Saltwater and hypertension

[Guest guest]

Hi Karen, & All,

 

Karen wrote:

> and how would (extra salt) affect BP?

 

I reckon that a large increase in salt intake would increase BP and risk

of CVA.

 

The Salt Institute at http://tinyurl.com/9pjub does not acccept this. It

says: “Is there any proven reason for us to grossly modify our salt intake

or systematically avoid table salt? Is this a proven healthy thing to do,

that is, will it save us from the major goals of antihypertensive therapy,

such as a later heart attack or stroke or kidney failure? Generally

speaking the answer is either a resounding no, or that, at best, there is

not any positive direct evidence to support such recommendations. And

equally relevant, what are the new risks you might be taking on by

avoiding salt?” (American Journal of Hypertension, (14)4:307-310.

 

Would we expect them to say anything else?

 

In contrast (and in line with majority medical belief), two recent

MetaAnalyses came to the opposite view:

 

Cochrane Database Syst Rev. 2004;(3):CD004937. Effect of

longer-term modest salt reduction on blood pressure. He FJ,

MacGregor GA. BACKGROUND: Many randomised trials assessing the

effect of salt reduction on blood pressure show reduction in blood

pressure in individuals with high blood pressure. However, there is

controversy about the magnitude and the clinical significance of the fall

in blood pressure in individuals with normal blood pressure. Several

meta-analyses of randomised salt reduction trials have been published

in the last few years. However, most of these included trials of very short

duration (e.g. 5 days) and included trials with salt loading followed by

salt deprivation (e.g. from 20 to 1g/day) over only a few days. These

short-term experiments are not appropriate to inform public health policy

which is for a modest reduction in salt intake over a prolonged period of

time. A meta-analysis by Hooper et al is an important attempt to look at

whether advice to achieve a long-term salt reduction (i.e. more than 6

months) in randomised trials causes a fall in blood pressure. However,

most trials included in this meta-analysis achieved a small reduction in

salt intake; on average, salt intake was reduced by 2 g/day. It is,

therefore, not surprising that this analysis showed a small fall in blood

pressure, and that a dose-response to salt reduction was not

demonstrable. OBJECTIVES: To assess the effect of the currently

recommended modest reduction in salt intake (WHO 2003; SACN 2003;

Whelton 2002), on blood pressure in individuals with normal and

elevated blood pressure.To assess whether the magnitude of the

reduction in blood pressure is dependent on the magnitude of the

reduction in salt intake. SEARCH STRATEGY: We searched MEDLINE,

EMBASE, Cochrane library, CINAHL, and reference list of original and

review articles. SELECTION CRITERIA: We included randomised trials

with a modest reduction in salt intake and a duration of 4 or more

weeks. DATA COLLECTION AND ANALYSIS: Data were extracted

independently by two persons. Mean effect sizes were calculated using

both fixed and random effect models using Review Manager 4.2.1

software. Weighted linear regression was used to examine the

relationship between the change in urinary sodium and the change in

blood pressure. We used funnel plots to detect publication and other

biases in the meta-analysis. MAIN RESULTS: Seventeen trials in

individuals with elevated blood pressure (n=734) and 11 trials in

individuals with normal blood pressure (n=2220) were included. In

individuals with elevated blood pressure the median reduction in 24-h

urinary sodium excretion was 78 mmol (4.6 g/day of salt), the mean

reduction in systolic blood pressure was -4.97 mmHg (95%CI:-5.76 to -

4.18), and the mean reduction in diastolic blood pressure was -2.74

mmHg (95% CI:-3.22 to -2.26). In individuals with normal blood

pressure the median reduction in 24-h urinary sodium excretion was 74

mmol (4.4 g/day of salt), the mean reduction in systolic blood pressure

was -2.03 mmHg (95% CI: -2.56 to -1.50) mmHg, and the mean

reduction in diastolic blood pressure was -0.99 mmHg (-1.40 to -0.57).

Weighted linear regression analyses showed a correlation between the

reduction in urinary sodium and the reduction in blood pressure.

REVIEWERS' CONCLUSIONS: Our meta-analysis demonstrates that a

modest reduction in salt intake for a duration of 4 or more weeks has a

significant and, from a population viewpoint, important effect on blood

pressure in both individuals with normal and elevated blood pressure.

