First ever long-term GM feeding study on pigs

August 2013
... more than 150 scientific studies have been done on animals fed biotech crops and to date, there is no scientific evidence of any detrimental impact” (biotech representative, CropLife International).
With a bit of cherry-picking of what constitutes appropriate scientific evidence this may be true. However, it's easy to see why no 'detrimental impact' has emerged. The 'scientific studies' has been largely based on animal models with little relevance to humans, on diets restricted to single GMOs, on very short time-scales, and on superficial data relevant only to commercial livestock production.

When a team of Australian and American scientists, led by Dr. Judy Carman, carried out an experiment which avoided the above short-comings, it raised concerns.

Carman's study used pigs (whose physiology is close to humans) and a real-life situation. The animals lived for their normal commercial life-span of 22-23 weeks when adulthood is attained. They were fed a routine mixture of GM corn and GM soya in feed closely controlled for texture and nutritional quality. Extensive data on growth, mortality, feed intake, blood parameters and organ changes were collected.

Significantly, the results on body weight and standard blood biochemistry, which the biotech industry have persuaded regulators are sufficient endpoints in health assessments, were entirely normal. However, a 25% increase in uterine weight in GM-fed pigs was suggestive of endocrine disruption, and a two- to four-fold higher incidence of severe stomach inflammation indicated chronic digestive system problems.

These are very important findings in view of the background to this investigation: the anecdotal evidence put forward by pig farmers.

An Iowa-based crop and livestock adviser and farmer reported
“For as long as GM crops have been in the feed supply, we have seen increasing digestive and reproductive problems in animals ... In my experience, farmers have found increased production costs and escalating antibiotic use when feeding GM crops. In some operations, the livestock death loss is high, and there are unexplained problems including spontaneous abortions, deformities of new-born animals, and an overall listlessness and lack of contentment in the animals. In some cases, animals eating GM crops are aggressive. This is not surprising, given the scale of stomach irritation and inflammation now documented.”
In Denmark, GM-associated diarrhoea , bloat and ulcers vanished when the pigs reverted to their conventional diet (see DANISH PIG FARMER WHISTLE-BLOWER - May 2012).

A previous, very short-term (31-day) experiment on male piglets fed a diet of MON810 'Bt' insecticidal maize recorded an increase in 'goblet cells' in the gut lining (see PIG FEEDING STUDY NOT REASSURING - February 2012). Goblet cells secrete a protective mucus layer. An increase in their numbers is a first response to the presence of harmful materials passing through.

It is these sick animals which become our food.

Predictably, the usual furore of criticisms erupted in response to the hint of GM-bad-news.

Mark Lynas, self-styled GM champion (see WHEN NON-NEWS IS BAD NEWS - April 2013) cherry-picked a few figures from Carman's data and tried to allege they were statistically significant (they weren't) and that they were being deliberately ignored. As Carman pointed out, only statistically significant findings were discussed in the paper “because this is the scientifically credible approach”. Lynas' claim that his (non-professional) reading of the scientific literature on climate change, has given him what it takes to understand GM technology is exposed for what it is.

Monsanto leapt (before it looked) to suggest that the uterine weight increases were simply caused by the pigs coming into estrus. In Carman's words since “everything except for the GM aspect of diet” was “randomised out” by the study design, the uterine changes were shown to be due to the diet. She continued if “Monsanto is actually suggesting that the GM diet caused a difference in the rates of estrus in the pigs. This is a hypothesis that is both interesting and worrying for health and should be followed-up.”


The most important criticism of Carman's pig study, because of its wider implications, is that the use of a routine commercial feed, which includes a cocktail of agri-chemicals, GM proteins and who-knows what else, “muddies the water” too much to interpret the results.

The current situation which has evolved with full regulatory approval is that non-GM parent crops for a valid scientific comparison of GM and non-GM are simply not available. Add to this that the agri-chemicals used on GM and non-GM crops will be different, and that pure non-GM seed can no longer be obtained. More seriously, in the case of the newer varieties such as SmartStax maize which looks set to gain approval in the EU and has multiple artificial genes stacked by cross-breeding, a valid parent replica simply can't be created. Carman's real-life experiment is the best science now possible.

Regulators are using the muddied situation they have encouraged as an excuse to deny us safety testing. However, as Carman pointed out, because the waters are muddied, any harmful effects will have to be greater to show statistical significance: this makes her finding even more ominous.

It's time our regulators got their act together and specified valid protocols, acceptable controls and up-to-date tests for routine use. Ask them to do this before they ask any pigs, or you, to eat GM.

  • Judy A. Carman et al., 2013, A long-term toxicology study on pigs fed a combined genetically modified (GM) soy and GM maize diet, Journal of Organic Systems, 8(1)
  • Evidence of GMO Harm in Pig Study, Sustainable Pulse, 11.06.13
  • Monica Eng, Pigs fed GM grain suffer health problems, study says, Chicago Tribune 11.06.13
  • Carey Gillam, Scientists say new study shows pig health hurt by GMO feed, Reuters, 11.06.13
  • Christoph Then, EU Commission presses ahead with SmartStqx pesticidal maize authorisation, Testbiotech, 10.07.13
  • Judy Carman, A specific reply to Mark Lynas,
  • Judy Carman, A specific reply to Monsanto

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