SAFETY OF GENETICALLY MODIFIED FOODSMODIFIED FOODS

Dr. Elsa A. MuranoDept. of Nutrition & Food ScienceTexas A&M University

OVERVIEWOVERVIEW

Evaluating safety of GM crops/foodsg y p /Guidelines“Substantial Equivalence”qSafety evaluation

Elements to considerToxicityAllergenicityg yUnintended effects

Case studies

SAFETY EVALUATION OF GM FOODS

Codex Alimentarius Commission d d id li f f adopted guidelines for safety

evaluation in 2003, amended in 2008:

11. A safety assessment is characterized by an assessment of a whole food or a component th f t ki g i t t b th thereof taking into account both intended and unintended effects; identifying new or altered hazards; and identifying hazards; and identifying changes, relevant to human health, in key nutrients.

CONCEPT OF “SUBSTANTIAL EQUIVALENCE”

Substantial Equivalence: Substantial Equivalence: “using conventional foods as a baseline for comparing th ti f GM the properties of a GM food”

food product is then regarded as safe as its conventional counterpart if conventional counterpart if substantial equivalence has been established

SAFETY EVALUATION

Substantial Equivalence is only a part of the safety evaluation

Helps identify similarities and potential differences in key potential differences in key components (nutrients, natural toxicants, etc.)

E l ti f Evaluation focuses on assessing the safety of uniquecomponents. or components p ppresent at altered levels

Unique components are typically PROTEINSPROTEINS

ELEMENTS TO BE CONSIDERED IN SAFETY EVALUATION OF GM CROPS/FOODS

Toxicity of the new proteinAllergenicity of the new proteinO f i t d d Occurrence of unintended effectsGene transfer to Gene transfer to microorganisms in the gutRole of the GM food in the dietInfluence of food processing

TOXICITYOF THE NEW PROTEINTOXICITYOF THE NEW PROTEIN

Lack of amino acid sequence h l g t k t i t ihomology to known protein toxinsRapid degradation during simulated digestionNo acute oral toxicity in rodentsNo subchronic toxicity in animals

But animal feeding studies are not But animal feeding studies are not perfect:

animals may not respond to small differencesAnimals are sensiti e to being fed Animals are sensitive to being fed one food in large amounts

ALLERGENICITY OF THE NEW PROTEINALLERGENICITY OF THE NEW PROTEIN

Main scenarios:The new protein may cause an allergic reactionThe new protein may be similar to a known allergen

Minor scenario:Minor scenario:The gene that codes for the new protein may cause genes in the plant that code for inherent allergens to turn “on”turn on

EVALUATION OF ALLERGENICITYEVALUATION OF ALLERGENICITY

Sequence similarity to known ll ( 35% b allergens (>35% by

examining 80 amino-acid piece)*Binding of the new protein to antibodies derived from subjects allergic to the j gsource of the geneResistance to digestion by pepsinpepsin

* Homology to small pieces (6 amino acids) has been shown to be non-predictive.

EVALUATION OF UNINTENDED EFFECTSEVALUATION OF UNINTENDED EFFECTS

Gene transfer may affect Gene transfer may affect other metabolites

Higher lignin content in Bt Higher lignin content in Bt maizeLower plant flavonoids in Lower plant flavonoids in herbicide-tolerant soybeans

Not widely evaluatedNot widely evaluated

EXAMPLES OF TESTING IN PRACTICEEXAMPLES OF TESTING IN PRACTICE

High-methionine soybeanSoybeans inherently deficient in sulfur amino acidsPioneer Hi bred developed new Pioneer Hi-bred developed new variety from Brazil nuts to enhance nutritional quality of chicken feed and lower costchicken feed and lower costScreening with sera from allergic subjects revealed new

t i i b protein in soybean was allergenicNever commercialized

EXAMPLES OF TESTING IN PRACTICEEXAMPLES OF TESTING IN PRACTICE

StarLink cornN i t t i i New variety containing gene developed by Aventis encoding for insecticide protein (Cry9C) from Bacillus thuringiensis (Bt)Cry9C protein not homologous with known allergensBut, was more resistant to digestion by pepsin than other Bt digestion by pepsin than other Bt proteinsNot approved for use as food for humans, only for feedC ti l l t Conventional corn later contaminated with StarLink variety was recalled and the variety was abandoned from use

LESSONS LEARNEDLESSONS LEARNED

Testing protocols are able to detect differences Testing protocols are able to detect differences between conventional and GM crops/foodNeed better monitoring to ensure cross pollination Need better monitoring to ensure cross pollination is prevented, and more research to determine appropriate “buffer zones”pp pRisk communication is still a challenge

StarLink corn did not compromise health of consumersStarLink corn did not compromise health of consumersSome conventional foods are allergenic, yet remain in the food supply