recommendations for dietary salt intake

Recommendations for Dietary Salt Intake

Lawrence J Appel, MD, MPHProfessor of Medicine, Epidemiology and

International Health (Human Nutrition)

Oct 22, 2008

Dietary Reference Intakes

IOM Panel on Water and Electrolytes

LARRY J. APPEL chair Johns Hopkins University, Baltimore, MD

DAVID H. BAKERUniversity of Illinois, Champaign-Urbana

ODED BAR-ORMcMaster University, Hamilton, ON

KENNETH L. MINAKER Massachusetts General Hospital & Harvard Medical School, Boston

R. CURTIS MORRIS, JRUniversity of California, San Francisco

LAWRENCE M. RESNICKNew York Presbyterian Hospital & Cornell University Medical College

MICHAEL N. SAWKA U.S. Army Research Institute of Environmental Medicine, Natick, MA

STELLA L. VOLPE University of Pennsylvania, Philadelphia

MYRON H. WEINBERGER Indiana University School of Medicine, Indianapolis

PAUL K. WHELTON Tulane University Health Sciences Center, New Orleans

ALLISON A. YATES Study Director (from June 2003)

PAUL R. TRUMBO Study Director (through May 2003)

Useful ConversionsUseful Conversions

Adequate Intake (AI)

Upper Level (UL)

Sodium (g) 1.5 2.3

Sodium (mmol) 65 100

Sodium Chloride (g) 3.8 5.8

Forms of Sodium• 90% of sodium consumed as

sodium chloride (salt)• Other forms:

–sodium bicarbonate–sodium in processed foods, such

as sodium benzoate and sodium phosphate

Sources of Dietary SodiumSources of Dietary Sodium

Inherent12%

FoodProcessing

77%

At the Table6%

During Cooking 5%

Mattes and Donnelly, JACN, 1991; 10: 383

(62 adults who completed 7 day dietary records)

Sodium Intake* at Baseline by BMI Category

BMI Category

Non-Overweight (n=44)

Overweight (n=238)

Obese (n=528)

mg of Na 2,991 3,708 4,235

% with Na < 2,300 mg

32% 20% 11%

* as estimated from 24 Hour Urinary Sodium Excretion

SETTING AN UPPER LIMIT

Potential Adverse Effects of Potential Adverse Effects of Excess Sodium IntakeExcess Sodium Intake

• Increased urinary calcium excretion (but no trials with bone mineral density or fractures)

• Increased left ventricular mass in cross-sectional studies (and one randomized trial)

• Increased risk of gastric cancer (ecologic studies, case-control studies)

• Increased blood pressure

Deaths fromStomach Cancer

(per 100,000Per year)

Adapted from Joossens, Int J Epi 1996;25:494-504

KOR

r=0.702P<0.001

JAPAN

CHI

POLCOL

HUN

POR

GDRITA

SPAFRG

CAN

FINNET

MALE.W

ARGDEN

BEL

USA

N.I

MEX

TOB

190

170

150

130

110

90

70

50

30

10

06 7 8 9 10 11 12 13 14

Salt Intake (grams/day)

ICE

Salt and Stomach Cancer: Ecological Analysis

Magnitude of the BP Problem

• 62% of strokes and 49% of CHD events attributed to elevated BP*

• 26% of adults worldwide (972 million) have hypertension**

• Estimated lifetime risk of developing hypertension is 90%***

*WHO, World Health Report 2002: Reducing Risks, Promoting Healthy Life, **Kearney Lancet 2005;305:217, ***Vasan, JAMA 2002;287:1003.

Stroke Mortality by Level of Usual Systolic BP*

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

Population-Based Strategy SBP Distributions

Population-Based Strategy SBP Distributions

Stamler R. Hypertension1991;17:I-16–I-20.Stamler R. Hypertension1991;17:I-16–I-20.

