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Sodium reduction, cardiovascular outcome and smoking
- Trevor LP Watts (20 April 2007)
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Ethics and Disease Prevention
- Bob Parke (23 April 2007)
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Public health implications of reducing sodium
- Kenneth A Hoekstra (24 April 2007)
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Re: Sodium reduction, cardiovascular outcome and smoking
- Nancy R. Cook (24 April 2007)
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The variability factors in the study of dietary sodium restriction on cardiovascular outcomes
- Munir E Nassar (28 April 2007)
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Salt sensitivity?
- Joan McClusky (28 April 2007)
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“Sodium Reduction” seems an enticing label, but what is the full recipe?
- Paul P Glasziou (29 April 2007)
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Health - the product of environment, culture and institutions
- M Justin S Zaman, WC1E 6BT (30 April 2007)
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BHF puts salt firmly on heart menu
- Qaim Zaidi (1 May 2007)
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Lowering Salt: Time for Action
- Michael Jacobson (1 May 2007)
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Overall benefit is what matters: disease specific outcomes are only explanatory variables
- C Kevin Connolly (2 May 2007)
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Hypertension and Moderate Restriction of Salt intake in Food is Beneficial as Preventive measure for Normotensives aswell as Hypertensives in West Bengal State of India
- Professor Pranab Kumar Bhattacharya, Bose Debdas Dept of Pathology IPGMER, Bhattacharya Rupak MSC(JU) Purbapalli, Sodepur KOlkata-110 Islam Shidul MD, Dipcard ,DM(cal) Dept. of Cardiology, ICVS IPGMER Kolkata-20, India Bhattacharya Palash MD(PGT) Pathology, IPGMER KOlkata-20, India (3 May 2007)
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Salt restriction may jeopardize the elimination of Iodine Deficiency Disorder
- Kishan Kumar Jani, Neeta Kumar, Mrityuanjay Kumar, Neeru Gupta (3 May 2007)
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Salt intake should be minimum but this minimum may differ in hot and cold countries
- Neeru Gupta, Kishan Kumar Jani (3 May 2007)
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Salt intake, temperature and iodization
- Francesco P Cappuccio (4 May 2007)
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Fluid replacement without electrolytes in hot weather can cause hyponatremia
- Kishan Kumar Jani, Neeru Gupta (5 May 2007)
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I met a Milly Mole
- Alexander Jablanczy (25 May 2007)
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Soluble Sea Salt is better
- GEORGE Y CALDWELL, Singapore 259858 (28 May 2007)
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Trevor LP Watts, senior lecturer and consultant in periodontology KCL Dental Institute at Guy's Hospital
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I am seriously concerned about the dietary sodium intervention study results and conclusions reported online (1) in BMJ, and making the front page of The Times on 20th April 2007. What concerns me most is that a simple search shows there is absolutely no reference to smoking data. Studies in my field show clearly that smoking can have such a pervasive effect on diseases that the only way to exclude its influence completely is by studying never-smokers (2). Furthermore, a range of other behavioural factors may affect cardiovascular health, as demonstrated in earlier Trials of Hypertension Reduction (TOHP) results. In the first TOHP study quoted, there is also little reference to smoking. In the second study, we were given the baseline data that approximately 9% were current smokers, but there was also a considerable cohort of around 36% who were past smokers. Without detailed attention to tobacco dose in the participants, the conclusions on mortality and sodium reduction are not justified. Furthermore, intervention groups in such studies may develop bias because of behavioural changes other than those in the intervention. How many other significant lifestyle changes were made by the participants in each group? It would be interesting to see the authors produce a further analysis limited to the 55% of their subjects who were never-smokers, assuming that the original proportions of groups are maintained in their commendable 77% response. Since the adjusted odds ratios each have a confidence interval close to unity, the case for dietary sodium reduction will be either definitely strengthened or weakened by the result. 1. BMJ, doi:10.1136/bmj.39147.604896.55 2. Hujoel PP, Drangsholt M, Spiekerman C, DeRouen TA (2002) Periodontitis-systemic disease associations in the presence of smoking – causal or coincidental? Periodontology 2000; 30: 50-61. Competing interests: None declared |
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Bob Parke, Bioethicist Humber River Regional Hospital M3N 1N1
