"Eat too many hot dogs and they can bite you back." That’s how Associated Press "science writer" Paul Recer started his Feb. 25 article about a new study linking consumption of (nutritionally incorrect) processed meats with type 2 diabetes.
It’s too bad the witty Recer wasn’t clever enough to report the study as the junk science it is.
Harvard University researchers studied diabetes among 42,054 men who were healthy in 1986. The men were surveyed in 1986, 1990 and 1994 about their diets. The researchers reported in Diabetes Care (March 2002) that frequent consumers of processed meats had 46 percent more diabetes than infrequent consumers.
Based on these results, Recer prominently featured the researchers’ recommendation that eating processed meats five or more times per week is "too much" and "We should change that eating pattern."
Buried at the end of Recer’s article was the researchers’ passive assent to the need for more research. Recer should have spotlighted the need for more research rather than the dietary recommendation. After all, this was the first time processed meats were linked with diabetes and one study doesn’t equate to scientific fact.
That’s only the start of the problems with the reporting of this dubious study.
The reported 46 percent increase in risk is a weak and flaky statistical association with little credibility. As the National Cancer Institute notes, "In studies of disease patterns in human populations, risks of less than 100 percent are considered small and usually difficult to interpret. Such increases may be due to chance, statistical bias or effects of confounding factors that are sometimes not evident."
Recer knows this.
In an October 1994 AP article, Recer reported, "Women who have abortions may increase their risk of breast cancer by 50 percent, according to a new study in the Journal of the National Cancer Institute." Recer couldn’t wait to debunk that politically incorrect result. His second sentence read, "Experts say the conclusion needs more study."
Several paragraphs later Recer wrote, "Dr. Lynn Rosenberg, who reviewed the study, said the results are ‘very preliminary and have not been confirmed.’" Rosenberg also said the 50 percent increased risk found by the study is actually a very small added risk."
For Recer, then, a 50 percent increase in risk is too small for an abortion-breast cancer link, but not for a processed meats-diabetes link?
The new study’s dietary data is of questionable reliability. Study subjects were asked only 3 times over 18 years about what they ate.
The researchers tried to justify relying on these data by claiming correlation between one week’s diet and survey responses in a food frequency questionnaire filled out by 127 of the study subjects.
This argument simply is silly.
It’s easy to remember accurately what you ate last week. It’s much more difficult, if not impossible, to remember accurately what you ate five years ago. This well-known, insurmountable problem is called "recall bias."
Though Recer downplayed recall bias in the meat study, his December 1996 article about abortion and breast cancer dismissed the reputed link largely because of recall bias. If recall bias is a problem with abortion, wouldn’t it be an even bigger problem with dietary history? What are you more likely to remember?
The meat study’s most glaring weakness is its statistical nature. The researchers didn’t show scientifically that any of the diabetes cases were caused by processed meat consumption.
Though Recer has prominently noted that abortion-breast cancer studies are merely statistical in nature, he omitted this criticism from his meat study article.
The Harvard researchers hypothesize that nitrites used as a preservative in processed meats might somehow play a role in the onset of type 2 diabetes. But they presented no direct evidence to support this idea.
If nitrites were causally related to type 2 diabetes, other major dietary changes might be in order.
For example, someone eating a bacon, lettuce, and tomato sandwich will show an increase in blood nitrite levels. Some of the increase is due to the bacon. But a larger amount is due to the lettuce and tomato.
Should we limit salad consumption, too?
Diabetes is no laughing matter. Recer nevertheless found humor in unjustifiably scaring readers about processed meats. What’s really hilarious is the notion that Recer is a fair-minded science journalist.
Steven Milloy is the publisher of JunkScience.com , an adjunct scholar at the Cato Institute and the author of Junk Science Judo: Self-defense Against Health Scares and Scams (Cato Institute, 2001).