American College of Physicians: Internal Medicine — Doctors for Adults ®

Tuesday, January 19, 2016

Fishy claims about best diets

We have all heard that eating fish is good for us, and the proposition is valid both empirically, and epidemiologically. But it begs a vital question just the same: good for us, compared to what?

What we know is that in general, people with diets that routinely include fish have better health outcomes than people with diets that don't. There are inevitably, however, systematic differences in such diets. People eating more fish may well benefit from fish-specific attributes, such as the omega-3 content of fatty fish, notably salmon, trout, and albacore tuna. They (we) may also benefit, however, because fish as a protein source supplants other, less salutary fare. Is the observable benefit principally derived from what the diet includes, or excludes? This is not an easy question to answer even when we wrestle with it directly, which to date we have mostly not done.

Fish is clearly good for us in the context of the prevailing, typical American diet, propagating around the globe, alas, in which the meat of pigs (i.e., bacon) is routinely garnish for the meat of cattle (i.e., burgers). Such meat-on-meat is further embellished as a matter of routine with everything from a bun of refined white flour (to say nothing of additions of not only rather copious salt, but also high fructose corn syrup), to ketchup (with more high fructose corn syrup), to such ominously vague concoctions as “special” sauce. Trading up in such context is not a challenge.

But what of the addition of fish to an already quite optimal vegetarian diet? Can we say if human health outcomes are demonstrably better with an optimized vegan diet, or an optimized pescetarian diet?

To date, to the best of my knowledge, we cannot.

To the extent that we mean what really matters most when we say “human health outcomes,” that is not a problem we are likely to redress any time soon. What really matters most is the combination of longevity and vitality; life in years, and years in life.

To show beyond meaningful doubt that any contender for best diet laurels is truly “the” champion using such a metric is a daunting challenge. We know, for instance, that nutritional effects, and inchoate taste preferences, originate in utero. We know as well that diet quality continues to influence health quality across the full expanse of the lifespan.

To prove, therefore, that Diet A is “better” than Diet B, to say nothing of Diets C-Q waiting in the wings, likely requires the randomization of women early in their pregnancies to the competing options. Because health differences are apt to be small when variations on the theme of “optimal” are being compared, the sample size would have to be huge, probably well into the thousands.

So, thousands of pregnant women would need to adhere to their assigned diet throughout their pregnancies, and then adhere to it some more during a required, standardized period of breast-feeding. Nutrients, after all, are transmitted through breast milk, as are flavors.

The true study participants, the babies, only get into the act once they are weaned and start eating solid food. At that point, the babies need to adhere to the assigned diet, forever.

Since our study metric includes longevity, and since people eating (and living) optimally see their 100th birthday far more often than the rest of us, we should plan for our study to run the better part of 100 years. The challenges are by now self-evident, I trust. Leaving alone the logistical nightmare of managing perfect fidelity to assigned diets by thousands of mothers at first, and then their newborns, we are left with a study that will cost an oppressively staggering sum, and will outlive any of the investigators involved at the start.

Suffice to say, it has not been done, and I advise against holding your breath while waiting.

Of course, we might content ourselves with lesser metrics. We certainly could compare equitably high-quality versions of vegetarian and pescetarian diets in a relatively short-term randomized trial, looking at such measures as cardiac risk markers, inflammatory cytokines, body composition, and more. Not only could such a trial be done, but frankly, it should be. My lab is working on related protocols as we speak, so we might get into the game.

We have had limited forays in this direction, looking over the years at the health effects of various foods. We have reported, for instance, that daily egg ingestion produces no discernible harms in healthy adults, hyperlipidemic adults, or even adults with coronary artery disease. But of course, this egg intake is against the backdrop of a rather typical American diet. We may well be better off eating more eggs, and fewer doughnuts, which was the thinking that motivated this line of inquiry in the first place.

My vegan colleagues, however, are quick to point out that the alleged “harmlessness” of eggs, and cholesterol, would disappear if superimposed on an optimal, plant-based diet at baseline. They may well be right, and it is a reminder to ask always about the attribution of effects to any given element of diet: compared to what?

In other cases, we have studied foods of such clearly established health benefit that our findings are of more reliably universal relevance. Nuts, for example, figure in all of the world's healthiest diets, and are consistently associated with an array of health benefits in epidemiologic research. In such context, our findings related to beneficial effects of walnuts in Type 2 diabetes and pre-diabetes may, perhaps, be spared the “compared to what?” proviso. The best of foods are good for us compared to just about anything.

By and large, though, my lab is much more about “how to” rather than “what to” when it comes to eating. We accept that the basic theme of salutary eating has been rather clear for decades, and that making far better use of what we already know is crucial, eminently possible, and much neglected. I thus hope other researchers take up the mantle for such studies as vegetarian versus pescetarian, because my team and I contend there may be a bigger fish to fry. Most of our time and energy is directed to a project all about putting what we do reliably know about diet and health to far better use for the benefit of people and planet alike.

There is, in general, something rather fishy about most claims regarding the single best way to eat. Namely, such tales tend to wag at us far more dogma than data. The matter is only decisively settled with research that for the most part has not been done, and at its logical extreme, almost certainly never will be.

As for fish per se, I am quite convinced that eating them is good for us in general, although maybe not compared to every conceivable baseline diet. But increasingly, I am preoccupied that eating them is clearly not good for the fish, or the oceans. The environmental impacts of our dietary choices are profound, and should be of increasing concern to all of us with an affection for this planet, or our children for that matter.

Claims about any given food or diet that go beyond the evidence are, in essence, fish tales- notorious for exaggeration. They are unfortunate, as they tend to obscure the reliability, volume, and consistency of evidence underlying genuinely common ground. Let us make our stand there, waders, optional.

David L. Katz, MD, FACP, MPH, FACPM, 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. He is a board certified specialist in both Internal Medicine, and Preventive Medicine/Public Health, and Associate Professor (adjunct) in Public Health Practice at the Yale University School of Medicine. He is the Director and founder (1998) of Yale University's Prevention Research Center; Director and founder of the Integrative Medicine Center at Griffin Hospital (2000) in Derby, Conn.; founder and president of the non-profit Turn the Tide Foundation; and formerly the Director of Medical Studies in Public Health at the Yale School of Medicine for eight years. This post originally appeared on his blog at The Huffington Post.

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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.

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.

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.

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.

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).

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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