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The reduction of blood pressure and hypertension which this research reports on raises very important population health issues from a bioethics perspective. When we think of bioethics we tend to think of it from a clinical perspective usually from an end of life care perspective such as in the cases of withdrawal of life support. However, we need to view health promotion from ethical lense as we could save a lot of people the harm of cardiac illness, strokes as well as the need for dialysis and kidney transplant. Resource allocation ethics is another area of bioethics which has come to the foreground to help guide decision makers in making fair and just allocation of limited resources. Dealing with resource allocation challenges is very stressful as decision makers carry the burden of potentially denying a needed service. The relationship of this article and others like it to resource allocation ethics is that by giving further evidence that by lowering sodium intake results in a reduction of cardiovascular disease. Using this information to advocate for changes can make diminish some of the resource allocation challenges presently faced in acute care. The ethical principle of justice requires public health professionals to look at how those in the lower socio-economic strata can have access to affordable low sodium diets. At present prepared low sodium foods can be more expensive than popularly available foods. This is of concern for those dependent on food banks as the common foods they receive contain high levels of sodium and sugars. In conclusion this research has ethical and social benefit as it provides further evidence to advocate for changes in sodium content for the collective benefit of our populations. Competing interests: None declared |
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Kenneth A Hoekstra, Assistant Professor Western States Chiropractic College, Portland OR 97230
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In the article by Cook et al (1), the authors discuss the impact of reducing sodium consumption on cardiovascular conditions other than blood pressure. Indeed, a 25% lower risk of a cardiovascular event was reported (1). This reduction in cardiovascular events is of great importance on many levels of public health: consider the economic burden for the treatment of high blood pressure (2); the harm reduction strategy of tobacco (3); or the ethical consequences of non-intervention for cholesterol reduction (4). Reducing sodium levels should have the same public pressure as these and other disease conditions. 1. Cook NR, Cutler JA, Obarzanek E, Buring JE, Rexrode KM, Kumanyika SK, Appel LJ, and Whelton PK. Long term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention (TOHP. BMJ 2007; 0: bmj.39147 2. Degli Esposti L, Valpiani G. Pharmacoeconomic burden of undertreating hypertension. Pharmacoeconomics 2004;22(14): 907-28. 3. Savitz DA, Meyer RE, Tanzer JM, Mirvish SS, Lewin F. Public health implications of smokeless tobacco use as a harm reduction strategy. Am J Public Health. 2006 Nov;96 (11):1934-9 4. Pearson TA. Population benefits of cholesterol reduction: epidemiology, economics, and ethics. Am J Cardiol. 2000 Jun 22;85(12A):20E -3E. Competing interests: None declared |
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Nancy R. Cook, Associate professor Brigham & Women's Hospital, Boston, MA 02215
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Previous publications have indicated that approximately 11% of participants in TOHP I [1] and 9% of participants in TOHP II [2] were current smokers, with approximately 57% and 54% never smokers, respectively. Thus the majority of TOHP participants were never smokers. More importantly, the TOHP studies were randomized trials, so that the intervention groups were balanced with respect to smoking and other cardiovascular risk factors; thus smoking is unlikely to be a confounder in these data. We have not looked at subgroups by smoking because of the reduced power within subgroups, and the lack of a pre-specified hypothesis for an interaction by smoking. As Dr. Watts suggests, it is not entirely possible to rule out the impact of other behavioral changes besides sodium on these findings. However, the intervention specifically targeted sodium, and did not advise participants to change other components of their diet or other lifestyle behaviors. It's possible that some of these changes may have occurred, but likely not nearly to the same extent as the reduction in sodium itself, the focus of the intervention. 1. Kumanyika SK, et al, for the Trials of Hypertension Collaborative Research Group. Feasibility and efficacy of sodium reduction in the trials of hypertension prevention, Phase I. Hypertension. 1993;22:502-512. 2. Appel LJ, Hebert PR, Cohen JD, et al. Baseline characteristics of participants in phase II of the Trials of Hypertension Prevention (TOHP II). Trials of Hypertension Prevention (TOHP) Collaborative Research Group. Ann Epidemiol. 1995;5:149-155. Competing interests: None declared |
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Munir E Nassar, Physician, cardiologist, retired Pittsford, NY 14534
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This is a well thought of and well analyzed study by Dr. Nancy Cook and Co-workers(BMJ 2007,334:885). However, several important variables were not alluded to, such as the genetic factors for cardiovascular dieases in the 744 persons in TOHP1 and in the 2382 persons in the TOHP2, with special reference to the gender differences in the age groups studied. Similarly the problem of compliance with a diet consisting of 3.6 gms sodium/24 hrs. Also how many times did those persons in the study dine out per week. Also food labels for sodium content are not that accurate. From a physiological point of view, the human kidneys conserve urinary sodium excretion per 24 hrs, when the renal blood flow has less sodium concentration, in cases of low sodium diet to maintain sodium balance in the body. Then there is lack of accurate follow up after the study terminated in 18 months from its onset. Finally, how significant is a reduction of only 1.7-0.8 in diastolic pressure even though the P value showed significance ? When it is common knowledge that blood pressure is a variable phenomenon and changes with or is affected by activity. In conclusion, it is difficult to say that the reported outcomes of reduction in blood pressure following dietary dodium restriction, and subsequent cardiovascular mortality and morbidity in this study is surreptitious or relatively accurate, with the knowledge that experience based evidence supports low sodium diet as beneficial in hypertension and cardiovascular diseases. Competing interests: None declared |
