Impossible Burger, Glyphosate, and Heme: What the Tests Found, How Regulators Ruled, and How It Compares With Beef

When the Impossible Burger moved from trendy restaurants to Burger King and grocery stores in 2019, it drew both enthusiasm and suspicion. Its signature ingredient, soy leghemoglobin, or “heme,” is produced by genetically engineered yeast and gives the plant-based patty its meat-like color and flavor. The company also switched to genetically modified soy protein. That year, the advocacy group Moms Across America announced that laboratory testing it commissioned had found glyphosate residues in an Impossible Burger, with headlines calling the levels high and cancer-causing.

This article examines what the testing showed and how the reported levels compare with regulatory limits, how heme is made and what regulators concluded about its safety, how plant-based burgers compare nutritionally with beef, and what research shows about their health effects.

Is the Impossible Burger healthy, and should the glyphosate in it worry me? The Impossible Burger is a plant-based patty whose signature ingredient is soy leghemoglobin (“heme”), made via genetic engineering. A 2019 advocacy test found trace glyphosate, but at levels far below safety limits. Nutritionally it is comparable to beef in protein but is ultra-processed and high in sodium. It avoids the risks of red and processed meat, so it is a reasonable choice, not a health food.

What Is in the Impossible Burger?

The Impossible Burger is made mainly from soy protein, oils, and binders, with its signature ingredient being soy leghemoglobin, or “heme,” produced by genetically engineered yeast to give a meaty taste and color. The Impossible Burger is made mainly from soy protein concentrate, coconut and sunflower oils, natural flavors, potato protein, binders such as methylcellulose and food starch, yeast extract, salt, added vitamins and minerals, and soy leghemoglobin. In 2019, the company reformulated its burger, switching from wheat protein to soy protein derived from genetically engineered, herbicide-tolerant soybeans. Leghemoglobin is a protein found naturally in the root nodules of soybeans and other legumes, where it carries oxygen. Like hemoglobin in animal blood, it contains heme, an iron-containing molecule that contributes to the color and characteristic flavor of meat when cooked.

Extracting leghemoglobin from soy roots would be impractical, so the company inserted the gene for soybean leghemoglobin into the yeast Pichia pastoris (also called Komagataella phaffii), which produces the protein during fermentation. The protein is then purified for use in the burger. This is a form of precision fermentation, similar to methods used to make insulin and some cheese-making enzymes.

Does the Impossible Burger Really Contain Glyphosate?

A 2019 advocacy group reported trace glyphosate in the Impossible Burger, since it is made from conventional soy, but the levels were far below regulatory safety limits and typical of many soy-containing foods. Moms Across America reported that a commercial laboratory found a combined 11.3 parts per billion (ppb) of glyphosate and its breakdown product, aminomethylphosphonic acid (AMPA), in an Impossible Burger sample, about 11 times the 1 ppb it reported in a Beyond Burger, and argued that any glyphosate in food is a concern. The finding is plausible because the burger uses soy protein from glyphosate-tolerant soybeans, which may be sprayed with glyphosate during the growing season.

To put the level in perspective, 11.3 ppb equals 0.0113 parts per million. The EPA’s tolerance for glyphosate residues in soybean seed is 20 parts per million, and soy protein is further diluted in the finished burger, so the reported level was far below legal limits. Impossible Foods responded by publishing its own testing of six lots for glyphosate, AMPA, and more than 300 other pesticides through an accredited laboratory, explaining that it uses a limit of detection of 0.005 ppm and that occasional low positive results are expected, even in organic crops. Regulatory limits do not settle debates about long-term effects of low-level exposure, discussed in our article on glyphosate science, but they show that the burger was not unusually contaminated compared with many common foods made from conventional grains and legumes.

Is the Heme in the Impossible Burger Safe?

