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Potassium and Blood Pressure: How to Test the Effects ofDASH Diet in your Patient with Hypertension?
  JOHTN
CLINICAL MANAGEMENT
Potassium and Blood Pressure: How to Test the Effects of
DASH Diet in your Patient with Hypertension?
Clarence E Grim
Professor
Hypertension Section, Medical College of Wisconsin, MilwaukeeUSA
Correspondence Author: Clarence E Grim, ProfessorHypertension Section, Medical College of Wisconsin, MilwaukeeUSA
e-mail: lowerbp2@mac.com
 
ABSTRACT
This article reviews the 90+ year history of increasing potassiumintake (K) and lowering sodium (Na) intake in the treatmentof hypertension (HTN). It then reviews the DASH Diet eatingplan as an intervention to lower blood pressure (BP) by bothincreasing K intake and lowering Na intake. The term DASHDiet Sensitive (DDS) HTN is used to describe those whoseBP decreases significantly when consuming the DASH Diet. Amethod to determine your patient's BP is outlined that has beenfound effective even in the most extreme form of salt-sensitiveHTN-classic primary aldosteronism. This requires a series ofhome BP measurements before starting and during the 14 daysof the DASH eating plan and checking a spot urine for Na/K/creatinine to monitor adherence. The beauty of this methodis that if the patient follows the recommendations exactly, themaximum systolic BP effect is apparent by 1 week and thediastolic effect in 2 weeks. Thus, only 3 weeks is required tosee if this is an effective intervention in your patient's HTN. Ifso, the next task is to determine if DASH is an eating plan thatyour patient (and family) can live with.
Keywords: Adherence, Blood pressure, Compliance, DASHdiet, Home blood pressure, Nocturia, Nutrition, Potassium,Sodium, Urine Na/K ratio.
How to cite this article: Grim CE. Potassium and Blood Pressure:How to Test the Effects of DASH Diet in your Patient withHypertension?. Hypertens J 2017;3(1):37-41.
Source of support: Nil
Conflict of interest: None
 
 

A BRIEF HISTORY OF POTASSIUM,
SODIUM, AND BLOOD PRESSURE


The role of dietary K in blood pressure (BP) regulation hasa long history in humans and animals. The exact mechanismof the effect of K on BP is not known, but in generalit seems to counteract the toxic effects of excess dietary Naon BP without affecting BP itself, yet increasing longevityin animals and humans. In 1928, Addison1 reportedthat adding potassium chloride (KCl) to symptomatichypertension patients (BP 170-262/84-152) lowered BP by ≥30/≥12 and improved not only BP but also the symptomsof severe HTN, especially edema. In 1931, Priddle2 reported11 patients with a systolic BP > 200 mm Hg whose BPfell an average of 64/24 over 1 to 18 weeks, which "wasconsidered quite noteworthy." More pronounced was theimprovement in the patient's clinical condition: insomnia,nervousness, dizziness, frequent headaches and shootingpains in the head have disappeared. A decrease of nyeturia(nocturia) was constantly experienced by the patientsas they improved. In cardiac failure with dyspnea andedema, compensation was quickly restored... . Patientswho were missed from the clinic for some time, uponinvestigation stated that they felt so well they could seeno need for returning... . It is believed it will be necessaryfor all cases with well established HTN to continueindefinitely their diet regulations (low sodium diet), andin many, the high intake of potassium as well.

 
It should be noted that although HTN is considered anasymptomatic condition, many patients today with drugresistantHTN have many of these same symptoms whichin my experience are relieved by the DASH eating plan.The most dramatic results of very low sodium (10 mM/day) and high-potassium diet were those published byKempner3 using the rice-fruit diet in 1940s. In a series ofpatients with overt congestive heart failure (CHF) andmalignant HTN, this regimen rapidly controlled BP andproduced dramatic regression of left ventricular hypertrophy(by chest X-ray and electrocardiogram) and clearingof Grade IV retinopathy (retinal photograms) in onlya few months. Even today, viewing this article's dramaticillustrations or improvement in patient status is amazingto view for students and fellows in HTN training.

