ВНИМАНИЕ! Очень низкое потребление соли так же опасно для сердечников, как и чрезмерное.

ВНИМАНИЕ! Очень низкое потребление соли так же опасно для сердечников, как и чрезмерное.

Эту информацию прислали из Канады моему другу, гипертонику со стажем. Суть статьи в заголовке. Сам текст (на английском) ниже – там все детали и научная дискуссия.

Исследование охватывало около 29 тыс. пациентов с сердечными проблемами.

Главный результат: очень низкое потребление соли повышает давление и вероятность не только кризов, но и инфарктов. Страдают от этого такжедругие системы организма.

<pre> </pre> <pre>----------------- </pre> <pre> </pre> <pre>LOW SODIUM INTAKE: A CAUSE FOR CONCERN FOR INCREASED CARDIOVASCULAR DISEASE EVENTS </pre> <pre>By Patrick V. Brady, Ph D, Nadim R.Khandaker, PhD, P. Eng., & Shirya Rashid, Ph D </pre> <pre>0NTARIO CENTRE FOR ENGINEERING AND PUBLIC POLICY</pre> <pre> </pre> <pre>LOW SODIUM INTAKE: A SURPRISING CARDIOVASCULAR RISK FACTOR IN INDIVIDUALS WITH ESTABLISHED CARDIOVASCULAR DISEASE </pre> <pre> </pre> <pre>Evidence from observational, epidemiological and clinical studies, such as those described above, seem to justify the World Health Organization’s</pre> <pre>ENGINEERING DIMENSIONS 45 </pre>

THE ADVERSE HEALTH EFFECTS of high salt intake are well established and recognized to the extent that regulatory agencies have established limits for high sodium content in potable water. A recent study from McMaster Univer sity published in The journal ofthe A merican M edical Association QAMA) has found that very low sodium intake can also have adverse health effects in high cardiovascular risk populations. With proliferation of point-of-use membrane water treatment systems such as reverse osmosis, it may be time for regulatory agencies to look at setting guidelines for a low threshold of sodium in potable water. T his article reports and debates this topical issue.

HIGH SODIUM INTAKE AND CARDIOVASCULAR DISEASE DEVELOPMENT IN HEALTHY POPULATIONS

It is well known that high sodium intake causes high blood pressure and cardiovascular evenrs

in individuals without a prior history of cardiovascular diseases-that is, in healthy individuals.

Sodium can be absorbed from drinking and cooking water and from dietary intake. For example, the well-known Dietary Approaches to Stop Hypertension (DASH) study showed strong evidence of short-term (one-month) effects of high sodium intake-a target of 150 mmol a day with an energy intake of 2100 kcal, reflecting typical consumption in the United States (Sacks eta!., 2001)-in causing elevations

in blood pressure in a dose-response manner in individuals with and without existing high blood pressure (hypertension).

Similarly, five large randomized trials that lasted at least one year showed significant longterm

effects of high sodium intake on blood pressure. Studies have also addressed whether high dietary sodium has subsequent effects on cardiovascular events and morbidity and mortality.

Among the longest studies, the Trials of Hypertension Prevention (TOHP) (Sacks eta!., 2001 and Kumanyika eta!., 2005) determined the long-term effects, over a period of 10 to 15 years, of high sodium levels on cardiovascular disease and mortality.

People with pre-hypertension with high sodium intake experienced a 25 to 30 per cent higher risk of cardiovascular events in the 10 to 15 years after the trial. This included increased heart attacks, stroke and cardiovascular death.

Consistent with this, a recent meta-analysis of 13 prospective studies reported that a 5-gram increase in salt intake (2 grams ofsodium) was associated with a significant increase in cardiovascular disease incidence (Strazzullo eta!., 2009).

LOW SODIUM INTAKE: A SURPRISING CARDIOVASCULAR RISK FACTOR IN INDIVIDUALS WITH STABLISHED CARDIOVASCULAR DISEASE

Evidence from observational, epidemiological and clinical studies, such as those described

above, seem to justifY the World Health Organizarion (WHO) and many national recommended guidelines of limiting urinary sodium excretion (a proxy for determining dietary sodium intake)

to between 1.5 to 2.3 grams a day. However, because most studies consisted of patient populations without a history of cardiovascular events, what had not yet been determined conclusively is whether the same sodium intake guidelines hold for those with established cardiovascular disease.