Soy leghemoglobin was reviewed by the FDA, which concluded it is safe to eat; it is the ingredient that gives the burger its meat-like flavor, aroma, and pink color when cooking. Because soy leghemoglobin had not previously been part of the human diet in significant amounts, its safety review drew attention. The company convened an expert panel that concluded in 2014 that the ingredient was generally recognized as safe. Meat+Poultry reported that the FDA sent the company a “no questions” letter on its GRAS determination in July 2018 for use in products sold cooked, such as in restaurants, and later determined that selling uncooked, red-colored patties directly to consumers required separate approval as a color additive, because the reddish color was important to the product’s appearance and marketability. Impossible Foods announced the FDA’s approval of its color additive petition on July 31, 2019.

The Center for Food Safety objected, arguing that the FDA’s 2018 letter was not an affirmation of safety and that the color additive approval was improperly granted. In 2021, the Ninth Circuit Court of Appeals upheld the FDA’s approval, finding that substantial evidence supported the agency’s conclusion of a reasonable certainty of no harm from use of up to 0.8 percent soy leghemoglobin protein in ground beef analogue products.

A 2018 safety evaluation in the International Journal of Toxicology by Rachel Fraser and colleagues at Impossible Foods reported that the leghemoglobin preparation was not genotoxic in standard tests and that 28-day feeding studies in rats established a no-observed-adverse-effect level of 750 milligrams per kilogram per day, more than 100 times the estimated 90th percentile human intake. Because the study was conducted by the company, critics called for independent and longer-term research, while regulators considered the data sufficient for the approved uses.

Is the Impossible Burger Healthier Than Beef?

What Research Shows About Health Effects

The Impossible Burger has comparable protein to beef, no cholesterol, and some fiber, but similar or higher sodium and saturated fat from coconut oil; it is different from beef, not clearly healthier overall. The SWAP-MEAT randomized crossover trial, published in 2020 in the American Journal of Clinical Nutrition by Anthony Crimarco, Christopher Gardner, and colleagues at Stanford, asked 36 generally healthy adults to eat about two servings per day of plant-based meat products for eight weeks and animal meat for eight weeks, keeping the rest of their diets similar. During the plant-based phase, participants had lower levels of trimethylamine N-oxide (TMAO), a compound linked to cardiovascular risk, lower LDL cholesterol, and slightly lower body weight, with no adverse effects on measured risk factors. The study was funded partly by Beyond Meat, which supplied products, though the company was not involved in the design or analysis. Longer and larger studies are needed to understand long-term health outcomes.

Critics note that plant-based meats are ultra-processed foods, a category associated with poorer health outcomes in observational research, and that whole plant foods such as beans, lentils, and whole grains offer more fiber and fewer additives. Supporters argue that plant-based meats can help people reduce red and processed meat consumption, which is linked to higher risks of heart disease, type 2 diabetes, and colorectal cancer. For most people, an occasional plant-based burger is neither a health food nor a health hazard; overall dietary patterns matter more.

Red and Processed Meat Risks

Interest in plant-based alternatives partly reflects evidence about meat. The International Agency for Research on Cancer’s 2015 evaluation, summarized by Véronique Bouvard and colleagues in The Lancet Oncology, classified processed meat as carcinogenic to humans (Group 1), based mainly on colorectal cancer, and red meat as probably carcinogenic (Group 2A). The working group estimated that each 50-gram daily portion of processed meat increased colorectal cancer risk by about 18 percent. A plain beef burger is red meat but not processed meat; plant-based burgers avoid these specific concerns but introduce their own considerations as processed foods.

Is the Impossible Burger Ultra-Processed?

Yes, the Impossible Burger is an ultra-processed food made from refined ingredients and additives; while it avoids red-meat risks, that processing is why some nutrition experts urge moderation rather than calling it a health food. Plant-based burgers are classified as ultra-processed foods under the widely used NOVA system because they are formulated from refined ingredients and additives. A 2019 inpatient randomized trial in Cell Metabolism by Kevin Hall and colleagues at the National Institutes of Health found that adults offered ultra-processed diets ate about 500 more calories per day and gained weight compared with when they were offered unprocessed diets matched for presented nutrients. That trial did not test plant-based meats specifically, and the SWAP-MEAT trial found favorable changes in some risk factors when plant-based meats replaced animal meat. Researchers continue to debate whether all ultra-processed foods carry similar risks or whether effects depend on specific products and what they replace.

