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Thursday, May 22, 2014

Of salt, 'saltation' and salience: the case for fixing what's broken

We have long had abundant reason to believe that most of us living in the modern world consume too much sodium and would benefit from consuming less. But whether the topic is salt, or saturated fat, or calories, or even the health effects of consuming vegetables and fruits, saltation (the jumping from one position to another) seems to be the prevailing inclination in modern nutrition. Certainly it is the inclination that predominates in the popular press. Salt is just the latest nutrient to get caught up in that proclivity.

This isn’t the first time salt claimed its 15 minutes of notoriety. Just less than a year ago, I was prompted to address this issue by an Institute of Medicine report questioning the gospel of “less is better” with regard to sodium intake. Two recent studies compel me to revisit the topic now. For those who like the punch line up front, I can tell you my conclusion is much as it was. I remain convinced that most of us consume too much salt, and would benefit from reducing our intake. And yes, of course, it’s possible to consume too little.

Of the 2 recent studies on salt intake and health outcomes, predictably the one that challenged the prevailing view garnered more media attention. That study, published in the American Journal of Hypertension in early April, was a meta-analysis examining sodium intake in populations around the world and its association with both all-cause mortality and cardiovascular disease.

The authors concluded that mortality and heart disease rates were higher among those with both low and high sodium intake, and lower for those with intake in the middle range. Because dietary guidelines from the relevant authorities, including the IOM, the CDC, and the U.S. Department of Agriculture all emphasize a reduction in our customarily excessive salt intake, the more provocative message in this study was the potential danger in consuming too little. So “salt guidelines are too low“ was the common pop culture assessment.

But there are a few problems with that conclusion. First, as the study authors stated, the increased risks of both heart disease and mortality were greater with high sodium intake, than with low. So if we were ranking our concerns based on this study alone, excess sodium would still be the bigger problem.

Second, the authors noted their meta-analysis was based almost entirely on observational, not intervention, trials. This meant studies simply looked at variation in sodium intake and compared that to variation in health outcomes. Studies like that beg the question: What accounted for the sodium variation in the first place? Some health conscious people may have a very low intake of sodium, but others likely to land there are people with maladies affecting the heart or kidneys, people who are under-nourished for any reason, and so on. The authors attempted to account for such considerations, but acknowledged a limited ability to do so. In other words, this study had limited capacity to tell us whether low sodium intake resulted in poor health, or whether poor health resulted in low sodium intake. Chances are there was some of both in the mix.

The more recent study, just published online in the British Medical Journal, took headlines in the opposite direction: Too much sodium is the problem after all. For this study, investigators tracked dietary patterns, including sodium intake, and sodium excretion, in representative samples of the population of England. Over the past decade, they tracked a number of dietary changes, and conducted analyses to determine the association of each with health outcomes. The particularly noteworthy findings were a reduction in sodium intake and excretion, associated with a population-wide reduction in mean blood pressure, in turn associated with a marked reduction in the mortality rate from both stroke and heart disease.

This study is subject to limitations of its own. But it does not suffer the problem of temporal association that bedevils the first. The gist is clear: A population-wide reduction in sodium intake over the past decade is almost certainly at least part of the reason for a population-wide reduction in blood pressure, and cardiovascular mortality.

But conclusions about sodium in our diets should not be based on any one study, whatever its strengths or weaknesses, but rather the overall weight of evidence. That remains rather clear. Average sodium intake levels in the U.S. and much of the modernized world are higher than advised. Intervention studies, such as DASH, that have lowered levels to approximate prevailing guidelines, have lowered blood pressure as a result. Blood pressure reduction in turn has been strongly and consistently associated with reduced risk of both heart disease and stroke.

But there is more. Paleo diet enthusiasts rightly note that our native dietary intake pattern is likely to be “good” for us, since it is the pattern to which we are adapted. That adaptation is a powerful influence. It’s why koala bears should eat eucalyptus leaves, and lions should eat wildebeest. It stands to reason that adaptation is relevant to our species as well. There are many implications of “native” eating for Homo sapiens, but one of them is a much higher intake of potassium than sodium. The modern diet typically reverses this ratio. Arguments for sodium reduction thus derive from both modern science, and paleoanthropology.

Finally, the source of sodium is a relevant consideration. Roughly 80% of the sodium in the typical American diet comes not from personal use of a salt shaker, but from salt processed into our food before ever we get our hands on it. This implies that sodium intake tends to come down with consumption of less processed foods overall. While reduced sodium intake is likely beneficial in such context, the context of a less processed diet is apt to be beneficial in a variety of ways. With sodium, as with other nutrients of concern, if we get the foods and dietary pattern right, nutrients tend to take care of themselves.

Of course, the contention that we should reduce ambient sodium intake not by focusing on sodium, but by eating “food, not too much, mostly plants,” invites the customary rebuttals: That’s elitist, unrealistic, too expensive, and too hard. I disagree with these assertions and have addressed them in very practical terms. My group has studied the costs of trading up to better, less-processed, and among other things, less-salty options in any given food category, and found that it can generally be done without spending more money. We have developed and studied a nutrition guidance system and a free food label literacy program, showing that both can help people get there from here. Of importance to everyone who isn’t a card-carrying member of the foodie elite, it is possible to trade up nutrition (and dial down sodium) without swapping out chips for chard; it’s possible to make meaningful progress by eating better chips.