Extensive studies in hypertensive rat models in 1957by Meneely et al,4 in 1958 by Dahl5 and in 1985 by Tobianet al6 showed that increasing K intake to animals withsalt-induced HTN reduced the damaging effects of ahigh-salt diet with marked reduction in mortality fromstroke, CHF, and renal disease despite not much of aneffect on the attained BP in many rat models of saltinducedHTN. The introduction of thiazide diuretics in1957 seemed to lower interest is using modifications ofdiet in the management of HTN.

In 1962, Priddle7 reported on his team's 30-yearexperiences in using low Na, high K intake recentlycombined with the addition of a thiazide diuretic, which had revolutionized their ability to slow the progressionof hypertensive cardiovascular disease due to HTN andthen to control BP using chlorothiazide 250 mg 5 daysa week, a 50 mM Na with an added 2 gm KCl. Many oftheir patients who had previously been difficult to controlnow had improved BP and their feeling of well-beingreturned. He noted that it was useful to monitor the urineNa/K ratio as a method of checking compliance withthe regimen. The ratio of Na/K decreased from ∼2.5 onthe ordinary diet to ∼2 on the Na-restricted diet and byadding a thiazide diuretic and K it decreased to 0.8. At thesame time, a series of elegant balance studies publishedin JAMA in Fallis and Ford8 (Fig. 1) demonstrated thatafter equilibration on the 50 mM Na, 50 mM K diet, theaddition of 50 mg hydrochlorothiazide (HCTZ) produceda significant fall in BP in only 7 days, likely related to theimpressive natriuresis as BP was not affected when theNa intake was increased to 100 mM/day.

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Clarence E Grim

Figure 1 shows the effects of this regimen on BP, Na,and K balance from the run in control diet by the additionof HCTZ. Note the sudden jump in sodium excretion, nochange in K balance, and the fall in mean arterial BP. Notshown are similar plots showing that increasing diet Kto 100 mM enabled HCTZ to be increased to 100 mg/day without significantly affecting serum K. In 1968, a similarprogram used by Priddle's team for up to 12 years reporteda 50% reduction in mortality in elderly9 patients from theMetropolitan Toronto Homes for the Aged attending theCardiovascular Clinic of the Geriatric Center for 4 years(LoNa, HiK, HTZ protocol) whose intake was validatedby 24-hour urine collections. For unknown reasons, thisinformation did not make it into general medical practicenor management of HTN guidelines. The association ofa retirement population's Na/K intake and stroke wasreported in a Southern California retirement communityin 1987.10 The higher the diet Na/K ratio, the greater thestroke rate. Two more recent studies on K supplementationemphasize the ability of increasing K intake to lower BP.In 1991, a Kenyan double-blind randomized trial added64 mM K/day K to 10 mg bendroflumethiazide11 in 84black patients with untreated HTN. K supplementationfor 28 weeks led to a decrease in diastolic BP from 108± 3 to 88 ± 4 mm Hg, which was similar to those takingthe thiazide. The authors concluded that this supportsthe notion that K supplementation may be an effectiveapproach in mildly hypertensive blacks. Today we wouldnot consider those with an entry BP average of 108 to be"mildly HTN." He et al12 added supplemental KCl or citrate to increase urinary potassium to an average of ∼160 mM/day and reduced BP by ∼11/5 in only 1 week. Thus, increasingK intake and lowering Na is an effective and rapidnondrug method to try in patients who are interested inthis approach.
 

Potassium and Blood Pressure: How to Test the Effects ofDASH Diet in your Patient with Hypertension?
Fig. 1: Most desirable regimen, accompanied by least negative potassium balance
 
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Potassium and Blood Pressure: How to Test the Effects of DASH Diet in your Patient with Hypertension?