This question was addressed by M.J. O'Donnell, Salim Yusuf and colleagues from the world-renowned Population Health Research Institute at McMaster University in their landmark study recently published in the journal ofthe American College ofCardiology, 2011. Their well-constructed srudy consisted of the largest (almost 29,000 participants) and most diverse (participants were recruited from 40 countries) group of individuals with established cardiovascular disease measured for sodium excretion, and

involved a long-term, 56-month follow-up. The individuals in the study were 55 years in age or older. In their study, high urinary sodium excretion of greater than 7 grams a day, not surprisingly, increased the risk of all cardiovascular events, including heart attack and stroke, in individuals with a history of cardiovascular disease. What was surprising is that low sodium excretion of less than 3 grams a day also increased the risk for cardiovascular disease-related mortality and congestive heart failure in individuals with established cardiovascular disease. This sodium range is below the levels recommended by WHO and most national guidelines.

T he authors of the study addressed the question of the biological causes underlying the increased risk of cardiovascular disease mortality in those with low sodium intake. They indicated that plausible explanations include the adverse effects of low blood sodium levels in causing very low blood

pressure or hypotension, which can lead to heart failure.

They also identified a role for low sodium levels in activating the renin-angiotensin and sympathetic nervous systems, which can induce congestive heart failure and rapid and irregular heart rates. Low sodium levels, they stared, also have adverse metabolic effects on blood levels of cholesterol-rich lipoproteins and insulin, which are risk factors for the development of atherosclerosis and coronary heart disease. Finally, low sodium levels can lead to a negative balance of magnesium and calcium.

PUBliC POliCY IMPliCATIONS

T he findings in the above landmark study have important public policy implications. As stated by the study authors, it justifies a more cautious approach to policies on sodium intake, targeting sodium intake reduction in populations consuming high sodium levels, and a guarded approach to moderate sodium intake recommendations. The findings also caution against low sodium intake recommendations for those with established cardiovascular disease. T hose with established cardiovascular disease comprise a patient population group that is expected to rapidly expand in the near future in most global populations, including Canada. Canada, like other Western nations, is experiencing an aging population that is expected to expand in numbers in the coming decades. Such an aging population is more likely to have a history of cardiovascular disease. For example, in Canada, the estimated lifetime risk of developing heart disease by 40 years of age is a very high 49 per cent for men and 32 per cent for women (Rashid and Francis, 2008). Low sodium intake can have disastrous consequences if the above study's results are applied to this group. In addition to increased risk of cardiovascular disease-related

mortality being the outcome of low sodium intake in this group, increased risk of congestive

heart failure is a serious problem, as 52 per cent die within the first five years of developing congestive

heart failure (Grigioni et al., 2005).

Another reason for the expected increase in the proportion of individuals with established cardiovascular disease in Canada is the obesity epidemic occurring in Western industrialized nations, including Canada. In the US, the percentage of individuals who are either overweight or obese-that is, individuals with a body mass index (BMI) of 25 kg/ m2 or more-is a staggering 60 to 70 per cent of the population (American Heart Association, 201 1). In Canada, as well, two out of every three adults are overweight or obese (Health Canada, 2006). T he prevalence of individuals who are specifically

obese-that is, individuals with a BMI of 30 kg/ m2 or more-is 34 per cent in the US and 24 per cent in Canada (Shields, Carroll and Ogden, 20 11). Obesity is a significant independent risk factor for cardiovascular disease development.

For example, cardiovascular disease occurrence was measured over 26 years in 5000 individuals

from the well-known Framingham studies (Hubert et al., 1983). The studies indicated that obesity, measured by percentage above desirable weight, on initial examination, was a significant predictor of the 26-year incidence of coronary heart disease and coronary and cardiovascular disease death in both men and women (Hubert et al., 1983). The above population trends make a strong case for initiating public policy debates on continual monitoring of both high and low sodium intake in the population and for research into their subsequent effects on cardiovascular health in the general population and those with established cardiovascular diseases.

