Cutting Salt by a Third Could Halve Hypertension Among Teens

November 23, 2010

November 23, 2010 (Chicago, Illinois) — Teenagers' favorite food, pizza, is helping elevate them to the dubious title of "age group that consumes the most salt," new US research shows. Cutting the consumption of such foods and thereby lowering overall salt intake by just half a teaspoon a day could reduce the number who are hypertensive by half, consequently cutting premature deaths from heart disease and stroke later in life, the data indicate.

Dr. Kirsten Bibbins-Domingo

The figures are based on statistical modeling of what would happen if teenagers and young adults could cut their salt consumption by 3 g per day, explained epidemiologist Dr Kirsten Bibbins-Domingo (University of California, San Francisco) during the American Heart Association (AHA) 2010 Scientific Sessions last week. The average teen eats 9 g of salt per day, and pizza tops the list of saltiest foods that adolescents consume. "It starts with salty bread, followed by salty tomato sauce, topped with salty cheese," she noted, and it is closely followed by bread, fast foods such as fried chicken or burgers, pasta, and condiments such ketchup.

"Teenagers are eating way above the recommended amount of salt per day, and blood pressure appears to be rising both in obese and nonobese teens," Bibbins-Domingo told heartwire . Trying to reduce the amount of salt people eat at this age may be a unique "window of opportunity, because healthy behaviors start in childhood and young adulthood" and could lead to numerous benefits, she said.

First, even low-level elevations in blood pressure put people at some risk, so any reduction in sodium and consequent fall in BP is advantageous, she says. Second, a reduction in blood pressure during the teenage years leads to lower BP as people age. And reducing salt at this stage of life would lead to physiologic adaptation to a lower-salt diet, and consequent lifelong adaptation of taste expectations. Also, one of the best ways to reduce salt--eating more fresh food, fruits, and vegetables--would have other health benefits, too, she noted.

Reducing Salt in the Diet is "a Major Challenge"

Most--80%--of salt comes from processed food, Bibbins-Domingo says, and given the fact that teenagers consume lots of fast food and snacks, this figure may be even higher in this age group. "It is a major challenge. We all lead busy lives, and it's hard to avoid prepackaged foods." Any attempts to reduce salt intake will need to be modeled on salt-reduction programs enacted in other countries, such as the UK, Australia, and Finland, she said.

Teenagers are eating way above the recommended amount of salt per day, and blood pressure appears to be rising both in obese and nonobese teens.

In these countries, food manufacturers have voluntarily reduced the salt in their foods and in some cases put "traffic-light" type labeling on products to help consumers pinpoint which ones are high in salt. "I think the most important thing is that all countries should focus on where salt is in their diets," Bibbins-Domingo says. In Japan, for example, the problem is usually salt added at the table in the form of soy sauce, she noted.

Many US companies have already joined the US National Sodium Reduction Initiative and voluntarily agreed to work to lower the amount of salt added to processed and prepared foods, she explained. "The US efforts have been modeled on the UK efforts, and that is a reasonable approach."

However, she believes that mandatory restrictions will also be necessary to help achieve the stated goals in the US. Moves are afoot to try to institute such regulations: in April, the US Institute of Medicine (IOM) advised the FDA that it should set stricter federal standards for the amount of salt that food manufacturers, restaurants, and food-service companies can add to their products, because such a strategy would make it easier for Americans to cut sodium consumption.

And a recent paper from Australia drew similar conclusions--that mandatory restrictions would provide the most benefits, Bibbins-Domingo noted.

Any Salt Reduction Should Be Performed Gradually

In the modeling predictions, which were presented as a poster by Bibbins-Domingo at the AHA meeting, she and her colleagues simulated the effects of reducing the salt in a teenage diet from an average of 9 g to 6 g per day and applied the results to the distribution of blood pressure and other cardiovascular risk factors in the US population.

They calculate that reducing salt by 3 g per day would have measurable health benefits, so that by the time these boys and girls reached the age of 50 there would be a 7% to 12% drop in coronary heart disease cases, an 8% to 14% reduction in new and recurrent heart attacks, a 5% to 8% cut in strokes, and a 5% to 9% decrease in all-cause mortality.

Physiologic studies suggest that as you eat less salt, your taste receptors downregulate in about six weeks.

Asked to comment on these findings, Dr Robert Eckel (University of Colorado Denver School of Medicine) pointed out that "this is just a calculation; it's somewhat artificial" and that "it is hypothetical as to whether this type of salt reduction is possible."

However, he does agree with Bibbins-Domingo that everyone should eat less salt, although he warned that cutting salt in the diet too abruptly could backfire. "A one-third reduction in dietary sodium would not be tolerated immediately," he told heartwire .

Bibbins-Domingo agrees, noting that the dietary sodium reductions attained in the UK were reached gradually, starting in 2003. "We are really encouraged by the efforts in the UK, which have been achieved by a combination of educating the public, working directly with the food industry, and being willing to follow it up with monitoring and surveillance, and it seems to have happened without people noticing. Physiologic studies suggest that as you eat less salt, your taste receptors downregulate in about six weeks."

The complete contents of Heartwire , a professional news service of WebMD, can be found at www.theheart.org, a Web site for cardiovascular healthcare professionals.

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