Eating less than one teaspoon of salt per day remains the ideal goal for Americans, according to a new study.
Most research has linked high sodium consumption with greater risks of stroke and cardiovascular disease. Evidence has shown that men and women age 51 or older, African Americans or those with hypertension, diabetes or chronic kidney disease face especially high risks.
But when several studies produced findings suggesting diets could be too low in sodium, the US Institute of Medicine (IOM) asked experts to review studies on the health effects of sodium.
The data "weren't entirely convincing," said Nancy Cook, lead author of the current study published in the journal Circulation, and a member of that expert panel.
Cook is a statistician at the Brigham and Women's Hospital and Harvard Medical School in Boston.
In an attempt to resolve the conflicting information, Cook and her team analysed data from a previous large study called the Trials of Hypertension Prevention (TOHP) designed to look at high blood pressure. The TOHP followed the field's "gold-standard" technique of measuring salt consumption in 24-hour urine samples.
Other salt consumption studies have used single urine collections or overnight samples, neither of which provide as much consistency and accuracy as samples that participants collected throughout an entire day and night.
"The quality of the sodium measures (in TOHP) is probably better than any other study out there," Cook said.
"We found there were no adverse effects with lower amounts of sodium and benefits continued to be seen at the lowest sodium levels," she said. The findings match up with most evidence available.
"People should realise - and it may be difficult to do with all of the conflicting information in the press - that quality differs from study to study," Cook said. "When you get down to the details, some studies are more reliable than others."
The average American still eats about 3,400 mg of salt per day - about one-and-a-half teaspoons - despite public health awareness efforts.
In a study published last year, Cook along with another group of researchers projected that up to 500,000 deaths could be avoided in the US each year if more Americans reduced salt in their diets (see Reuters Health story of February 14, 2013 here: reut.rs/1g7ZMxi.
Main food culprits containing high sodium include bread, cured meat, pizza, poultry, soup, cheese and snacks, wrote Lyn Steffen of the University of Minnesota School of Public Health in Minneapolis in an editorial that accompanied the new study.
On the nutritional facts panel on food packaging, if the sodium amount per serving is 5 per cent daily value, then that is a low-sodium product, Steffen said. Products with 20 per cent daily value are high-sodium.
Even though modern lifestyle is busy, Dr. Graham MacGregor of Queen Mary University and chairman of the World Action on Salt and Health lobby group, suggested a solution: "If you cook fresh vegetables, potatoes, pasta and rice with fresh meat or fish, make more than you can consume, you can then put portions in the freezer and use this on different occasions so that the food can be instantly ready."
In restaurants, the challenge to eat less salt can be greater. "You can request that no salt be added," Cook said.
"If you suddenly cut all sodium from your meals, then things will taste bland," Cook said. "So it's important to lower sodium gradually and get accustomed to lower amounts of salt."
As the body adjusts to lower sodium levels, then foods with high sodium may be less appealing, she said.