By Dr. Sue Klapholz, M.D., Ph.D., Vice President of Nutrition and Health at Impossible Foods
May 21, 2020
Note: With the launch of Impossible Burger 2.0 in grocery stores, we’ve expanded our general allergy information section and added some updates to our ingredient and allergen information to provide even greater transparency.
The major food allergens are proteins, most of which are resistant to heat, acid and digestive enzymes. Most foods contain thousands of different proteins, but only a tiny fraction of them have ever triggered allergies. Milk, eggs, peanuts, tree nuts, soy, wheat, fish and crustacean shellfish account for 90% of allergic reactions to food. But many other foods can occasionally elicit an allergic reaction.
In order to develop an allergy, a person must first be exposed to something in the environment that triggers an immune response. In the case of food allergies, the route of exposure is usually ingestion, but may be inhalation, skin contact or injection.
On first exposure, a susceptible individual makes immunoglobulin-E antibodies (IgE) to the allergen, but doesn’t show signs of an allergy. On second and subsequent exposures to the same allergen, the allergen is able to bind to IgE antibodies that are present on the surface of cells of the immune system (e.g., mast cells), which then release a number of chemicals, including histamine, into the body.
This is what causes an allergic response.
Symptoms appear within minutes to 2 hours (and usually within 30 minutes) of eating the responsible food. The allergic reaction may include all or some of the following: itching, hives, sneezing, wheezing, nausea, vomiting and diarrhea. More rarely, the symptoms can be severe and even life threatening, including swelling of the throat, difficulty breathing and a drop in blood pressure, leading to anaphylactic shock. In the United States, almost 11% of adults and 8% of children have food allergies, and the numbers are increasing. According to FARE (Food Allergy Research & Education), the prevalence of food allergies in the US is roughly doubling every 10 years. Although the true incidence of anaphylaxis is unknown, estimates of the annual rate of anaphylaxis to food range from 0.4-10 in 100,000 people.
We know that the physical state of an allergen — whether a protein is in its native uncooked form, or is fully or partially denatured by cooking — and the amount of allergen to which a person is exposed can have a big impact on whether or not an allergic reaction is triggered. For example, some people are allergic to raw but not baked apples, while others may be allergic to cooked but not raw peas. Some people with proven allergy to peanuts can tolerate a small amount of peanuts while others have severe reactions to even the tiniest quantities. Similarly a food containing a very concentrated form of protein, such as pea protein, may cause allergic symptoms in a person who does not react to eating a serving of whole peas, which contains much less total protein.
Allergies commonly first occur during childhood, but can begin at any age. The frequency of adult-onset allergies is increasing, and for unknown reasons, food allergies that develop in adulthood tend to be more severe. A recent study found that almost half of American adults with food allergies developed at least one food allergy after age 18. And these allergies are often to foods a person has eaten many times before. Therefore, it is important to never disregard allergic symptoms, even in association with familiar foods.
One common type of allergic reaction — one that many people do not recognize as an allergy — is called oral allergy syndrome (OAS) or pollen-food syndrome.
OAS can occur in people who are already allergic to pollen from trees, grasses or weeds. It turns out that pollen (an inhaled allergen) contains proteins that are similar in structure to certain proteins found in many fruits, vegetables, nuts and seeds. Antibodies to pollen may be able to recognize and trigger a response to these allergens too.
In adults, up to 60% of food allergic reactions are due to cross-reactivity between foods and pollen. For example, when someone who is allergic to birch pollen consumes an apple or almonds, that person may experience oral allergy symptoms: itchy or tingling mouth, scratchy throat, or even swelling of the lips, tongue and throat. These symptoms are usually short-lived and mild because the heat of the mouth and/or stomach acid and digestive enzymes inactivate the allergen — and stop the allergic reaction. Many of the foods that cause OAS when raw are not allergenic when cooked because the heat of cooking inactivates the allergen.
A small percentage of the time, however, the allergens that cause OAS can trigger a more severe reaction — even anaphylaxis. Oral symptoms such as tingling or itching can be the first warning of a pending generalized allergic reaction. It’s therefore very important to pay attention to oral signs and symptoms as indicators of allergy, and to stop eating any food that triggers these symptoms.
In some cases, a delayed onset of symptoms makes the association between a specific food and an allergic reaction more challenging to diagnose.
Alpha-Gal syndrome. Serious allergic reactions to “red meat” (i.e., meat from mammals, like beef, pork or lamb) are a growing worldwide problem. The allergies develop when people are sensitized by tick bites to galactose-α-1,3-galactose (“alpha-gal” for short), — a kind of sugar molecule that’s abundant in tissues from every mammal except monkeys, apes and humans. Sensitized individuals typically develop symptoms, ranging in severity from hives to life-threatening anaphylaxis. Unlike typical food allergies, where the reaction usually occurs within half an hour of consuming the triggering food, the reaction to alpha-gal occurs 3 - 6 hours after red meat consumption.