Soy Allergy and Other Considerations

Because the Impossible Burger is made mainly from soy protein, it is unsuitable for people with soy allergies. Its heme is a soy protein produced by yeast, so it is also a soy-derived ingredient. People who avoid genetically engineered ingredients will want to note that both the soy protein and the heme involve genetic engineering, and that the product carries bioengineered disclosure where required. People with high blood pressure may want to compare sodium levels among plant-based and beef burgers. For those seeking whole-food plant proteins, bean, lentil, or grain-based burgers made at home or with simple ingredients are alternatives with more fiber and fewer additives.

Environmental Claims

Plant-based meat companies market their products as more environmentally friendly than beef, citing lower greenhouse gas emissions, land use, and water use. Life-cycle analyses commissioned by companies and independent studies of plant-based foods generally support lower environmental footprints compared with beef, which is among the most resource-intensive foods. However, results depend on assumptions about production systems, and grazing practices vary widely. Environmental advantages are a major reason some consumers choose plant-based burgers, separate from health considerations.

Key Facts at a Glance

An advocacy group reported 11.3 ppb of glyphosate and AMPA in an Impossible Burger in 2019, far below EPA’s 20 ppm tolerance for soybean seed. Soy leghemoglobin is produced by genetically engineered yeast; the FDA issued a no-questions GRAS letter in 2018, approved it as a color additive in 2019, and the Ninth Circuit upheld the approval in 2021. A company study found no adverse effects in rats at over 100 times estimated human intake. An eight-week crossover trial found plant-based meat lowered TMAO, LDL cholesterol, and weight compared with animal meat. Processed meat is classified as a Group 1 carcinogen and red meat as Group 2A.

How to Read Plant-Based Burger Labels

Ingredient lists on plant-based burgers can be long. Key items to look for include the main protein source (soy, pea, wheat, or a mix), fats (coconut oil contributes saturated fat; sunflower or canola oils are more unsaturated), sodium content per serving, binders such as methylcellulose, and any added vitamins and minerals such as B12, iron, and zinc. Some products are fortified to match nutrients found in beef. Comparing the Nutrition Facts panels of different brands and of lean ground beef helps shoppers choose based on their priorities, whether lower saturated fat, lower sodium, higher protein, or fewer ingredients.

Organic and Non-GMO Plant-Based Options

Consumers who want plant-based burgers without genetically engineered ingredients or glyphosate-tolerant crops can choose products certified organic or Non-GMO Project Verified. Several brands use organic pea, soy, or other proteins. These products typically do not contain heme from engineered yeast and may taste less like beef. Homemade burgers from beans, lentils, mushrooms, and grains offer full control over ingredients. Because glyphosate residues are generally higher in conventional grains and legumes sprayed before harvest, organic sources reduce exposure for those concerned.

Who Funds the Debate

Debates over plant-based meat involve parties with financial and ideological stakes. Plant-based meat companies fund some research and marketing that emphasizes health and environmental benefits. Livestock and meat industry groups have funded campaigns criticizing plant-based products as ultra-processed or chemical-laden. Advocacy groups opposed to GMOs and pesticides highlight genetic engineering and glyphosate. Each perspective presents selective information. Readers can evaluate claims by looking at who conducted the testing or research, whether results were peer-reviewed, and how findings compare with regulatory limits and broader evidence.

What the Glyphosate Numbers Mean

Parts per billion measurements can sound alarming without context. One part per billion is equivalent to about one second in 32 years. At 11.3 ppb, a quarter-pound (113-gram) patty would contain roughly 1.3 micrograms of glyphosate and AMPA combined. For comparison, the EPA’s chronic reference dose for glyphosate is 1 milligram per kilogram of body weight per day, which for a 70-kilogram adult equals 70,000 micrograms. These comparisons do not resolve scientific debate about low-dose effects, but they show that the reported residue was a tiny fraction of the level regulators consider safe for daily lifetime exposure.

