Thursday, May 15, 2014
What we don't know about eating fat
Most humans have spent most of human history nearly starving to death. So it’s no surprise that we spend a lot of time thinking about food. And it’s no surprise that food has acquired cultural, social, and religious significance in almost every society. Because food is so important, and because it’s nearly impossible for us not to ascribe powerful effects to anything important to us, every society imbues special health properties to various foods.
From believing that some foods are aphrodisiacs to believing that some foods improve sleep or fertility or athleticism, superstitions about the effects of food on health are ubiquitous. But we are modern, rational creatures that would never subscribe to such claptrap. Right? Wrong. We also cling to our own mythology about the health effects of food but we dress up our ignorance in scientific words. We (correctly) sneer at anyone who asserts that ingesting powdered rhinoceros horn improves erectile function. After all, there’s no scientific reason to even believe such a thing, and the connection between a rhinoceros horn and erectile dysfunction is purely visual. That’s like eating a giraffe because you want to be taller.
But take the assertion that eating saturated fat increases the risk of heart disease. We all believe that. After all, saturated fat is a molecule. Molecules are very scientific, which means there are men in white lab coats somewhere with blinky machines proving that saturated fats are very, very bad to eat. In fact, current cardiovascular guidelines from respected groups like the American Heart Association suggest low consumption of saturated fats and high consumption of polyunsaturated fats. And the American Heart Association would never recommend rhinoceros horn.
This is an important reminder that we know much less than we believe, but before we dive into it, allow me a paragraph to make sure we know what we’re talking about.
There are 3 families of energy containing molecules in food: fats, carbohydrates, and proteins. Fats are further subdivided into saturated fats and unsaturated fats. Saturated fats are typically found in dairy products and fatty meats and are typically solid at room temperature (like butter, lard, and beef fat). Unsaturated fats are found in vegetable oils and fish oils and are typically liquid at room temperature (like olive oil).
For decades we have been hearing and repeating to our patients that saturated fats are unhealthy for hearts and unsaturated fats are healthy. A meta-analysis (study of studies) published in the current issue of Annals of Internal Medicine attempted to review all the studies that have ever examined the link between saturated and unsaturated fats and cardiovascular health. What they found was underwhelming. There were 45 observational studies, the kind that I routinely criticize in my posts and urge readers to ignore. There were 27 randomized studies that looked at the effects of fatty acid supplementation on heart disease. All of them tested whether supplements of unsaturated fatty acids (like fish oil) helped prevent stroke and heart attacks. None of them tested whether supplements of saturated fatty acids (lard capsules!) increased cardiovascular risks.
The results were meh. The data as a whole showed no significant increase in risk from saturated fats, nor decrease in risk from unsaturated fats. The authors conclude: “[T]his analysis did not yield clearly supportive evidence for current cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of saturated fats.”
Not surprisingly none of the experts quoted in the media coverage said the simple truth, which is that we have no idea if dietary fats affect health apart from the calories they contain. It would be nice to hear an expert declare, “We have no clue about whether some fats are healthy or unhealthy” since that statement would be solidly supported by the evidence.
How did saturated fat’s bad reputation ever get started? I’m not sure. It’s conceivable some observational study that should have been ignored suggested that saturated fat was unhealthy. It’s also possible that saturated fat’s ignominy began because lard and butter look so much like the fat in a cholesterol plaque that blocks an artery. Olive oil is liquid. How could that block an artery? Maybe the whole idea was as simple-minded and as visual as the rhinoceros horn remedy.
Saturated Fat Is Back! (NPR)
Saturated fat ‘ISN’T bad for your heart’: Major study questions decades of dietary advice (Daily Mail Online)
Review questions effects of saturated fats on heart disease (Fox News)
Association of Dietary, Circulating, and Supplement Fatty Acids With Coronary Risk: A Systematic Review and Meta-analysis (Annals of Internal Medicine)
Even More Studies You Should Ignore (my last post about fish oil)
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. Holding privileges at Cedars-Sinai Medical Center, he is also an assistant clinical professor at UCLA's Department of Medicine. This post originally appeared at his blog.
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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, 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, 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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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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.
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.
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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)
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.
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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.
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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
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.
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.
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.
The Public Library of Science's open access materials include a blog.
One of the most popular anonymous blogs written by an emergency room physician.