Monday, October 17, 2011


These are the days when every food ingredient that goes into a food product is extensively debated regarding its safety or usefulness. Even salt, consumed for centuries by humans is not spared! Of course no one has quarrel regarding consumption of salt "moderately" but the million dollar question is what can be construed as moderate? Opinions differ from expert to expert and country to country but WHO with a global canvas recommends levels of daily consumption which it considers safe. Here again many do not agree with its recommendation. Here is a very exhaustive commentary on this vexed issue, though after going through it, it will still be difficult to come to any conclusion!

Salt has been taxed, monopolized, treasured and fought over for thousands of years. Today's scientists are waging a modern-day salt war. In the 1970s, American researchers experimenting on rats found very high doses of salt raised blood pressure. Some of the most-cited evidence on salt and health came in a 1988 international study called InterSalt, which surveyed more than 10,000 men and women in scores of populations across the world. The study included four remote tribes in Brazil, Kenya and New Guinea whose people had the lowest salt intake and were also found to have the lowest blood pressure and very few, if any, cases of hypertension. Although these findings were disputed by parties including the Salt Institute, it wasn't long before a scientific consensus emerged that too much salt is bad for you. A 2005 study in the PubMed journal found almost 1 billion people around the world have high blood pressure, which makes the heart work too hard, hardens the walls of the arteries and can cause other problems such as heart failure, kidney disease, and blindness. Cardiovascular diseases are the leading cause of death globally, claiming 17.1 million lives a year. A substantial number of these deaths are put down to smoking, which raises the risk of hypertension, strokes and heart attacks. In the past few years, governments have begun to act. Under its health-promoting mayor Michael Bloomberg, New York City pledged in 2010 to coordinate a U.S.-wide effort to cut salt in restaurant and packaged foods by 25 percent. National sodium reduction strategies have been adopted across Europe and inAustralia, China and India. Scores of health authorities around the world advise that we should aim to reduce our salt intake from the roughly 9 to 12 grams a day we eat now down to around 6 grams, about a teaspoonful a day. Since around 75 percent of all the salt we consume comes from packaged and processed
food, rather than from what we sprinkle on top of it, food manufacturers have been in the firing line. Under pressure from health authorities and the WHO, the food industry, which stands accused of using salt to boost the flavor, shelf-life and profit of what would otherwise be bland ingredients, has taken action. Big brands like Heinz, Kellogg's, Nestle, Pepsico, General Mills and others have been steadily reducing sodium levels in their foods. According to Susan Jebb, a nutrition adviser to the UK government, Britain is leading the way, forcing foodmakers to make some "impressive" reductions including a 30 percent reduction in salt in bread, about a 50 percent cut in branded breakfast cereals and around 25 percent in pasta sauces. Among the health-conscious at least, a salt-shaker on the dining table is becoming almost as frowned on as an ashtray.

But the findings that policy-makers have accepted as settled are not as clear-cut among scientists. A study in July by the much-respected Cochrane Library, which conducts meta-analyses of scientific data by grouping together the best studies on a subject and pooling the results,found no evidence that reducing salt intake cuts the risk of developing heart disease or dying before your time. In that study Rod Taylor, a professor of health services research at Exeter University, analyzed seven randomized controlled trials covering more than 6,500 people and found that although cutting down did appear to lead to slight reductions in blood pressure this did not translate into lower risk of heart disease or premature death. In one group of people, those with pre-existing heart conditions, reducing salt was actually associated with an increase in the likelihood of premature death. Taylor said he did not receive payment from, or have links to, the salt industry. His study was funded by a grant from the UK government's National Institute for Health Research. Taylor's study came hot on the heels of another, by Belgian scientists, which was published in the Journal of the American Medical Association (JAMA). That found people who ate lots of salt were no more likely to get high blood pressure, and were statistically less likely to die of heart disease, than those with low salt intake.

Against the above background, what should be the attitude of the consumer? Is reducing salt is really beneficial? Will the present level of salt consumption lead to premature death? If reduced salt intake can lower blood pressure (BP), especially in high BP consumers, why not adopt such a diet regime? What about the salt "balancing" system human body has which is supposed to excrete excess salt? Can there be a universal salt intake standard when it is known that those living in hot, humid, tropical climates excrete lot of salt through perspiration? Probably normal and healthy consumers must take their own decision regarding what is best for them till a universal consensus emerges on this issue while high BP patients may reduce salt intake to get the supposed benefit of low salt ingestion.



Morton Satin said...

Dr. Potty

I very much enjoyed your review of the salt-health issue. I am currently the Vice-President of the Salt Institute. I left a quite retirement to get involved in this debate because of the amount of myth-information that was out in the public. I should say that for 16 years I was Chief of the Food and Agro-Industries Service and Director of the Agricultural Division at FAO in Rome. I believe a colleague of yours (Dr. Parpia) served in my Division before I joined FAO.

Down to salt. No one disputes that lowering blood pressure can be beneficial for some individuals. The debate centers on the strategy one chooses to lower blood pressure. If one is able to get a better diet with more fresh salads, green vegetables and fruit or if one does more regular physical exercise, then blood pressure can be reduced without any negative consequences. That is good.

However, dietary salt reduction as a primary lifestyle strategy to reduce blood pressure does present negative consequences. Consumption of anything less than 120 mmols of sodium per day stimulates the renin-angiotensin-aldosterone axis - the body's natural response to insufficient salt consumption. The RAA system signals the kidneys to recoup sodium from the waste stream and return it to the circulatory system. Unfortunately, elevated RAA results in a cascade of negative consequences including insulin resistance, epithelial impairment, metabolic syndrome and cognitive impairment (all published in peer-reviewed journals).

Fortunately, the wisdom of the body is active throughout the world and there is hardly a country where the per capita consumption of salt is below 7.2 g or 120 mmols sodium. The exception are the primitive rainforest types or those that simply do not have access to salt. These people have chronic high levels of RAA and a life expectancy of 42 - 48 years. By the way, the reason for no age-related rise in the BP of the Yanomamo and Xingu tribes mentioned in Intersalt has more to do with their genetics than with their salt consumption - they lack the D/D genotype. I repeatedly provided the references to the Editor of the Dietary Reference Intakes, but he has refused to revise his statements.

Thus salt reduction is the classic Trojan Horse of hypertension policy - it looks attractive on the surface because some individuals may experience a drop of 2 - 6 mm Hg in systolic pressure, but hidden underneath are great risks. Everyone forced to go below 120 mmols sodium will experience elevated RAA - a known risk factor for cardiovascular and diabetes outcomes. Trading off one risk factor for another is not a particularly wise bargain.

My biggest disappointment lies with all the public health agencies who have elected to continually ignore all the evidence that cautions against population-wide salt reduction in order to pursue an agenda driven far more by ideology than science. They seem to believe that if you ignore evidence long enough, it may go away. They also seem to forget that our physiology answers to a far higher authority than the WHO or the IOM. Fortunately, up until now, the wisdom of the body has taken precedence over imprudent policies, and people consume enough salt to prevent elevated RAS. However, if salt will ever be regulated, then we should monitor the health of our citizens very, very carefully, since the preponderance of available science indicates such a strategy holds great risks for us all.

Dr. V.H . Potty said...

Well said Dr Satin. I entirely agree with you. It may be premature to orchestrate any moderation policy for normal healthy people.V H Potty