State of the Science on the Health Risks of GMO Foods

From The Institute for Responsible Technology

We all know stories of tobacco, asbestos, and DDT. Originally declared safe, they caused widespread death and disease. Although their impact was vast, most of the population was spared. The same cannot be said for sweeping changes in the food supply. Everyone eats; everyone is affected. The increase in several diseases in North America may be due to the profound changes in our diet. The most radical change occurred a little over a decade ago when genetically modified (GM) crops were introduced. Their influence on health has been largely ignored, but recent studies show serious problems. Genetically modified organisms (GMOs) have been linked to thousands of toxic or allergic‐type reactions, thousands of sick, sterile, and dead livestock, and damage to virtually every organ and system studied in lab animals,  Nearly every independent animal feeding safety study shows adverse or unexplained effects.

GM foods were made possible by a technology developed in the 1970s whereby genes from one species are forced into the DNA of other species. Genes produce proteins, which in turn can generate characteristics or traits. The promised traits associated with GMOs have been sky high—vegetables growing in the desert, vitamin fortified grains, and highly productive crops feeding the starving millions. None of these are available. In fact, the only two traits that are found in nearly all commericialized GM plants are herbicide tolerance and/or pesticide production.

Herbicide tolerant soy, corn, cotton, and canola plants are engineered with bacterial genes that allow them to survive otherwise deadly doses of herbicides. This gives farmers more flexibility in weeding and gives the GM seed company lots more profit. When farmers buy GM seeds, they sign a contract to buy only that seed producer’s brand of herbicide. Herbicide tolerant crops comprise about 80% of all GM plants. The other 20% are corn and cotton varieties that produce a pesticide in every cell. This is accomplished due to a gene from a soil bacterium called Bacillus thuringiensis or Bt, which produces a natural insect‐killing poison called Bt‐toxin. In addition to these two traits, there are also disease resistant GM Hawaiian papaya, zucchini and crook neck squash, which comprise well under 1% of GMO acreage.


Rhetoric from the United States government since the early 1990s proclaims that GM foods are no different from their natural counterparts that have existed for centuries. The Food and Drug Administration (FDA) has labeled them “Generally Recognized as Safe,” or GRAS. This status allows a product to be commercialized without any additional testing. According to US law, to be considered GRAS the substance must be the subject of a substantial amount of peer‐reviewed published studies (or equivalent) and there must be overwhelming consensus among the scientific community that the product is safe. GM foods had neither. Nonetheless, in a precedent‐setting move in 1992 that some experts contend was illegal, the FDA declared that GM crops are GRAS as long as their producers say they are. Thus, the FDA does not require any safety evaluations or labeling of GMOs. A company can even introduce a GM food to the market without telling the agency.

Such a lenient approach was largely the result of the influence of large agricultural corporations According to Henry Miller, who had a leading role in biotechnology issues at the FDA from 1979 to 1994, “In this area, the US government agencies have done exactly what big agribusiness has asked them to do and told them to do.” The Ag biotech company with the greatest influence was clearly Monsanto. According to the New York Times, “What Monsanto wished for from Washington, Monsanto and, by extension, the biotechnology industry got. . . . When the company abruptly decided that it needed to throw off the regulations and speed its foods to market, the White House quickly ushered through an unusually generous policy of self‐policing.”

This policy was heralded by Vice President Dan Quayle on May 26, 1992. He chaired the Council on Competitiveness, which had identified GM crops as an industry that could boost US exports. To take advantage, Quayle announced “reforms” to “speed up and simplify the process of bringing” GM products to market without “being hampered by unnecessary regulation.”2 Three days later, the FDA policy on non‐regulation was unveiled.

The person who oversaw its development was the FDA’s Deputy Commissioner for Policy, Michael Taylor, whose position had been created especially for him in 1991. Prior to that, Taylor was an outside attorney for both Monsanto and the Food Biotechnology Council. After working at the FDA, he became Monsanto’s vice-president. 

*Note from Mom*  Michael Taylor is now being considered to head “Food Safety” by the Obama adminstration.   Write the White House and tell them, no thanks!


