Low Sodium Levels Linked To Cognitive Impairment in Older Adults

MedicalResearch.com Interview with:

Dr. Kristen L. Nowak PhD Division of Renal Diseases and Hypertension University of Colorado Anschutz Medical Campus Aurora, CO 80045

Dr. Nowak

Dr. Kristen L. Nowak PhD
Division of Renal Diseases and Hypertension
University of Colorado Anschutz Medical Campus
Aurora, CO 80045

MedicalResearch.com: What is the background for this study?  

Response: Subtle impairments in cognition are common with aging, even in the absence of clinically apparent dementia. Mild hyponatremia is a common finding in older adults; however, the association of lower serum sodium with cognition in older adults is currently uncertain.

We hypothesized that lower normal serum sodium would be associated with prevalent cognitive impairment and the risk of cognitive decline over time in asymptomatic, community-dwelling older men.

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DASH Diet and Sodium Reduction Can Have Big Impact in Improving Blood Pressure

MedicalResearch.com Interview with:

Stephen P. Juraschek, MD, PhD Instructor of Medicine Beth Israel Deaconess Medical Center/Harvard Medical School

Dr. Juraschek

Stephen P. Juraschek, MD, PhD
Instructor of Medicine
Beth Israel Deaconess Medical Center/Harvard Medical School 

MedicalResearch.com: What is the background for this study? What are the main findings?

Response: The DASH-Sodium trial demonstrated that both the DASH diet and sodium restriction, individually and combined, lowered blood pressure in adults with pre-hypertension or stage 1 hypertension. Whether these effects varied by level of blood pressure prior to starting these interventions was unknown. In a secondary analysis of the original DASH diet it had been observed that the effects from DASH were greater among adults with higher blood pressure (systolic greater than or equal to 140 mm Hg) at baseline with the appearance of even greater effects among people with baseline systolic blood pressures above 150 mm Hg. However, this has never been shown. Furthermore, it was unknown whether sodium reduction followed a similar linear trend of greater effects among adults with more severely uncontrolled systolic blood pressure.

In our study, we found that effects were indeed greater in adults with a baseline systolic blood pressure of 150 mm Hg or greater. Furthermore, the combined systolic blood pressure-lowering effect from both interventions was as high was 20 mm Hg. This is a magnitude comparable if not greater than medications for lowering blood pressure.

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Salt Content in Restaurant Food Remains High

MedicalResearch.com Interview with:

Julia Wolfson, PhD MPP Assistant Professor Department of Health Management and Policy Department of Nutritional Sciences University of Michigan School of Public Health Ann Arbor, MI 48109

Dr. Wolfson

Julia Wolfson, PhD MPP
Assistant Professor
Department of Health Management and Policy
Department of Nutritional Sciences
University of Michigan School of Public Health
Ann Arbor, MI 48109

MedicalResearch.com: What is the background for this study? What are the main findings?

Response: Over the past several years, Large chain restaurants in the United States have made some progress in introducing new lower calorie items on their menus. Since 2012, calories of items consistently on restaurant menus in all years have not significantly change. In this study, we examined the sodium content of restaurant menu items among 66 of the 100 largest restaurants in the US. We examined sodium content among items on the menu in all years (2012-2016) and among newly introduced items in 2013, 2014, 2015 and 2016 compared to items on the menu in 2012 only.

We found that sodium content of menu items on the menu in all years did not change, but that restaurants were introducing new, lower sodium menu items. However, sodium content of restaurant menu items remains high. This is important because diets high in sodium are associated with serious adverse health outcomes including hypertension, stroke and cardiovascular disease.

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Salt Intake From Packaged Foods Decreasing But Still Too High

MedicalResearch.com Interview with:

Jennifer Poti, PhD Research Assistant Professor Nutritional Epidemiology Gillings School of Global Public Health University of North Carolina at Chapel Hill

Dr. Poti

Jennifer Poti, PhD
Research Assistant Professor
Nutritional Epidemiology
Gillings School of Global Public Health
University of North Carolina at Chapel Hill

MedicalResearch.com: What is the background for this study?

Response: Although strong evidence links excessive sodium intake to hypertension, a leading risk factor for cardiovascular disease, the majority of American children and adults have sodium intake that exceeds the recommended upper limit for daily sodium intake.

To lower sodium intake at the population-level, the Institute of Medicine has recommended that reducing sodium in packaged foods will be essential and has emphasized the need to monitor sodium in the US food supply. However, little is known about whether sodium in packaged foods has changed during the past 15 years.

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Children Eating Too Much Salt At Every Meal

MedicalResearch.com Interview with:

Zerleen S. Quader, MPH CDC

Zerleen S. Quader

Zerleen S. Quader, MPH
CDC

MedicalResearch.com: What is the background for this study? What are the main findings?

