[My post building on this piece, “Single-Study Syndrome and the G.M.O. Food Fight,” is published at Dot Earth.]
Anti-GMO groups push new study claiming big impacts on longevity, cancer rates in rats fed Roundup-ready corn. Study has quickly attracted scientific criticism. One issue is the rat breed (they normally develop tumors after two years). Single-study syndrome?
[UPDATE 10 p.m.: The food researcher and writer Marion Nestle, a supporter of GM labeling, called the study “weirdly complicated” in an excellent look at the work posted by Tim Carman of the Washington Post.]
[UPDATE Sept. 20, 6:45 a.m.: In Rosie Mestel’s Los Angeles Times article, one scientist said the combination of a tumor-prone rat breed and small sample size created big problems: “Another red flag was that tumor rates didn’t increase in line with the dose of GMOs fed to animals, as scientists would expect to see if the genetically engineered corn were to blame, said Kevin Folta, a plant molecular biologist at the University of Florida in Gainesville. Instead, ‘you are likely seeing variation of normal tumor incidence in a small population of rats,’ he said.”]
For a broader view of the literature on animal diets and GM, read this review paper from 2011: ”Assessment of the health impact of GM plant diets in long-term and multigenerational animal feeding trials: A literature review”
The aim of this systematic review was to collect data concerning the effects of diets containing GM maize, potato, soybean, rice, or triticale on animal health. We examined 12 long-term studies (of more than 90 days, up to 2 years in duration) and 12 multigenerational studies (from 2 to 5 generations). We referenced the 90-day studies on GM feed for which long-term or multigenerational study data were available. Many parameters have been examined using biochemical analyses, histological examination of specific organs, hematology and the detection of transgenic DNA. The statistical findings and methods have been considered from each study. Results from all the 24 studies do not suggest any health hazards and, in general, there were no statistically significant differences within parameters observed. However, some small differences were observed, though these fell within the normal variation range of the considered parameter and thus had no biological or toxicological significance. If required, a 90-day feeding study performed in rodents, according to the OECD Test Guideline, is generally considered sufficient in order to evaluate the health effects of GM feed. The studies reviewed present evidence to show that GM plants are nutritionally equivalent to their non-GM counterparts and can be safely used in food and feed.
[UPDATE, Sept. 20: For more on risks, Roundup-ready corn (the variety used in the study) and the herbicide Roundup, read geneticist Michael Eisen’s June blog post: “#GMOFAQ How Bt corn and Roundup Ready soy work, and why they should not scare you.”]
Some good points on why people shouldn’t be jumping to conclusions over this study. If a second study that is conducted in a better way confirms the results, by all means, worry.