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Joan McClusky, medical writer New York, NY 10003
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This is an interesting article, but it fails to take into consideration the possible role played by salt sensitivity. Salt restriction has little effect on blood pressure in the population as a whole, but can significantly affect blood pressure of both hypertensive and normotensive people who are salt sensitive. Salt sensitivity is also associated with blood pressure, cardiovascular events, and all-cause mortality among both hypertensive and normotensive persons. (Franco, J Am Coll Nutr June 2006). This study fails to show what percentage of the study populations-- both hypertensive and normotensive--showed a decline in blood pressure with salt restriction and how this was related to subsequent cardiac events. Instead, it prompts calls of "sodium reduction for all"--and promises reduced cardiovascular disease--when such effects--and such restrictions-- may only be applicable to a small subset of the population, who can be readily identified with a salt-restriction trial. Competing interests: None declared |
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Paul P Glasziou, General Practitioner and Professor of Evidence-Based Medicine University of Oxford, OX3 8AY
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Reading this study on a Friday evening, I found myself wondering if it could help my hypertensive patients on Monday morning? Unfortunately not: the prescription for "sodium reduction" in this paper is not usable by my fellow general practitioners. The paper gives little more than the name of the dish, not the details of the recipe: "Individual and weekly group counseling sessions were offered initially, with less intensive counseling and support thereafter, specific to sodium reduction." How do I translate that vague description for my patients? Those rare clinicians diligent enough to track down reference 23 would find a fuller, but still insufficient, description there[1]. A brief summary of what I understood is: (i) an individual session followed by 10 weekly group 90 minute sessions with a nutritionist, followed by a transitional stage of some additional sessions (ii) Topics in the weekly sessions included Getting Started, sodium basics, the morning meal, midday sources of sodium, the main meal, planning ahead, creative cooking, eating out, food cues, and social support, (iii) the sessions included sampling of foods, discussion of articles on sodium reduction, and problem-solving, (iv) patients kept diaries at least 6 days per week, and urine sodiums were measured. Helpful, though daunting, it still misses so many details that I (or a dietician) would need, such as the specific handouts and articles used with the patients, the diaries, the sodium "scorekeepers" etc, that I don't know how to replicate this. But there is sufficient detail to make it clear that this form of “salt reduction” is probably impractical in primary care. Though the editorial suggested "You might try talking salt in your next consultation" that does not seem viable based on either this paper or the previous publications. That is a pity. As a fan of non-drug interventions, I'd like to be able to share them with my patients. But so often the description of what clinicians and patients need to do is so woefully inadequate, that it is unusable. If authors are interested in uptake, they need to make interventions practiceal, and provide us with sufficient details and materials. In the internet world, space limitations are no longer an excuse. 1. Hebert PR, Bolt RJ, Borhani NO, Cook NR, Cohen JD, Cutler JA, et al. Design of a multicenter trial to evaluate long-term life-style intervention in adults with high-normal blood pressure levels. Trials of hypertension prevention (phase II). Trials of hypertension prevention (TOHP) collaborative research group. Ann Epidemiol 1995;5:130-9. Competing interests: None declared |
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M Justin S Zaman, Clinical Research Fellow in Epidemiology and Specialist Registrar in Cardiology University College London, WC1E 6BT
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I note Paul P Glasziou's desparate plea for a 'description of what clinicians and patients need to do'. However, as Professor Cappuccio states in his editorial, 'In Westernised countries, people derive salt mostly from bread and processed food and only a small proportion comes from discretionary use'. Barry Bloom [1] has argued that 'that one of the myths of the modern world is that health is determined largely by individual choice and is therefore a matter of individual responsibility when most behaviour is socially patterned and reinforced in groups'. The wider environment impacts on the health of an individual in addition to individual behavioural and biological influences. It is not simply about adding salt at the dinner table, but understanding the considerable role that players such as the food industry play in public health. Health protection through national fiscal and legislative policies should have a higher priority than health promotion interventions applied to general, primary care and workforce populations. Chronic disease epidemiology is increasingly being replaced by ‘eco-epidemiology’ [2] where the focus is more on prevention of disease through governance, fiscal and environmental policies rather than targeting individual lifestyle modification. The ‘high-risk’ strategy, the traditional medical approach to prevention, identifies individuals at high-risk of subsequent cardiovascular disease events who are then offered behavioural or pharmacological interventions.In contrast, the ‘population strategy’ seeks to control the determinants of incidence in the population as a whole. [3] Geoffrey Rose argued that the ‘high-risk’ strategy was the traditional medical approach to prevention and though this approach allowed the doctor to identify appropriate interventions for their