High blood pressure: Sodium may not be the culprit
It seems that salt's association blood pressure and heart disease along contributing to the results of sodium and high blood pressure; about 82% study replicates the relationship between sodium and blood pressure, but it. This relationship between sodium and potassium in the diet is known as as decreasing sodium when it comes to reducing blood pressure. The connection between high salt intake and elevated BP became widely recognized.
Another example of the effect of life-style changes including dietary sodium intake on BP is that of the Yi people, an ethnic minority living in southwestern China. Blood pressure rose very little with increasing age 0. In contrast, Yi migrants and Han people who lived in urban areas consumed a sodium-rich diet and experienced a much greater increase in BP with progressive aging 0. These findings suggest that changes in life-style, including higher intake of dietary sodium, contributed to higher BP among Yi migrants.
A large number of epidemiologic, evolutionary, and clinical studies have confirmed that salt intake is an important factor in elevating the BP in humans. The first double-blind controlled study of moderate salt restriction was performed in the early 's by MacGregor et al. Patients were advised to reduce dietary salt intake. After 2 weeks of sodium restriction, patients were entered into an 8-week double-blind randomized crossover study of 'Slow Sodium' Ciba, 10mmol of sodium per tablet versus slow sodium placebo.
The mean supine BP was 7. They suggested that moderate sodium restriction should become part of the management of essential hypertension. Followed by this study, many large observational and epidemiological investigations conducted worldwide link between high salt intake and hypertension. INTERSALT study was one of the first large international epidemiologic studies on sodium intake and hypertension using a standardized method for measuring hour urinary sodium.
This study, which was a crosssectional assessment of 10, subjects aged sampled from 52 centers around the world, attempted to relate sodium intake to BP from an epidemiological perspective. Sodium excretion ranged from 0. In individual subjects within centerssalt intake was significantly related to BP. Four centers found very low sodium excretion, low BP, and little or no upward slope of BP with age. Across the other 48 centers sodium was significantly related to the slope of BP with age but not to median BP.
The study demonstrated a significant positive relationship between salt intake and BP in individual subjects within centers. In an initial analysis of 48 of the 52 centers, no significant association between sodium intake and median BP was found. However, after inclusion of the remaining 4 centers, in which the average sodium consumption was 0.
Furthermore, it also found that populations with low average daily salt intakes had low BP and very little or no increase in BP with age Mean sodium excretion was 0. Mean BP was Systolic and diastolic BP were not higher at older than at younger ages in men. In women, systolic pressure was lower at older ages.
In this tribe, there was a low average population BP, no hypertension and no positive slope of BP with age in a population with very low salt intake. Salt institute criticized that in an initial analysis of 48 of the 52 centers, no significant association was noted between sodium intake and median BP. However, the INTERSALT's investigators re-analyzed their data and showed that the highly significant within-population association between salt intake and BP across all 52 centers was virtually unchanged.
Lowering sodium intake by mmol was associated with a 3mmHg decrease in systolic BP There are several studies on the effect of reducing the salt intake on BP on a community levels. In the intervention community, there was a widespread health education effort to reduce the dietary salt intake.
The fall in BP involved the whole community, normotensives and hypertensive individuals alike, and the response did not differ between the young and the old or between men and women. Those with the greatest fall in salt excretion tended significantly to be also those who showed the greatest fall in BP. The other long-term trial was carried out in Tianjin in China as part of a community-based intervention program to reduce non-communicable diseases This intervention was based on examinations of independent cross-sectional population samples in 1, persons and 2, persons in the intervention and matched reference areas.
High blood pressure? Reducing salt intake alone will not solve it | ScienceNordic
The food recall method was used to measure dietary salt intake. The mean reduction in salt intake was 1. During the same period, the sodium intake increased significantly in men of the reference area. In the intervention area, the mean systolic BP decreased by 3mmHg for the total population and by 2mmHg for normotensive people. The decrease in systolic BP was significant for both hypertensive and normotensive subjects. Another long-term trial was performed in two Belgian towns of 12, and 8, inhabitants, situated within 50 km of each other The low-sodium intervention in one town was mainly directed at women and implemented through mass media techniques, while the control town was merely observed.
During the study a total of 2, subjects were examined. However, both systolic BP No significant difference was observed in the evolution of mean systolic and diastolic pressures that declined to the same extent in the two towns during the trial. In women of the intervention town, hour urinary salt excretion decreased by 1. This negative result may be explained by the small reduction in salt consumption that would be insufficient to observe a net effect on BP in the Belgian environment.
