Processed meat labels saying "uncured" and "no nitrites added" are misleading

A large body of evidence reviewed by the World Health Organization found that processed meat consumption increases the risk of cancer. Seeking to alleviate consumer concern, food companies label some of their products as "uncured" or "no nitrites added." However, these products may have essentially as much nitrites or nitrates as regular products.

In an August 29 report from Consumer Reports (CR), policy analyst (and Friedman School Ph.D. student) Charlotte Vallaeys explained the issue.

“Thanks to the topsy-turvy world of government food labeling rules, ‘no nitrites’ doesn’t mean no nitrites,” says Charlotte Vallaeys, senior food and nutrition policy analyst at CR. Instead, it means that the nitrates and nitrites used to “cure”—or preserve and flavor—meat come from celery or other natural sources, not synthetic ones, such as sodium nitrate or nitrite.

The issue was picked up in August by NPR in a report by Allison Aubrey.

This issue also is the subject of a new citizen petition from the Center for Science in the Public Interest (CSPI) and Consumer Reports, which in turn led USDA to open a public comment period until Nov. 12.

Meanwhile, I remain concerned that the federal government's Dietary Guidelines for Americans (DGA) for 2020-2025 may overlook scientific evidence on processed meat and cancer risk. It is important for USDA and DHHS to review this evidence directly, as its own topic, not just tangentially when it arises as part of broader studies of dietary patterns. That scientific issue was covered in a blog post in early August, noting our recent article in Milbank Quarterly.

In related work, my colleague Dr. David Kim and several co-authors and I have a new article in the American Journal of Preventive Medicine (AJPM), published today, with a modeling analysis of the health benefits that could arise if warning labels or a tax on processed meat effectively reduced intake and thereby reduced cancer risk. The abstract concludes:

The model shows that implementing tax or warning labels on processed meats would be a cost-saving strategy with substantial health and economic benefits. The findings should encourage policy makers to consider nutrition-related policies to reduce cancer burden.

Preventing chronic disease (evidence versus Google's featured snippets)

Scientifically dubious information may sometimes appear in Google's "featured snippets."

An online search -- in Google of course -- turns up all sorts of scammy sites offering advice on how to optimize web content so that it appears in these featured snippets.

When we Google "preventing Parkinson's", we get advice to consume the co-enzyme CoQ10, but research in the journal Neurological Science found no benefit.

Similarly, when we Google "preventing colon cancer," we get a featured snippet with advice from Mayo Clinic (a reputable source):

Make lifestyle changes to reduce your risk
You can take steps to reduce your risk of colon cancer by making changes in your everyday life. Take steps to:

• Eat a variety of fruits, vegetables and whole grains. Fruits, vegetables and whole grains contain vitamins, minerals, fiber and antioxidants, which may play a role in cancer prevention. Choose a variety of fruits and vegetables so that you get an array of vitamins and nutrients.
• Drink alcohol in moderation, if at all. If you choose to drink alcohol, limit the amount of alcohol you drink to no more than one drink a day for women and two for men.
• Stop smoking. Talk to your doctor about ways to quit that may work for you.
• Exercise most days of the week. Try to get at least 30 minutes of exercise on most days. If you've been inactive, start slowly and build up gradually to 30 minutes. Also, talk to your doctor before starting any exercise program.
• Maintain a healthy weight. If you are at a healthy weight, work to maintain your weight by combining a healthy diet with daily exercise. If you need to lose weight, ask your doctor about healthy ways to achieve your goal. Aim to lose weight slowly by increasing the amount of exercise you get and reducing the number of calories you eat.

That is mostly good advice, with one big omission. Authoritative research summaries from the World Cancer Research Fund (WCRF) and American Cancer Society (ACS) recommend lowering risk of colorectal cancer by eating less processed meats (such as bacon and sausage).

These authoritative sources appear further down the list of Google results for "preventing colon cancer," overshadowed by the incomplete information in the featured snippet.

Pretty much everything you read about cancer from authoritative sources is likely to be worth taking seriously

Here is my paraphrase of the most important results from a study by Schoenfeld and Ioannidis in the current issue of the American Journal of Clinical Nutrition:

• Meta-analyses do fairly well at correctly stating their conclusions.  Meta-analyses are quantitative literature reviews that combine results from across studies, essentially increasing the sample size and breadth.
• For example, Schoenfeld and Ioannadis looked at 9 meta-analyses showing an association between consuming particular foods (I think of foods such as fruits and vegetables) and reduced risk of cancer. For all 9, the results were statistically significant at conventional levels (p<.05).
• Schoenfeld and Ioannadis looked at 4 meta-analyses showing an association between consuming particular foods (I think of foods such as processed meats) and increased risk of cancer.  For 3 of the 4, the results were statistically significant at conventional levels (p<.05).
• While the meta-analyses did well at reporting results, individual studies sometimes report results in their abstracts even when they were not statistically significant.  Some of these reported results may be attributed to random happenstance rather than real cancer effects. This is why it is unwise to change eating habits with every new study.  It is wiser to rely on the balance of scientific evidence connecting particular foods to cancer risks and benefits.

Based on these results, you may be interested in the excellent collections of meta-analyses and systematic literature reviews available from a well-respected source such as the World Cancer Research Fund and the American Institute of Cancer Research. The new paper by Schoenfeld and Ioannadis reflects fairly well on the type of research posted by the WCRF and AICR.

But, journalists will report the conclusions of the new study to say something completely different from the above.  In the endless search for novelty, journalists write each day that everything you previously believed about diet and health is mistaken.

For example, Sarah Kliff at the Washington Post's Wonkblog writes today under the headline: "Pretty much everything you eat is associated with cancer. Don’t worry about it." 

Food industry public relations folks will love this message.

To make things worse, Kliff garbles the statistical material (see the comments to the Wonkblog post):

Don’t panic yet, though: The vast majority of those studies, Schoenfeld and Ioannidis found, showed really weak associations between the ingredient at hand and cancer risk. A full 80 percent of the studies had shown statistical relationships that were “weak or nominally significant,” as measured by the study’s P-values.

This description seems to ignore the meta-analyses and also it seems to describe perfectly fine statistically significant results (p<.05) as if they were "weak or nominally significant."

Perhaps the authors share some of the responsibility.  Kliff quotes the author:

“I was constantly amazed at how often claims about associations of specific foods with cancer were made, so I wanted to examine systematically the phenomenon,” e-mails study author John Ioannidis ”I suspected that much of this literature must be wrong. What we see is that almost everything is claimed to be associated with cancer, and a large portion of these claims seem to be wrong indeed.”

As with climate change skepticism, people twist genuine heterogeneity in scientific results to cast doubt on both marginal claims and widely accepted claims alike.  I wish that neither journalists nor authors would cavalierly say that most of the literature is wrong, when even the new study shows quite trustworthy results for the authoritative meta-analyses that actually merit attention from the public.

Just for example, the balance of scientific evidence from WCRF and AICR suggests that fruits and vegetables reduce risk and that red meats and processed meats increase risks of certain cancers.  Such conclusions based on meta-analyses fare well in the new AJCN study.