patient in clinic, it was palliative and temporary in that it did not seek to alter the underlying causes of the disease but to identify individuals who were particularly susceptible to those causes. As Schwartz and Carpenter have pointed out, focusing on individual level determinants of health while ignoring more important macro-level determinants is akin to obtaining the right answer to the wrong question. [4] Public health policies need to take into account the role that agriculture, trade, education, the physical environment, town planning and transport have on cardiovascular disease aetiology. Political action that induces changes in urban planning, education and policies regarding the agriculture, food, and tobacco industries are needed. [5] Vested interests that would conflict with the prevention of cardiovascular disease, such as those of the food industry, must be considered. Until then, 'interventions' such as health promotion 'salt reduction' campaigns and pleading to patients to throw away the salt cellar in afternoon surgery will make a barely discernable difference to population salt levels. 1. http://www.hsph.harvard.edu/faculty/barry-bloom/ 2. Susser, M. & Susser, E. 1996, "Choosing a future for epidemiology: II. From black box to Chinese boxes and eco-epidemiology", Am.J.Public Health, vol. 86, no. 5, pp. 674-677. 3. Rose, G. 1985, "Sick Individuals and Sick Populations", International Journal of Epidemiology, vol. 14, no. 1, pp. 32-38. 4. Schwartz, S. & Carpenter, K. M. 1999, "The right answer for the wrong question: consequences of type III error for public health research", American Journal of Public Health, vol. 89, no. 8, pp. 1175- 1180. 5. Pekka, P., Pirjo, P., & Ulla, U. 2002, "Influencing public nutrition for non-communicable disease prevention: from community intervention to national programme--experiences from Finland", Public Health Nutr., vol. 5, no. 1A, pp. 245-251 Competing interests: None declared |
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Qaim Zaidi, Ethnic Strategy Co-ordinator 14 Fitzhardinge St London W1H 6DH
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EDITOR- Cook’s article brought welcome attention to the impact of salt on coronary heart disease. While fat and sugar are frequently mentioned in dietary advice, salt has had a lower profile as a cause of health problems, including heart disease. Certain ethnic groups such as the African Caribbean and South Asian tende to have higher rates of cardiovascular disease and heart disease. A reduction in salt intake plays an important role in tackling this disparity. The British Heart Foundation (BHF) takes the salt issue very seriously and is working to tackle this problem amongst these groups in particular. In 2005 we ran a very high profile salt awareness campaign for the Muslim community during the month of Ramadan This was an ideal opportunity to reach thousands of Muslims.During the BHF and Food Standards Agency (FSA),campaign we trained over two hundred Imams so that they could provide basic advice on following a healthy lifestyle. Particular emphasis was placed on salt reduction,as during the month of Ramadan the eating pattern for Muslims can change to include many unhealthy snacks. Our ongoing work since has included social marketing campaigns, extensive use of ethnic media, television, newspapers, and outreach workers to raise awareness of the importance of salt, and how to read confusing food labels. Unfortunately, many ethnic food products still don’t have to use appropriate labels, making it difficult for many to know the true salt content of the food that they buy. We are now embarking on another high profile BHF campaign, supported by the Food Standards Agency, where we will be targeting social cooking at gurdwaras and mandirs (places of worship for Sikhs and Hindus) where food is prepared for thousands of people. By encouraging salt and fat reduction in these places we hope to have a real impact. We will also be running workshops and seminars on healthy eating. We have been working with places of worship for many years and have observed that messages given there by the religious leaders are perceived by congregations as being more credible than those received from other sources. Places of worship allow health messages to reach to individuals, whole families and their social networks. We are committed to reducing inequalities in heart health and are working to demonstrate that innovative and cost effective BHF projects such as these will help reduce the burden of cardiovascular disease in South Asian communities. Qaim Zaidi, ethnic strategy co-ordinator
Competing interests: None declared |
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Michael Jacobson, executive director, Center for Science in the Public Interest Washington, DC 20009
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The intervention study by Cook et al. that linked lower sodium consumption to lower risk of cardiovascular disease should (but probably won’t) silence the Salt Institute and other naysayers who have been muddying the waters for years. (1,2) As public health advocates have urged for decades, people in many countries should consume less sodium. The British Food Standards Agency deserves plaudits for its campaign to persuade manufacturers and restaurants to use less salt. A preliminary analysis by Consensus Action on Salt and Health has found strong signs of progress. (3) Whether such voluntary reductions will endure remains to be seen. The picture is not so bright in the United States, where the Food and Drug Administration (FDA) has resisted all efforts to mandate sodium reductions. Indeed, the FDA has resisted several formal petitions and two lawsuits by the Center for Science in the Public Interest to regulate salt. The FDA still considers salt to be “generally recognized as safe,” which means that companies can use as much as they wish. Despite some companies’ insistence that they use only as much salt as necessary, different brands of the same product show large variations in sodium. For instance, one major brand of diced tomatoes contains twice as much sodium as another brand. (4) Such examples demonstrate that many companies could use dramatically less salt. And it also indicates that the FDA (and agencies in other nations) could set limits on the sodium content of different categories of food. Cutting sodium consumption in half in the United States would save on the order of 150,000 lives per year, which translates into economic benefits in excess of $1 trillion over 20 years. (5,6) The time surely has come for vigorous voluntary action by industry and strong health measures by governments. 