: salt substitutes which replace sodium with potassium
 ​

geoff​

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