The connection between diet, obesity, and cancer: Nutrition experts explore the evidence

Dietary and lifestyle changes guided by registered dietitian nutritionists and other professionals can help reduce the incidence and progression of obesity-related cancers and support the recovery of cancer survivors


Philadelphia, March 27, 2018

About one third of cancer cases are estimated to be linked to dietary and other modifiable risk factors, especially for obesity-related cancers such as breast, colorectal, ovarian, endometrial, kidney, gallbladder, esophageal, and pancreatic cancers. In this special theme issue of the Journal of the Academy of Nutrition and Dietetics, food and nutrition practitioners and other health professionals take an in-depth look at the relationship between nutrition, obesity, and cancer prevention, treatment, and survival and identify research gaps for future prevention research efforts.

The United States has a high burden of cancer. The American Cancer Society estimates there will be more than 1.7 million new cases diagnosed in 2018 and around 610,000 cancer deaths. Studies strongly suggest that diet is associated with cancer and that obesity increases the risk of many types of cancer as well as several chronic diseases, including type 2 diabetes, cardiovascular disease, hypertension, and chronic inflammation.

Key issue highlights:

Obesity prevalence in the US has tripled over the last 50 years. In 2016, a report by the International Agency for Research on Cancer highlighted that excess body fatness increases the risk for 13 types of cancer. Lead investigator Stephen D. Hursting, PhD, MPH, professor, Department of Nutrition, University of North Carolina at Chapel Hill, and colleagues review the multiple mechanisms underlying the obesity-cancer link. Their detailed review also assesses the dietary interventions that are being implemented in preclinical and clinical trials.

Image of men's and women's obesity associated with increased risk of developing and dying from various cancers

Obesity is associated with increased risk of developing and dying from the following cancers: breast (in postmenopausal women), ovarian, liver, gallbladder, kidney (renal cell), colon, pancreatic, gastric, esophageal (adenocarcinoma), endometrial, thyroid, multiple myeloma, and meningioma. Obesity is also associated with progression (but not incidence) of prostate cancer.

“Obesity-associated metabolic perturbations are emerging as major drivers of obesity-related cancer, including alterations in growth factor signaling, inflammation, and angiogenesis,” explained Dr. Hursting. “Preclinical evidence suggests that dietary interventions, such as calorie restriction, intermittent fasting, low-fat diet and the ketogenic diet, have the potential to reverse some of these obesity-associated alterations; however, more clinical data are needed to confirm translation to human subjects.”

A group led by Guido Eibl, MD, from the Department of Surgery, David Geffen School of Medicine at UCLA, on behalf of the Consortium for the Study of Chronic Pancreatitis, Diabetes, and Pancreatic Cancer, reviews the current knowledge pertaining to obesity and type 2 diabetes as risk factors for pancreatic ductal adenocarcinoma (PDAC), one of the deadliest cancers. Although the risk factors promoting PDAC development have been known for several decades, their underlying molecular mechanisms and interactions have just recently begun to be explored. The article highlights the risk factors for PDAC development and progression, their interplay and underlying mechanisms, and the relation to diet, and outlines research gaps and opportunities.

High quality epidemiologic studies associate obesity with an increased risk of PDAC, however, there are many unanswered questions. For example, the beneficial effects of weight reduction and bariatric surgery on improving insulin resistance are known, but their role in decreasing PDAC incidence is still essentially unknown.

“Altogether, given the high mortality of PDAC and the expected increase in obesity and diabetes over the next few decades, efforts should be undertaken to mechanistically understand the link between obesity, diabetes, and PDAC. Preclinical animal models are available that will facilitate the study of these important interactions to advance our knowledge, so that the obesity- and diabetes-driven burden of PDAC can be curbed,” commented Dr. Eibl.

Consumption of dietary energy density (DED) has been associated with weight gain in adults. DED is the ratio of energy (kilocalories or kilojoules) intake to food weight (grams) and is a measure of diet quality. Cynthia A. Thomson, PhD, RD, professor, Mel and Enid Zuckerman College of Public Health, The University of Arizona, and colleagues present results of an investigation into the association between baseline DED and obesity-associated cancers in over 90,000 postmenopausal women enrolled in the observational study or the calcium and vitamin D trial and hormone replacement therapy trials of the Women’s Health Initiative. Investigators found that DED was associated with higher risk of any obesity-related cancer. Of note, the higher risk was restricted to women with normal BMI.