Reduction in SBPmmHg

235

Reduction in SBPmmHg

235

% Reduction in Mortality % Reduction in Mortality

Reduction in BP

Reduction in BP

After Intervention

After Intervention

Before InterventionBefore Intervention

Stroke CHD Total

-6 -4 -3-8 -5 -4-14 -9 -7

Effect of Reduced Sodium Intake on Blood Pressure

• > 50 trials of sodium reduction on blood pressure

• 10 dose response trials• 3 trials of sodium reduction as a means to

prevent hypertension

Sodium: Dose Response TrialsSodium: Dose Response Trials

Luft, 1979 (14 non-hypertensive)

40

60

80

100

120

140

160

180

200

0.23(10)

6.9(300)

13.8(600)

18.4(800)

27.6(1200)

34.5(1500)

grams/day (mmol/day)

SBP (mm Hg)

DBP (mm Hg)

+7+2+5+1+1

+6+4+2+2+4


MacGregor, 1989 (20 hypertensive)

406080

100120140160180200

1.1 (50) 2.3 (100) 4.6 (200)


SBP (mm Hg)

DBP (mm Hg)

+8* +8*

+4* +5*


Johnson, 2001 (n=17 non-hypertensive elderly)

4060

80100120

140160

180200

0.92 (40) 2.1(90) 3.2(140) 5.5 (240) 7.8 (340)


SBP(mmHg)

DBP (mmHg)

+6.1

+7.6 +3.5

+0.3 +3.7 -0.1 +1.6

-0.7

0.001≤ P <0.01*

0.01≤ P <0.05*


Johnson, 2001 (n=15 elderly with isolated systolic hypertension)

40

60

80

100

120

140

160

180

200

0.92 (40) 2.1(90) 3.2(140) 5.5 (240) 7.8 (340)


SBP (mmHg)

DBP (mmHg)

+9.0 +1.8 +4.1 +6.0

-0.3+3.1 +0.3 +3.4

0.001≤ P <0.01*

0.01≤ P <0.05*

Johnson, 2001 (n=8 elderly with systolic-diastolic hypertension)

406080

100120140160180200

0.92 (40) 2.1(90) 3.2(140) 5.5 (240) 7.8 (340)


SBP (mmHg)

DBP (mmHg)

+8.0 +4.1 +5.4 +0.7

-0.41.

+1.2 +1.6+3.0

0.001≤ P <0.01*

0.01≤ P <0.05*


Sodium Dose Response Trials: DASH-Sodium Trial*

120

125

130

135

SystolicBlood

Pressure

Control Diet

DASH Diet

1.5 (65) 2.4 (106) 3.3 (143) Sodium Level: gm/d (mmol) per day

+2.1

+1.3+1.7

+4.6 +6.7p<.0001

+3.0P<.0001

*Sacks, 2001 (412 prehypertensive and hypertensive adults)

Factors Associated with Increased Salt Sensitivity

• Fixed factors– Middle and older-aged persons– African-Americans– Genetic Factors – Individuals with:

• Hypertension• Diabetes• Chronic Renal Insufficiency

• Modifiable– Low potassium intake– Poor quality diet

Effect of Sodium Reduction (Higher to Lower) in African-Americans and Non-African-Americans on the Control Diet

-12

-10

-8

-6

-4

-2

0

Ch

ang

e in

BP

Systolic BP Diastolic BP

African-Americans Non-African-Americans

- 8.0†

P<.001

- 4.5†

P<.001 - 5.1

P<.001

- 2.2

P<.001

0 † P-interaction < 0.05

Bottom Line on Sodium Chloride

• The relationship between salt (sodium chloride) intake and blood pressure is direct and progressive without an apparent threshold

Arguments Made by Those who Oppose Sodium Reduction

• No clinical trial has tested the effects of sodium reduction on clinical cardiovascular outcomes

• Only those who are ‘salt sensitive’ should reduce their salt intake

• Other lifestyle factors (weight, potassium, DASH diet, exercise) are more important than sodium

• Sodium reduction has effects on plasma renin activity, lipids and insulin resistance that potentially mitigate the beneficial effects of blood pressure reduction

Effects of Reduced Na Intake on CVD: Longterm Results from the Trials of Hypertension Prevention (Cook et al, BMJ, 2007)

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

SETTING A LOWER LIMIT

Obligatory Losses of Sodium Obligatory Losses of Sodium (in g/d and mmol/d)(in g/d and mmol/d)

Source of Loss g/d mmol/d

Urine 0.005 to 0.035 0.2 to 1.5

Skin (nonsweating) 0.025 1.1

Feces 0.010 to 0.125 0.4 to 5.4

Total 0.040 to 0.185 1.7 to 8.0

Source: Dahl (1958)

Rationale for a Lower Limit

• Nutrient Adequacy: – ensure that the overall diet provides an

adequate intake of other important nutrients

• Replacement of Sweat Losses: – cover sodium sweat losses in unacclimatized

individuals who are exposed to high temperatures or who are moderately physically active.

Lower Limit: Two Caveats

• The AI of 65 mmol/d does not apply to highly active individuals, such as endurance athletes, who lose large amounts of sweat on a daily basis.

• Inadequate sodium intake is not a public health problem

Sodium Recommendations from Sodium Recommendations from IOM ReportIOM Report

• Upper Limit (UL):

2.3 g (100 mmol)/day for adults • Adequate Intake (AI):

1.5 g (65 mmol)/day for adults

2005 Dietary Guidelines

Scientific Advisory Committee Report“Technical Report”

Dietary Guidelines for Americans, 2005“Policy Document”

Finding Your Way to a Healthier You: Based on the Dietary Guidelines for Americans

“Public Document”

Implementation Tools DASH eating plan Food Label My Pyramid

www.healthierus.gov/dietaryguidelines

2005 Dietary Guideline Scientific Advisory Committee

Janet King, PhD, RD (Chair)Children’s Hospital Oakland Research Institute, Oakland, CA

Lawrence J. Appel, MD, MPH Johns Hopkins Medical Institutions, Baltimore, MD

Yvonne L. Bronner, ScD, RD, LD Morgan State University, Baltimore, MD

Benjamin Caballero, MD, PhDJohns Hopkins University Bloomberg School of Public Health, Baltimore, MD

Carlos A. Camargo, MD, DrPHHarvard University, Boston, MA

Fergus M. Clydesdale, PhD,University of Massachusetts, Amherst, Amherst, MA

Vay Liang W. Go, MD University of California at Los Angeles, Los Angeles, CA

Penny M. Kris-Etherton, PhD, RD Penn State University, University Park, PA

Joanne R. Lupton, PhDTexas A&M University, College Station, TX

Theresa A. Nicklas, DrPH, MPH, LN Baylor College of Medicine, Houston, TX

Russell R. Pate, PhD University of South Carolina, Columbia, SC

F. Xavier Pi-Sunyer, MD, MPHColumbia University College of Physicians and Surgeons, New York, NY

Connie M. Weaver, PhD Purdue University, West Lafayette, IN

August 2004 Recommendations from the Scientific Advisory Committee

1. Consume a variety of foods within and among the basic food groups while staying within energy needs

2. Control calorie intake to manage body weight

3. Be physically active every day

4. Increase daily intake of fruits and vegetables, whole grains, and reduced-fat milk and milk products

5. Choose fats wisely for good health

6. Choose carbohydrates wisely for good health

7. Choose and prepare foods with little salt

8. If you drink alcoholic beverages, do so in moderation

9. Keep food safe to eat

2005 Dietary Guidelines for Americans from Policy Document

• 41 Key Recommendations in Dietary Guidelines– 23 for General Public– 18 for Special Populations

• 3 Key Messages in Consumer documents– ‘Make smart choices from every food group’– ‘Find your balance between food and physical

activity’– ‘Get the most nutrition out of your calories’

SODIUM RECOMMENDATIONS

• For general population:– consume less than 2,300 mg (approximately 1 teaspoon of

salt) of sodium per day

• For individuals with hypertension, blacks, and middle-aged and older adults: – consume no more than 1,500 mg of sodium per day

recommendations for dietary salt intake

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