Common Myths

“The Impossible Burger has dangerous levels of glyphosate.” Reported levels were far below regulatory limits, though they reflect use of glyphosate-tolerant soy.

“Heme is a synthetic chemical.” Soy leghemoglobin is a protein naturally found in soybean roots, produced here by engineered yeast.

“Plant-based means healthy.” Plant-based burgers are processed foods; their healthfulness depends on what they replace and overall diet.

“Beef has no additives, so it is always healthier.” Unprocessed beef has few ingredients, but red meat intake is linked to some disease risks.

Key Terms

Soy leghemoglobin: A heme-carrying protein from soybean roots, produced by engineered yeast for plant-based burgers.

GRAS: Generally Recognized as Safe, a regulatory pathway for food ingredients.

Color additive: A substance that imparts color to food, requiring specific FDA approval.

AMPA: Aminomethylphosphonic acid, the main breakdown product of glyphosate.

TMAO: Trimethylamine N-oxide, a compound produced from nutrients in animal foods and linked to cardiovascular risk.

The Bottom Line

The 2019 glyphosate test of the Impossible Burger found residues consistent with its use of glyphosate-tolerant soy, but at levels far below regulatory limits and comparable to many foods made from conventional grains and legumes. Its heme ingredient, made by engineered yeast, was reviewed and approved by the FDA, with the approval upheld in court, though critics wanted more independent testing. Nutritionally, plant-based burgers offer no cholesterol and some fiber but are processed and often high in sodium; a short trial found improvements in some cardiovascular risk factors when they replaced animal meat. Consumers can choose based on their priorities, and those wishing to avoid GM ingredients or glyphosate residues can choose organic or whole-food plant proteins.

Cooking and Food Safety

Plant-based burgers should be handled with similar food safety practices as ground meat: keep them refrigerated or frozen, cook them thoroughly according to package directions, and avoid cross-contamination with raw meat. Although plant ingredients do not carry the same pathogens associated with ground beef, such as certain E. coli strains, any perishable food can harbor bacteria if mishandled. Leftovers should be refrigerated promptly. For people with soy allergies, cross-contact in restaurants can be a concern, so asking about preparation is wise.

Further Reading

FDA records describe the review of soy leghemoglobin as a color additive. Court documents and news coverage explain the legal challenge and its outcome. Peer-reviewed studies cited here address leghemoglobin safety testing, the SWAP-MEAT trial, ultra-processed diets, and red and processed meat. Our articles on glyphosate science and precision fermentation provide additional context on the technologies and debates involved.

A Balanced View

The Impossible Burger sits at the intersection of several debates: genetic engineering, pesticide residues, processed foods, and the environmental and health effects of meat. Alarming headlines about glyphosate overstated the risk based on reported levels, while marketing claims about health benefits can overstate what a processed product offers. A balanced view recognizes that plant-based burgers can be a reasonable occasional choice, particularly as a substitute for processed or red meat, while whole-food plant proteins remain the most nutritious plant-based option.

Nutrients Added to Plant-Based Burgers

Many plant-based burgers are fortified with nutrients typically found in meat, such as vitamin B12, zinc, iron, niacin, and riboflavin, to help people replacing meat meet their needs. Vitamin B12 is particularly important because it occurs naturally almost only in animal foods. Iron from plant sources is less readily absorbed than heme iron from meat, though heme from leghemoglobin may differ from plant iron. People who follow vegetarian or vegan diets should ensure adequate B12 from fortified foods or supplements regardless of whether they eat plant-based burgers.

Reading labels can show which nutrients have been added and in what amounts relative to daily values.