Sodium is an essential nutrient; of course we could, in principle, eat too little. We could, as well, drink too much water. Or exercise too much. Or sleep excessively. Or spend too much time fortifying bonds of friendship. I suppose we might devote too much of each day to hugging.

But really, what are the odds? We sleep and hug too little, work and stress too much. The theoretical dangers of overshooting are not a good reason to neglect what is currently broken.

Average sodium intake in the U.S. hovers well about 3,000 mg per day. While there is legitimate debate about health effects at levels below 2,300 mg per day, there is little about levels between here and there. Just to hit the targets in which we do have confidence, we have a long way to go. So it seems very premature to start encouraging people to worry about overshooting.

The prevailing fashion in nutrition, if not all of health news, is contrarianism. Cutting back on salt was yesterday’s news. If today’s news were the same as yesterday’s news, we might not be confused, and desperately in need of tomorrow’s news to help sort it all out. We can’t have that! So as never before, contrarians and iconoclasts own the headlines.

But they don’t really own the science, which is, as ever, a product of the gradual accumulation of data and genuine understanding over time, not the single study that grabs 15 minutes in the spotlight. And they don’t own our common sense, which should tell us that worrying about doing too much is not a good reason to avoid doing enough.

The “salutatory” headlines notwithstanding, an excess of sodium is the salient, clear, and present danger for modern societies. While allowing for the hypothetical hazards of going too far, we should focus for now on fixing what we know to be broken.

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Blog log

Members of the American College of Physicians contribute posts from their own sites to ACP Internistand ACP Hospitalist. Contributors include:

Albert Fuchs, MD
Albert Fuchs, MD, FACP, graduated from the University of California, Los Angeles School of Medicine, where he also did his internal medicine training. Certified by the American Board of Internal Medicine, Dr. Fuchs spent three years as a full-time faculty member at UCLA School of Medicine before opening his private practice in Beverly Hills in 2000.

And Thus, It Begins
Amanda Xi, ACP Medical Student Member, is a first-year medical student at the OUWB School of Medicine, charter class of 2015, in Rochester, Mich., from which she which chronicles her journey through medical training from day 1 of medical school.

Auscultation
Ira S. Nash, MD, FACP, is the senior vice president and executive director of the North Shore-LIJ Medical Group, and a professor of Cardiology and Population Health at Hofstra North Shore-LIJ School of Medicine. He is Board Certified in Internal Medicine and Cardiovascular Diseases and was in the private practice of cardiology before joining the full-time faculty of Massachusetts General Hospital.

Zackary Berger
Zackary Berger, MD, ACP Member, is a primary care doctor and general internist in the Division of General Internal Medicine at Johns Hopkins. His research interests include doctor-patient communication, bioethics, and systematic reviews.

Controversies in Hospital Infection Prevention
Run by three ACP Fellows, this blog ponders vexing issues in infection prevention and control, inside and outside the hospital. Daniel J Diekema, MD, FACP, practices infectious diseases, clinical microbiology, and hospital epidemiology in Iowa City, Iowa, splitting time between seeing patients with infectious diseases, diagnosing infections in the microbiology laboratory, and trying to prevent infections in the hospital. Michael B. Edmond, MD, FACP, is a hospital epidemiologist in Iowa City, IA, with a focus on understanding why infections occur in the hospital and ways to prevent these infections, and sees patients in the inpatient and outpatient settings. Eli N. Perencevich, MD, ACP Member, is an infectious disease physician and epidemiologist in Iowa City, Iowa, who studies methods to halt the spread of resistant bacteria in our hospitals (including novel ways to get everyone to wash their hands).

db's Medical Rants
Robert M. Centor, MD, FACP, contributes short essays contemplating medicine and the health care system.

Suneel Dhand, MD, ACP Member
Suneel Dhand, MD, ACP Member, is a practicing physician in Massachusetts. He has published numerous articles in clinical medicine, covering a wide range of specialty areas including; pulmonology, cardiology, endocrinology, hematology, and infectious disease. He has also authored chapters in the prestigious "5-Minute Clinical Consult" medical textbook. His other clinical interests include quality improvement, hospital safety, hospital utilization, and the use of technology in health care.

DrDialogue
Juliet K. Mavromatis, MD, FACP, provides a conversation about health topics for patients and health professionals.

Dr. Mintz' Blog
Matthew Mintz, MD, FACP, has practiced internal medicine for more than a decade and is an Associate Professor of Medicine at an academic medical center on the East Coast. His time is split between teaching medical students and residents, and caring for patients.

Everything Health
Toni Brayer, MD, FACP, blogs about the rapid changes in science, medicine, health and healing in the 21st century.

FutureDocs
Vineet Arora, MD, FACP, is Associate Program Director for the Internal Medicine Residency and Assistant Dean of Scholarship & Discovery at the Pritzker School of Medicine for the University of Chicago. Her education and research focus is on resident duty hours, patient handoffs, medical professionalism, and quality of hospital care. She is also an academic hospitalist.