“The demonstrated effect in normal-weight women in relation to risk for obesity-related cancers is novel and contrary to our hypothesis,” remarked Dr. Thomson. “This finding suggests that weight management alone may not protect against obesity-related cancers if women favor a diet pattern indicative of high energy density. Higher DED in normal-weight women may promote metabolic dysregulation independent of body weight, an exposure known to increase cancer risk.

DED is a modifiable risk factor. Nutrition interventions targeting energy density as well as other diet-related cancer preventive approaches are warranted to reduce cancer burden among postmenopausal women.

In a pilot intervention among 46 cancer survivors aged 60 years or older, Wendy Demark-Wahnefried, PhD, RD,professor of Nutrition Science, University of Alabama at Birmingham, and colleagues, posed the question of whether a home vegetable gardening intervention was feasible among older cancer survivors, and whether it was associated with improvements in diet and other health-related outcomes. Participants were randomized to receive a year-long vegetable gardening intervention immediately or to a wait-list control arm.

Investigators found the gardening intervention was well accepted, safe, and feasible and also significantly improved reassurance of worth and reduced gains in central adiposity. Data also suggested that it increased vegetable and fruit consumption by approximately one serving per day.

“Results suggest that future larger studies are warranted. A fully powered randomized controlled trial is currently underway and recruiting 426 older cancer survivors across Alabama,” noted Dr. Demark-Wahnefried.

Nancy J. Emenaker, PhD, MEd, RDN, LD, and Ashley J. Vargas, PhD, MPH, RDN, both registered dietitian nutritionists from the National Institutes of Health, review the scientific evidence linking diet and cancer. They explain the inconsistencies in the nutrition and cancer scientific literature and the issues that registered dietitian nutritionists (RDNs) face when translating this complex information for patients.

“RDNs are uniquely positioned to provide balanced, evidence-based information from peer-reviewed literature to help at-risk and cancer patients understand the strength of the evidence guiding individual health decisions,” observed Dr. Emenaker and Dr. Vargas. “Despite the best efforts of nutrition science researchers, inconsistencies exist across the diet-cancer prevention scientific literature. Clinical trials are the gold standard of research, but the body of scientific data should be compelling before translating scientific findings to our at-risk, presumed healthy patients for disease prevention and patients with a good prognosis undergoing treatment.”

“RDNs play such an important role in both cancer prevention and cancer care. Our profession is involved in research to investigate diet-cancer relationships, as well as supporting individuals and communities in making lifestyle changes for cancer prevention and treatment. RDNs are integral in providing quality care by implementing evidence-based interventions,” added Linda Snetselaar, PhD, RDN, LD, endowed chair and professor, Department of Epidemiology, College of Public Health, University of Iowa, and Editor-in-Chief of the Journal of the Academy of Nutrition and Dietetics.

---

Notes for editors
The articles are:

“Translating Mechanism-Based Strategies to Break the Obesity−Cancer Link: A Narrative Review,” by Laura A. Smith, MPH, RD; Ciara H. O’Flanagan, PhD; Laura W. Bowers, PhD, RD; Emma H. Allott, PhD; and Stephen D. Hursting, PhD, MPH (DOI: https://doi.org/10.1016/j.jand.2017.08.112)
Author contact: Stephen D. Hursting at hursting@email.unc.edu

“Diabetes Mellitus and Obesity as Risk Factors for Pancreatic Cancer,” by Guido Eibl, MD; Zobeida Cruz-Monserrate, PhD; Murray Korc, MD; Maxim S. Petrov, MD, PhD, MPH; Mark O. Goodarzi, MD, PhD; William E. Fisher, MD; Aida Habtezion, MD; Aurelia Lugea, PhD; Stephen J. Pandol, MD; Phil A. Hart, MD; and Dana K. Andersen, MD (http://dx.doi.org/10.1016/j.jand.2017.07.005)
Author contact: Guido Eibl, at Geibl@mednet.ucla.edu

“Association between Dietary Energy Density and Obesity-Associated Cancer: Results from the Women’s Health Initiative,” by Cynthia A. Thomson, PhD, RD; Tracy E. Crane, PhD, RD; David O. Garcia, PhD; Betsy C. Wertheim, MS; Melanie Hingle, PhD, MPH, RDN; Linda Snetselaar, PhD, RDN; Mridul Datta, PhD, RD; Thomas Rohan, MBBS, PhD, DHSc; Erin LeBlanc, MD, MPH; Rowan T. Chlebowski, PhD; and Lihong Qi, PhD, MS (http://dx.doi.org/10.1016/j.jand.2017.06.010)
Author contact: Cynthia A. Thomson at cthomson@email.arizona.edu

