I am a strong supporter of labeling GMO foods. Consumers have the right to know. That’s enough of a reason to support California’s Prop. 37. There is no need to muddy the waters with difficult-to-interpret science. My e-mail inbox was flooded with messages yesterday about the new long-term rat study reporting that both GMO corn and Roundup (glyphosate herbicide) increase mammary tumors in mice. The study, led by Gilles-Eric Séralini, concludes:

The results of the study presented here clearly demonstrate that lower levels of complete agricultural glyphosate herbicide formulations, at concentrations well below officially set safety limits, induce severe hormone-dependent mammary, hepatic and kidney disturbances… the significant biochemical disturbances and physiological failures documented in this work confirm the pathological effects of these GMO and R treatments in both sexes.

These results are so graphically shocking (see the paper’s photographs), and so discrepant from previous studies (see recent review in the same journal), that they bring out my skeptical tendencies. (Note: Although Séralini is apparently a well known opponent of GMOs, his study–and that of the review–were funded by government or other independent agencies). For one thing, the study is weirdly complicated. To its credit, it went on for two years (much longer than the typical 90 days for these kinds of studies). But it involves ten separate groups of 20 mice each (10 males and 10 females) fed diets containing GMO (Roundup-resistant) corn, grown with Roundup or not, or fed control diets (non-GMO corn) with or without Roundup added to their drinking water at three different levels. I needed a table to keep this straight. CONTROL AND TREATMENT GROUPS GROUP %CORN IN DIET CORN TREATED WITH GIVEN ROUNDUP TO DRINK ROUNDUP HERBICIDE Non-GMO Control 33% No GMO Corn 11% No GMO Corn 22% No GMO Corn 33% No GMO Corn 11% Yes GMO Corn 22% Yes GMO Corn 33% Yes Non-GMO Corn 33% No 0.1 ppb (level in tap water). Non-GMO Corn 33% No 0.09% (level contaminating feed) Non-GMO Corn 33% No 0.5% (half the level used in agriculture) Complicated studies require careful interpretation. Here are the main tumor results.

LINES: The dotted line is the control. The three corn doses (11%, 2 2%, 33%) correspond to thin, medium and bold lines, respectively. BARS: 0 = Control. R = Roundup. A, B, and C correspond to the three levels of Roundup in drinking water.

Besides complications, the study raises several issues:

Incomplete data: the authors state that “All data cannot be shown in one report and the most relevant are described here.” I’d like to know more about what the control rats ate and whether there were differences in the amounts of diets consumed, for example. – Lack of dose response: the authors explain that 11% did as much harm as 33% as a threshold effect. This requires further study to verify. – Statistical significance: The paper doesn’t report confidence intervals for the tumor data (the bars don’t look all that different to me).

The California Prop. 37 proponents (and I’m totally with them) already have a strong “right to know” argument. They don’t need to be distracted by the kinds of scientific arguments that are already raging about this study (see, for example, the British Science Media Centre’s collection of criticisms). For more information about the study: The British Sustainable Food Trust has a website devoted to this study. Tim Carman wrote about it in the Washington Post (I’m quoted) Andrew Pollack has a sensible piece in the New York Times France calls for a ban on GM foods Additional clarification: I very much favor research on this difficult question. There are enough questions about this study to suggest the need for repeating it, or something like it, under carefully controlled conditions. This article originally appeared in Food Politics September 20, 2012.

  • Yrrek

    Thank you for all the links. I really appreciate it when online news articles link to their sources and items being referenced.

  • I think we also need to caution strongly about jumping to conclusions about GMO foodstuffs as a whole from the basis of one study from one GMO food. This study is further complicated by the tie-in between the use of the herbicide RoundUp and the GMO resistance to RoundUp. The only conclusive result I see from the graphs is that female rats have a much higher rate of tumors.
    There are other uses of GMO besides RoundUp resistance. One of our customers is developing a GMO cantaloupe with a smooth skin which would improve food safety by allowing it to be thoroughly washed.

  • Maje

    This is what I don’t get. What is the difference if the poison is in a little bit or a lot for how long. Isn’t a poison, still a poison? If you continue to eat little bits of poison, every day, don’t you think that it would co-inside with all the health related problems for the past few years?

  • cómo es posible que hayan sacado un producto modificado sin un profundo estudio sobre su implicancia en la salud? seguimos a merced de las grandes corporaciones? ésta es una forma de hacer control de natalidad en connivencia con la industria farmacéutica? da para pensar que seguimos siendo borregos que nos mueven como quieren… 🙁
    Translation: “How they may have taken a modified product without a thorough study of its implications on health? Still at the mercy of large corporations? This is a way to make birth control in collusion with the pharmaceutical industry? Gives to think that we are still moving sheep as we want … : (

  • Ena Valikov

    I found your responses rational and measured. I feel compelled to add
    1. The OECD regulatory framework calls for the number of experimental animals used in the study. This is the same framework used by GMO manufacturers to show the food is safe to eat; with the only difference being that the duration is only 90 days
    2. We should be questioning whether 90 days is a period sufficient to notice ANY chronic adverse effects. Even if one were to discount most of the study the inescapable fact remains that none of the adverse effects would be see in 90 days!
    3. I agree that LONG TERM feeding trials and replication of this study is very important; if you do a literature search, you will Not find long term feeding trials (of 2yrs duration)of any significance in the literature, while we are expected to eat these novel foods for Generations.

  • candy

    Just think if these studies were done before the GMO corn was introduced into the market place…
    That is the most disturbing thing about GMOs – insufficient research prior to approval for use and no or insufficient studies on consuming the pesticide residuals on the plants.
    The FDA failed the people on this and Chemical companies have made their profits at a great cost to us.

  • Yrrek

    Having re-read through your op-ed piece here and the article itself, I notice you’ve got a discrepancy. The study used rats while you call them mice. It’s a relatively minor detail, but what’s up with that? You clearly read the article so it seems weird to have made that mistake and continually repeated it.

  • michael sentkewitz

    GMO’s will be the death of us. I ofen wonder if the people behind this science eat the food they are trying to force on the public

  • Here is a response to this study: