Salt, Heart Disease, and Stroke

Norm Campbell

1) The role of increased blood pressure as a determinant of adverse outcomes2) The health risks of high dietary salt

Global Leading Risk Factors for Death 2004

Global Health Risks. Mortality and burden of disease attributable to selected major risksWHO 2009

Systolic blood pressure greater than 115 mmHg

The Burden of HypertensionBlood Pressure* As A Cardiovascular Risk

• Attributable Risk – Overall ½ of heart and stroke*– Stroke 60-70%*– Heart failure 50%– Heart attack 25%– Kidney failure 20%– Dementia– Many other vascular diseases

* Systolic blood pressure greater than 115 mmHg

The Burden of HypertensionLifetime risk of Hypertension

(in Normotensive Women and Men aged 55-65 years)

Risk of Hypertension %

0 2 4 6 8 10 12 14 16 18 20

Years to Follow-up

Women

Risk of Hypertension %

Years to Follow-up

0 2 4 6 8 10 12 14 16 18 20

Men

JAMA 2002: Framingham data.

100

80

60

40

20

0

100

80

60

40

20

0

•BP is well known to rise BP is well known to rise with age in modern with age in modern industrialized societies.industrialized societies.

•If people move from an If people move from an area that does not have area that does not have hypertension to an area hypertension to an area that does, they develop that does, they develop hypertension hypertension

Societies that eat unprocessed foods, are physical Societies that eat unprocessed foods, are physical active and lean do not develop hypertensionactive and lean do not develop hypertension

Meneton et al, 2005Meneton et al, 2005

Salt and Hypertension

Salt and Sodium

CONFUSING TERMINOLOGY !!!!

5 gm salt is 2000 mg sodium

2300 mg sodium is about a teaspoon of salt (sodium chloride) 100 mmol of sodium or salt 5.8 gm (5800 mg) of salt (NaCl)

Salt, hypertension and vascular diseaseA vast array of evidence involving 1000s of

studies

• Animal studies; hypertension and vascular disease

• Migration studies

• Epidemiological studies; cross sectional and cohort; hypertension and vascular disease

• Clinical trials; hypertension and some vascular disease

Salt: Meta-analysesThe Cochrane Library 2006;3:1-41; Key features: random allocation; >2.3 g/day reduction in salt; >4 weeks duration; isolated intervention

Hypertensive Median age 50 (range 24-73)Reduction of BP 5.1 (5.8 – 4.3) / 2.7 (3.2-2.2) mmHg; Reduction of 4.5g salt/day, Baseline salt intake 7g – 11gTreatment salt intake 3.25g – 7.2g

Normotensive median age 47 (range 22-67) Reduction of BP 2.0 (2.6 –1.5) / 1.0 (1.4-0.6) mmHg; Reduction of salt 4.25g/day Baseline salt intake 7.25g – 11.5gTreatment salt intake 3.25g – 7.75g

Meta analysis on different levels of reduction in dietary salt on blood pressure

Hypertension 2003;42:1093-1099

Effect of 'small' reductions in systolic blood pressure on cardiovascular and total death

From Whelton, P. K. et al. JAMA 2002;288:1882-1888

Estimated effects on hypertension, CVD and related costs if dietary salt reduced

• 30% reduction in prevalence of hypertension by reducing salt to recommended levels

• 8.5 million deaths averted worldwide over 10 years by reducing salt intake 15%

• Slightly more cost effective than efforts to reduce tobacco use in low to middle income countries.

• In the USA cost savings of 10-30 billion dollars/yr and reduced CVD events by up to 260,000/yr, deaths up to 90,000/yr from reducing salt by 3 g/day

Salt and other health issues

• Reversibility, aging and in utero effects• Direct (non BP related) vascular and cardiac

damage• Obesity and related diseases (e.g. diabetes)• Asthma• Kidney stones• Osteoporosis• Gastric Cancer (promoter)

How much salt is unhealthy?

• Difficult to answer accurately as BP increases as dietary salt increases

• Small amounts are in primitive diets relative to current intake (about 1/10th)

• Rapid or extensive reductions in dietary salt are associated with increases in lipid and glucose values

• In those not yet acclimatized, physical activity in hot dry climates increases salt losses in sweat and the amount of dietary salt required

Salt intake recommendations

• WHO: less than 5 g salt (sodium <2000 mg)/day

How much salt do you consume?

1) Far too much

2) Too much

3) Just about right

4) Too little

THE SALT YOU EAT COMES FROM PROCESSED FOODS

Salt intakes around the world

• With few exceptions the average consumption of populations is over 5.8 g/day after age 5 and many over 10 g/day

• In developed economies the vast majority of salt is added in food processing (~80%)

• In undeveloped economies most salt is added at home in cooking and at table

• In transition economies, salt at home and in food processing is an issue.

Int J Epi 2009;38:791-813

Discussion

• Salt intakes around the world are much higher than physiological levels that humans evolved on

• The high intakes are linked to major causes of death and disability throughout the world

• Reducing dietary salt is estimated to be one of the most effective and cost effective interventions to improve health.

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