High blood pressure: Sodium may not be the culprit
Since then, many animal studies showed a causal relationship between dietary sodium and hypertension and in human studies, established that the average BP . Jun 15, For some people, high salt intake can cause high blood pressure — and create a vicious Looking at the Link Between Salt and Heart Failure. If your parents or close blood relatives have had high blood pressure, you are more It also means checking labels, because up to 75 percent of the sodium we.
Our findings add to growing evidence that current recommendations for sodium intake may be misguided.
Salt and your health, Part I: The sodium connection
Moore Potassium as important as sodium The importance of dietary potassium is also underlined in this study. The team found that individuals with the lowest blood pressure were those who had the highest intake of sodium and potassium. Conversely, those with the highest blood pressure had the lowest intake of sodium and potassium. The authors conclude that: This study does support the finding of a clear inverse association between potassium, magnesium, and calcium and blood pressure change over time.
Perhaps in the future, methods of screening for salt sensitivity might help to establish which individuals need to be more careful.
As more studies conclude that sodium's role in hypertension is less vital than once thought, dietary recommendations are sure to change in line with the findings. 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.
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.
Salt and your health, Part I: The sodium connection - Harvard Health
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. 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. 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. Lewis Dahl presented evidence that a diet high in sodium contributes to high blood pressure.
His hypothesis was soon questioned by other researchers, and the sodium controversy has raged ever since. Why did the link between sodium and blood pressure generate so much heat? Part of the reason stems from the body's intrinsic complexity: And the complexities of human behavior are just as daunting as those of human biology; dietary potassium, calcium, and many other nutrients influence blood pressure, as do exercise, body weight, alcohol use, and stress.
Additional challenges result from the methods scientists use to study the link between diet and hypertension. Blood pressure can fluctuate widely from minute to minute; if sustained, even small changes in blood pressure can have a large impact on lifetime risk. Plus, sodium consumption can vary substantially from day to day. Studies that rely on dietary history can differ from those that measure the amount of sodium in a person's daily urine, which should be a more accurate reflection of how much sodium has been consumed on a given day.
Some people are more sensitive to sodium than others. And experiments that subject volunteers to a high or low consumption of sodium are necessarily brief, at least compared to the months and years it takes for blood pressure to affect health. Little by little, though, a consensus has emerged. Most researchers, scientific advisory boards, and government agencies agree that reducing dietary salt will lower blood pressure, reduce the risk of heart attack and stroke, and save lives — up tolives a year in the United States alone, according to the American Medical Association Council on Science and Public Health.
Salt and resistant hypertension Many excellent antihypertensive drugs are available. But that doesn't mean these patients with resistant hypertension are beyond help. An important study of resistant hypertension reported that a low-sodium diet reduced systolic blood pressure by a whopping Sodium restriction will never replace blood pressure medications — but it sure will help.
- Salt's effects
- High blood pressure: Sodium may not be the culprit
- Dietary Salt Intake and Hypertension
Impressive evidence Although not all studies agree, a large body of evidence points to sodium as an important contributor to high blood pressure. After reviewing the results of animal experiments, population studies, and clinical trials, the World Health Organization described the evidence that high dietary sodium causes hypertension as "conclusive. To check other factors that affect blood pressure, each subject was also evaluated for obesity, alcohol use, and dietary potassium.
The result demonstrated a clear link between dietary sodium and blood pressure: It didn't take long for scientists to spot a weak link in the chain between sodium and blood pressure: That means Americans who eat a lot of salt don't necessarily have higher blood pressure than those who eat less.
Even within a single country, such as the United States, blood pressure rises more steeply with age in people who take in large amounts of sodium than in people who eat less salt. This means you It's easy to dismiss salt as the other guy's problem. Current guidelines say no adult should consume more than 2, mg of sodium a day, and that people with hypertension, all middle-aged and older adults, and all African Americans should consume no more than 1, mg a day.
Where do you fit in? So if you're like the rest of us, you'll benefit from cutting your dietary salt. DASHing doubts Demonstrating a link between dietary sodium and blood pressure is one thing, showing that cutting down on salt will lower blood pressure is another.
Early trials of reduced sodium diets produced mixed results, largely because the patient populations, test diets, and experimental designs varied so greatly.
That led many people to take advice about dietary sodium with a grain of salt. That skepticism was understandable, at least untilwhen a major trial put things in perspective. Researchers evaluated three diets: