Sodium & StrokeToo much of a good thing…

2009

Preventing StrokesOne At a Time

Learning Objectives

Upon completion, participants will be able to: Practice according to the Canadian Best

Practice Recommendations for Stroke Care, 2008 as it relates to sodium

Educate patients on how sodium impacts their risk of stroke

Counsel patients on their individual sources of sodium

Partner with patients & families to develop an individualized plan for risk factor management

Presentation used with permission of Dr. Kevin Willis,

Canadian Stroke Network

Canadian Best Practice Recommendations for Stroke Care, updated 2008

2.1 Sodium: The recommended daily sodium intake from

all sources is the Adequate Intake by age. For persons 9-50 years, the Adequate Intake is 1500 mg. Adequate Intake decreases to 1300 mg for persons 50-70 years and to 1200 mg for persons > 70 years. A daily upper limit of 2300mg should not be exceeded by any age group.

See www.sodium101.ca for sodium intake guidelines

CMAJ 2008;179(12 Suppl):E1-E93 #2.1

Recommendations for Adequate Sodium Intake by Age

Age Sodium Intake per Day (mg)

0-6 months 120

7-12 months 370

1-3 years 1000

4-8 years 1,200

9-50 years 1,500

50-70 years 1,300

> 70 years 1,200

CMAJ 2008;179(12 Suppl):E1-E93 #2.1

High Blood Pressure:Major Component of Chronic Disease Risk

Proportion of incidence due to high blood pressure (Systolic >115 mmHg)

Stroke 70-75%Congestive Heart Failure 50% Ischemic Heart Disease 25%Renal Failure 20%

High blood pressure is the leading cause of mortality worldwide Lancet 2006 367:1747

High Blood Pressure: Sick Populations

Study of Kenyan nomads and London civil servants

Average systolic BP in nomads=118 mmHg Average systolic BP in civil servants = 138

mmHg

Rose G. Int. J. Epi. 1985 14: 32-38

Canada’s Population is Sick!

*2005 Ontario data. CMAJ 2008 178:1458

24% adults and 52% of seniors have hypertension*

1995-2005 Prevalence increased by 60%*

Is getting Sicker!

And is expected to get Worse!

Further 60% increase in prevalence projected by 2025 Lancet 2005 365:217

Key Public Heath Question

• Not due to characteristics of individuals – a shift in the whole distribution at the population level

• To make an impact on hypertension we need to control the factors that determine the population mean

Why is hypertension largely absent in some populations while in others it is common?

Salt (Sodium) and Hypertension

Sodium Low consumption of

fruits & vegetables Weight Low exercise Alcohol in excess

A Brief History…

The Yellow Emperor’s Classic of Internal Medicine written in

China over 2,000 years ago notes*:

“Hence if too much salt is used for food, the pulse hardens”

*Veith, I. (Translator) U of California Press, 2002.

For millions of years daily sodium intake < 400 mg/day - genetically programmed level

Recent change to 3-4,000 mg/day - a major physiological challenge

Salt: Increasing the Pressure

• High sodium fluid retention B.P.• Kidneys excrete sodium fluid retention B.P. • Prolonged high sodium intake may reset thresholds set by

kidneys.• Kidneys are less able to remove sodium as we age.• Genes (14) responsible for Mendelian forms of hypo- or

hypertension are all involved in renal sodium handling.• Low dietary potassium renal sodium retention B.P.• Signaling pathway in vasculature responds to sodium but

does not regulate basal B.P. (Nat. Med. 2008 14:64).

Mechanisms by which dietary sodium increases arterial pressure are not fully understood

Sodium and Blood Pressure

Animal studies Human Genetic

Studies Epidemiological

Studies

Migration studies Interventional

Studies Treatment Studies

Evidence:

Animal Studies Chimps: 2 groups of 13 (age 5-18y) Control group usual veg. & fruit diet, low Na+,high K+

Intervention group fed increasing amounts of salt over 84 weeks

*Nature Med 1995; 1:1009-16

Intervention Change in mean B.P. vs. controls

5g/d 19 weeks +12 mmHg (systolic)

10g/d 3 weeks, 15g/d 36 weeks

+26 mmHg

15g/d 26 weeks +33 mmHg

0g/d 20 weeks Control levels• Similar study (127 chimps) finds effect of Na+ on B.P.

persists over 2 year time course (Circulation 2007 116:1563).

