MILAN, Italy — Are the current recommendations to lower sodium intakes to 1500 mg/day an unjustified target that just makes everybody's life miserable, or are the thresholds a valid attempt to alter food culture and provide future generations with a low-sodium environment that reduces the risk of hypertension and cardiovascular disease?
These were the two positions taken today during a debate here at the European Society of Hypertension 2013 Scientific Sessions by Dr Salim Yusuf (McMaster University, Hamilton, ON) and Dr Pasquale Strazzulo (Federico II University of Naples, Italy).
Arguing that the importance of salt in hypertension and cardiovascular events has been overestimated, Yusuf said there is "absolutely no rationale for the guidelines" and that the targets were simply "numbers pulled out of a hat." Yusuf added that the targets would require changing the lifestyle of billions of individuals worldwide and doing so would be based on weak evidence.
"I would say let's not make the whole world miserable," said Yusuf. "Let us enjoy a moderate amount of salt in our food and have fun."
Dissenting Opinions Even Among Professional Societies
The American Heart Association (AHA) recommends that Americans consume no more than 1500 mg of sodium per day. The 2010 Dietary Guidelines for Americans recommends a daily sodium intake of 2300 mg for the general population and 1500 mg for individuals 51 years of age and older, African Americans, or individuals with hypertension, diabetes, or chronic kidney disease.
However, the AHA and federal recommendations were challenged recently by the US Institute of Medicine (IOM). In a new report, the IOM said there is ample evidence supporting a positive relationship between higher levels of sodium intake and the risk of cardiovascular disease, which is based on past research showing the effect of high levels of sodium consumption on blood pressure, but there are no advantages to lowering intake among individuals who consume a moderate amount of sodium.
The IOM went so far as to state that the evidence is not strong enough to recommend lowering daily sodium intake to the 1500- to 2300-mg/day range.
Just this week, the ESH and European Society of Cardiology published new guidelines for the management of hypertension. In them, they recommend individuals consume no more than 5 to 6 g of salt per day. This translates into approximately 2000 to 2300 mg of sodium per day.
Data From the PURE Study
During the debate, Yusuf presented data from approximately 70 000 patients in the large-scale Prospective Urban Rural Epidemiology (PURE) study, showing that less than 5% of individuals consumed <2300 mg of sodium per day. Once the analysis was adjusted by repeated measures for regression to the mean, Yusuf said nobody in the PURE study consumed <2300 mg of sodium per day. Other international surveys showed that the mean sodium consumption was approximately 3700 mg per day, with China taking in the most, at 5000 mg per day.
"That means that we are making guidelines to levels that nobody in the world consumes," said Yusuf. "How sensible is that?"
Despite there being very little change in sodium intake over the past 50 years, the incidence of stroke has declined 70% in the US, he added. Yusuf agrees that sodium intake is related to blood pressure, but not at the current targets. The effect on blood pressure is also quite small, he said, noting that sodium levels >5000 mg/day have a larger effect on systolic blood pressure, while typical consumption only has a small impact. In fact, he said the data suggest there is no rationale for lowering sodium to <3000 mg/day for any purported benefits on blood pressure.
Now Presenting for the Defense . . .
Arguing for lower levels of sodium, Strazzulo said the United Nations is currently aiming for a 30% reduction in global sodium intake in the next decade, and that this is a crucial objective for disease prevention. Strazzulo cited evidence from the DASH study showing that a stepwise reduction in sodium resulted in stepwise reduction in blood pressure, with systolic blood pressure reduced significantly when individuals reduced salt intake from 12 g per day to 3 g per day (daily sodium levels from 4700 mg to 1100 mg).
Strazzulo does not believe that lowering sodium targets to <3000 mg per day is a futile exercise or an arbitrary one. He cited data from the Northern Manhattan Study (NOMAS) showing that individuals who consumed more than 4000 mg per day of sodium had more than double the risk of stroke compared with those who consumed less than 1500 mg.
Yusuf, on the other hand, said the totality of evidence suggests a J-shaped relationship between sodium intake and clinical outcomes. While the data confirm a higher risk with increased sodium levels, it's at a level significantly higher than the US threshold of 1500 to 2300 mg/day. Also, analyses that compared moderate vs low sodium intakes found no increased risk of clinical events with individuals consuming moderate amounts.
"Extreme sodium reduction is not practical or desirable," said Yusuf. While it may make sense to aggressively lower sodium levels in countries that consume large amounts, such as in China, or in hypertensive individuals still consuming lots of sodium, more data is needed to show how reducing these levels affects cardiovascular events, he added.
Strazzulo, however, disagrees, saying that exposure to salt/sodium is a lifelong process that starts in childhood and clinicians and policy makers need to do something to create a global low-sodium environment. Getting individuals down to 5 to 6 g/day over an extended period of time won't even be noticed, and the time to start is now.
"We have to do this for the young generations, for our children, so that they do not become dependent on high-salt intakes as their parents and grandparents have."
Heartwire from Medscape © 2013
Cite this: Salt in the Wound: Experts Debate Lowering Worldwide Sodium Intakes - Medscape - Jun 17, 2013.