Taylor’s policy needed to create the impression that unintended effects from GM crops were not an issue. Otherwise their GRAS status would be undermined and they would need the extensive testing and labels that are normally required for food additives. But internal memos made public from a lawsuit showed that the overwhelming consensus among the agency scientists was that GM crops can have unpredictable, hard‐to‐detect side effects. Various departments and experts spelled these out in detail, listing allergies, toxins, nutritional effects, and new diseases as potential dangers. They urged superiors to require long‐term safety studies.3 In spite of the warnings, according to public interest attorney Steven Druker who studied the FDA’s internal files, “References to the unintended negative effects of bioengineering were progressively deleted from drafts of the policy statement (over the protests of agency scientists).”4

FDA microbiologist Louis Pribyl, PhD, wrote about the policy, “What has happened to the scientific elements of this document? Without a sound scientific base to rest on, this becomes a broad, general, ‘What do I have to do to avoid trouble’‐type document. . . . It will look like and probably be just a political document. . . . It reads very pro‐industry, especially in the area of unintended effects.

The scientists’ concerns were not only ignored, their very existence was denied. The official FDA policy stated, “The agency is not aware of any information showing that foods derived by these new methods differ from other foods in any meaningful or uniform way.”6 In sharp contrast, an internal FDA report stated, “The processes of genetic engineering and traditional breeding are different and according to the technical experts in the agency, they lead to different risks.”7 The FDA’s deceptive notion of no difference was coined “substantial equivalence” and formed the basis of the US government position on GMOs.

Many scientists and organizations have criticized the US position. The National Academy of Sciences and even the pro‐GM Royal Society of London8 describe the US system as inadequate and flawed. The editor of the prestigious journal Lancet said, “It is astounding that the US Food and Drug Administration has not changed their stance on genetically modified food adopted in 1992. . . . The policy is that genetically modified crops will receive the same consideration for potential health risks as any other new crop plant. This stance is taken despite good reasons to believe that specific risks may exist. . . . Governments should never have allowed these products into the food chain without insisting on rigorous testing for effects on health.”9 The Royal Society of Canada described substantial equivalence as “scientifically unjustifiable and inconsistent with precautionary regulation of the technology.”


There are several reasons why GM plants present unique dangers. The first is that the process of genetic engineering itself creates unpredicted alterations, irrespective of which gene is transferred. The gene insertion process, for example, is accomplished by either shooting genes from a “gene gun” into a plate of cells, or using bacteria to infect the cell with foreign DNA. Both create mutations in and around the insertion site and elsewhere.11 The “transformed” cell is then cloned into a plant through a process called tissue culture, which results in additional hundreds or thousands of mutations throughout the plants’ genome. In the end, the GM plant’s DNA can be a staggering 2‐4% different from its natural parent.12 Native genes can be mutated, deleted, or permanently turned on or off. In addition, the insertion process causes holistic and not‐well‐understood changes among large numbers of native genes. One study revealed that up to 5% of the natural genes altered their levels of protein expression as a result of a single insertion.

The Royal Society of Canada acknowledged that “the default prediction” for GM crops would include “a range of collateral changes in expression of other genes, changes in the pattern of proteins produced and/or changes in metabolic activities.”13 Although the FDA scientists evaluating GMOs in 1992 were unaware of the extent to which GM DNA is damaged or changed, they too described the potential consequences. They reported, “The possibility of unexpected, accidental changes in genetically engineered plants” might produce “unexpected high concentrations of plant toxicants.”14 GM crops, they said, might have “increased levels of known naturally occurring toxins,” and the “appearance of new, not previously identified” toxins.15 The same mechanism can also produce allergens, carcinogens, or substances that inhibit assimilation of nutrients.

Most of these problems would pass unnoticed through safety assessments on GM foods, which are largely designed on the false premise that genes are like Legos that cleanly snap into place. But even if we disregard unexpected changes in the DNA for the moment, a proper functioning inserted gene still carries significant risk. Its newly created GM protein, such as the Bt‐toxin, may be dangerous for human health (see below). Moreover, even if that protein is safe in its natural organism, once it is transferred into a new species it may be processed differently. A harmless protein may be transformed into a dangerous or deadly version. This happened with at least one GM food crop under development, GM peas, which were destroyed before being commercialized.