Response: Sodium reduction is considered a key public health strategy to reduce cardiovascular disease nationwide, and this study is the latest in ongoing CDC efforts to monitor U.S. sodium intake.

Eating habits and taste for salt are established early in life by what children eat. Eating too much sodium can set them up for high blood pressure now and health problems later. Previous evidence suggests that one in nine children already has blood pressure above the normal range, and strong evidence has shown that reducing sodium intake reduces blood pressure – and lowering blood pressure lowers the risk of cardiovascular disease among adults. With voluntary efforts already underway by some manufacturers to lower the sodium and added sugar content in some of their products, these findings help provide a baseline to monitor changes in the food industry, as well as sodium intake among U.S. youth.

We examined data from the 2011-2012 National Health and Nutrition Examination Survey (NHANES) to determine sodium intake by major food category, place and eating occasion. We found that average sodium intake among participants was 3,256 mg, and that doesn’t include salt added at the table. On the day of assessment, nearly 90 percent exceeded the upper level of sodium recommended for a healthy diet.

• There were some variations based on age and gender. For example:
o Average intake was highest among high school-aged children
o Girls had significantly lower daily intake than boys (for example, 2,919 mg versus 3,584 mg)
• In addition, we found that ten types of food make up nearly half of youth sodium intake nationwide, including pizza, bread, lunch meats and snack foods.

We also analyzed where the foods were obtained and found that approximately 58 percent of sodium comes from store foods, 16 percent from fast food and pizza restaurants and 10 percent from school cafeteria foods. And when we looked at occasion, we discovered that 39 percent of sodium intake was consumed at dinner, 31 percent at lunch, 16 percent from snacks and 14 percent from breakfast.
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Lower Salt Intake Linked To Decreased Blood Pressure, Heart Disease and Mortality

MedicalResearch.com Interview with:

Nancy Cook ScD Professor of Medicine, Harvard Medical School Professor in the Department of Epidemiology Harvard T.H. Chan School Public Health Brigham & Women’s Hospital Division of Preventive Medicine Boston, MA 0221

Dr. Nancy Cook

Nancy Cook ScD
Professor of Medicine, Harvard Medical School
Professor in the Department of Epidemiology
Harvard T.H. Chan School Public Health
Brigham & Women’s Hospital Division of Preventive Medicine
Boston, MA 02215

MedicalResearch.com: What is the background for this study? What are the main findings?

Response: The association of sodium intake with later mortality has been controversial. While there is a well-accepted effect on blood pressure, the effects of sodium on later cardiovascular disease, and particularly mortality, have been subject to dispute. While the adverse effects of high sodium are now widely accepted, effects at lower levels of sodium intake are less clear. Some recent studies have found a J-shaped relationship, with increased disease rates among those consuming lower levels of sodium, contrary to the effects on blood pressure.

In contrast, we found a direct linear relationship of usual intake of sodium with later mortality over 20 years of follow-up. Those with the lowest sodium intake experienced the lowest mortality. Our measure of intake was based on the average over 1-3 years of several measures of 24hr urine sodium excretion, the gold standard of sodium measurement. This is much more precise than measurements based on a single 24hr sodium excretion or especially on a spot urine sample, which is used in many publications that found the J-shaped curve. Our data were assessed in a healthy cohort of men and women without hypertension or cardiovascular disease, so had less potential bias due to these factors. We thus believe that our results showing the lowest mortality among those consuming the lowest levels of sodium are more accurate.

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High Salt Intake Linked to Increased Cardiovascular Disease in CKD Patients

MedicalResearch.com Interview with:

Jiang He, M.D., Ph.D. Joseph S. Copes Chair and Professor Department of Epidemiology School of Public Health and Tropical Medicine Tulane University, New Orleans

Dr. Jiang He

Jiang He, M.D., Ph.D.
Joseph S. Copes Chair and Professor
Department of Epidemiology
School of Public Health and Tropical Medicine
Tulane University, New Orleans

MedicalResearch: What is the background for this study?

Dr. Jiang He: Chronic kidney disease is associated with increased risk of end-stage renal disease, cardiovascular disease, and all-cause mortality. A positive association between sodium intake and blood pressure is well established in observational studies and clinical trials. However, the association between sodium intake and clinical cardiovascular disease remains less clear. Positive monotonic, J-shaped, and U-shaped associations have been reported. Methodologic limitations, including inconsistencies in dietary sodium measurement methods, could be contributing to these conflicting findings. Furthermore, no previous studies have examined the association between sodium intake and incident cardiovascular disease among patients with chronic kidney disease.