Glass Hospital
John H. Schumann, MD, FACP, provides transparency on the workings of medical practice and the complexities of hospital care, illuminates the emotional and cognitive aspects of caregiving and decision-making from the perspective of an active primary care physician, and offers behind-the-scenes portraits of hospital sanctums and the people who inhabit them.

Gut Check
Ryan Madanick, MD, ACP Member, is a gastroenterologist at the University of North Carolina School of Medicine, and the Program Director for the GI & Hepatology Fellowship Program. He specializes in diseases of the esophagus, with a strong interest in the diagnosis and treatment of patients who have difficult-to-manage esophageal problems such as refractory GERD, heartburn, and chest pain.

I'm dok
Mike Aref, MD, PhD, FACP, is an academic hospitalist with an interest in basic and clinical science and education, with interests in noninvasive monitoring and diagnostic testing using novel bedside imaging modalities, diagnostic reasoning, medical informatics, new medical education modalities, pre-code/code management, palliative care, patient-physician communication, quality improvement, and quantitative biomedical imaging.

Informatics Professor
William Hersh, MD, FACP, Professor and Chair, Department of Medical Informatics & Clinical Epidemiology, Oregon Health & Science University, posts his thoughts on various topics related to biomedical and health informatics.

David Katz, MD
David L. Katz, MD, MPH, FACP, is an internationally renowned authority on nutrition, weight management, and the prevention of chronic disease, and an internationally recognized leader in integrative medicine and patient-centered care.

Just Oncology
Richard Just, MD, ACP Member, has 36 years in clinical practice of hematology and medical oncology. His blog is a joint publication with Gregg Masters, MPH.

KevinMD
Kevin Pho, MD, ACP Member, offers one of the Web's definitive sites for influential health commentary.

MD Whistleblower
Michael Kirsch, MD, FACP, addresses the joys and challenges of medical practice, including controversies in the doctor-patient relationship, medical ethics and measuring medical quality. When he's not writing, he's performing colonoscopies.

Medical Lessons
Elaine Schattner, MD, FACP, shares her ideas on education, ethics in medicine, health care news and culture. Her views on medicine are informed by her past experiences in caring for patients, as a researcher in cancer immunology, and as a patient who's had breast cancer.

Mired in MedEd
Alexander M. Djuricich, MD, FACP, is the Associate Dean for Continuing Medical Education (CME), and a Program Director in Medicine-Pediatrics at the Indiana University School of Medicine in Indianapolis, where he blogs about medical education.

More Musings
Rob Lamberts, MD, ACP Member, a med-peds and general practice internist, returns with "volume 2" of his personal musings about medicine, life, armadillos and Sasquatch at More Musings (of a Distractible Kind).

Prescriptions
David M. Sack, MD, FACP, practices general gastroenterology at a small community hospital in Connecticut. His blog is a series of musings on medicine, medical care, the health care system and medical ethics, in no particular order.

Reflections of a Grady Doctor
Kimberly Manning, MD, FACP, reflects on the personal side of being a doctor in a community hospital in Atlanta.

The Blog of Paul Sufka
Paul Sufka, MD, ACP Member, is a board certified rheumatologist in St. Paul, Minn. He was a chief resident in internal medicine with the University of Minnesota and then completed his fellowship training in rheumatology in June 2011 at the University of Minnesota Department of Rheumatology. His interests include the use of technology in medicine.

Technology in (Medical) Education
Neil Mehta, MBBS, MS, FACP, is interested in use of technology in education, social media and networking, practice management and evidence-based medicine tools, personal information and knowledge management.

Peter A. Lipson, MD
Peter A. Lipson, MD, ACP Member, is a practicing internist and teaching physician in Southeast Michigan. The blog, which has been around in various forms since 2007, offers musings on the intersection of science, medicine, and culture.

Why is American Health Care So Expensive?
Janice Boughton, MD, FACP, practiced internal medicine for 20 years before adopting a career in hospital and primary care medicine as a locum tenens physician. She lives in Idaho when not traveling.

World's Best Site
Daniel Ginsberg, MD, FACP, is an internal medicine physician who has avidly applied computers to medicine since 1986, when he first wrote medically oriented computer programs. He is in practice in Tacoma, Washington.

Other blogs of note:

American Journal of Medicine
Also known as the Green Journal, the American Journal of Medicine publishes original clinical articles of interest to physicians in internal medicine and its subspecialities, both in academia and community-based practice.

Clinical Correlations
A collaborative medical blog started by Neil Shapiro, MD, ACP Member, associate program director at New York University Medical Center's internal medicine residency program. Faculty, residents and students contribute case studies, mystery quizzes, news, commentary and more.

Interact MD
Michael Benjamin, MD, ACP member, doesn't accept industry money so he can create an independent, clinician-reviewed space on the Internet for physicians to report and comment on the medical news of the day.

PLoS Blog
The Public Library of Science's open access materials include a blog.

White Coat Rants
One of the most popular anonymous blogs written by an emergency room physician.

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