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 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.
MedicalResearch.com: What should readers take away from your report?
Response: Consuming lower levels of sodium, as advocated by the American Heart Association, and the US Dietary Guidelines, will lead to lower blood pressure, lower risk of cardiovascular disease, and lower subsequent mortality.
MedicalResearch.com: What recommendations do you have for future research as a result of this study?
Response: More information is needed on the exact mechanisms of the effects of sodium on cardiovascular disease and mortality. While blood pressure is an important intermediary, it does not explain the full effect on later events.
MedicalResearch.com: Is there anything else you would like to add?
Response: Current consumption of sodium in the US and many other countries is very high. Much of the sodium we consume is found in processed food. The FDA has now recommended a gradual reduction in sodium content in many such foods, which should lead to lower rates of hypertension as well as cardiovascular disease and mortality.
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