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
Intervention Incidence of CHD
Death from any cause
Salt reduction: 3 g/dayLow estimate 66,000 ± 5800 51,000 ± 7100
High estimate 110,000 ± 9200 81,000 ± 11,000
Smoking cessation 41,000 ± 10,000 84,000 ± 9300Weight loss 59,000 ± 3500 36,000 ± 2000Statin therapy 52,000 ± 5600 5400 ± 540Pharmacologic 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
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) Na -> BP in cross-sectional, multi-population studies
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
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)
Syst
olic
Blo
od P
ress
ure
Undeveloped
Developed
Isolated primitive tribes
USA
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) 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
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
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
Syst
olic
Blo
od P
ress
ure
(mm
HG
)
High Intermediate Low
3,450 mg/day 2,300 mg/day 1,150mg/day
Syst
olic
Blo
od P
ress
ure
(mm
Hg)
120
1
25
130
13
5
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) 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 Na intake -> CVD across most samples
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
Effects of Reduced Na on CVD Events:
Results from 3 Randomized TrialsINTERVENTION OUTCOME FU
TONE (2001) 639 Elderly ↓ Na 21% ↓
CVD events 2.3 yrs
Taiwan Veterans (2006) 1,981 Elderly
↓ Na /↑ K Salt
41%* ↓CVD
Mortality2.6 yrs
TOHP Follow-up (2007) 3,126 Prehypertensives ↓ Na 30%* ↓
CVD events 10-15 yrs
*p<0.05
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) 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 Na intake -> CVD across most samples
• Population interventions Na intake associated with CVD mortality in Japan, Finland, U.K.
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
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
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) 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 Na intake -> CVD across most samples
• Population interventions Na intake associated with CVD mortality in Japan, Finland, U.K.
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
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)
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) 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 Na intake -> CVD across most samples
• Population interventions Na intake associated with CVD mortality in Japan, Finland, U.K.
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
“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
. adu
lts, 2
0-74
yea
rsS
alt c
onsu
mpt
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