1. Cook NR, Cutler JA, Obarzanek E, et al. BMJ 2007;334:885-93. 2. Salt Institute. 15th salt reduction health outcomes study muddies water. http://www.saltinstitute.org/rss/health-other/index.html. (accessed May 1, 2007) 3. Consensus Action on Salt and Health. Media release. www.actiononsalt.org.uk/media/press_releases/awareness%20events/salt_awareness_week_2007.doc. (accessed May 1, 2007) 4. Center for Science in the Public Interest. Salt Assault: brand-name comparisons of processed foods. 2005. http://www.cspinet.org/new/pdf/salt_report_update.pdf. (accessed May 1, 2007) 5. Havas S, Roccella EJ, Lenfant C. Reducing the public health burden from elevated blood pressure levels in the United States by lowering intake of dietary sodium. Am J Public Health. 2004;94:19-22. 6. Center for Science in the Public Interest. Salt: the forgotten killer. 2005. http://cspinet.org/new/pdf/salt_report_with_cover.pdf. (accessed May 1, 2007) Competing interests: None declared |
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C Kevin Connolly, Retired Physician Richmond, N Yorkshire DL11 7TP
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We all want to live as long and healthy lives as possible. It matters little to the individual what ultimately kills him or impairs his health, be it cardiovascular disease or something else, so long as the event is delayed as long as possible. Healthy survival is therefore always the proper primary outcome measure in public health studies, and disease specific outcomes must be seen as explanatory and not outcome variables. The longer the period of the study, the healthier the population or the lower risk of the specific disease studied, the more strictly this principle should be adhered to. It should have been applied in this study, which is a good example. However no significant reduction in overall mortality was demonstrated and non cardiovascular morbidity not discussed, so there is no justification on this evidence to advocate the actions discussed. If it were confirmed statistically after a longer period of observation the apparent discrepancy between cardiovascular and overall mortality would require explanation. Might relative salt deprivation at times of physical stress be relevant? Availability of funds for disease specific research, and so its bulk, depends more on its attractiveness to the charity giving public and political demand, which often coincide, than to scientific priority. This leads to a covert conflict of interest which is no less potentially compromising than many more obvious ones. This should be recognized by those who funding comes relatively easily. The consequences can be avoided in primary prevention studies by always presenting and publicizing the results primarily in terms of what really matters, general health and overall survival, pointing than disease specific benefits merely help to explain the changes involved. Competing interests: Retired respiratory physician;one of the specialties traditionally less able to raise money for research |
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Professor Pranab Kumar Bhattacharya, Professor of Pathology, Incharge of Cytogenetics, Blood Bank,VCTC, Ex-Incharge Malaria Clinic Institute of Post Graduate Medical Education & Research -244a AJC Bose Road, Kolkata-700020, India, Bose Debdas Dept of Pathology IPGMER, Bhattacharya Rupak MSC(JU) Purbapalli, Sodepur KOlkata-110 Islam Shidul MD, Dipcard ,DM(cal) Dept. of Cardiology, ICVS IPGMER Kolkata-20, India Bhattacharya Palash MD(PGT) Pathology, IPGMER KOlkata-20, India
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Hypertension is a silent killer. Diastolic Blood pressure persistently higher by 5.0mmHg is associated with 34% increase in stroke and 21% rise of coronary heart disease in Indian People. Prevalence of hypertension amongst the black people including Indian is greater at every age beyond adolescence and thus hypertension plays a strongest risk factor amongst population of West Bengal for the Acute Myocardial infraction and in Stroke. Other important factors are Cigarettes/ Bidi smoking and Diabetes Mellitus. After the age of 50, Isolated systolic hypertension ( SBP 160 and DBP 90-95 mmHg) more common pattern (75%) as a consequence of arterial stiffness, systolic level continues to rise with age, while diastolic level tends to remain plateau during the 6th decade of life. No Single cause is known for most cases of essential hypertension has been documented in West Bengal state/ Indian people. There are however multiple causes of development of hypertension and these are Genetic Predisposition(30-60%) causes related with angiotensinogen gene mutation, multiple environmental factors, fetal life under nutrition , stress, smoking, sympathetic over activity, obesity, endothelial dysfunction, NO, endothelin, alcohol, physical inactivity. Role of high salt intake in food in excess contributes to hypertension in Indian population & in West Bengal state. The epidemiologic evidence, that salt supports a close association
between hypertension and high ratio of Nacl (table salt) intake are
a) in multiple
population, the raise of BP with age is directly co-related with
increasing level of dietary salt intake.
However there is no conclusive experimental evidence that salt
intake causes hypertension in all people who are normo-tensive otherwise.
