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Preventing Strokes
One At a Time
Sodium & Stroke
Too much of a good thing…
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
 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 for sodium intake
CMAJ 2008;179(12 Suppl):E1-E93 #2.1
Recommendations for Adequate
Sodium Intake by Age
Sodium Intake per Day
0-6 months
7-12 months
1-3 years
4-8 years
9-50 years
50-70 years
> 70 years
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
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!
24% adults and 52% of seniors have hypertension*
Is getting Sicker!
1995-2005 Prevalence increased by 60%*
And is expected to get Worse!
*2005 Ontario data. CMAJ 2008
Further 60% increase in prevalence projected by 2025
Lancet 2005 365:217
Key Public Heath Question
Why is hypertension largely absent in some populations
while in others it is common?
• 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
Salt (Sodium) and Hypertension
 Sodium
Low consumption of fruits &
 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”
 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
*Veith, I. (Translator) U of California Press, 2002.
Salt: Increasing the Pressure
Mechanisms by which dietary sodium increases arterial
pressure are not fully understood
• High sodium  fluid retention  B.P.
• Kidneys  excrete sodium  fluid retention   B.P. 
• Prolonged high sodium intake may reset thresholds set by
• 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).
Sodium and Blood Pressure
Animal studies
 Human Genetic Studies
 Epidemiological Studies
Migration studies
 Interventional Studies
 Treatment Studies
Animal Studies
*Nature Med 1995; 1:1009-16
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
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
Randomized 412 adults (mixed B.P. status, racial groups, sexes) to:
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
Consume diet for consecutive 30 day periods in random order at
each of 3 levels of salt
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
NEJM 2001; 344:3-10
-7 (NT)
Blood Pressure and Stroke
Based on trial data
n =190,000
Stroke 2004 35:1024
10 mmHg
30% reduction
in risk
*Registry data
35% strokes*
65% strokes*
110 115 120 125 130 135 140 145 150 155
Systolic B.P. (mmHg)
Blood Pressure and Stroke
 Clinical
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
Sodium (salt) in our Diet
Natural Discretionary
Health Minimum
180 mg/d
Manufactured food processing
Reference Standard**
Adequate Intake*
1,500 mg/d (3.8 g salt) 2,400 mg/d (6.1 g salt)
Tolerable Upper Intake*
2,300 mg/d (5.8 g salt)
3,000 – 4,000 mg/d (8-10 g salt)
*Health Canada. Dietary Ref. Intake Reports
**2003 labeling legislation
Public Health Impact
~3,500 mg/day
~1,500 mg/day (AI)
BP ~5 mmHg
• 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…
Sodium in our Food: Hard to Avoid
Food (CCHS 2004 data)
Pizza, sandwiches, subs, burgers, hot dogs*
Liquid milk products
Poultry and poultry dishes
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 levels
 As salt levels are gradually reduced taste
buds become more sensitive
 Studies 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
 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
Sodium & Stroke
Sodium Website
 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
Canadian Best Practice Recommendations for Stroke Care, updated 2008