The role of a low sodium diet in the management of hypertension Dave Glover Consultant Nephrologist, Wrexham
Salt
Aims Is it all a bit Woman s Own / Daily Mail? Current guidelines An idea about salt What is the evidence? What can we do?
Introduction Incidence of hypertension 31% of men 28% of women How much it costs the NHS Consuming less than six grams of salt per day would prevent a further 17,500 premature deaths every year and save the economy around 4 billion In US, by reducing salt by 3g / day 120,000 less cases of CAD 66,000 less cases of stroke 92,000 less deaths Save $24 billion
Yes it is
But what are the FACTS?
Current Guidelines On average we eat 8.1g of salt a day in the UK Men 9.3g, women 6.8g
Current Guidelines Current UK DoH guideline: 11 years and over 6g of salt a day (2.4g sodium) WHO Guideline (2012) Maximum 5g per day
The Evidence - background Primary (Essential) Hypertension is common in high (>2.3g) sodium intakes Rare in societies with <1.2g Na intake 1,2 Chloride also important Without each other, volume expansion and rise in BP not seen (in Na sensitive patients) Salt sensitive patients more likely to develop hypertension 3 Obese, metabolic syndrome, elderly, CKD, African- Americans 1.Sodium and potassium in the pathogenesis of hypertension. AdroguéHJ et al N Engl J Med. 2007;356(19):1966. 2. Intersalt revisited: further analyses of 24 hour sodium excretion and blood pressure within and across populations. Intersalt Cooperative Research Group. BMJ. 1996;312(7041):1249. 3. Incidence of hypertension in individuals with different blood pressure salt-sensitivity: results of a 15-year follow-up study. Barba G et al J Hypertens. 2007;25(7):1465.
Salt how much?? 1g Na = 2.5g NaCl 5g NaCl 1 tsp 4.1g salt 0.8g salt / 40g 0.3g salt / 30g 1.9g salt/ tin
The Evidence Salt restriction can reduce BP in normotensive, prehypertensive and hypertensive individuals Long term benefits Over 30 years Salt restriction reduces age related rise in BP 1 Meta analysis of 34 trials 2 Average salt reduction of 4.4g salt/day (to 5g / day) > 4weeks 5/3 mmhg fall in BP in hypertensives Correlation with urinary sodium excretion 1.Intersalt revisited: further analyses of 24 hour sodium excretion and blood pressure within and across populations. Intersalt Cooperative Research Group.Elliott P, Stamler et al. BMJ. 1996;312(7041):1249. 2.Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials. He FJ et al. BMJ. 2013;346:f1325.
The Evidence
The Evidence effect on drugs Limiting Na lowers intracellular volume Enhances effects of antihypertensives Not Ca ch blockers though Increases renin release dependent More responsive to ACE or ARB Fall of 9/3mmHg (ACE and thiazide group) 1 Proteinuric CKD (non-diabetic) 2 BP is more Ang II ACE + Na restriction > ACE + ARB 1. Sodium restriction in hypertensive patients treated Effects on BP and proteinuria with a converting enzyme inhibitor and a thiazide. Singer Dr et al. Hypertension. 1991;17(6 Pt 1):798. 2. Moderate dietary sodium restriction added to angiotensin converting enzyme inhibition compared with dual blockade in lowering proteinuria and blood pressure: randomised controlled trial. Slagman Mcet al.bmj. 2011;343:d4366.
The Evidence - DASH Dietary Approaches to Stop Hypertension 1997 1 459 hypertensive patients (160/80-95) 3 weeks run in, 8 weeks treatment Control Diet Fruit and Veg diet Combination diet DASH Diet Low fruit and veg, high snacks, sweets, meats and sat. fat Rich in fruit, veg, low in snacks and sweets Rich in fruit and veg and low fat dairy. Low in snacks sweets, meats and sat. / total fat 1. A clinical trial of the effects of dietary patterns on blood pressure. DASH Collaborative Research Group. Appel LJ et al. N Engl J Med. 1997;336(16):1117.
DASH - Results
DASH - Results Control Diet Diet Effect Effect in Hypertensives Fruit and Veg Diet 2.8/1.1 mmhg 7.2/2.8 mmhg DASH Diet 5.5/3.0 mmhg 11.4/5.5 mmhg NA
DASH + Low Na 1 412 patients Control or DASH diet 3.5g, 2.3g, 1.2g Na 8.75g, 5.75g, 3g salt 30 days on each Na intake 1. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. DASH- Sodium Collaborative Research Group. Sacks FM et al. N Engl J Med.
DASH + Low Na - Results Sig drop in sys and dias BP in all groups High Na control vs Low Na DASH = 8.9/4.5mmHg (11.5/ in hypertensives)
DASH + Low NA + Lifestyle = Premier 810 patients Randomised Prepared own food Behavioural intervention DASH + above Advice only weight loss, activity, Na restriction and alcohol restriction 4.3/2.6mmHg Large BP drop in advice only group Poor dietary adherence DASH/ Low Na = Lifestyle
Outcomes CVD and mortality No definitive answers Need large samples and long studies (20K > 5years) Regression to normal salt diet after study Randomised studies 2 meta analyses failed to show mortality benefits 1,2 1 shows reduction CV events Population studies 1 Reduced dietary salt for the prevention of cardiovascular disease: High Na independently a meta-analysis increases of randomized CV controlled risk trials and death Taylor RS et al. Am J Hypertens. 2011;24(8):843. 2. Salt reduction lowers cardiovascular risk: meta-analysis of outcome trials. He FJ et al. Lancet. 2011;378(9789):380.
Outcomes - Renal Antiproteinuric effect of RAS inhibitors and non DHP Ca Ch blockers is impaired with high Na intake (even with good BP) REIN and REIN-2 High vs low salt diet Blunted ramipril response at 3 months Prolonged protein reduction in low salt group (4 years) ESRD (32 vs 16%) at 4 years
Other interventions Low K Fish oil / Fish High fibre
How to achieve this Any questions?