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Salt (Sodium) Intake, Stroke & Cardiovascular Disease
Table salt consists of the elements sodium and chloride, both of which are essential for life. There is a great deal of clinical research suggesting that more than 5 to 6 grams of salt intake per day (which is equal to 2 to 2.4 grams of sodium) is associated with a significant increase in the risk of developing high blood pressure which, in turn, is associated with a significantly increased risk of stroke and cardiovascular disease. Unfortunately, in most countries, the average daily salt intake for adults is considerably greater than 6 grams per day. Moreover, in many countries of the world, the average daily adult intake of salt is a whopping 12 grams per day, or almost 5 grams of sodium per day.
In the United States, the American Heart Association (AHA) currently recommends no more than 2.3 grams of sodium intake per day (equivalent to 5 grams, or about one teaspoon, of salt per day). At the same time, the AHA also states that the ideal daily intake of sodium should actually be about 1.5 grams per day but, in an acknowledgment regarding the high intake of salt-rich processed foods in the United States, the AHA considers the 2.3 gram per day dietary sodium target to be more “realistic” for Americans.
There is considerable public health research data suggesting that the reduction of average daily adult salt intake, to 6 grams per day, or less, would result in a significant lowering of blood pressure in both people with and without high blood pressure. Based upon these research findings, some public health experts have predicted that lowering the average daily salt intake below 6 grams per day could reduce the incidence of stroke by almost 25 percent, and the incidence of cardiovascular disease by almost 20 percent. Unfortunately, there have not been any large-scale prospective, randomized, placebo-controlled clinical research trials performed to validate these estimates. On the other hand, there have been multiple short-term prospective public health trials that have followed groups (cohorts) of patients in terms of their dietary intake of salt and the incidence of stroke and cardiovascular disease events. Now, a newly published research study, in the British Medical Journal, has performed a meta-analysis of 13 of these “prospective cohort” studies, encompassing a total of 177,025 patient volunteers, with average durations of patient follow-up ranging from 4 to 19 years. (Meta-analysis is a method of combining the data from multiple different clinical studies into a single “super-study,” in an effort to improve the validity of the resulting data, as well as the conclusions that are reached from such data.)
Among these more than 177,000 patient volunteers, there were 11,000 “vascular events” observed, including stroke and heart attacks (myocardial infarctions). When the incidence of these vascular events was analyzed, along with dietary salt intake, the patients with the highest daily salt intake were observed to experience a 23 percent greater risk of stroke, and a 17 percent greater risk of cardiovascular disease, when compared to the adults who consumed less salt on a daily basis.
The increasing consumption of salt-rich processed foods throughout both the developed and underdeveloped countries of the world has been pushing daily salt intake to ever higher levels, with many Western countries reporting average daily adult salt intake of nearly 10 grams per day. In other countries, and most notably in Asia and Eastern Europe, dietary practices that include a high concentration of heavily salted foods have pushed daily salt intake into the 10 to 12 gram per day range for the average adult.
The World Heart Federation estimates that there are 5.5 million annual deaths from stroke across the globe, and an additional 17.5 million annual deaths from cardiovascular disease. Based upon the increased incidence of stroke and cardiovascular disease predicted by this meta-analysis study, even a rather modest decrease in the average adult daily salt intake, to the World Health Organization’s target of 5 grams per day, should result in 1.25 million fewer deaths per year from stroke and nearly 3 million fewer annual deaths from cardiovascular disease around the world. Needless to say, this is a tremendous potential public health dividend from a rather simple alteration in our dietary habits. (On the surface, reducing our daily salt intake would appear to be a rather simple goal. However, the more complicated reality is that to achieve even the World Health Organization’s rather liberal target of 5 grams of salt per day, our entire food chain would have to be comprehensively reexamined and overhauled.)
The world’s increasing consumption of highly-processed foods, which often contain high levels of salt as a preservative, are largely responsible for the high levels of salt intake in the developed world (in addition to a preference for salt-cured foods in much of Asia and Eastern Europe). In the United States, the sodium content of most processed foods is readily available on food packages. Unfortunately, most restaurants in the United States have not been as forthcoming about the sodium content of the food on their menus (as well as other important nutritional information), and so it continues to be very difficult to determine the actual salt content of much of what we eat here in the United States and, indeed, throughout much of the world.
Note: Weekly Health Update is currently undergoing an extensive upgrade to better serve its tens of thousands of health-conscious readers around the world. Beginning in January 2010, newly archived columns will be available by selecting the “Archives” tab on the right side of your screen (all archived columns prior to January 2010 will continue to be available by selecting the “Archives 2007-2009” tab at the top of the screen.)
Disclaimer: As always, my advice to readers is to seek the advice of your physician before making any significant changes in medications, diet, or level of physical activity
Dr. Wascher is an oncologic surgeon, a professor of surgery, a cancer researcher, an oncology consultant, and a widely published author