A major advance in nutritional management of HTNwas the publication of the DASH Diet studies whichhave included investigation of the effects of DASH onBP control systems. The best review of all aspects of theinitial DASH program are contained in the supplementto the Journal of the American Dietetic Association in1999.13 It is recommended reading for all who wish togain a detailed understanding of DASH Diet Program.Most relevant to our discussion here is the observationthat the components of the DASH Diet shift the "pressurenatriuresis curve" so that BP is less affected by changes insodium intake than when ingesting a standard Americandiet.14 Furthermore, the DASH eating plan improves thepatient's sense of well-being,15 which is unusual whenone uses pharmacological interventions. Thus, the BPeffects of increasing K intake (and lowering Na) in mostwith high BP are worth testing in all patients beforeimplementing drug therapy. Those with drug-resistantHTN are also good candidates as one of the most commoncauses of drug resistance is due to high-salt and lowpotassiumintake. The next question is how to do this inone's practice? I have used urinary monitoring of Na/Kas discussed below to monitor compliance with dietarychanges so you and the patient can better understandhow they are doing in their new eating program.

Physiology of the Urine Na/K Ratio and its
use in Monitoring a Low Na and High K
Intake as on the DASH Diet


As noted earlier, the monitoring of Na/K in patients hasbeen recommended since 19627 to document compliancewith high K, low Na diet.

 
The ability of the Na/K ratio to reflect Na and Kbalance under ever acute changes in sodium balance isshown in Graph 1.16 In normals, acute changes in sodiumbalance only lower the Na/K to < 1 under severe sodiumdepletion. Note that the Na/K ratio in urine collectedevery 4 hours only reached < 1 when sodium retention inthe urine became extreme after sodium depletion with theLasix. More extensive information on Na and K changesin normotensive and hypertensives with this protocoloriginally designed to quantitate the renin-angiotensin-aldosterone system and sodium metabolism is detailedelsewhere.17

As can be seen in Graph 1, the Na/K ratio in urine monitoredevery 4 hours increased acutely with saline (sodium)loading and only became < 1 at the extreme Na depletionafter 20 hours of Na loss due to the low Na intake (10 mMon "Lasix Day") and the three doses of Lasix. Thus, anNa/K < 1 is unlikely to occur in subjects even under acutechanges in Na and K intake and output. Longer balancestudies described below show the power of measuring theNa/K to assess daily Na and K intake in HTN.18

Using the "Sleep Urine" to Monitor Dietary
Sodium Compliance


Luft et al19 have shown that a night-time collection, whichI call the "sleep urine," is the best to document dietarycompliance for sodium intake. The "sleep urine" is thatpassed from the time of retiring to sleep until the firstvoiding in the morning on arising. Placing the collectionbottle on the toilet before going to bed has been a usefulway to improve the complete collection of this sleepsample. Using controlled metabolic conditions, Luft et al20demonstrated that only one sleep urine was needed todocument (>85% probability) that a patient was on lowsodiumdiet (65 mM/day). Studies using the chloridetest dipstick in hypertensives required two sleep urinesto classify as being on a low Na intake (< 60 mM/day). Use of this feedback improved dietary compliance20 andin hypertensives improved BP control and lowered needfor medications.21 This can also be done by lab assay forNa or using a newer chloride dipstick available for homeuse.22 However, taking KCl as a supplement will affect theaccuracy of this method23 and thus needs to be includedin the evaluation of the dipstick results. A spot urine isalso acceptable at least for the Na/K ratio. If the Na/K ina urine is not < 1, a patient is not DASHing.

Potassium and Blood Pressure: How to Test the Effects ofDASH Diet in your Patient with Hypertension?
Graph 1: Changes in urine Na/K ratio with acute changes in sodium balance in normals

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Clarence E Grim

How to do the DASH in your Practice

All guidelines recommend "healthy lifestyle interventions"before starting pharmaceutical methods, butmost physicians tell me their patients never seem toget any effect. I believe this is because most dietary Naand K interventions are not properly monitored withurine Na/K measurement to document adherence tothe regimen. Thus, when patients state that they arefollowing a prescribed low-sodium diet (< 100 mg Na),80% of those who provided a 24-hour urine were noton the prescribed intake.24 My response to patientswho fail to get a BP lowering effect from the DASHeating plan is to only accept failure if compliance isdocumented by checking the urine Na/K or as I say"Show me the pee!"