NEED TO REGULATE LOW SODIUM LEVELS IN POTABLE WATER

T he observation by O'Donnell er al. (201 1) that low sodium excretion is associated with increased cardiovascular disease mortality and events in

high cardiovascular disease risk diverse populations should be of interest to water professionals where membrane technologies are being more commonly introduced to treat source water or even treated water at the point of use. This is more prevalent in regions of the world with water high in salinity, such as water in coastal regions and brackish water in arid regions of the world.

Membrane treatment systems utilized in JULY/AUGUST 2012 these regions, in particular reverse osmosis (RO) ONTARIO CENTRE FOR ENGINEERINGsystems, which are used to desalinate water for

19 AND PUBLIC POLICY potable drinking use, produce water that is low in sodium and other minerals.

RO systems are modular with a low footprint and are being used more extensively in pointof-use applications. In the desert southwest US, for example, RO water stations are as common as gas stations in rural and urban communities.

Low sodium is also of concern in regions where the only source of potable water is rain water, which is naturally low in sodium. Even in regions where saline water is not of concern, application of RO systems is quite noticeable.

One only needs to go to the local grocery store to see RO water-filling stations or point-of-use RO systems and accessories being sold.

Regulatory bodies, such as WHO and the US Environmental Protection Agency, have guidelines for municipalities for high sodium in their treated water. In light of the article by O'Donnell et al. (2011), it may be time for the regulatory agencies to look at the need for advisories for low sodium in drinking water. Albeit, there is a practice to put back calcium and magnesium salts to counteract the decreased levels of minerals in the treated water and to prevent corrosion of the distribution system. To decrease

cardiovascular disease events, it may need to become a future practice to add sodium as well.

At the very least, municipalities and departments of public health engineering should make it a practice to inform members of the public who are at high risk of cardiovascular disease that, if they are drinking and cooking with very low sodium water, they may need to augment their salt intake.

REFERENCES

Grigioni, Francesco et al. "Contribution of Ischemic Mitral Regurgitation to Congestive Heart Failure after Myocardial Infarction." Journal of theAmerican College of Cardiology. Volume 45, Number 2, January 2005.

Hubert, H. B. et al. "Obesity as an Independent Risk Factor for Cardiovascular Disease: a 26-year Follow-up of Participants in the Framingham Heart Study." Circulation. Volume 67, Number 5, May 1983.

Kumanyika, S.K. et al. "Sodium Reduction for Hypertension Prevention in Overweight Adults: Further Results from the Trials of Hypertension Prevention Phase II." Journal of Human Hypertension. Volume 19, Number 1, January 2005.

O'Donnell, Martin J. et al. "Urinary Sodium and Potassium Excretion and Risk of Cardiovascular Events." Journal of theAmerican Medical Association. Volume 306, Number 20, November 2011 .

Rashid, Shirya and Gordon A. Francis. "Statins and Primary Prevention: Is all the Evidence In?" Canadian Journal of Cardiology. Volume 24, Number 4, April 2008.

Sacks, Frank M. et al. "Effects on Blood Pressure of Reduced Dietary Sodium and the Dietary Approaches to Stop Hypertension (DASH) Diet. " DASH Sodium Collaborative Research Group. New England

www.peo.on.ca

Journal of Medicine. Volume 344, Number 1, January 2001.

Shields, Margot, Margaret D. Carroll, and Cynthia l. Ogden. "Adult Obesity Prevalence in Canada and the

United States." NCHSData Brief No. 56, Hyattsville, MD: National Center for Health Statistics. Advances in Nutrition. Volume 2, Number 4, July 2011 .

Strazzullo, Pasquale et al. "Salt Intake, Stroke, and Cardiovascular Disease." British Medical Journal. Volume 339, November, 2009.

Подготовил к публикации Сергей Каменский 22 авг. 2012