Salt, Hypertension & Health Presenters name Institution
High blood pressure Tobacco High cholesterol Underweight Unsafe sex High BMI Physical inactivity Alcohol Indoor smoke from solid fuels Iron deficiency 0 1 2 3 4 5 6 7 8 Attributable Mortality (In millions; total 55,861,000) Proportion of deaths attributable to leading risk factors worldwide (WHO 2000) Ezzati et al. WHO 2000 Report. Lancet. 2002;360:1347-60.
Organ damage related to hypertension Cerebrovascular disease - transient ischemic attacks - ischemic or hemorrhagic stroke - vascular dementia Hypertensive retinopathy Left ventricular dysfunction Coronary artery disease - myocardial infarction - angina pectoris - congestive heart failure Chronic kidney disease - hypertensive nephropathy GFR < 60 ml/min/1.73 m2) - albuminuria - ESRD/dialysis Peripheral artery disease - intermittent claudication
High blood pressure as a cardiovascular risk factor Systolic blood pressure > 115 mmHg causes: overall 50% of heart and stroke 60-70% of strokes Hypertension > 140/90 mmHg causes: heart Failure 50% heart attack 25% kidney failure 20%
14 16 18 20 14 16 18 20 0 4 6 8 10 12 0 4 6 8 10 12 2 2 Risk of hypertensionincreases with age Risk of Hypertension % Risk of Hypertension % 100 100 Women Men 80 80 60 60 40 40 20 20 0 0 Years to Follow-up Years to Follow-up Future risk in normotensive women and men aged 65 years JAMA. 2002: Framingham data.
Risk of stroke mortalityincreases with age 80-89 years 70-79 years 60-69 years 50-59 years Systolic blood pressure (mm Hg) Prospective Studies Collaboration. Lancet. 2002;360:1903-13.
Lifestyle risk factors for hypertension • high dietary salt intake • obesity • high alcohol intake • physical inactivity • smoking • inadequate vegetable and fruit intake • inadequate milk product intake
In summary • Hypertension is a leading risk factor for death and disability. • Hypertension is a major cardiovascular risk factor. • Hypertension is very prevalent and has a large impact on health care resource use. • Lifestyle factors influence blood pressure including dietary salt.
Higher dietary salt increases death from stroke in the EU Adapted from Perry IJ et al. J Hum Hypertens. 1992;6:23-25.
CHD Death CVD Death All Death 1.75 1.50 High salt intake 1.25 Hazard Ratio 1.00 Lower salt intake 0.75 0.50 High salt intake increases risk of death He FJ, MacGregor GA. J Hum Hypertens. 2002;16:761-70.
International scientific and health organizations conclude that high dietary salt: • increases blood pressure • is a health risk WHO/FAO technical report recommends less than 5 g of salt per day Nishida C et al. Public Health Nutr. 2003;7:245-50.
Excess salt intake raises blood pressure in animals Rats Pigs Mice Dogs Rabbits Chickens Baboons Chimpanzees Green monkeys Spider monkeys • Such studies provide us • with detailed information • regarding how salt may • affect blood pressure • its time course • underlying mechanisms • what to expect in humans
Animal studies suggest: • Excess salt intake can cause a slow and progressive increase in blood pressure. • In time, salt restriction may not fully restore blood pressure to original levels. • Acute salt restriction may underestimate the accumulated effects of lifelong salt exposure. Van Vliet et al, 2006
Excess salt intake increases morbidity and mortality in animals • Morbidities • cardiac hypertrophy • vascular hypertrophy • vascular stiffening • renal damage • hyperlipidaemia • insulin resistance • Mortality • hypertensive encephalopathy • stroke • heart failure • premature death Progressive (left to right) effect of salt exposure on LVH in salt sensitive (DS, top row) vs salt resistant (DR, bottom row) rats. From Inoko Am J Physiol. 1994;267:H2471-82.
Animal studies summary • The ability of excess salt to raise blood pressure appears to be a general characteristic in mammals, including humans. • The effects of salt on blood pressure are complex, having several distinct components: • - acute vs slow-progressive; • - reversible vs irreversible. • Many individual systems and mechanisms contribute to the effect of salt on blood pressure.
Renal mechanisms forsalt-dependent hypertension • Acute high salt intake • - renal retention of fluid blood pressure • Chronic high salt intake • - resets renal threshold for salt excretion less salt excretion • - peripheral resistance • - subnormal vasodilation to salt load Nat. Med. 2008 14:64
Acute salt sensitivity of blood pressure Salt sensitivity is well defined by the steady state relationship between salt intake and blood pressure (“chronic pressure natriuresis relationship”, or “renal function curve”).
Factors that lead to salt sensitivity of blood pressure • intrauterine growth retardation (IUGR) • low nephron mass • renal disease • inflammation, injury, etc • genetic abnormalities • exogenous agents (e.g. DOCA) • ageing - salt excretion
4 2 0 -2 Change in Systolic Blood Pressure (mmHg) -4 Normotensives -6 -8 Hypertensives -10 -12 -130 -50 -70 -90 -110 -30 Change in Urinary Salt (mmol/24h) Lower salt reduces systolic blood pressure He FJ, MacGregor GA. J Hum Hyptens. 2002;16:761-70.
Effect of longer-term modest salt reduction on blood pressure: meta-analysis* Cochrane Review criteria for sodium studies to include in analysis: • random allocation of subjects to treatment/control groups • >920 mg/day reduction in dietary sodium • >4 weeks duration • no concomitant interventions Hypertensive subjects (20 trials), median age 50 (range 24-73) Normotensive subjects (11 trials), median age 47 (range 22-67) * He FJ, MacGregor GA. Cochrane Database of Syst Rev. 2004;Issue 1. Art. No.: CD004937.