Comparing Plant-Based Brands

Plant-based burgers differ substantially by brand. Some use soy protein, others pea protein, wheat gluten, or blends. Fat sources range from coconut oil to canola or sunflower oil. Sodium varies widely. Some brands use heme or beet juice for color, while others use simpler ingredients. Organic and non-GMO options exist for consumers prioritizing those attributes. Comparing labels for protein, saturated fat, sodium, fiber, and ingredient lists helps consumers find products matching their health goals, taste preferences, and values.

Whole-food veggie burgers made from beans, grains, and vegetables generally offer more fiber and fewer additives but differ in taste and texture from meat analogues.

Questions Readers Often Ask

Is the heme in plant-based burgers the same as in meat? Both contain the same heme molecule, carried by different proteins. Does eating plant-based burgers provide iron? They contain iron, though absorption may differ from meat. Do plant-based burgers contain hormones or antibiotics? No, though conventional beef may come from animals given growth-promoting treatments, which organic beef prohibits. Are plant-based burgers suitable for children? They can be part of a balanced diet, though whole foods should form the foundation, and families should watch sodium intake.

Can people with celiac disease eat them? Some brands are gluten-free, but formulations vary, so checking labels is essential.

The Market for Plant-Based Meat

Plant-based meat sales grew rapidly in the late 2010s and early 2020s, then slowed as some consumers tried products and did not continue buying, citing taste, price, and concerns about processing. Companies have reformulated products to improve taste and nutrition and to lower prices. Fast-food partnerships brought plant-based burgers to mainstream menus, though some chains reduced offerings when demand fell short of expectations. The market’s trajectory reflects both genuine interest in alternatives to meat and consumer skepticism about highly processed foods.

Public debates about ingredients such as heme and residues such as glyphosate have influenced some consumers’ perceptions, alongside price and taste.

Looking Ahead

Plant-based and alternative protein technologies continue to evolve, including precision fermentation for dairy and egg proteins, cultivated meat grown from animal cells, and hybrid products blending plant and animal ingredients. Regulators are developing frameworks for these products, and consumers will face new labeling and safety questions. The Impossible Burger debates over heme, GMOs, and residues offer a preview of discussions to come. Independent research on long-term health effects of these products, and transparent testing for contaminants, will help consumers make informed choices.

Practical Takeaways

If you enjoy plant-based burgers, they can be part of a balanced diet, especially as a substitute for processed or red meat. Compare labels for sodium and saturated fat. If you want to avoid genetically engineered ingredients or glyphosate residues, choose organic or non-GMO verified products or make your own bean or lentil burgers. Keep the overall dietary pattern in mind: whole grains, legumes, vegetables, fruits, nuts, and seeds form the foundation of healthy plant-forward eating. Treat alarming headlines about trace residues with context, comparing reported levels with regulatory limits and broader evidence.

Key Lessons in Brief

Context matters when interpreting residue tests; compare reported levels with regulatory limits and typical exposures. Regulatory review of novel ingredients can be challenged and tested in court. Processed plant-based foods differ from whole plant foods nutritionally. Replacing processed meat with plant-based alternatives may improve some risk factors. And consumer choice is best informed by balanced information rather than either marketing or alarm.

How Residue Testing Works

Laboratories test foods for pesticide residues using methods such as liquid chromatography with mass spectrometry, which can detect very small amounts. Results depend on the sample, method, and detection limit, and a single sample may not represent all production lots. Regulatory monitoring programs, such as the USDA Pesticide Data Program and FDA residue monitoring, test many samples across foods to assess typical exposure. Independent tests commissioned by advocacy groups can raise questions but should be interpreted alongside broader monitoring data and regulatory standards.

For readers who want to follow residue issues more broadly, the USDA Pesticide Data Program publishes annual summaries showing which foods most often contain residues and how levels compare with tolerances, providing useful context for individual product tests reported in the news.

Such programs consistently show that most foods tested fall within legal limits, while highlighting specific crops where residues are more common, information that can guide shoppers who want to prioritize organic purchases.

Combining such data with personal priorities about cost, taste, and values supports informed choices at the grocery store and when eating out at restaurants or fast-food chains.

