Sodium Intake and Cardiovascular Disease: Rationale for Policy Action Thomas Farley, MD MPH Joan H. Tisch Distinguished Fellow in Public Health Policy

Sodium Intake and Cardiovascular Disease:

Rationale for Policy Action

Thomas Farley, MD MPHJoan H. Tisch Distinguished Fellow in Public Health Policy

Roosevelt House at Hunter College

InterventionIncidence of

CHDDeath from any cause

Salt reduction: 3 g/day

Low estimate 66,000 ± 5800 51,000 ± 7100

High estimate 110,000 ± 920081,000 ± 11,000

Smoking cessation 41,000 ± 10,000 84,000 ± 9300

Weight loss 59,000 ± 3500 36,000 ± 2000

Statin therapy 52,000 ± 5600 5400 ± 540

Pharmacologic treatment of HTN

100,000 ± 11,000

80,000 ± 10,000

Source: Bibbins-Domingo K et al. Projected Effect of Dietary Salt Reductions on Future Cardiovascular Disease. 2010. New England Jounral of Medicine. 362:590-9.

Annual Estimated Reductions in Deaths and Cardiovascular Events:

Comparison Across Various Interventions

Background

• Extremely common in U.S. and other “modern” populations:• High sodium consumption

• High blood pressure

• Cardiovascular disease

• Questions:• Does chronic high level of sodium consumption contribute to

high blood pressure and to cardiovascular mortality?

• Would reductions in sodium consumption lead to reductions in blood pressure and reductions in cardiovascular mortality?

Evidence Supporting Na+ Intake Increases Cardiovascular Disease Risk

• Animal studies Na -> BP in many species, including primates

• Observational studies in humans BP -> Cardiovascular disease (CVD)

Prospective Studies Collaboration, Lancet, 2002 He FJ and MacGregor GA. A comprehensive review of salt and health. J Hum Hypertension 2009;23:363Appell LJ et al. The importance of population-wide sodium reduction as a means to prevent cardiovascular disease and stroke. Circulation 2011;123:1138Whelton PK et al. Sodium, blood pressure, and cardiovascular disease. Circulation 2012;126

Stroke Mortality by Systolic BP

Prospective Studies Collaboration, Lancet, 2002: Meta-analysis of 61 prospective studies with 2.7m person-yrs, 11.9k deaths

Definition of Hypertensio

n



• Observational studies in humans BP -> Cardiovascular disease (CVD) Na -> BP in cross-sectional, multi-population studies


Sodium Intake vs. Blood Pressure in 24 Populations

Law MR et al, BMJ 1991;302:811-5

60

70

80

90

100

110

120

130

140

150

0 50 100 150 200 250 300 350 400

Sodium Intake (mmol/day)

Sys

toli

c B

loo

d P

ress

ure

Undeveloped

Developed

Isolated primitive tribes

USA



• Observational studies in humans BP -> Cardiovascular disease (CVD) Na -> BP in cross-sectional, multi-population studies Na -> BP in migration studies Na -> CVD across most samples

• Intervention trials (short term)• Treatment to BP -> CVD Na intake -> BP in meta-analyses


Limiting Sodium Intake Reduces Blood Pressure

DASH-Sodium Trial

Sacks FM et al. Effects on Blood Pressure of Reduced Dietary Sodium. NEJM. 2001 Jan 4;344(1):3-10

120

125

130

135

High 3,000 mg Intermediate 2,300 mg Low 1,500 mg

Sodium Intake

Sys

tolic

Blo

od

Pre

ssu

re (

mm

HG

)

High Intermediate Low

3,450 mg/day 2,300 mg/day 1,150mg/day

Sy

sto

lic B

loo

d P

res

sure

(m

m H

g)

120

1

25

130

13

5




• Intervention trials (short term)• Treatment to BP -> CVD Na intake -> BP in meta-analyses Na intake -> CVD across most samples


Effects of Reduced Na on CVD Events:

Results from 3 Randomized Trials

INTERVENTION OUTCOME FU

TONE (2001) 639 Elderly

↓ Na21% ↓

CVD events2.3 yrs

Taiwan Veterans (2006) 1,981 Elderly

↓ Na /↑ K Salt

41%* ↓CVD

Mortality2.6 yrs

TOHP Follow-up (2007) 3,126 Prehypertensives

↓ Na30%* ↓

CVD events10-15 yrs

*p<0.05





• Population interventions Na intake associated with CVD mortality in Japan, Finland, U.K.


