Blood Pressure : Salt's effects on your body
Dietary intake of sodium, or salt, both because of its might explain variation in blood pressure came. Hypertension can be defined as a blood pressure of /90 mmHg or higher. relationship between salt intake and the increase in blood pressure with age (Fig . A high salt intake has been shown to increase not only blood pressure but also . may explain the greater decreases in blood pressure with reduced sodium intake . The relationship of salt intake and blood pressure is direct and progressive.
In these two meta-analyses, it was claimed that salt reduction had no or very little effect on blood pressure in normotensive individuals. However, detailed examination of these two meta-analyses showed that their data collection and analysis were flawed. Recently, there has been a hot debate whether current salt intake is too high from a health perspective.
There were studies reporting the influence of salt intake on overall cardiovascular diseases such as He et al. They suggested that salt reduction prevented the onset of cardiovascular diseases. They also found that it was the obese and not the non-obese who benefited.
The hazards ratios for coronary heart disease, cardiovascular disease, and all-cause mortality, associated with a mmol increase in 24 hour urinary sodium excretion, were 1. The frequency of acute coronary events rose significantly with increasing sodium excretion. They concluded that high sodium intake predicted mortality and risk of coronary heart disease, independent of other cardiovascular risk factors, including blood pressure.
In a study by O'Donnell et al. Therefore, a salt reduction strategy may be a useful tool for preventing cardiovascular diseases. However, to the contrary, Alderman et al. In the presidential address of the 21st International Society of Hypertension meeting inAlderman 48 advocated that the relationship between salt intake and the risk of cardiovascular diseases is J-shaped and that salt intake at 5 to 6 g per day might be characterized by the lowest risk of cardiovascular diseases. InStolarz-Skrzypeket al.
During a median follow up of 7.
The hour sodium excretion at baseline did not predict either total mortality or fatal combined with nonfatal cardiovascular events. In a subgroup of 1, participants who had both BP and sodium excretion measured at baseline and at last follow-up were followed up for a median of 6. The annual increases in BP averaged 0.
However, in multivariable-adjusted analyses of individual participants, a mmol increment in hour sodium excretion was associated with a significant 1. They concluded that lower urinary sodium excretion was associated with higher cardiovascular disease CVD mortality. These findings contradict a large body of evidence that established elevated salt consumption as a risk factor for CVD.
However, many researchers including He et al. In the same year, Taylor et al. Of these, hypertensive and normotensive individuals were separately analyzed. Salt reduction was associated with reductions in urinary salt excretion of between 27 and 39mmol per 24 hour and reductions in systolic blood pressure between 1 and 4mmHg.
Pooled relative risks RRs comparing the intervention with the reference groups for all-cause mortality were 0. Salt restriction increased the risk of all-cause mortality in patients with heart failure RR, 2. In both hypertensive and normotensive individuals, salt reduction slightly decreased the incidence of cardiovascular diseases, although there was no significant difference. These authors found no strong evidence that salt reduction reduced all-cause mortality or CVD morbidity in normotensives or hypertensives.
A single RCT showed an increase in the risk of all-cause death in those with congestive heart failure receiving a low-sodium diet. In contrast, He et al. They reported that salt reduction at 2. However, in most studies supporting the fact that salt reduction increases the risk of cardiovascular diseases, methodological problems have been indicated 4749or study subjects were high-risk patients 46 In conclusion, a moderate reduction of dietary salt intake is generally an effective measure to reduce blood pressure.
The WHO strongly recommended to reduce dietary salt intake as one of the top priority actions to tackle the global non-communicable disease crisis and has urged member nations to take action to reduce population wide dietary salt intake to decrease the number of deaths from hypertension, cardiovascular disease and stroke. Future research may inform aspects of optimal sodium reduction strategies and the intake targets for populations.
Reducing salt intake in populations. No benefit seen in sharp limits of salt in diet. The New York Times. Salt, Diet and Health: Cambridge University Press; High salt intake, its origins, its economic impact, and its effect on blood pressure.
A brief history of salt. The history of salt-aspects of interest to the nephrologist.
- Salt's effects
Reducing population salt intake worldwide: From evidence to implementation. Intersalt Cooperative Research Group. Results for 24 hour urinary sodium and potassium excretion. Buss D, Robertson J. Her Majesty's Stationery Office; Links between dietary salt intake, renal salt handling, blood pressure, and cardiovascular diseases. Salt, blood pressure andcardiovascular disease. Should we eat less salt? Ambard L, Beaujard E. Causes de l' hypertension arterielle.
Treatment of hypertensive vascular disease-with the rice diet. Observations on dietary sodium chloride. J Am Diet Assoc.
The effect of increased salt intake on blood pressure of chimpanzees. Effects of diet in essential hypertension: Results with unmodified Kempner rice diet in fifty hospitalized patients. An epidemiologic study of hypertension in Newfoundland. Can Med Assoc J.
The Kenyan Luo migration study: Migration-induced changes in blood pressure: Clin Exp Pharmacol Physiol. Migration, blood pressure pattern, and hypertension: Double-blind randomised crossovertrial of moderate sodium restriction in essential hypertension. Results for 24h urinary sodium and potassium excretion. Blood pressure and electrolyte excretion in the Yanomamo Indians, an isolated population.
Salt and blood pressure: Changes in sodium intake and blood pressure in a community-based intervention project in China. Salt intake and blood pressure in the general population: Randomized trials of sodium reduction: Am J Clin Nutr.