Almost all people in the state of West Bengal, India consume high sodium(
salt) diet (approx 10-12 gram/day) in cooking foods and a certain
percentage of them develops hypertension ,which suggest a variable degree
of blood pressure sensitivity to Na intake and this sodium sensitivity
may be result of defect of renal sodium excretion · A decrease in filtration surface by a congenital or acquired deficiency
in nephron number or in function · Both excess of sodium intake and renal retention of sodium would presumably work primarily on increasing fluid volume and cardiac output. A number of other factors may work primarily on the equation BP=COxPR. Most of these factors can cause both functional contractions & structural remodeling and hypertrophy The goal of therapy of Hypertension is to reduce the Blood Pressure diastolic level lower than 85 and systolic level below 130mmHg (j curve) to avoid the myocardial infractions & stroke. Amongst the non pharmacological treatment of Hypertension Stopping Smoking is Very important, Others are Weight Reductions, Taking Fish of Cold & sea Water( Omega-3-PUFA), Aerobic exercise helps to reduce the level of diastolic BP 4--5 mmHg. Evidence incriminating the typically high sodium chloride content of Diet of the persons in the developing , industrialized countries was presented as a cause of Hypertension. In hypertensive subjects modest restriction of dietary sodium intake down to level 70mmol/day can reduce blood pressure 4/3 mmHg. In an analysis by He and MacGregor of 28 well controlled intervention studies that lasted at lest 4 weeks in which daily intake (based on urinary Na excretion) was reduced by a median of 78mmol/ 24 hours, blood pressure fell an average of 5.0/2.7mmHg in 734 hypertensive subjects and 2/1mmHg of 220 normo-tensive subjects. More over Alderman et al reported a four fold increase of myocardial infraction over an average 3.8 years follow up among treated hypertensive whose initial 24 hours urinary sodium excretion was lowest quartile averaging 65mmol/day in male subjects(6). Moderate Salt restriction is worth while. Reduction of BP possible with universal reduction of sodium intake of 50mmol/day (<2gram/day) causes reduction of incidence of stroke 22% and reduction of CHD16%. But not all hypertensive persons respond well to moderate degree of sodium restriction. They are sensitive to Na. Blacks and elderly persons are found more responsive to moderate degree of sodium restriction. It is perhaps because of their lower rennin responsiveness. Nonetheless if Blood pressure does not fall with moderate degree of sodium restriction, patients may still be benefited. Multiple cardiovascular and normo vascular ill effects have been noted with high sodium intake. In a prospective follow up of 2400 finish men & women a 100mmol/day higher sodium excretion was found to be accompanied by 45% increase in hazard ratio of cardiovascular disease and 28% increase in all case mortality Sodium chloride (salt) restriction is thus useful for all purposes as a preventive measure in those Indian population who are even normo-tensive and more certainly as partial therapy in those who are hypertensive. The easiest way to accomplish moderate amount of Nacl salt restriction is to substitute natural foods for the processed food and fast food which are increasing in the Indian Market as well as in Market of West Bengal metropolis cities, because natural foods contain low sodium & high in Potassium whereas most processed and fast foods have had sodium added and potassium removed. The Government in states and in central level should mandate reduction of salt added to most processed and fast foods. Moderate to severe sodium restriction also have beneficial effect on hypertensive who are on ACE inhibitors or with Diuretic therapy as it will increase the efficacy of antihypertensive. Additional benefits of Na restriction on LVH, improve renal function sign& symptoms of asthma in men, reduce urinary ca++ wastage offering protection from kidney stones(7) But authors know if that restriction of Nacl9salt) to 110mmol/day even is very difficult for all class population. When strong and repeated attempts are made to restrict dietary sodium in 2-3 meals a day average consumption becomes 175-200mmol/day(12-15 gram/day) So additional guide line should be * Add no sodium chloride to food during cooking to make your food testy & salty **If salty test is at all required add 1/2 Nacl and1/2 Kcl in preparation or only Kcl *** Avoid all fast packet and processed foods References 1)Carvalho .J JM; Baruzzi RG, Howard PF et al “ Blood Pressure in four remote population in the Intersalt study “ Hypertension 1989:14: 238-246 2)Intersalt co-operative Research group, Intersalt: an International study of electrolyte excretion and Blood pressure, Result for 24 hours urinary sodium & potassium Excretion “ Br.Med. J 1988;297:319-28 3)Svetkey.LP; Timmons PZ, Emovon.O etal “ Association of hypertension with B2 & alfa2c-10 adrenergic receptor genotype “ Hypertension 1996:27:1210-15 4)Tao.Q_F, Holleberg.NK, PriceDA, Graves SW “ Sodium pump Iso form specificity for digitalis like factor isolated from human peritoneal dialysate “ Hypertension 1991:29:815-21 5)Sealey.JE, Blumenfeld.JD, Bell GM etal “ On the renal basis of essential hypertension nephron heterogeneity with discordant rennin secretion and sodium excretion causing a hypertensive vasoconstriction- volume relation “ Hypertension 1988:6:763-77 6)Alderman M.H, Madhavan.Scohen etal “ Low urinary sodium is associated with greater risk of myocardial infraction among treated hypertensive men” Hypertension 1995:25”1144-52 7)Norman. M. Kaplan “ Clinical Hypertension 7th edition by BI waverly Pvt. Ltd ,New Delhi, Indian Reprint 1998 ,ISBN –81-7431-040-1 in chapter “treatment of Hypertension non drug therapy Page 159-74 Authors= Professor Pranab Kumar Bhattacharya MD(cal), Ficpath(ind) Professor of Pathology, Institute of Post Graduate Medical Education & Research(IPGMER) 244A AJC Bose Road Kolkata-20 ,India 2) Dr. Debdas Bose MBBS, (NBU), MD(Post Graduate Trainee Pathology), IPGMER,Kolkata-20 3) Mr. Rupak Bhattacharya MSC(JU) Purbapalli PO-Sodepur, 24 Parganasd(North) West Bengal, Kolkata-110 4) Dr. Sahidul Islam MD(cal), Dip card(cal), DM (cal), RMO cum Clinical Tutor Dept.of Cardiology, Institute of of Post Graduate Medical Education & Research(IPGMER) 244A AJC Bose Road Kolkata-20 ,India 5) DR. Palash Bhattacharya MBBS(cal), MD(PGT)Dept of Pathology,Institute of Post Graduate Medical Education & Research(IPGMER) 244A AJC Bose Road Kolkata-20 ,India Competing interests: None declared |
