Dietary guidelines, processed meat, and risk of cancer

In a public comment submitted today, my colleagues Fang Fang Zhang, Jennifer Pomeranz, and I encourage the 2020-2025 Dietary Guidelines Advisory Committee (DGAC) to evaluate the entire scientific literature on processed meat and colon cancer risk.

The DGAC is the external committee that summarizes the scientific evidence on nutrition and health, which two federal departments, USDA and DHHS, then use in writing the actual Dietary Guidelines for Americans, an influential document in U.S. nutrition policy.

USDA and DHHS have determined that the 2020-2025 DGAC may only address topics that were explicitly given in a list of questions by the departments.

One of the questions is: "What is the relationship between dietary patterns consumed and risk of certain types of cancer?"

Our public comment today recommends that the DGAC include the entire scientific literature on processed meat and cancer risk, as part of its systematic review of evidence on dietary patterns and cancer.

Why is this even in doubt?

As our recent article in the Milbank Quarterly recounts, in the previous 2015-2020 Dietary Guidelines for Americans, the federal government muddled its message on processed meat and cancer.

On the one hand, it included lower intake of processed meat in a list of characteristics of healthy eating patterns: "Lower intakes of meats, including processed meats; processed poultry; sugar-sweetened foods, particularly beverages; and refined grains have often been identified as characteristics of healthy eating patterns."

On the other hand, it said that processed meats can be recommended as long as sodium, saturated fats, added sugars, and total calories are within limits. This latter favorable comment in the official policy document from USDA and DHHS had no basis in the earlier independent scientific report from the 2015-2020 DGAC.

Even though it is not responsible for the final DGA report, we think the 2015-2020 DGAC report may have overlooked some of the important research on processed meat and colon cancer, by interpreting the words "dietary patterns" too strictly, screening out some research on processed meat merely because this one food category is not a "dietary pattern."

Why is the cancer risk from processed meat important?

The issue is important because the best available systematic literature reviews concluded that consuming processed meat increases the risk of colon cancer. In particular, see authoritative reports from the International Agency for Research on Cancer and the World Cancer Research Fund and American Institute of Cancer Research.

Luxian Zeng, Fang Fang Zhang, other colleagues, and I recently reported in the Journal of the Academy of Nutrition and Dietetics (JAND) on trends in processed meat intake based on data from the Nutrition and Health Examination Survey (NHANES). While red meat declined, processed meat held steady in recent years. This issue is big enough to matter for national nutrition policy.

What are the policy implications of ignoring this issue?

Currently, far from encouraging reductions in processed meat intake, the federal government supports advertising and marketing programs to increase consumption. The semi-public checkoff programs have been covered previously in this blog. Just to give one current illustration, here is advertising from the federal government's pork checkoff program for bacon and ice cream. If the Dietary Guidelines for Americans were based on a full evaluation of the scientific literature about processed meat and colon cancer, it might facilitate policies to encourage reductions, or at the very least a halt to these advertising programs encouraging yet more processed meat consumption.

National Pork Board advertising endorsed by USDA.