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

Tuesday, December 1, 2015

WHO classifies processed meats as carcinogenic

This week a group of researchers in the World Health Organization (WHO) released a study that caused a bit of a kerfuffle. The group, the International Agency for Research on Cancer (IARC), published a paper classifying processed meat as a carcinogen. What's processed meat? According to the authors, it's “meat that has been transformed through salting, curing, fermentation, smoking, or other processes to enhance flavour or improve preservation.” That includes products like hot dogs, salami, bacon, and jerky.

The headlines in the popular media are enough to make any meat lover go through all of Kubler-Ross's stages of grief. But before we foreswear hot dogs forever, let's understand exactly what the study found.

The first important point is to understand what the IARC does, and what it doesn't do. The IARC is only tasked with weighing evidence about whether substances increase the risk of cancer. They found fairly strong evidence that processed meat causes cancer. So they classified processed meat as a carcinogen in the same group as tobacco smoke, sunlight, and alcohol. All of the substances in this group have high-quality evidence suggesting that they increase the risk of certain cancers. What the IARC doesn't do is figure out the magnitude of that risk. Whether the cancer risk is huge or tiny is irrelevant to the IARC; they're just trying to impartially weigh the evidence that something is carcinogenic.

The group assessed more than 800 epidemiological studies and found a strong connection between the consumption of processed meat and cancer, especially colorectal and stomach cancer.

My regular readers will know that at this point I will usually object that none of the studies were randomized. It's true that to prove that a diagnostic test or a treatment is effective, I demand randomized evidence. But in studies of what we eat or how we live, randomization is frequently impossible. After all, the evidence that smoking causes lung cancer was all based on epidemiological (non-randomized) studies. It's fun to imagine randomizing thousands of people into 2 groups, and then insisting that one group never have processed meats, and feeding the second group a quarter pound of bacon daily. Then we would follow them for decades and count the cancer cases. That might be great science, but it would be an expensive logistical nightmare. So observational studies is as good as we're likely to get.

So let's figure out the magnitude of the cancer risk so we can have a sense of whether eating that next hot dog is comparable to going over Niagara Falls in a barrel, or more like walking on gravel while holding scissors.

The study found an 18% increase of colorectal cancer per 50 gram per day increase in consumption of processed meat. Some quick Googling revealed that a typical hot dog weighs 48 grams, very close to the 50 grams cited in the study. So a hot dog every single day will increase the risk of colorectal cancer by 18%. According to the American Cancer Society, the lifetime risk of colorectal cancer is 4.84%. An 18% increase in that risk would yield a 5.71% risk. Some quick arithmetic yields the conclusion that for every 115 people that switch from consuming no processed meats to eating a hot dog every single day, 1 additional case of colorectal cancer would result. That's a lot of hot dogs. A person eating a hot dog daily will consume tens of thousands of hot dogs. 115 of such people will consume millions of hot dogs. So it takes over a hundred people consuming millions of hot dogs to yield one additional case of colorectal cancer. That's not nothing, but it's a very small risk. Numerically, it's much, much smaller than the cancer risk from smoking.

If you have health concerns that guide what you should be eating, then the cancer risk from processed meat should be the last thing on your mind. If you have diabetes, you should minimize the amount of carbohydrates you eat. The risk from poor sugar control from eating the hot dog bun would be much higher than the cancer risk from eating the hot dog. So eat the hot dog, and forget the bun.

So, like much else in life, processed meats come with a small health risk. A serving of it once or twice a week is likely to increase your risk by so little, that it doesn't deserve your attention. If you want to do something meaningful to minimize your health risks, buckle your seatbelts, stop smoking, and have your cholesterol and blood pressure checked occasionally.
Learn more:
Meat Is Linked to Higher Cancer Risk, W.H.O. Report Finds (New York Times)
Bacon Causes Cancer? Sort of. Not Really. Ish. (Wired)
Red Meats Linked to Cancer, Global Health Group Says (Wall Street Journal)
Carcinogenicity of consumption of red and processed meat (The Lancet Oncology, free registration required)
Lifetime Risk of Developing or Dying From Cancer (American Cancer Society)

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
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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