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Controversy Over Salt Content Continues

Salt-SodiumMedicalResearch.com Interview with:
Prof Andrew Mente PhD
Clinical Epidemiology and Biostatistics, McMaster University
Hamilton, Canada

MedicalResearch.com Editor’s Note:  Dr. Mente discusses his Lancet publication regarding salt intake below.  Dr. Mente’s findings are disputed by the American Heart Association (AHA).  A statement from the AHA follows Dr. Mente’s comments.

MedicalResearch.com: What is the background for this study? What are the main findings?

Prof. Mente: Several prospective cohort studies have recently reported that both too little and too much sodium intake is associated with cardiovascular disease or mortality. Whether these associations vary between those individuals with and without high blood pressure (hypertension) is unknown.

We found that low sodium intake (below 3 g/day), compared to average intake (3 to 6 g/day), is associated with more cardiovascular events and mortality, both in those with high blood pressure and in those without high blood pressure. So following the guidelines would put you at increased risk, compared to consuming an sodium at the population average level, regardless of whether you have high blood pressure or normal blood pressure.

High sodium intake (above 6 g/day) compared to average intake, was associated with harm, but only in people with high blood pressure (no association in people without high blood pressure).

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Only a Few Neurons in Brain Responsible For Salt Hunger

MedicalResearch.com Interview with:

Matthew Bailey PhD Faculty Principal Investigator British Heart Foundation Centre for Cardiovascular Science The University of Edinburgh, Edinburgh, United Kingdom.

Dr. Mathew Bailey

Matthew Bailey PhD
Faculty Principal Investigator
British Heart Foundation Centre for Cardiovascular Science
The University of Edinburgh, Edinburgh, United Kingdom.

MedicalResearch.com: What is the background for this study?

Dr. Bailey: This study started with our interest in salt homeostasis and long term blood pressure, so it’s firmly rooted in the cardiovascular/renal disease risk factor arena. We were interested in salt-sensitivity- why does blood pressure go up in some people when they eat salt but not in others. I’m a renal physiologist, so we had a number of papers looking at renal salt excretion and blood pressure. We initially used a gene targeting approach to remove a gene (Hsd11b2) which acts as a suppressor of the mineralocorticoid pathway. It’s mainly expressed in the kidney and when we deleted the gene  throughout the body we saw a number of renal abnormalities all associated with high mineralocorticoid activity. This was consistent with the “hypertension follows the kidney” theory of blood pressure control. There is a human disease called “Apparent Mineralocorticoid Excess”- there are people do not have the gene and are thought to have renal hypertension. Our study threw up some anomalies which we couldn’t easily interpret but suggested that the brain was involved. We moved to a more refined technology that allowed us to knockout a gene in one organ system but not another. We knew the gene was in the brain and localized to a very restricted subset of neurons linked to salt-appetite and blood pressure control. Previous studies had shown that these neurons were activated in salt-depleted rats (ie rats that needed to eat salt). We started there but didn’t anticipate that the effect on salt hunger and on blood pressure would be so large because renal function is -as far as we can tell- normal.

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Nearly All Americans Consume More Salt Than Recommended

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Sandra L Jackson PhD Epidemic Intelligence Service, CDC Division for Heart Disease and Stroke Prevention National Center for Chronic Disease Prevention and Health Promotion Atlanta, Georgi

Dr. Sandra Jackson

MedicalResearch.com Interview with:
Sandra L Jackson PhD
Epidemic Intelligence Service, CDC
Division for Heart Disease and Stroke Prevention
National Center for Chronic Disease Prevention and Health Promotion
Atlanta, Georgia

Medical Research: What is the background for this study? What are the main findings?

Dr. Jackson: Sodium reduction is an important public health strategy to reduce cardiovascular disease, and this study was the latest in CDC’s ongoing effort to monitor U.S. sodium intake. These findings reveal that nearly all Americans – regardless of age, race and gender – consume more sodium than is recommended for a healthy diet.

Specifically, over 90 percent of children (2 to 18) and 89 percent of adults (19 and up) eat more than the recommended limits in the 2015-2020 Dietary Guidelines for Americans, and that doesn’t even include salt added at the table. The newly released guidelines recommend limiting sodium to less than 2,300 mg per day for people over the age of 14, and less for those younger.

The analysis also examined specific populations. Among adults, a larger proportion of men (98 percent) than women (80 percent) consume too much sodium. Among people at greater risk of developing heart disease or stroke – such as people age 51 and older, African Americans and individuals with high blood pressure or pre-hypertension (blood pressure higher than normal but not in the “high” range) – more than three out of four exceed 2,300 mg per day. Adults with hypertension consume slightly less sodium than other adults, and may be trying to follow physician’s advice to reduce sodium. However, 86 percent of adults with hypertension still consume too much.

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