Successful Labeling Model: Finland

• 1970s: begin focus on sodium reduction

• 1993: required "high salt content" warning on packaged food

• 1979-2002: salt intake ↓ 23% in men and 28% in women

• Over three decades coronary heart disease deaths reduced by 80% in middle aged adults

Karppanen, H., and Mervaala, E. Sodium Intake and Hypertension. Progress in Cardiovascular Diseases. 2006; 49 (2):59-75.

Laatikainen, T. et al. Sodium in the Finnish Diet: 20-year trends in urinary sodium excretion among the adult population. Euro J Clin Nutr. 2006; 60: 965-970







Leading Health Care Organizations Agree: Na Intake Must be Reduced

• American Medical Association (AMA)

• American Heart Association (AHA)

• American Public Health Association (APHA)

• Institute of Medicine (IOM)

• National Heart, Lung, and Blood Institute (NHLBI)• World Health Organization (WHO)







“Definitive” Intervention Trial?

• Randomized controlled trial of 28,000 people for >5 yrs to low vs. high Na intake

• Not feasible• Compliance?

• 80% Na comes from processed food

• 5 years?

• Ethics?

Current U.S. RecommendationsAnd Disagreements

• U.S. Dietary Guidelines for Na intake• <2,300 mg/day for low-risk

• <1,500 mg/day for those >50 yrs, blacks, those with hypertension, renal disease, diabetes

• IOM recommendations (new)• <2,300 mg/day for all

• “insufficient evidence to determine” if < 1,500 mg

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

NHANES I1971-74

NHANES II1976-80

NHANES III1988-94

NHANES IV1999-00

Sodium Consumption in U.S.

Briefel RR, Johnson CL. Secular trends in dietary intake in the United States. Annu Rev Nutr. 2004;24:401-431

U.S

. ad

ults

, 20

-74

year

sS

alt

cons

umpt

ion

(mg/

day)

2005 U.S. Dietary Guidelines recommendation for adults

Recommended limit for people with hypertension, blacks, middle aged and older

NSRI 5 yr Goal

Not All Disagreement is Healthy Scientific Skepticism

• Salt Institute• Membership is global salt-producing companies

• E.g. Cargill, Morton Salt, International Salt Company, United Salt Corporation

• Attack science showing that salt intake is unhealthy

• Some leading critics funded by Salt Institute• E.g. David McCarron (220 scientific publications)

Lead Poisoning: Symptom of A Deeper Problem?

• “[LIA’s lead expert at Harvard Joseph Aub] felt that children that have subnormal appetites, or the disease known as ‘pica’ which caused them to chew on inedible articles, were subnormal to start with!”• Felix Wormser, Secretary of Lead Industry Association (LIA) in

response to study on association between lead levels and learning/behavior problems, 1944

Markowitz & Rosner, “Deceit and Denial: The deadly politics of industrial pollution.” U of CA Press, 2002. Chapter 2

Value of Scientific Doubt

• Strong tendency in public policy-making toward inaction

• Opponents need not prove anything• Doubt is often sufficient to paralyze action

• Think climate change

Na Consumption in Paleolithic Era

• Humans hunter-gatherers

• Diet – all low in Na• Fruit & berries

• Nuts

• Seeds

• Roots, tubers

• Meat

• Fish

• Insects

• Salt in short supply -> craving

• Estimated Na consumption < 1,000 mg/day

Lindeberg S. Am J Hum Biol 2012;24:110-115

Konner M, Eaton SB. Nutr Clin Practice 2010;25:594

Key Questions - Reframed

• Does chronic high level of sodium consumption contribute to high blood pressure and to cardiovascular mortality?

• Would reductions in sodium consumption lead to reductions in blood pressure and reductions in cardiovascular mortality?

• Is it safe to feed people 3-4x as much Na as we evolved eating?

Conclusions

• Scientific evidence, taken in its entirety, makes compelling case that Na intake is far too high• Leading to high blood pressure and

unnecessary heart disease and stroke

• We should reduce Na in food supply

• Inaction is dangerous• Tens of thousands of unnecessary deaths per

year

Documents

Sodium Intake and Cardiovascular Disease: Rationale for Policy Action Thomas Farley, MD MPH Joan H. Tisch Distinguished Fellow in Public Health Policy