Effect of reduced dietary sodium on blood pressure: A meta-analysis of randomized controlled trials. Effects of sodium restriction on blood pressure, renin, aldosterone, catecholamines, cholesterols, and triglyceride: The effects of nonpharmacologic interventions on blood pressure of persons with high normal levels. Effects of weight loss and sodium reduction intervention on blood pressure and hypertension incidence in overweight people with high-normal blood pressure: Long term effects of dietary sodium reduction on cardiovascular disease outcomes: Sodium reduction and weight loss in the treatment of hypertension in older persons: N Engl J Med.
Effect of modest salt reduction on blood pressure: Implications for public health. Dietary sodium intake and subsequent risk of cardiovascular disease in overweight adults. Urinary sodium excretion and cardiovascular mortality in Finland: Urinary sodium and potassium excretion and risk of cardiovascular events. Salt intake, stroke, and cardiovascular disease: Low urinary sodium is associated with greater risk of myocardial infarction among treated hypertensive men.
Fatal and nonfatal outcomes, incidence of hypertension, and blood pressure changes in relation to urinary sodium excretion. Does reducing salt intake increase cardiovascular mortality?
Reduced dietary salt for the prevention of cardiovascular disease: Salt reduction lowers cardiovascular risk: Overall, the results of cross-sectional studies have been inconsistent and inconclusive. Experimental Studies of Sodium and Blood Pressure Because association does not prove causality, the salt to blood pressure relationship needed experimental validation. Animal studies have shown that sodium reduction can lower pressure, and, conversely, that sodium addition, as was the case in a study involving a dozen chimpanzees, could elevate arterial pressure.
There is enormous variation between individuals on the effect of salt on pressure Figure 1. This may be associated with genetic variation. Perhaps the best estimate of the effect of sodium intake on blood pressure can be gained from meta-analyses of randomized trials.
Meta-analyses can only reflect the studies included. Unfortunately, well-designed and conducted studies involved considerable variation in sodium consumption, and many were of short duration.
Nevertheless, the most rigorous meta-analyses are in general agreement. It would appear that the largest decline is achieved when small groups of subjects were studied for short periods of time. It has been difficult to sustain, beyond a year, either the blood pressure reduction, or the sodium restriction in free-living subjects. It should be noted, however, that a sustained decrease of even a few mmHg could, assuming the method in its achievement produced no harm, reduce morbidity and mortality more than is currently achieved by restricting treatment to patients with high blood pressure.
It is that possibility that energizes advocates of sodium restriction. The multiple studies supporting these conclusions are sufficiently robust to make it unlikely that further study will alter their essential findings. Other Effects of Sodium Reduction Attempts to alter one aspect of the interior milieu may produce other effects. It is not surprising that so profound and pervasive an intervention as dietary manipulation designed to alter sodium intake by half would also produce non-blood pressure effects.
Moreover, just as individuals vary in the way that sodium modulation effects blood pressure, it is to be expected that other physiological responses may also vary. Blood pressure is not even the only haemodynamic effect of variation in dietary sodium. Increasing attention is being paid to arterial compliance as a measure of vascular health. New, non-invasive techniques now make it possible to assess compliance in the clinical setting.
It has been shown that in hypertensive and normal subjects, arterial compliance is positively related to urinary sodium excretion. Increased aldosterone activity, also stimulated by reduced sodium intake, has similar unwanted cardiovascular effects.
It has now been shown that, in people whose blood pressure increases with sodium restriction, a higher sodium intake actually decreased left ventricular workload, and this was in contrast to the salt sensitive subjects. In this regard, the recent report by Weinberger, 17 revealing greater cardiovascular mortality in salt sensitive than insensitive subjects, suggests that these phylogenic characteristics may have real clinical relevance. Since the Weinberger observational study included no data on actual sodium intake, it is not possible to draw any inferences about whether sodium intake might have influenced outcomes of either group.
Dietary Salt Intake and Hypertension
The point of these examples is, of course, that intervention on sodium, like virtually all other medical interventions, will have multiple effects. The only way to determine the total or health effects of these interventions is to determine their effect on the quality and duration of life.
In fact, limiting weight gain did produce those desired outcomes. Unfortunately, at the same time, this intervention unexpectedly increased fetal morbidity and mortality. Women are no longer advised to avoid weight gain in pregnancy. It has been shown in rodents that a restricted sodium intake, while reducing blood pressure, also stunts growth and shortens life. In Japan, where sodium intakes tend to be high, life expectancy is among the highest in the world. Thus, ecological data, albeit weak evidence, provides no suggestion that a reduced sodium intake will extend life, nor that a high sodium intake is inconsistent with a prolonged life expectancy.Nutrition : How to Reduce High Blood Pressure with Diet
Epidemiological data, in which individual sodium intake and health outcomes are linked, is the next level of evidence through which to determine whether dietary sodium might influence the length or quality of life.
Unfortunately, despite intense interest in this issue, regrettably little solid data are available. This may lead to angina sharp pains in the chest when being active.
Dietary Salt Intake and Hypertension
With this condition the cells in the heart don't work as well as they should because they are not receiving enough oxygen and nutrients. However, lowering blood pressure may help to alleviate some of the problems and reduce the risk of greater damage. If this happens, then the part of the heart that was receiving the blood no longer gets the oxygen and nutrients it needs and dies.
The result is a heart attack. The best way to prevent a heart attack is to stop the arteries becoming damaged. And one of the best ways of doing this is keep your blood pressure down by eating less salt. Eating too much salt raises your risk of a stroke Brain The raised blood pressure caused by eating too much salt may damage the arteries leading to the brain. At first, it may cause a slight reduction in the amount of blood reaching the brain.
This may lead to dementia known as vascular dementia.