Are sandwiches really the healthiest choice?
The study, conducted by the US Department of Agriculture (USDA) Agricultural Research Service (ARS) and investigators at the Food Surveys Research Group, is published in the Journal of the Academy of Nutrition and Dietetics.
Data came from the What We Eat in America NHANES 2009-2010 survey, in which 5,762 adults over the age of 20 recorded everything they ate and drank the previous day.
The researchers then assigned each food and beverage with one or more food codes so their nutritional content could be assessed.
The team found that on any given day, 49% of adults in the US eat at least one sandwich, and sandwiches comprise one fifth of total daily sodium intake.
The 2010 Dietary Guidelines for Americans set the maximum daily sodium intake at 2,300 mg, but for those over 50, African-Americans and those with high blood pressure, diabetes or chronic kidney disease, the recommended amount is 1,500 mg per day.
According to the Centers for Disease Control and Prevention (CDC), high sodium consumption raises blood pressure. High blood pressure is a major risk factor for heart disease and stroke, the first and fourth leading causes of death in the US.
Sandwiches contribute to 30-46% of daily sodium intake guidelines
The researchers, led by study co-author and ARS nutritionist Rhonda Sebastian, say that sandwiches present a challenge for survey researchers because they can contain different ingredients.
Fast facts about sodium intake
- Research suggests a dose-dependent relationship between high salt consumption and high blood pressure - as sodium intake increases, so does blood pressure for most people
- Compared with blood pressure increases with age observed in most Western countries, populations that consume diets low in salt do not not experience such increases
- Though the maximum recommended daily intake of sodium is 2,300 mg, Americans over the age of 2 average a daily sodium intake of more than 3,400 mg.
For the survey, participants reported the components of their sandwich individually, which the researchers then coded separately with multiple food codes.
They say, for example, a ham and cheese sandwich could have been coded as distinct amounts of bread, ham, cheese, lettuce and mayonnaise. But some sandwiches, particularly fast-food sandwiches, were coded with a single food code (i.e. turkey submarine sandwich with cheese, lettuce, tomato and spread).
In previous studies, such sandwiches were only represented by a single food code, and those studies found that sandwiches were responsible for about 4% of daily sodium intake.
"In 2009-2010, only about 20% of all sandwiches were represented by a single food code," says Sebastian. "For that reason, previously published estimates of sandwich contributions to sodium intake that were based on only single-code sandwiches are considerably underestimated."
However, by including sandwiches that were coded both ways, the investigators of this study found that sandwiches actually account for one fifth of total sodium intake. Additionally, for adults, sandwiches alone contribute to 30% of the less restrictive daily sodium guideline and 46% of the stricter guideline.
The authors say that because sandwiches are frequently consumed and contribute to significant sodium intake, "substituting lower-sodium for higher-sodium ingredients in sandwiches could significantly influence sodium intakes."
'Consumer choice plays a vital role'
Another finding from the study revealed that people who ate sandwiches also had a "significantly higher" energy intake, compared with those who did not.
In detail, those who ate a sandwich on the survey day consumed around 300 calories more, and they also had higher total sodium intakes per day - around 600 mg more than those who did not eat a sandwich.
Commenting on their findings, co-author and ARS nutritionist Cecilia Wilkinson Enns says:
"The unanticipated finding that sandwich consumption is associated with higher overall intake of energy underscores the importance of making healthful choices of sandwich ingredients. Many sandwiches, such as burgers and franks, and common sandwich components, such as yeast breads, cheese and cured meats, are among the top contributors not only to sodium but also to energy in the diets of adult Americans."
She adds that although many public health campaigns focus on reducing sodium in the food supply, "consumer choices still play a vital role."