Frequently Asked Questions

Does the Impossible Burger contain glyphosate?

A 2019 advocacy group reported finding trace amounts of glyphosate in the Impossible Burger, which is unsurprising since it is made from conventionally grown soy, and glyphosate is widely used on soybeans. However, the levels detected were far below the safety limits set by regulators and comparable to amounts in many everyday soy-containing foods. The trace glyphosate is not considered a meaningful health risk at these levels.

What is the “heme” in the Impossible Burger?

The heme in the Impossible Burger is soy leghemoglobin, a protein naturally found in soy plants that the company produces using genetically engineered yeast. It gives the burger its meaty flavor, aroma, and the way it appears to “bleed” and brown when cooked. The FDA reviewed soy leghemoglobin and concluded it is safe to eat, and it is the ingredient that most distinguishes the product from other veggie burgers.

Is the Impossible Burger healthier than a beef burger?

It is different rather than clearly healthier. The Impossible Burger provides comparable protein to beef, contains no cholesterol, and adds some fiber, but it can have similar or higher sodium and saturated fat, the latter from coconut oil. It avoids the risks associated with red and processed meat, but it is also ultra-processed. Whether it is “healthier” depends on what you compare it to and your overall diet.

Is the Impossible Burger safe to eat?

Yes, for most people the Impossible Burger is safe to eat. Its key novel ingredient, soy leghemoglobin, was evaluated and deemed safe by the FDA, and the trace glyphosate reported in it is far below safety limits. The main caveats are that it contains soy, an allergen, and that it is an ultra-processed food high in sodium, so it is best eaten in moderation like other processed foods.

Is the Impossible Burger considered ultra-processed?

Yes. The Impossible Burger is made from refined ingredients like soy protein concentrate, oils, and various additives and binders, which places it in the ultra-processed food category. Diets high in ultra-processed foods are linked to health concerns, which is why some nutrition experts suggest treating plant-based meat as an occasional alternative to meat rather than a daily health food, alongside whole plant foods like beans and vegetables.

References

1. Fraser RZ, Shitut M, Agrawal P, et al. Safety Evaluation of Soy Leghemoglobin Protein Preparation Derived From Pichia pastoris, Intended for Use as a Flavor Catalyst in Plant-Based Meat. International Journal of Toxicology. 2018;37(3):241–262. PMID 29642729
2. Crimarco A, Springfield S, Petlura C, et al. A randomized crossover trial on the effect of plant-based compared with animal-based meat on trimethylamine-N-oxide and cardiovascular disease risk factors in generally healthy adults: Study With Appetizing Plantfood—Meat Eating Alternative Trial (SWAP-MEAT). American Journal of Clinical Nutrition. 2020;112(5):1188–1199. PMID 32780794
3. U.S. EPA. 40 CFR 180.364 Glyphosate; tolerances for residues. ecfr.gov
4. Impossible Foods. Our Commitment to Food Safety: How and Why We Test Impossible Products for Pesticides. 2019. impossiblefoods.com
5. Impossible Foods. Impossible Foods Receives Approval for Its Color Additive Petition From US Food and Drug Administration. July 31, 2019. impossiblefoods.com
6. Meat+Poultry. Impossible Foods receives color additive approval from FDA. 2019. meatpoultry.com
7. Center for Food Safety. 5 Myths Impossible Burger is Serving Up. October 2019. centerforfoodsafety.org
8. FoodNavigator-USA. Impossible Foods applauds 9th Circuit ruling over safety of its heme. May 2021. foodnavigator-usa.com
9. Bouvard V, Loomis D, Guyton KZ, et al. Carcinogenicity of consumption of red and processed meat. Lancet Oncology. 2015;16(16):1599–1600. PMID 26514947
10. Hall KD, Ayuketah A, Brychta R, et al. Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake. Cell Metabolism. 2019;30(1):67–77.e3. PMID 31105044

Last updated: October 6, 2026