FDA scientists were also quite concerned about the possibility of inserted genes spontaneously transferring into the DNA of bacteria inside our digestive tract. They were particularly alarmed at the possibility of antibiotic resistant marker (ARM) genes transferring. ARM genes are employed during gene insertion to help scientists identify which cells successfully integrated the foreign gene. These ARM genes, however, remain in the cell and are cloned into the DNA of all the GM plants produced from that cell. One FDA report wrote in all capital letters that ARM genes would be “A SERIOUS HEALTH HAZARD,” due to the possibility of that they might transfer to bacteria and create super diseases, untreatable with antibiotics.

Although the biotech industry confidently asserted that gene transfer from GM foods was not possible, the only human feeding study on GM foods later proved that it does take place. The genetic material in soybeans that make them herbicide tolerant transferred into the DNA of human gut bacteria and continued to function. That means that long after we stop eating a GM crop, its foreign GM proteins may be produced inside our intestines. It is also possible that the foreign genes might end up inside our own DNA, within the cells of our own organs and tissues.

Another worry expressed by FDA scientists was that GM plants might gather “toxic substances from the environment” such as “pesticides or heavy metals,”16 or that toxic substances in GM animal feed might bioaccumulate into milk and meat products. While no studies have looked at the bioaccumulation issue, herbicide tolerant crops certainly have higher levels of herbicide residues. In fact, many countries had to increase their legally allowable levels—by up to 50 times—in order to accommodate the introduction of GM crops.

The overuse of the herbicides due to GM crops has resulted in the development of herbicide resistant weeds. USDA statistics show that herbicide use is rapidly accelerating. Its use was up by 138 million pounds in the first nine years of GM crops.17 But over the next two years, it jumped by another 120 million pounds (estimated). Between 2005 and 2006, the use of Roundup herbicide—used on GM Roundup Ready crops—was up by 38%. And because Roundup is becoming less effective on weeds, farmers are now using more toxic herbicides, such as 2‐4D, which has increased by 237% from 2004 to2006.18

All of the above risks associated with GM foods are magnified for high‐risk groups, such as pregnant women, children, the sick, and the elderly. The following section highlights some of the problems that have been identified.


The very first crop submitted to the FDA’s voluntary consultation process, the FlavrSavr tomato, showed evidence of toxins. Out of 20 female rats fed the GM tomato, 7 developed stomach lesions.19 The director of FDA’s Office of Special Research Skills wrote that the tomatoes did not demonstrate a “reasonable certainty of no harm,”20 which is their normal standard of safety. The Additives Evaluation Branch agreed that “unresolved questions still remain.”21 The political appointees, however, did not require that the tomato be withdrawn.1

According to Arpad Pusztai, PhD, one of the world’s leading experts in GM food safety assessments, the type of stomach lesions linked to the tomatoes “could lead to life‐endangering hemorrhage, particularly in the elderly who use aspirin to prevent [blood clots].”22 Dr. Pusztai believes that the digestive tract, which is the first and largest point of contact with foods, can reveal various reactions to toxins and should be the first target of GM food risk assessment. He was alarmed, however, to discover that studies on the FlavrSavr never looked passed the stomach to the intestines. Other studies that did look found problems.

Mice fed potatoes engineered to produce the Bt‐toxin developed abnormal and damaged cells, as well as proliferative cell growth in the lower part of their small intestines (ileum).23 Rats fed potatoes engineered to produce a different type of insecticide (GNA lectin from the snowdrop plant) also showed proliferative cell growth in both the stomach and intestinal walls (see photos).24 Although the guts of rats fed GM peas were not examined for cell growth, the intestines were mysteriously heavier; possibly as a result of such growth.25 Cell proliferation can be a precursor to cancer and is of special concern.

Rats fed GM potatoes showed proliferative cell growth in the stomach and intestines.

1 Calgene had submitted data on two lines of GM tomatoes, both using the same inserted gene. They voluntarily elected to market only the variety that was not associated with the lesions. This was not required by the FDA, which did not block approvals on the lesion‐associated variety. The FlavrSavr tomato has since been taken off the market. After the FlavrSavr, no other biotech company has submitted such detailed data to the FDA.


The state of the liver—a main detoxifier for the body—is another indicator of toxins.