“Pilot Randomized Controlled Trial of a Home Vegetable Gardening Intervention among Older Cancer Survivors Shows Feasibility, Satisfaction, and Promise in Improving Vegetable and Fruit Consumption, Reassurance of Worth, and the Trajectory of Central Adiposity,” by Wendy Demark-Wahnefried, PhD, RD; Mallory G. Cases, PhD; Alan B. Cantor, PhD; Andrew D. Frugé, PhD, RD; Kerry P. Smith, MS; Julie Locher, PhD; Harvey J. Cohen, MD; Yuko Tsuruta, MD, PhD; Michael Daniel, Rishabh Kala, PhD; and Jennifer F. De Los Santos, MD https://doi.org/10.1016/j.jand.2017.11.001)
Author contact: Wendy Demark-Wahnefried at demark@uab.edu

“COMMENTARY: Nutrition and Cancer Research: Resources for the Nutrition and Dietetics Practitioner,” by Nancy J. Emenaker, PhD, MEd, RDN; and Ashley J. Vargas, PhD, MPH, RDN (https://doi.org/10.1016/j.jand.2017.10.011)
Author contact: Nancy J. Emenaker at emenaken@mail.nih.gov

They appear in the Journal of the Academy of Nutrition and Dietetics, volume 118, issue 4 (April 2018) published by Elsevier.

For the complete table of contents visit http://jandonline.org/issue/S2212-2672(17)X0006-3. Full text of these articles is available to credentialed journalists upon request. Contact Eileen Leahy at +1 732 238 3628 or andjrnlmedia@elsevier.com to obtain copies.

Information specifically for journalists is located at http://jandonline.org/content/media.

Related videos
ONCOLOGY AND NUTRITION: APRIL 2018 JAND ISSUE HIGHLIGHTS

http://jandonline.org/pb/assets/raw/Health%20Advance/journals/jand/jand_ec_118_4.mp4

EDITOR’S PODCAST ON CANCER AND DIABETES:
Pancreatic Cancer: The New Type 3c Diabetes JAND Editor-in-Chief Linda Snetselaar, PhD, RDN, LD, FAND interviews Dana K. Andersen, MD, with the National Institute of Diabetes and Digestive and Kidney Diseases. Drs. Snetselaar and Andersen discuss the physiological connection between cancer and diabetes, the difference between type 2 diabetes and type 3c, and the role of dietary intervention in treatment.
http://jandonline.org/pb/assets/raw/Health%20Advance/journals/jand/jand_ec_118_4_a.mp4

AUTHOR’S VIDEO: DED AND OBESITY-ASSOCIATED CANCER
http://jandonline.org/pb/assets/raw/Health Advance/journals/jand/jand_pr_117_8_1.mp4

About the Journal of the Academy of Nutrition and Dietetics
The official journal of the Academy of Nutrition and Dietetics, the Journal of the Academy of Nutrition and Dietetics is the premier source for the practice and science of food, nutrition, and dietetics. The monthly, peer-reviewed journal presents original articles prepared by scholars and practitioners and is the most widely read professional publication in the field. The Journal focuses on advancing professional knowledge across the range of research and practice issues such as: nutritional science, medical nutrition therapy, public health nutrition, food science and biotechnology, food service systems, leadership and management and dietetics education. www.jandonline.org

About the Academy of Nutrition and Dietetics
The Academy of Nutrition and Dietetics is the world’s largest organization of food and nutrition professionals. The Academy is committed to improving the nation’s health and advancing the profession of dietetics through research, education, and advocacy. www.eatright.org

About Elsevier
Elsevier is a global information analytics business that helps institutions and professionals advance healthcare, open science and improve performance for the benefit of humanity. Elsevier provides digital solutions and tools in the areas of strategic research management, R&D performance, clinical decision support and professional education, including ScienceDirect, Scopus, SciVal, ClinicalKey and Sherpath. Elsevier publishes over 2,500 digitized journals, including The Lancet and Cell, more than 38,000 e-book titles and many iconic reference works, including Gray's Anatomy. Elsevier is part of RELX Group, a global provider of information and analytics for professionals and business customers across industries. www.elsevier.com

Media contacts
Eileen Leahy
Elsevier
+1 732 238 3628
andjrnlmedia@elsevier.com

Rhys Saunders
Academy of Nutrition and Dietetics
+1 800 877 1600, ext. 4769
media@eatright.org