Research Roundup

Noteworthy nutrition studies highlighted by members of The Chan School’s Department of Nutrition

1) Jackson, S. L., King, S. M. C., Park, S., Fang, J., Odom, E. C., & Cogswell, M. E. (2015). Health professional advice and adult action to reduce sodium intakeAmerican Journal of Preventive Medicine.

A studysalt published in the American Journal of Preventive Medicine found that more than half of U.S. adults surveyed are trying to reduce their sodium intake, and that advice from a medical professional is strongly associated with reducing sodium intake.

  • The researchers analyzed data from the optional sodium module on the 2013 Behavioral Risk Factor Surveillance System, a nationwide state-based telephone survey. The data used in this study was gathered from 173,778 (non-institutionalized) respondents from 26 states, the District of Columbia, and Puerto Rico.
  • 53% of adults overall reported taking action to reduce their sodium intake. This percentage was higher among blacks (68%) and Hispanics (63%). The prevalence of taking action was highest among those who received medical advice (83%), followed by adults taking antihypertensive medications (75%), adults with a history of cardiovascular disease (75%), adults with diabetes (74%), and adults with kidney disease (73%). The prevalence was lowest among 18 to 24 year-olds (29%).
  • 23% of adults reported receiving medical advice to reduce their sodium intake, and receiving this advice was associated with taking action (prevalence ratio=1.59; 95% CI=1.56, 1.61), independent of sociodemographic and health characteristics.

2) Anderson, C. A., Cobb, L. K., Miller, E. R., Woodward, M., Hottenstein, A., Chang, A. R., … & Appel, L. J. (2015). Effects of a behavioral intervention that emphasizes spices and herbs on adherence to recommended sodium intake: Results of the SPICE randomized clinical trialThe American Journal of Clinical Nutrition102(3), 671-679.

The results of a behavioral intervention published in The American Journal of Clinical Nutrition showed that study participants who used more spices and herbs when cooking consumed less salt, suggesting counselling sessions which show participants how to make food taste good without relying too much on salt can be beneficial for health and well-being.

  • The study included adults 18 years and older. The Dietary Guidelines for Americans recommends 1500 mg of sodium per day for this demographic. The mean age was 61 years old, and the mean BMI was 30. Of the study population, 88% were African American, and 63% had high blood pressure.
  • In the first phase of the study, 55 individuals were given a low-sodium diet for four weeks to get them used to eating less salt. Participants were provided all food, snacks, and beverages.
  • In the second phase, 40 participants from phase 1 were randomly assigned to either a behavioral intervention to reduce sodium intake or a self-directed control group for 20 weeks. The behavioral intervention included individual and group counseling sessions emphasizing the use of spices to replace salt, as well as keeping track of how much sodium they were consuming.
  • At the end of phase 2, the mean 24-hour sodium excretion was 956.8 mg/day lower in the behavioral intervention group than in the control group. These findings suggest that counseling which emphasizes the use of spices and herbs in cooking, along with guided sodium reduction, can help people reduce their sodium intake.

3) Wielgosz, A., Robinson, C., Mao, Y., Jiang, Y., Campbell, N. R., Muthuri, S., & Morrison, H. (2015). The Impact of Using Different Methods to Assess Completeness of 24‐Hour Urine Collection on Estimating Dietary SodiumThe Journal of Clinical Hypertension.

The standard method of determining sodium intake is the 24-hour urine test, in which all urine over a 24-hour period is collected in one or more containers and then sent to a lab for analysis. However, this has the potential for human error. A study published in The Journal of Clinical Hypertension found that depending on the method used for assessing complete urine collection, the estimate of mean sodium intake varied by almost 3600 mg per 24-hour period – a substantial difference.

  • In 2009, 507 volunteers were recruited from the Champlain Community Heart Healthy Study in Eastern Ontario to conduct a 24-hour urine survey for dietary sodium.
  • The “gold standard” for ensuring the accuracy of 24-hour sodium collection involves administering para-aminobenzoic acid (PABA) three times during the urine collection, as this chemical is almost completely excreted in the urine during the 24-hour collection period. However, this is rather complex for participants and can be costly, so other indirect methods for assessing urine collection are more commonly used. In this study, the investigators focused on creatinine excretion rate to determine the accuracy of urine collection. Men typically excrete 15-25 mg/kg every 24 hours, while women excrete 10-24 mg/kg every 24 hours. However, creatinine excretion rates are affected by many factors, including diet, muscle mass, kidney function, substances competing with creatinine for renal transporters, ethnicity, and age.
  • Four creatinine-based urine inclusion/exclusion criteria were applied to analyses, and the results were then compared. One analysis excluded samples for which the measured creatinine excretion rate was biologically implausible. The second only included those individuals whose creatinine levels fell within the standard creatinine excretion rates. The third method excluded only those with low values of measured creatinine excretion rates. The fourth used a linear regression model to estimate the expected creatinine excretion rate from a regression equation, built on records with standard creatinine rates; samples were then excluded if the 24-hour creatinine excretion was less than 15% or greater than 50% of their predicted expected rate.
  • Depending on the method used for assessing complete urine collection, mean sodium intake varied between 3648 mg/24 hours and 7210 mg/24 hours.
  • The large degree of variation indicates a strong need to establish more pragmatic yet cost-effective methods to accurately measure sodium intake from 24-hour urine tests.

This month’s Research Roundup was compiled by Aviva Musicus, a first-year doctoral student whose research includes food marketing, labeling, and the effectiveness of sugar-sweetened beverage regulation. She previously worked at the Center for Science in the Public Interest, where she conducted research and lobbied for added sugar and sodium reduction, the elimination of trans fats from the food supply, and improved agricultural biotechnology regulations.