Fact Check: PCRM’s Dietary Guidelines for Cancer Prevention
Yesterday the Physicians’ Committee for Responsible Medicine (PCRM), a pro-vegan advocacy group, issued its own Dietary Guidelines for Cancer Prevention. In drawing up these guidelines, PCRM interpreted scientific evidence previously collected and analyzed in the American Institute for Cancer Research/World Cancer Research Fund Expert Report.
We at AICR are always pleased to see our reports on cancer risk’s connection to diet, weight management and physical activity cited as the authoritative resources we know them to be. We pride ourselves on our reports’ scientific rigor, comprehensiveness and – above all – objectivity. Physicians, nurses, registered dietitians, researchers, educators, and policy makers rely on our reports for authoritative and evidence-based guidance.
This is why, on those occasions when any advocacy group cites our reports to advance their message, it is important to clarify the distinctions between what that advocacy group is saying, and what our own independent panel of experts has concluded.
Bottom Line: Focus on Plant Foods
When it comes to the take-home message, both the AICR Dietary Guidelines for Cancer Prevention and the PCRM Dietary Guidelines for Cancer Prevention focus on eating a variety of plant foods.
PCRM’s recommendations to decrease cancer risk also include avoiding dairy foods and alcohol, avoiding both red and processed meats, not cooking any meats, including fish, at high temperatures, and consuming soy in particular.
Their recommendations on avoiding alcohol and processed meats echo AICR’s own. But in other areas, our rigorous process of scientific review reached slightly different conclusions.
AICR’s analysis of the available evidence strongly suggests that vegetables, fruits, whole grains and beans should be the focus of each meal – we suggest filling at least 2/3 of your plate with plant foods, leaving only 1/3 or less of for animal protein (meat or dairy). That “or less” is an important part of AICR’s message – we acknowledge that individuals may wish to eliminate animal foods from their diets for a host of reasons, and offer guidance to help them do so.
But while AICR’s Guidelines for Cancer Prevention do include the advice to limit red meat (beef, lamb, pork) intake to 18 ounces (cooked) per week, and to avoid processed meat (hot dogs, cold cuts, sausage, bacon), there was insufficient evidence on poultry and fish to reach any conclusion.
And while our report found that diets high in calcium are a probable risk factor for prostate cancer, it also found that milk intake is linked to a lower risk for colon cancer. Because AICR’s Recommendations address themselves to all cancers, the AICR expert panel chose to offer no recommendation on dairy intake, at least until more data and subsequent analyses clarify the issue.
The evidence in this area, and many others, including soy and high-temperature cooking, is still emerging, and the process of updating the conclusions of the 2007 AICR/WCRF Expert Report is now well underway. Although PCRM did not cite them, we have produced several Continuous Update Project (CUP) Reports, cancer site by cancer site, which are adding to our understanding, and will be consulted by AICR’s expert panel as they update our Dietary Recommendations in 2017.
Diet Is Not The Whole Story
It’s worth noting that the PCRM Dietary Guidelines for Cancer Prevention focus exclusively on food choices, and make no mention of the link between obesity and cancer risk. This is concerning, as obesity is on track to overtake smoking as the number one cause of preventable cancer in the U.S.
Excess body fat is a clear risk factor for eight different cancers (colorectum, postmenopausal breast, esophagus, endometrium, kidney, pancreas, gallbladder and ovary. This is why the first of AICR’s Dietary Guidelines for Cancer Prevention is to avoid overweight and obesity.
Evidence also shows that regular physical activity lowers risk for cancer, both by helping to prevent obesity and by regulating the body’s hormone levels in protective ways.
AICR’s Expert Report and follow-up CUP Reports clearly and consistently show that diet is only one aspect of a cancer-protective lifestyle. This is why our messages about cancer prevention always include information about weight management and physical activity alongside messages about dietary change.
AICR is pleased to see our hard work cited. But the public needs to know the difference between a global, objective analysis of the available evidence and one advocacy group’s interpretation of it.