GMO corn: a scientific study

A recent study from France (paper is here but not free) showed that genetically-modified corn negatively affected the health of rats. The press is reporting on this in a variety of ways, and I think there is a lot of bad information in the articles I am seeing. Science is messy, so it is impossible to have a straightforward take-away (like "GMO's are bad") from this study. I'll try to clarify what I can...

1. What is this GMO corn? Why does it exist?

   This corn is a genetically modified organism (GMO) that was made in a laboratory to be immune from Roundup, a weed control chemical. If a farmer plants a field with this corn the entire field can be sprayed with Roundup to control weeds. Normal corn would be hurt by Roundup.

2. What experiment was done?

   Scientists in France fed rats different food for 2 years. The different groups were:

   • Normal water and non-GMO corn (not treated with Roundup)
   • Normal water and a mix of normal and GMO corn in 3 different fractions (not treated with Roundup)
   • Normal water and a mix of normal and GMO corn in 3 different fractions (Treated with Roundup)
   • Water with different levels of Roundup in it and non-GMO corn (not treated with Roundup)
   This means that the researchers should be able to see if the presence of Roundup is having an effect and separately they should be able to see if the GMO corn alone has an effect.

   The researchers took blood samples from the rats periodically to study their health and studied the rats' organs after the rats died.

3. Did the GMO corn have an effect?

This is where science is hard. The answer isn't a clear yes or no - it has lots of caveats and statistics. Female rats died earlier from GMO corn (with or without Roundup) and earlier from Roundup alone. Male rats don't show as strong of an effect. Tumors usually developed earlier in female rats, especially when drinking roundup directly.

But not all of the data make sense. For instance, blood chemicals were used to look for evidence of kidney failure. The results look bad for GMO corn only and Roundup only, but the GMO corn with roundup doesn't show a measurable effect.

Bottom Line: The data presented in the paper cannot exclude a hypothesis that Roundup and GMO corn does not affect the health female rats.

What about the criticisms and responses? Many of the responses particularly frustrated me:

1. Each group was only 10 rats. That isn't big enough to see anything!

Biology is really hard, and it is super expensive to take care of and monitor 200 rats for 2 years. This is a HUGE study compared to what I see in pre-clinical cancer research. This study could be used to get funding for a much bigger study, but studies don't get much bigger than this.

2. These were a special type of rat that gets cancer easily. Of course they got cancer!

These are the epitome of white lab rats. It made perfect sense to use these.

3. The health problems didn't increase with increasing dose. So this is just random variation, not causality.

It could be a threshold effect - there is a dose window where it increases, but above that there is no change. This is relatively common and makes sense - after all, taking 10 times a normal dose of medicine won't make you 10 times better...

4. Other studies have shown that GMO's are safe

This is true. But, this study has gone longer and looked at more variables than some other studies have. Additionally, you should ask how many of the "other studies" were funded by Monsanto or other groups that want to show GMO's are safe. I'm not saying the other studies are all bad, but each study needs to be evaluated individually rather than counting the number results that say "effect" versus "no effect".

Apparently the French Prime Minister has released a statement saying "I have demanded a fast procedure, about a few weeks, to verify the scientific value of the study". Unfortunately, the best way to verify scientific value is to repeat the study. That will take more than 2 years! It is possible for other scientists to review the data from the study. Also, further statistical analysis could be done on the data.

These types of GMO crops are relatively new and it is possible there could be health effects we don't yet understand. This study shouldn't cause you to panic and not eat corn, but more study is warranted.