November 6, 2014

Presenter:

Robert P. Heaney, MDJohn A. Creighton University Professor/Professor of Medicine

Creighton UniversityModerator:

James M. Rippe, MD – Leading cardiologist, Founder and Director, Rippe Lifestyle Institute

Approved for 1 CPE (Level 2) by the Commission on Dietetic Registration, credentialing

agency for the Academy of Nutrition and Dietetics.

NUTRI-BITES®

Webinar Series

Sodium: Too much, too little or just

right?

Original recording of the November 6, 2014 webinar and PDF download of presentation available at:www.ConAgraFoodsScienceInstitute.com

 Based on this webinar the participant will be able to:Review the evolution of sodium intake recommendationsUnderstand the physiology related to regulating sodium metabolismDiscuss latest findings of the association of sodium intake to health outcomesOutline practical dietary strategies dietitians can offer clients as the science on sodium evolves

NUTRI-BITES®

Webinar Series

Sodium: Too much, too little or just right?

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SOME SODIUM INTAKE FACTS 2004 IOM recommendations for adults:

< 1,500 mg/day up to age 50< 1,300 mg/day from 50 to 70< 1,200 mg/day after age 70

mean Na intake in U.S. & Europe:3,450 mg/day (95% probability range: 2,600–5,000 mg/day)

this intake has been stable for at least 50 years in forty five 1st world nations

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NUTRIENT RESPONSE CURVE*

Intake of Nutrient

Risk

of D

eficien

cy

Risk

of T

oxicity

UL

RDA

EAR

*DRI book; IOM (2006)

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RISK AT BOTH EXTREMES

5

Intake

Risk

of H

arm

deficiencytoxicity

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THE DRI PROCESS

first, the consequences of inadequate and excessive intakes are defined

data describing intakes needed to avoid those consequences is gathered

an intake just sufficient to avoid inadequacy is defined as the requirement

recognizing that individuals will have differing requirements, an average requirement is estimated (the EAR)

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THE SODIUM DRIs

the IOM noted that Na effects arose not from Na, per se, but from NaCl, the form in which ~90% of ingested Na enters the body

the IOM stated that there was not enough evidence regarding NaCl effects to establish the usual DRIs, and so proposed, instead, an AI

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THE SODIUM DRIs

the adverse effect with increasing salt intake, which the AI seeks to minimize, is elevated blood pressure

the IOM, in effect, ignored adverse effects at low intakes, i.e., the panel used a linear model rather than a U-shaped model

this explains why the BP data and the health outcomes data disagree

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STARTING INTAKE MATTERS

9

Intake

Risk

of H

arm

H

ealt

h o

utc

om

es

are

the

pro

xy

CVD RISK vs. Na INTAKE

17 country study

N = 101,945 mean follow-

up: 3.7 years O’Donnell et

al. NEJM 371:612 (2014)

10

Sodium Excretion (g/day)

0 2 4 6 8 10 12

Odds R

atio

1.0

1.5

2.0

2.5

3.0

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DASH–I*

three-way trial of dietary intervention standard American diet diet high in fruits and vegetables diet high in fruits & vegetables plus

low-fat milk (~730 mg extra Ca)

Na intake held constant at ~3000 mg across all three diets

*Appel et al., NEJM 1997; 336:1117-24

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DASH-I: Conclusions

BP reduction was as large as produced by standard anti-hypertensive mono-therapy regimens

if applied at a population level, the full DASH diet would reduce incidence of stroke by 27 % MIs by 15 %

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DASH – ANOTHER CONCLUSION the possibly harmful effects of high

Na intake are magnified when the diet is inadequate in Ca and K

high Ca & K intakes mitigate the possible harm of high Na intakes

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THE NUTRIENT PROBLEM

the field lacks a consensus on how to define “normal” or “adequate”

that leaves the field virtually without a target to aim at

and forces reliance upon empirical evidence that, e.g., intake A is “better” by some measurable endpoint than intake B

the evidence must be in the form of RCTs

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RAAS – A RESCUE MECHANISM

sympathetic activity

NaCl reabsorption & water retention

aldosterone secretion

arteriolar constriction & rise in BP

ADH secretion from pituitary

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angiotensinogen

renin

angiotensin I angiotensin II

ACE

renal

blood flow

. . . but notice: when you

reduce Na intake below a

critical level, you activate

mechanisms that try to raise

BP

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RISK CURVE FOR BP LOWERING 5-yr non-

concurrent cohort study

398,419 hypertensive pts. at Kaiser SoCal

risk of death &/or ESRD

Sim et al., J Am Coll Cardiol 2014; 64:588–97

Systolic Blood Pressure

<110110–120

120–130

130–140

140–150

150–160

160–170

>170A

dju

sted H

azard

Ratio

0

1

2

3

4

5

6

7

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CONCLUSIONS the risk curve for Na is the same as for

other nutrients: U-shaped risk of harm rises at both extremes of

intake the lowest risk range seems to be at about

the current U.S. average Na intake there is no evidence to justify efforts to

decrease average salt intake we should be emphasizing increasing Ca

and K intakes, rather than decreasing Na intake