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Kishan Kumar Jani, Chief Medical Officer Civil Hospital, Shahdra, Delhi-110032, Neeta Kumar, Mrityuanjay Kumar, Neeru Gupta
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Editor- Salt restriction is the most effective and efficient way of reducing the burden of hypertension and other cardiovascular diseases and unquestionably there is no equal to this strategy in prevention of this scourge. But, there is one theoretical hitch in its actual practice. Iodine deficiency is a problem for almost all countries of the world1. While traditionally associated with cretinism and goiter, iodine deficiency has broad effects on central nervous system development that can occur in the absence of either condition2. Any maternal iodine deficiency results in a range of intellectual, motor, and hearing deficits in offspring2. This loss in intellectual capacity limits educational achievement of populations and the economic progress of nations2. In 1990, most countries and international agencies pledged the virtual elimination of iodine deficiency by the year 20001. Salt iodization is the strategy used in prevention of Iodine Deficiency Disorders. Progress made since this historic World Summit for Children in 1990 has been outstanding. Approximately 70% of households in the world used iodized salt by 2000, compared with less than 20% in 1990. It is estimated that at least 85 million newborns out of 130 million annual births are protected from a loss in learning ability that would otherwise have occurred2. So, in such cases the iodine content of the salt may be stepped up so that the recommended dose of iodine is delivered. A safe daily intake of iodine is between 50 mcg and 1000 mcg3. But raising the iodine content of the salt may be a difficult task and may not be achieved so easily as it involves production, marketing etc. Other measures include iodized oil, iodized water, and iodine drops; all are occasionally useful, but the long range solution should generally be iodized salt1. Alternatively, these subjects may be supplied iodine in some other forms like, among available preparations, iodine containing syrups can be given in appropriate doses. References: 1. Dunn JT. Seven deadly sins in confronting endemic iodine deficiency, and how to avoid them. J Clin Endocrinol Metab. 1996 ;81(4):1332-5. 2. Maberly GF, Haxton DP, van der Haar F. Iodine deficiency: consequences and progress toward elimination. Food Nutr Bull. 2003 ;24(4 Suppl):S91-8. Food Nutr Bull. 2003;24(4 Suppl):S91-8. 3. Ranganathan S. Iodised salt is safe. Indian J Public Health. 1995 ;39(4):164-71. Competing interests: None declared |
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Neeru Gupta, Assistant Director General Indian Council of Medical Research, Ansari Nagar, New Delhi-110029., Kishan Kumar Jani
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Editor- Sir, it is apt that salt should be restricted in order to prevent hypertension as conveyed by trials of hypertension prevention in the research paper by Cook et al1. But the maximum permissible salt intake will differ in hot and cold countries. As also evidenced in history, wayback in 1930, Mahatma Gandhi took out Dandi March against salt taxation in India because salt is needed in this hot country due to excessive sweating. Even Cricket umpires from cold countries often take salt tablets while umpiring during hot dry weather in India. So such large, randomized, prospective trials should also be supported in these countries to work out the salt intake for the purpose. Reference: 1. Long term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention (TOHP) Nancy R Cook, Jeffrey A Cutler, Eva Obarzanek, Julie E Buring, Kathryn M Rexrode, Shiriki K Kumanyika, Lawrence J Appel, and Paul K Whelton BMJ 2007 334: 885. Competing interests: None declared |
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Francesco P Cappuccio, Chair of Cardiovascular Medicine & Epidemiology Warwick Medical School, Coventry CV2 2DX UK
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Dear Sir/Madam, a brief point of clarification to the issues raised by N Gupta and KK Jeni. The practice of providing salt supplements in hot climates is ill- advised. The sweat is a minor route of sodium excretion complementing renal excretion. As we eat less salt, our sweat will contain less salt in the same way as urine will, concept already known in the 18th century during the Slave Trade in West Africa. As we sweat more, as in hot and humid environments, the risk is dehydration, i.e. loss of fluids. Hence appropriate water intake should be adviced, not salt supplements. The potential conflict of population policies of salt reduction for the prevention of cardiovascular disease and of the use of iodised salt for the prevention of iodine deficiency was highlighted in a World Health Organization (WHO) Technical Workshop held in Paris at the end of 2006. The results and recommendations are summarised in a recent report published in April 2007. Following that meeting WHO has convened a second Technical Workshop held in Luxembourg in early 2007 with the view of harmonising the two policies. There is consensus that the two public health messages are contrasting and that a long term solution shold be sought. A number of alternatives should be considered: (i) increasing the concentration of iodine per part of salt so as to deliver the safe amount of iodine (and fluoride in some South American countries) with less total salt intake; (ii) actively monitoring not only iodine excretion as a measure of adherence to the policy of salt iodization but also urinary sodium excretion to provide a surveillance tool for the implementation of population salt reduction; (iii) exploring cheap and sustainable alternatives to the delivery of iodine to the most vulnerable groups, mainly children and women of child-bearing age, in the long term to avoid the use of salt. Competing interests: None declared |