Lower dietary salt reduced blood pressure in hypertensive adults 20 trials, 802 individuals dietary salt lowered by 4.5 g/day from baseline of 7 - 11 g/d to 3.25 – 7.2 g/d blood pressure lowered by 5.1/2.7 mm Hg He FJ, MacGregor GA. Cochrane Database of Syst Rev. 2004;Issue 1. Art. No.: CD004937.
Lower dietary salt reduces blood pressure in normotensive adults 11 trials, 2,220 subjects dietary salt lowered by 4.25 g/day from baseline of 7.25 – 11.5 g/d to 3.25 – 7.75 g/d blood pressure lowered by 2.0/1.0 mm Hg He FJ, MacGregor GA. Cochrane Database of Syst Rev. 2004;Issue 1. Art. No.: CD004937.
Effects of salt reduction on blood pressure over time Obarzanek E et al. Hypertension. 2003;42:459-67.
Lower salt as part of a healthy diet Methodology • randomized 412 adults (mixed blood pressure status, racial groups, sexes) to: • control diet - low in fruit, vegetables and dairy, fat content typical of US diet • DASH diet - high in fruit, vegetables and low-fat dairy, reduced fat content • consume diet for consecutive 30 day periods in random order at each of 3 levels of salt DASH-Sodium Collaborative Research Group. N Engl J Med. 2001;344:3-10.
Results: diet and salt intake DASH-Sodium Collaborative Research Group. N Engl J Med. 2001;344:3-10.
Salt restriction reduces blood pressurein children and infants • Children (average age 13) • reduced dietary salt 42% • reduced blood pressure 1.17/1.29 mmHg • Infants (less than one year) • reduced dietary salt 54% • reduced systolic blood pressure 2.47 mmHg Hypertension. 2006;48:861-9.
In summary • High dietary salt increases blood pressure, which is a health risk. • Lower salt consumption decreases blood pressure. • Other dietary factors can also reduce blood pressure.
Healthcare cost savings in Canadaby reducing dietary sodium Using the Cochrane Review data • a reduction in average dietary sodium intake by 4.5g/d (from 8.8g to 4.3g in Canada) would result in • 30% fewer people with hypertension • almost double the blood pressure treatment and control rate • hypertension care cost savings of $430 to $538 million/yr Can J Cardiol. 2007;23:437-43.
Impact of reducing blood pressure through dietary sodium • Annual reduction in incidence of • myocardial infarction (5%) • strokes (13%) • heart failure (17%) • Reduction in health care costs associated with the overall predicted 8.6% reduction in CVD • $1.7 billion per year in Canada and $18 billion in the United States Can J Cardiol. 2008;24:497-501.
Observed effect of lower saltintake on cardiovascular events in TOHP trials • 25-30% lower risk of cardiovascular events in those who had been in the low salt groups • 1.9 -2.5 g/day reduction in dietary salt during intervention BMJ. 2007;334:885-92.
Changes in diastolic blood pressure, salt intake and stroke deaths in Finland 5600 mg 3360 mg DBP Stroke Salt Karppanen H et al. Progress, Cardiovascular Disease. 2006;49:59-75.
Salt intake and obesity • High dietary salt increases thirst and fluid consumption. • Many of the fluids consumed contain simple sugars or alcohol and contribute to caloric intake. • 20-30% of the excess calories consumed by children and adolescents are through increased beverage consumption associated with high salt intake. • Therefore high salt diets are likely to be a significant factor in the obesity epidemic. He FJ et al. Hypertension. 2008;51:629-34.
Relationship between salt intake and fluid consumption in children and adolescents R=0.40 p<0.001 He FJ et al. Hypertension. 2008;51:629-34.
Salt and other health effects • obesity and related diseases (e.g. diabetes) • asthma • kidney stones • osteoporosis • gastric cancer
Dietary salt intake for adults • In Canada and the USA • 3.25 - 3.75 g/day (age dependant) is estimated to be adequate for most adults (adequate intake (AI)) • 5.75 g/day is above the upper limit recommended for health (upper limit (UL)) • WHO/FAO technical report has indicated dietary salt intake should be less than 5 g/day DRI, IM 2003
Prevalence of excessive intakes: What we eat in America, NHANES 2001-2002
Where in our diet does salt come from? In regions where most food is processed or eaten in restaurants • 12% natural content of foods • “hidden” salt: 77% from processed food – manufactured and restaurants • “conscious” salt:11% added at the table (5%) and in cooking (6%) J Am College of Nutrition. 1991;10:383-93.
Where in our diet does salt come from? • In regions where most food is prepared and eaten at home, large amounts of salt may be added in cooking or at the table.
Salt in our food: why? • boosts flavor, texture and shelf life of foods • salt and sodium phosphates increase water binding capacity of meat products • salty snacks make you thirsty!
Our taste for salt:would we miss it ? • Taste buds get used to high salt levels. • As salt levels are gradually reduced taste buds adapt. • Only takes a few weeks to enjoy food with less salt and reveal subtle flavors.
In summary • In the Americas, people consume an unhealthy amount of salt. • This can cause hypertension, a leading risk for death and disability. • The solution is to reduce salt in commercially manufactured food and promote healthy eating. • We need to educate the public and patients. • We need to provide leadership in our communities. • The outlook for improvement is cautiously optimistic.
Key messages • Dietary salt is an important contributor to high blood pressure. • Reducing salt lowers blood pressure and prevents cardiovascular disease. • Salt intake in the Americas is higher than the levels recommended for health.