These results support other evidence suggesting that a modest and

long-term reduction in population salt intake could reduce strokes, heart

attacks, and heart failure. Furthermore, our meta-analysis demonstrates

a correlation between the magnitude of salt reduction and the

magnitude of blood pressure reduction. Within the daily intake range of

3-12g/day, the lower the salt intake achieved, the lower the blood

pressure. Publication Types: Meta-Analysis Review PMID: 15266549

[PubMed - indexed for MEDLINE]

 

Cochrane Database Syst Rev. 2004;(1):CD003656. Related

Articles, Links Update of: Cochrane Database Syst Rev.

2003;(3):CD003656. Advice to reduce dietary salt for prevention of

cardiovascular disease. Hooper L, Bartlett C, Davey SG, Ebrahim S.

MANDEC, University Dental Hospital of Manchester, Higher Cambridge

Street, Manchester, UK, M15 6FH. BACKGROUND: Restricting sodium

intake in elevated blood pressure over short periods of time reduces

blood pressure. Long term effects (on mortality, morbidity or blood

pressure) of advice to reduce salt in patients with elevated or normal

blood pressure are unclear. OBJECTIVES: To assess in adults the long

term effects (mortality, cardiovascular events, blood pressure, quality of

life, weight, urinary sodium excretion, other nutrients and use of anti-

hypertensive medications) of advice to restrict dietary sodium using all

relevant randomised controlled trials. SEARCH STRATEGY: The

Cochrane Library, MEDLINE, EMBASE, bibliographies of included

studies and related systematic reviews were searched for unconfounded

randomised trials in healthy adults aiming to reduce sodium intake over

at least 6 months. Attempts were made to trace unpublished or missed

studies and authors of all included trials were contacted. There were no

language restrictions. SELECTION CRITERIA: Inclusion decisions were

independently duplicated and based on the following criteria: 1)

randomisation was adequate; 2) there was a usual or control diet group;

3) the intervention aimed to reduce sodium intake; 4) the intervention

was not multifactorial; 5) the participants were not children, acutely ill,

pregnant or institutionalised; 6) follow-up was at least 26 weeks; 7) data

on any of the outcomes of interest were available. DATA COLLECTION

AND ANALYSIS: Decisions on validity and data extraction were made

independently by two reviewers, disagreements were resolved by

discussion or if necessary by a third reviewer. Random effects meta-

analysis, sub-grouping, sensitivity analysis and meta-regression were

performed. MAIN RESULTS: Three trials in normotensives (n=2326),

five in untreated hypertensives (n=387) and three in treated

hypertensives (n=801) were included, with follow up from six months to

seven years. The large, high quality (and therefore most informative)

studies used intensive behavioural interventions.Deaths and

cardiovascular events were inconsistently defined and reported; only 17

deaths equally distributed between intervention and control groups

occurred. Systolic and diastolic blood pressures were reduced at 13 to

60 months in those given low sodium advice as compared with controls

(systolic by 1.1 mm Hg, 95% CI 1.8 to 0.4, diastolic by 0.6 mm hg, 95%

CI 1.5 to -0.3), as was urinary 24 hour sodium excretion (by 35.5 mmol/

24 hours, 95% CI 47.2 to 23.9). Degree of reduction in sodium intake

and change in blood pressure were not related. People on anti-

hypertensive medications were able to stop their medication more often

on a reduced sodium diet as compared with controls, while maintaining

similar blood pressure control. REVIEWER'S CONCLUSIONS:

Intensive interventions, unsuited to primary care or population

prevention programmes, provide only minimal reductions in blood

pressure during long-term trials. Further evaluations to assess effects

on morbidity and mortality outcomes are needed for populations as a

whole and for patients with elevated blood pressure.Evidence from a

large and small trial showed that a low sodium diet helps in

maintenance of lower blood pressure following withdrawal of

antihypertensives. If this is confirmed, with no increase in cardiovascular

events, then targeting of comprehensive dietary and behavioural

programmes in patients with elevated blood pressure requiring drug

treatment would be justified. Publication Types: Meta-Analysis Review

PMID: 14974027 [PubMed - indexed for MEDLINE]

 

Best regards,

 

 

Tel: (H): +353-(0) or (M): +353-(0)

 

 

 

 

Ireland.

Tel: (W): +353-(0) or (M): +353-(0)

 

 

 

" Man who says it can't be done should not interrupt man doing it " -

Chinese Proverb

 

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