These results suggest that a reduction in salt consumption is difficult to achieve with mass media techniques and in women and in subjects aged 50 years or more, the intervention did achieve some success, but BP was not affected. There were many randomized clinical trials performed to test the effects of reducing salt intake on BP. Thirty-two trials with outcome data for 2, subjects were included. Pooled BP differences between treated and control groups were highly significant for all trials combined.
The effects on blood pressure by lowering sodium in hypertensive and normotensive subjects were Weighted linear-regression analyses across the trials showed dose responses, which were more consistent for trials in normotensive subjects.
These analyses yielded estimates, per mmol of sodium reduction, of There is no evidence that sodium reduction as achieved in these trials presents any safety hazards. They concluded that the BP reduction with a substantial lowering of dietary sodium in the US population could reduce cardiovascular morbidity and mortality.
However, in two other meta-analyses 3435it was claimed that salt reduction had very little effect on BP in individuals with normal BP and a reduction in population salt intake was not warranted.
The meta-analysis by Midgley et al. Decreases in BP were larger in trials of older hypertensive individuals and small and non-significant in trials of normotensive individuals. They concluded that dietary sodium restriction for older hypertensive individuals might be considered, but the evidence in the normotensive population does not support current recommendations for universal dietary sodium restriction. Another meta-analysis by Graudal et al. They concluded that these results do not support a general recommendation to reduce sodium intake.
However, these two meta-analyses were criticized by some authors because the data included was flawed. Both meta-analysis included trials of very short duration with comparing the effects of acute salt loading to abrupt and severe salt restriction for only a few days. It is inappropriate to include the acute salt restriction trials in a meta-analysis where the implications of the findings are to apply them to public health recommendations for a long-term. It is possible that acute and large reduction in salt intake increases sympathetic activity, stimulates the renin-angiotensin system which would counteract the effects on BP.
Subsequently, several large-scale intervention studies showing significant antihypertensive effects of salt reduction in diet were performed by several groups. In TOHP I 36the patients were randomized to three life-style change groups weight reduction, sodium reduction, and stress managementone of which was a low sodium diet.
At 18 months follow-up, weight reduction intervention produced weight loss of 3. They concluded that weight reduction was the most effective strategy tested for reducing BP in normotensive persons. Sodium reduction was also effective for reducing BP. Compared with the usual care group, BP decreased 2.
At 36 months, BP decreases remained greater in the active intervention groups than in the usual care group weight loss group, 1. Differences were statistically significant for systolic BP in the sodium reduction group. TOPH I and II will presumably remain the best evidence supporting the beneficial effect of a moderate reduction of salt intake in the general population The intervention studies of salt intake reduction are often conducted with other life-style modifications.
TONE study 39 was performed to determine whether weight loss or reduced sodium intake is effective in the treatment of older persons aged 60 to 80 years with hypertension. The authors randomized obese participants to reduced sodium intake, weight loss, both, or usual care, and the non-obese participants to reduced sodium intake or usual care.
After a median follow-up of 29 months range monthsthe composite outcome occurred less frequently among those assigned vs. The mean change in blood pressure for participants assigned to sodium reduction alone was This study, however, has to be interpreted with caution including selection of adherent and well educated patients only There was no difference between sodium-restricted and control patients in the incidence of cardiovascular events 44 [ TONE study showed significant antihypertensive effects of salt reduction in diet.
The level of salt restriction effective for maintaining a normal BP after the discontinuation of an antihypertensive drug was TONE study demonstrated that a reduced sodium intake and weight loss, alone or combined, could effectively control hypertension Another well-conducted landmark study was the DASH Dietary Approaches to Stop Hypertension -Sodium trial 40a week well controlled feeding trial provided the most robust evidence about the effect of salt intake on human BP.
Each intake of salt was maintained for 30 days. Two different diets that is the control diet and the DASH diet, which is rich in fruits, vegetables and low-fat dairy products, were tested. When the participants were shifted from a high sodium diet to a normal sodium diet, the systolic BP decreased by 2. When they were shifted from a normal sodium diet to a low sodium diet, there was a further reduction in systolic BP of 4.
The adherence to the diet of participants was monitored, not only by measuring hour urine sodium at the end of each period but also their daily food diaries.Should You Restrict Your Salt Intake?
There was a very significant difference in systolic The blood pressures were all significantly lower on the DASH diet. There was a greater reduction in systolic pressure when blood pressure was initially high and in women, but most importantly the blood pressure-lowering effect of reducing the salt intake was observed in all categories of the population, in particular in normotensive as well as in hypertensive people.