Treatment Study: DASH Sodium

Control diet - low in fruit, veg and dairy, fat content typical of US DASH diet - high in fruit, veg and low-fat dairy, reduced fat content Consume diet for consecutive 30 day periods in random order at

each of 3 levels of salt

NEJM 2001; 344:3-10

Intervention

Change in mean B.P. vs. control (systolic)

Control diet DASH diet

9g/d salt Control level - 6 mmHg

6g/d salt - 2 mmHg - 7 mmHg

3g/d salt - 7 mmHg - 9 mmHg

-7

Randomized 412 adults (mixed B.P. status, racial groups, sexes) to:

-7 (NT)-

11(HT)

Blood Pressure and Stroke

110 115 120 125 130 135 140 145 150 155

Systolic B.P. (mmHg)

StrokeRisk(log)

30% reduction in risk

10 mmHg

35% strokes* 65% strokes*

Based on trial data n =190,000

Stroke 2004 35:1024

*Registry data

Blood Pressure and StrokeClinical cut-off points do not reflect continuous

relation between B.P. and health outcomes“Normotensives” get strokes too – key is to reduce

population risk!10 mmHg reduction in systolic B.P. reduces

individuals stroke risk by >30%Mean systolic B.P. reductions of 5-10 mmHg are

potentially achievable by reducing sodium consumption.

-7

-7

Sodium (salt) in our Diet

Natural~15%

Discretionary~15%

Manufactured food processing~70%

Adequate Intake*1,500 mg/d (3.8 g salt)

Tolerable Upper Intake*2,300 mg/d (5.8 g salt)

Reference Standard**2,400 mg/d (6.1 g salt)

3,000 – 4,000 mg/d (8-10 g salt)

Health Minimum180 mg/d

*Health Canada. Dietary Ref. Intake Reports

**2003 labeling legislation

Public Health Impact

~3,500 mg/day(current) ~1,500 mg/day (AI)

• Decrease hypertension prevalence by 30% (CJC 2007 23:437)

• Prevent 30 premature deaths per day from Stroke and IHD, ~15% all CV events (CJC 2008 24:497)

• Likely positive impact on obesity, osteoporosis, stomach cancer, kidney disease, asthma, etc…

BP ~5 mmHg

Sodium in our Food: Hard to Avoid

Food (CCHS 2004 data) %

Pizza, sandwiches, subs, burgers, hot dogs* 19.1

Soups 7.4

Pasta 5.7

Liquid milk products 4.0

Poultry and poultry dishes 3.8

Potatoes 3.4

Cheese 3.2

Cereals 3.0

*Breads 14.0

Sodium in our Food: Why?

$ Cheap way to boost flavor, texture and shelf life of poor quality foods

$ Salt and sodium phosphates increase water binding capacity of meat products

$ Salty snacks make you thirsty!

$Food – (fiber, nutrients, flavor) + (salt, sugar, fat) = $$Processed

food

Sodium in our Food: Would we miss it?Taste buds are used to high salt levelsAs salt levels are gradually reduced

taste buds become more sensitiveStudies have shown that it only takes a

few weeks to enjoy food with less salt and reveal subtle flavors

Reducing Canada’s blood pressure

Sodium reduction is easiest and most practical dietary change does not necessarily need a change in food

choice provided less sodium added by food industry.

Sodium reduction can be achieved by: Clear labeling of all foods to which sodium is

added Gradual reduction of sodium added to all foods A public campaign on health benefits

Canada takes action

Multi-stakeholder Working Group formed by Heath Canada

Will follow international efforts (UK)Legislation if food industry does not meet

voluntary targets

www.sodium101.ca

Sodium & Stroke

http://www.lowersodium.ca Can link to a national sodium initiative

with PowerPoint presentations for public and health care professionals if you like or continue for slide set developed and used with permission from Dr. Kevin Willis, Canadian Stroke Network

Sodium Website

Canadian Best Practice Recommendations for Stroke Care, updated 2008

www.canadianstrokestrategy.ca