Rats fed the GNA lectin potatoes described above had smaller and partially atrophied livers.26

Rats fed Monsanto’s Mon 863 corn, engineered to produce Bt‐toxin, had liver lesions and other indications of toxicity.27

Rabbits fed GM soy showed altered enzyme production in their livers as well as higher metabolic activity.28

The livers of rats fed Roundup Ready canola were 12%–16% heavier, possibly due to liver disease or inflammation.29

Microscopic analysis of the livers of mice fed Roundup Ready soybeans revealed altered gene expression and structural and functional changes (see photos).30 Many of these changes reversed after the mice diet was switched to non‐GM soy, indicating that GM soy was the culprit. The findings, according to molecular geneticist Michael Antoniou, PhD, “are not random and must reflect some ‘insult’ on the liver by the GM soy.” Antoniou, who does human gene therapy research in King’s College London, said that although the long‐term consequences of the GM soy diet are not known, it “could lead to liver damage and consequently general toxemia.”31 Rats fed Roundup Ready soybeans also showed structural changes in their livers. 32


In the FlavrSavr tomato study, a note in the appendix indicated that 7 of 40 rats died within two weeks and were replaced.33 In another study, chickens fed the herbicide tolerant “Liberty Link” corn died at twice the rate of those fed natural corn.34 But in these two industry‐funded studies, the deaths were dismissed without adequate explanation or follow‐up.

In addition, the cells in the pancreas of mice fed Roundup Ready soy had profound changes and produced significantly less digestive enzymes;35 in rats fed a GM potato, the pancreas was enlarged.36 In various analyses of kidneys, GM‐fed animals showed lesions, toxicity, altered enzyme production or inflammation.37,38 Enzyme production in the hearts of mice was altered by GM soy.39 And GM potatoes caused slower growth in the brains of rats.


Allergic reactions occur when the immune system interprets something as foreign, different, and offensive, and reacts accordingly. All GM foods, by definition, have something foreign and different. And several studies show that they provoke reactions. Rats fed Monsanto’s GM corn, for example, had a significant increase in blood cells related to the immune system.50 GM potatoes caused the immune system of rats to respond more slowly.51 And GM peas provoked an inflammatory response in mice, suggesting that it might cause deadly allergic reactions in people.52

It might be difficult to identify whether GM foods were triggering allergic responses in the population, since very few countries conduct regular studies or keep careful records. One country that does have an annual evaluation is the UK. Soon after GM soy was introduced into the British diet, researchers at the York Laboratory reported that allergies to soy had skyrocketed by 50% in a single year.53 Although no follow‐up studies were conducted to see if GM soy was the cause, there is evidence showing several ways in which it might have contributed to the rising incidence of allergies:

• The only significant variety of GM soy is Monsanto’s “Roundup Ready” variety, planted in 89% of US soy acres. A foreign gene from bacteria (with parts of virus and petunia DNA) is inserted, which allows the plant to withstand Roundup herbicide. The protein produced by the bacterial gene has never been part of the human food supply. Because people aren’t usually allergic to a food until they have eaten it several times, it would be difficult to know in advance if the protein was an allergen. Without a surefire method to identify allergenic GM crops, the World Health Organization (WHO) and others recommend examining the properties of the protein to see if they share characteristics with known allergens. One method is to compare the amino acid sequence of the novel protein with a database of allergens. If there is a match, according to the WHO, the GM crop should either not be commercialized or additional testing should be done. Sections of the protein produced in GM soy are identical to shrimp and dust mite allergens,54 but the soybean was introduced before WHO criteria were established and the recommended additional tests were not conducted. If the protein does trigger reactions, the danger is compounded by the finding that the Roundup Ready gene transfers into the DNA of human gut bacteria and may continuously produce the protein from within our intestines.55

• In addition to the herbicide tolerant protein, GM soybeans contain a unique, unexpected protein, which likely came about from the changes incurred during the genetic engineering process. Scientists found that this new protein was able to bind with IgE antibodies, suggesting that it may provoke dangerous allergic reactions. The same study revealed that one human subject showed a skin prick immune response only to GM soy, but not to natural soy.56 Another study showed that the levels of one known soy allergen, called trypsin inhibitor, were as much as seven times higher in cooked GM soy compared to a non‐GM control.57

• GM soy also produces an unpredicted side effect in the pancreas of mice—the amount of digestive enzymes produced is dramatically reduced.58 If a shortage of enzymes caused food proteins to breakdown more slowly, then they have more time to trigger allergic reactions. Thus, digestive problems from GM soy might promote allergies to a wide range of proteins, not just soy.