The DASH-sodium trial supports that a low sodium diet leads to lower blood pressure.
This observation is very important for the public health issue of lowering salt intake. Most acknowledge that this study reliably confirmed the benefit of dietary sodium restriction in BP management. However, the DASH diet was significantly different from the control diet in terms of more fruits, vegetables, low-fat dairy foods, fish, nuts, potassium, calcium, magnesium, and dietary fiber. Although the group on the DASH diet had a lower urinary sodium excretion, this does not necessarily imply that the benefit was being solely caused by a dietary sodium reduction.
In addition, this study did not evaluate the long-term effects of the intervention and the clinically relevant variables, such as mortality or morbidity.
InHe and MacGregor 41 demonstrated that a modest salt intake reduction caused significant falls in BP in both hypertensive and normotensive individuals. The median reduction in hour urinary sodium excretion was 78 mmol in hypertensives and 74mmol in normotensives.
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- High blood pressure: Sodium may not be the culprit
- Salt's effects
The pooled estimates of BP fall were 4. Weighted linear regression analyses showed a dose response relationship between the change in urinary sodium and BP. They demonstrated that a modest reduction in salt intake for a duration of 4 or more weeks does have a significant and important effect on BP in both hypertensive and normotensive individuals.
These findings in conjunction with other previous evidence relating salt intake to BP make a strong case for a reduction in population salt intake, which will lower population BP and therefore reduce cardiovascular mortality.
Many meta-analyses, so far, on the effect of salt reduction on BP have shown consistent reductions in BP in those with high blood pressure, but there has been some controversy about the magnitude of the fall in BP in normotensive individuals 34 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.
So health recommendations are to eat no more than seven to eight grams of salt NaCl a day for healthy people, and be particularly aware if you have kidney disease or raised blood pressure. Most unprocessed foods are naturally low in salt, such as fruit, vegetables, oats, rice, potatoes, fresh meat and fish. In fact, you consume most salt through products such as bread, sandwich fillings, or ready meals. It is estimated that about 70 to 80 per cent of daily salt intake is through industrially processed food.
Salt is added as a very cheap flavour boost by the food producers. So it is these processed foods and not the salt shaker on the kitchen table that are the biggest salt-sinners.
No need to fear a lack of salt If you are a healthy person then you cannot eat too little salt because the body holds onto it incredibly well.
After a short period of eating a low-salt diet your body hardly excretes any salt in sweat, faeces, or urine.
In some cases, the salt content of urine can be less than that of tap water. But you can conversely lose salt if you are sick, for example by diarrhoea or vomit or extreme sport. And in this case, salt loss can become critical as salt controls the volume of fluid that surrounds cells and plasma and it can therefore lead to low blood pressure, in severe cases lack of blood supply to critical organs, and circulatory collapse and death.
There is no need to worry about a sudden high salt intake if you are otherwise healthy.
Shutterstock The combination of salt and water loss is especially dangerous for small children. The World Health Organisation WHO estimates thatinfants and toddlers under the age of five die each year, especially in developing countries, by simple gastrointestinal infections.
Where it is not by the infection itself that causes these deaths but the loss of salt and water. Potassium stored in nerve and muscle cells Unlike sodium, potassium is concentrated in the bodies 1, billion cells.
Dietary Salt Intake and Hypertension
This pump transports potassium in and sodium out of the cells. Its function was described by the Danish researcher, Jens Christian Skou, who in won a Nobel Prize for chemistry for his work at Aarhus University performed in the s. If the potassium balance is upset you notice it in your muscles. For example, low potassium concentration in blood plasma makes it harder to stimulate the cells, leading to reduced muscle strength and making it harder to lift shopping bags. It can even lead to paralysis.
Too much or too little potassium can kill Unlike sodium, small changes in the concentration of potassium can be deadly. A normal blood plasma potassium concentration is between 3. For example, some US states use potassium injections to execute prisoners on death row, where too much potassium in the blood ultimately leads to cardiac arrest. Just as with sodium, the kidneys maintain the balance of potassium in and out of our bodies. If you eat a meal containing a tray of fresh strawberries and some new potatoes in June, you actually receive a deadly dose of potassium.
Conversely, the kidneys hold onto potassium if levels have dropped due to diarrhoea or vomiting. But if your kidneys do not function properly and if you are not on dialysis, rising potassium concentration can lead to death within days. Facts Sources of potassium include: Apricots, bananas, oranges, lemons, grapefruit, plums, grapes, figs, olives, blueberries, peaches, gooseberries, tomatoes, apples, prunes, and raisins.
Other good sources include: