Yet another salt and blood pressure study

A place to get your questions answered from McDougall staff dietitian, Jeff Novick, MS, RDN.

Moderators: JeffN, carolve, Heather McDougall

Yet another salt and blood pressure study

Postby brec » Tue Apr 25, 2017 6:43 pm

News article:
"Low-sodium diet might not lower blood pressure: Findings from large, 16-year study contradict sodium limits in Dietary Guidelines for Americans"

Abstract:
High blood pressure (HBP) is a major modifiable risk factor for cardiovascular disease. To reduce blood pressure, current U.S. Dietary Guidelines recommend limiting sodium intake to 2.3 g/day for healthy individuals under the age of 50, while adults over age 50 as well as all African-Americans, and anyone with HBP, diabetes or chronic kidney disease is advised to limit sodium intake to 1.5 g/day. Very limited evidence is available to support these recommendations. Recent studies have called these guidelines into question and identified the need to consider the intakes of other minerals such as potassium, magnesium, and calcium in addition to sodium in relation to BP regulation. We used data from 2,632 normotensive subjects, ages 30-64 years, in the Framingham Offspring Study. Detailed dietary records were collected over six days and used in these analyses to address the question of the long-term effect of dietary sodium in particular on systolic (SBP) and diastolic blood pressures (DBP) over 16 years of follow-up. To account for possible confounding of these effects by body size, we used linear regression models to derive nutrient residuals as exposure variables. We used longitudinal mixed models to calculate the adjusted mean SBP and DBP levels over 16 years of follow-up in association with mineral intake. Confounding factors retained in the final models included age, sex, education, height, physical activity, cigarette smoking, and alcohol intake. Each of the weight-adjusted minerals was first classified into quintiles of intake. While we expected dietary sodium intake to be positively associated with both SBP and DBP, the opposite was found. Adjusted mean SBP levels at the end of follow-up across quintiles of increasing sodium intake were 134.5, 132.2, 132.3, 130.3, and 128.3 mm Hg, respectively. DBP results were similar, ranging from 78.1 to 75.5 with increasing dietary sodium intake. Dietary potassium, as expected, was inversely (linearly) associated with both SBP and DBP (SBP ranging from 134.2 to 129.4 mm Hg, in the lowest and highest quintiles of intake, respectively; DBP ranged from 78.2 to 75.6 mm Hg with increasing intake). Results for calcium and magnesium were very similar to those for potassium. We also explored the combined effects of dietary sodium with intakes of other minerals. To do this, we classified sodium intake as <2.5 vs. ≥2.5 g/day and potassium as <2.3 vs. ≥2.3 g/day. After 16 years of follow-up, those with the lowest SBP and DBP levels (129.5 and 75.6 mm Hg, respectively) were those with higher intakes of both sodium and potassium while those with the highest SBP and DBP levels (135.4 and 79.0 mm Hg, respectively) were those with lower intakes of both. The combined effects of both magnesium and calcium with sodium were very similar to those of potassium. These long-term data from the Framingham Study provide no support for lowering sodium intakes among healthy adults to below 2.3 g/day as recommended. This study does support the finding of a clear inverse association between potassium, magnesium, and calcium and blood pressure change over time. Support or Funding InformationNational Dairy Council, National Heart, Lung and Blood Institute's Framingham Heart Study (Contract No. HHSN268201500001I)


This is a presentation today at the American Society for Nutrition Scientific Sessions and annual meeting during the Experimental Biology 2017 meeting, so I don't think a paper is available as yet.
brec
 
Posts: 348
Joined: Wed Nov 28, 2012 3:37 pm

Re: Yet another salt and blood pressure study

Postby JeffN » Tue Apr 25, 2017 7:39 pm

This data is similar to the data that is supposed to show no association between SFA intake and CVD, (which I'm sure you believe).

Garbage data in and garbage conclusions out.

They do not say how sodium intake was measured but odds are it was not very accurate since it was an observational study. If it ever gets peer-reviewed & published we'll know for sure, but don't get to excited yet.

Observational data of people in developed countries are confounded by the tendency of those with elevated BP or HTN in older family members to limit (or at least report limiting) salt intake.

This fairly recent NEJM editorial I posted in the salt thread explains why many of the studies suggesting that a low salt intake may increase CVD and/or total mortality are seriously flawed

viewtopic.php?f=22&t=23557&p=537367&#p537367

SOUNDING BOARD
Dietary Sodium and Cardiovascular Disease Risk — Measurement Matters
June 1, 2016
DOI: 10.1056/NEJMsb1607161
http://www.nejm.org/doi/full/10.1056/NEJMsb1607161

Hypertension is a common and major risk factor for the leading U.S. killer, cardiovascular disease.1-5 Reducing excess dietary sodium can lower blood pressure, with a greater response among persons with hypertension.6-9 Nine of 10 Americans consume excess dietary sodium, defined as more than 2300 mg per day.10,11 Many leading medical and public health organizations recommend reducing dietary sodium to a maximum of 2300 mg per day on the basis of evidence indicating a public health benefit.11-17 Yet this benefit has been questioned, mainly on the basis of studies suggesting that low sodium intake is also associated with an increased risk of cardiovascular disease.18-22

In science, conflicting evidence from studies with methods of different strengths is not uncommon. Studies that measure sodium intake vary widely in their methods and should be judged accordingly. Accurate measurement matters.23-26 Paradoxical findings based on inaccurate sodium measurements should not stall efforts to improve the food environment in ways that enable consumers to reduce excess sodium intake. Gradual, stepwise sodium reduction, as recommended by the Institute of Medicine,27 remains an achievable, effective, and important public health strategy to prevent tens of thousands of heart attacks and strokes and save billions of dollars in health care costs annually.28

Full article
http://www.nejm.org/doi/full/10.1056/NEJMsb1607161


Interestingly, in Framingham almost everyone develops HTN (well over 90% prior to their 80th B-Day) and yet in human populations that consume a low-salt or no salt added diet their whole lives few people ever develop HTN.

I would recommend reading my salt thread which is also kept alive and updated and discusses the "limiting sodium is dangerous" studies.

Even those on WFPB diets like to hear good news about their (still) bad habits.

In Health
Jeff
User avatar
JeffN
 
Posts: 9412
Joined: Tue Jan 08, 2008 5:56 am

Re: Yet another salt and blood pressure study

Postby JeffN » Wed Apr 26, 2017 5:38 am

As I figured, the study was based on food recall.

This is just another BS reverse causality study.

Not sure what is worse, that these people actually printed this crap with such well known methodological flaws (that they should be ashamed of), or that overly enthusiastic people (who should know better) fall for this crap, when these same people wouldn't fall for this crap if the same flaws were in regard to fat, dairy, eggs, saturated fat etc.

In Health
Je
User avatar
JeffN
 
Posts: 9412
Joined: Tue Jan 08, 2008 5:56 am


Return to Jeff Novick, RD

Who is online

Users browsing this forum: No registered users and 9 guests



Welcome!

Sign up to receive our regular articles, recipes, and news about upcoming events.