Taking Home Blood Pressure

As a baseline BP I recommend taking for at least 1 weekbefore beginning the DASH. If on meds this should betaken in the AM before meds. After sitting for 5 minutesrest, the BP should be taken three times. Averaging thelast two gives a more stable BP reading. This should becontinued during the 2 weeks of the DASH testing. Dailyreadings are needed as some will get a very quick fall inBP on the DASH and may need to step down their otherBP meds, if any. Plotting the daily average BP will quicklyenable the patient and your staff to determine if the BPhas fallen from the baseline over the next 2 weeks.

The DASH Diet for Hypertension Book

Since the paperback DASH diet book by Thomas Mooreet al25 came out in 1991 based on the low-sodium versionof the DASH26 Diet, I have used this to guide patients fromall walks of life who are interested in trying to managetheir BP by "nondrug" means or who were referred to mefor drug-resistant HTN. Before retiring, I had the bookstocked in the pharmacy or gift shop of the hospital whereI was practicing. Now it is available as an eBook as notedin the citation. The results in those who adhere to theplan have been dramatic not only in BP reduction. Themost striking effect has been seen in patients with classichypokalemic primary aldosteronism with drug-resistant HTN. The BP almost always falls to goal in 1 week (ormarkedly improves), the serum K has normalized in days,and the profound symptoms of hypokalemia mentionedearlier disappear by 2 weeks. Some who have been ina near bed-ridden state have quickly returned to theirnormal state of health and once again are able to exerciseand resume their job responsibilities. For examples ofthe effect in these drug-resistant patients I recommendthat one go to our Yahoo Group "Hyperaldosteronism"and read these patients' stories going back over 10 years.Many of my patients have told me this book saved theirlives and their jobs as their BP becomes controlled andtheir feeling of well-being returns - perhaps because theyare able to stop many of their other BP meds that maybe making them not feeling well. Adding the measurementof Na/K even in a spot urine helps give you and thepatient feedback on their Na/K intake. Adding a urineCr to the spot urine20 enables one to use the formuladeveloped by Mann to estimate the 24 hour intake as well.Sampling of the mid-day urine improved the prediction.
 
This DASH book first reviews the science behind theDASH Diet in easy to understand terms for most patientsand then challenges them to a 14-day trial. It next reviewsconcisely the problem of HTN and then discusses howthe DASH was tested. After reviewing the keys to movingto the DASH eating plan it provides the exact menu onemust follow for 14 days to test the DASH's effect on theirBP (Chap 9) with the goal of Na < 1,500 mg and >4,700 mgK/day. There are also a number of recipes that can beused once the DASH has been shown to lower their BP tomaintain the program. As reported in the original DASHstudies, many patients report that they feel better thanthey did before the DASH and many with HTN or primaryaldsoteronism can lower/stop their other BP meds underphysician guidance. They can also observe that when theystray from the DASH the BP quickly rises again. Thusmeasuring BP at home gives quick feedback that theyneed to review what they are eating. Using an App thatenables them to track diet Na and K intake (myfitnesspal)is also useful as a learning tool to alert them to indiscretions.Some worry about BP rising too during testing theDASH before starting BP meds. During the controlled lowNa DASH studies a systolic BP of more than 170 mm Hgor a diastolic BP of more than 105 mm Hg was used tohalt the DASH study if it occurred during the 6 weeks ofthe original studies. No patients had such an increase inBP during the low-sodium version of the DASH studies.

SUMMARY
  • Adding potassium by pill or diet and lowering sodiumby diet or doing both with the DASH Diet are usefulinterventions to improve BP.
  • Compliance is easy to monitor to document a goal of< 1,500 mg Na and >4,700 mg K by testing spot or thesleep urine for Na, K, and creatinine.
  • Blood pressure lowering is quick and nearly maximumby 2 weeks.
  • A method to test this in only 3 weeks is presented.

 
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Potassium and Blood Pressure: How to Test the Effects of DASH Diet in your Patient with Hypertension?

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