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Kishan Kumar Jani, Chief Medical Officer Civil Hospital, Shahdra, Delhi-110032, Neeru Gupta
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Sir , First of all, we thank Dr. Francesco P Cappuccio, Chair of Cardiovascular Medicine & Epidemiology, Warwick Medical School for satisfying our queries and removing our apprehensions to a great extent. But, according to Harrison’s Principles of Internal Medicine,15th edition (page 274, Table 49-2), sweating is one cause of primary sodium loss (secondary water gain) and causes hypoosmolal hyponatremia. Sodium imbalance might result from excessive Na+ loss or from gross overhydration. In most work or exercise lasting < 3-4 hr, the major concern is that fluid be available to prevent heat-related illnesses, which can be prevented if fluid and electrolyte losses are balanced with intake1. In a study, comparing the thermal exercise with running, both sodium and chloride concentrations were much lower in the sweat induced by thermal exposure than that induced by the running exercise (p less than 0.01) 2. We do agree that more salt seems to be lost through exercise- induced sweating than by just sitting in a hot environment. But water or cold drinks are ingested to combat heat without salt replacement which may cause hypoosmolality. And, rural countries based on agriculture, have populations engaged in moderate to severe physical labour who work in hot weather. And there are studies to support that excessive sodium loss occurs when exercise is done in heat3. Besides there is a paper by E.R. Echiner that suggests that heat cramping is caused by salty sweating and also recommends, for heat cramping, the solution is saline4. So it is upto the senior colleagues to decide what the recommendations should be like…. References: 1. Armstrong LE, Epstein Y. Fluid-electrolyte balance during labor and exercise: concepts and misconceptions. Int J Sport Nutr. 1999 Mar;9(1):1- 12. 2. Fukumoto T, Tanaka T, Fujioka H, Yoshihara S, Ochi T, Kuroiwa A. Differences in composition of sweat induced by thermal exposure and by running exercise. Clin Cardiol. 1988 Oct;11(10):707-9. 3. Vrijens DM, Rehrer NJ. Sodium-free fluid ingestion decreases plasma sodium during exercise in the heat. J Appl Physiol. 1999 Jun;86(6):1847- 51 4. Eichner ER. The role of sodium in 'heat cramping'. Sports Med. 2007;37(4-5):368-70. Competing interests: None declared |
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Alexander Jablanczy, MD office
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I am sure the authors got a bit of a rise out of obfuscating with millimoles thereby assuring as Prof Glasziou hinted that no MD on this planet could possibly derive any benefit for his patients from this excellent study. As I hobble into my office I am constantly accosted by millimoles and significant differences. Sad to say but the only deep scientific and usable information on Na content of foods was not in some hallowed textbook of medicine cardiology or nephrology but a thirty year old Readers Digest and a twenty year old Time magazine both being a major miracle as I never read them. There I learned what I had imparted to my patients over the decades that a tomato or a cucumber has 5 to 10 mg Na and a pickle 200mg and a glass of tomato juice 150mg. Then about a year ago a miracle happened in Canada all foods have to be labelled with portion Na mass. So now I can tell my patients with congestive heart failure and hypertension and renal failure that they may eat anything with less than 100mg Na, and moderately up to 100 and 200 mg but are forbidden anything over 300 mg Na per portion size. Here it gets tricky. Even a salt free or no added salt can of tuna or salmon will have 50 to 80 mg Na per portion size which is a quarter can. Therefore a whole can will be 200 or 320 mg in toto. Back on the shelf. A bran muffin has 375 to 450 mg Na. Will never go near a Tim Hortons ever. KFCD piece of chicken 5000 mg same for Swiss Chalet. Never set foot in those places let alone eat what they have to offer. Porck hock 7500 mg Na back in the freezer. Curious none of these even Canadian food labels ever mention a millimole or Avogadros number only mg. They also fail to disclose the atomic number and electron volts and isotopes of sodium. Tsk tsk. Even with these labels it is almost impossible to Competing interests: None declared |
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GEORGE Y CALDWELL, General Practitioner 31 Balmoral Park, #18-33,, Singapore 259858
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Instead of Sir William Osler's dictum of "Don't take salt!" it would have been better had he said drink enough water so that you pass urine six times a day. Not coffee, tea or milk. That water would dissolve and excrete the excess salt. Sodium Chloride is very necessary and in Tropical countries should not be forbidden. Patients should always be advised to drink that extra quantity of water, more so in the hotter seasons, and this often alone will bring down their Diastolic Blood Pressure without resorting to Anti-hypertensive tablets. Sea Salt dissolves. The water also prevents kidney stones from forming in those hot seasons. Competing interests: None declared |
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