Is Salt Really So Bad?
Experts Disagree About Its Role in High Blood Pressure
By Salynn Boyles
Reviewed By Michael Smith, MD
on Thursday, September 25, 2003
WebMD Medical News
Sept. 25, 2003 -- If you have high blood pressure, you've probably been told to reduce the salt in your diet, but new findings are challenging the idea that sodium is a major culprit in promoting high blood pressure.
Researchers who have argued against the salt-blood pressure link for almost two decades presented new data Thursday suggesting that high blood pressure is much more closely linked to a diet low in minerals such as calcium, potassium, and magnesium than sodium intake. The data were presented at the American Heart Association's (AHA) 57th annual high blood pressure research conference in Washington, D.C.
But don't toast the news with a round of salt-rimmed margaritas just yet. An AHA spokesman tells WebMD that the findings are based on shaky science that is much less convincing than another large study published two years ago, which found a strong link between salt and high blood pressure.
"The best trials we have had clearly indicate that sodium intake does impact blood pressure," says Daniel Jones, MD, who is dean of the school of medicine at the University of Mississippi Medical Center.
Poor Diet May Be to Blame
In the newly reported study, roughly 33,000 people had their blood pressures recorded and answered dietary questions.
Researchers divided the participants' sodium, calcium, and total mineral intake into four groups and found that while blood pressure did not vary significantly according to sodium intake, higher calcium intake was associated with lower blood pressure. In one of the most recent surveys, higher mineral intake was also linked to lower blood pressure.
"We believe that as a rule, high sodium intake is a marker of a poor quality diet," says lead researcher David McCarron, MD. "The [new study] data indicate that it is not the sodium per se that affects blood pressure, but the lack of calcium, magnesium, potassium, and probably some other minerals and vitamins." McCarron is a longtime paid consultant for the salt industry.
But Jones counters that surveys such as this present an incomplete and potentially flawed picture of nutritional status because they rely on participants to remember the foods they have eaten. He says the clinical trial known as the Dietary Approaches to Stop Hypertension (DASH) sodium study was much more convincing.
In that trial, 412 participants ate either a typical diet or a highly controlled diet that was low in sodium and fat and high in calcium, fruits, and vegetables. Researchers found that reducing the salt in the diet had a direct impact on blood pressure levels, even when the participants did not have high blood pressure.
McCarron has challenged the latest DASH findings. He tells WebMD that the government and Harvard University researchers who published the study did not include information on subgroups who did not benefit from lowering their salt intake, such as men younger than 45 with normal blood pressure.
"The recommendations from the DASH sodium trial are that all Americans should reduce their sodium intake to 1,500 mg a day," he says. "The previous recommendation was 2,300 mg a day, and nobody could do that. All I'm saying is show me the data that proves this is necessary."
SOURCES: American Heart Association's 57th Annual Fall Conference and Scientific Sessions of the Council for High Blood Pressure Research in association with the Council on the Kidney in Cardiovascular Disease, Washington, D.C., Sept. 23-26, 2003. David McCarron, MD, nephrologist, Oregon Health & Science University, Portland, Ore. Daniel Jones, MD, dean of the school of medicine, University of Mississippi Medical Center, Jackson, Miss.