• The higher amount of Roundup herbicide residues on GM soy might create reactions in consumers. In fact, many of the symptoms identified in the UK soy allergy study are among those related to glyphosate exposure. [The allergy study identified irritable bowel syndrome, digestion problems, chronic fatigue, headaches, lethargy, and skin complaints, including acne and eczema, all related to soy consumption. Symptoms of glyphosate exposure include nausea, headaches, lethargy, skin rashes, and burning or itchy skin. It is also possible that glyphosate’s breakdown product AMPA, which accumulates in GM soybeans after each spray, might contribute to allergies.]

It is interesting to note that in the five years immediately after GM soy was introduced, US peanut allergies doubled. It is known that a protein in natural soybeans cross‐reacts with peanut allergies, i.e. soy may trigger reactions in some people who are allergic to peanuts.59 Given the startling increase in peanut allergies, scientists should investigate whether this cross‐reactivity has been amplified in GM soy.


For years, organic farmers and others have sprayed crops with solutions containing natural Bt bacteria as a method of insect control. The toxin creates holes in their stomach and kills them. Genetic engineers take the gene that produces the toxin in bacteria and insert it into the DNA of crops so that the plant does the work, not the farmer. The fact that we consume that toxic pesticide in every bite of Bt corn is hardly appetizing.

Biotech companies claim that Bt‐toxin has a history of safe use, is quickly destroyed in our stomach, and wouldn’t react with humans or mammals in any event. Studies verify, however, that natural Bt‐toxin is not fully destroyed during digestion and does react with mammals. Mice fed Bt‐toxin, for example, showed an immune response as potent as cholera toxin, 60, became immune sensitive to formerly harmless compounds,61 and had damaged and altered cells in their small intestines.62 Moreover, when natural Bt was sprayed over areas around Vancouver and Washington State to fight gypsy moths, about 500 people reported reactions—mostly allergy or flu‐like symptoms.63,64 Farm workers and others also report serious reactions6566676869 and authorities have long acknowledged that “people with compromised immune systems or preexisting allergies may be particularly susceptible to the effects ofI The Bt‐toxin produced in GM crops is “vastly different from the bacterial [Bt‐toxins] used in organic and traditional farming and forestry.”71 The plant produced version is designed to be more toxic than natural varieties,72 and is about 3,000‐5,000 times more concentrated than the spray form. And just like the GM soy protein, the Bt protein in GM corn varieties has a section of its amino acid sequence identical to a known allergen (egg yolk). The Bt protein also fails other allergen criteria recommended by the WHO, i.e. the protein is too resistant to break down during digestion and heat.

If Bt‐toxin causes allergies, then gene transfer carries serious ramifications. If Bt genes relocate to human gut bacteria, our intestinal flora may be converted into living pesticide factories, possibly producing Bt‐toxin inside of us year after year. The UK Joint Food Safety and Standards Group also described gene transfer from a different route. They warned that genes from inhaled pollen might transfer into the DNA of bacteria in the respiratory system.73 Although no study has looked into that possibility, pollen from a Bt cornfield appears to have been responsible for allergic‐type reactions.

In 2003, during the time when an adjacent Bt cornfield was pollinating, virtually an entire Filipino village of about 100 people was stricken by mysterious skin, respiratory, and intestinal reactions.74 The symptoms started with those living closest to the field and spread to those further away. Blood samples from 39 individuals showed antibodies in response to Bt‐toxin, supporting—but not proving—a link. When the same corn was planted in four other villages the following year, however, the symptoms returned in all four areas—only during the time of pollination.75

Bt‐toxin might also trigger reactions by skin contact. In 2005, a medical team reported that hundreds of agricultural workers in India are developing allergic symptoms when exposed to Bt cotton, but not when

axposed to natural varieties.76 They say reactions come from picking the cotton, cleaning it in factories, loading it onto trucks, or even leaning against it. Their symptoms are virtually identical to those described by the 500 people in Vancouver and Washington who were sprayed with Bt (see table on next page).

Bt Spray


runny nose,

exacerbations of asthma

Watery, red

Itching, burning,





some in hospital

Bt Cotton

Sneezing, runny nose


Itching, burning, eruptions, red, swelling


some in hospital

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