Food protein-induced enterocolitis syndrome (FPIES). FPIES is a relatively rare, but increasingly prevalent, non-IgE-mediated food allergy that was first described in children in the 1970s. FPIES manifests as delayed gastrointestinal symptoms: vomiting and/or diarrhea 1-4 hours after ingestion of a specific food. FPIES is most common in infants and children, and only recently has been described in adults. In one study of adults with FPIES, the median time of symptom onset was 3 hours after eating, with a 1-11 hour range, and symptoms prominently included abdominal pain in addition to vomiting and/or diarrhea. As with typical adult-onset food allergies, the adult form of FPIES is acquired after years of tolerating the responsible food. In infants, cow milk and soy milk are common triggers, in children, it is often grains such as rice and oats, and in adults, the most common triggers are seafood and eggs. However, reactions to many other foods, including soy and potatoes, have been reported.
While we can’t analyze buns, condiments, seasonings, side dishes or other ingredients that accompany the Impossible Burger everywhere it’s sold, we can provide information about the Impossible Burger itself, so that consumers with allergies can make informed choices.
The Impossible Burger is made from the following ingredients: soy protein, potato protein, coconut oil, sunflower oil, two culinary binders -- methylcellulose and food starch, a natural preservative -- cultured dextrose, a natural antioxidant -- mixed tocopherols, natural flavors, yeast extract, salt, plus several B vitamins and zinc. One more special ingredient — heme — in the form of soy leghemoglobin, contributes to the characteristic taste and color of meat and catalyzes the creation of all the other delicious flavors when cooked.
The heme in the Impossible Burger is identical to the heme humans have been consuming for hundreds of thousands of years in animal meat. Heme itself is a natural and abundant component in every cell in our own bodies, and therefore cannot trigger an allergic reaction. In nature, heme is always bound to specialized proteins, like hemoglobin in our blood cells or myoglobin in our muscles.
The heme in our product is bound by a protein called soy leghemoglobin, just as heme in animal muscle is carried by myoglobin. Soy leghemoglobin is completely unrelated to any of the proteins responsible for a soy allergy. Scientists at Impossible Foods, and independent experts in food safety and allergenicity, have comprehensively analyzed the ingredient in the Impossible Burger and concluded that it poses an extremely low risk of allergenicity.
We performed extensive allergenicity testing on leghemoglobin; the results of these tests convincingly showed that it has a very low potential to be an allergen and is very safe to eat. The results of our studies have been published in the peer-reviewed journal Molecular Nutrition and Food Research, and the data are also available on the US Food and Drug Administration (FDA) website.
The Impossible Burger contains a couple of ingredients that may cause an allergic reaction in a small percentage of susceptible individuals. These are described below. The FDA requires explicit labeling of eight common food allergens whenever they might be present in a food: milk, eggs, peanuts, tree nuts, soy, wheat, fish and crustacean shellfish. Our ingredient list and allergen statement, which declare the presence of soy, are located on our product packaging and on our website. They are also provided to the distributors, chefs and restaurateurs who work with our product.
Soy is the major source of protein in the Impossible Burger. Its primary form in our product is soy protein concentrate, with a tiny amount of soy protein isolate. In the US, approximately 0.5% of children are allergic to soy. Soy allergy generally occurs early in childhood and is often outgrown by age 3. The majority of children with a soy allergy will outgrow the allergy by the age of 10. Allergic reactions are typically mild (e.g., rash or hives, itching in the mouth, nausea, vomiting or diarrhea, stuffy or runny nose, wheezing or other asthma symptoms), but rarely can be severe (e.g., anaphylaxis). While soy allergies acquired in childhood are usually outgrown at a young age, a recent study ranks soy allergy among the top 5 most common adult-onset allergies. People with known or suspected allergy to soy should not consume the Impossible Burger.
Potato is the second major source of protein in the Impossible Burger. It is present in the form of isolated potato protein. Potato allergy is relatively uncommon, and severe allergic reactions to potatoes are rare. As with soy, there are a number of proteins in potatoes that can elicit an allergic reaction in susceptible individuals. More people are allergic to raw potatoes than to cooked potatoes, but some are allergic to both. The most common allergic reactions to raw potatoes are respiratory symptoms (e.g., runny nose, wheezing) and/or a skin rash (contact dermatitis) when potatoes are handled (e.g., during peeling). Allergic individuals can also experience adverse GI symptoms (nausea, diarrhea) and/or eczema after eating cooked potatoes. Allergy to latex and certain pollen are risk factors for potato allergy. Although rare, either raw or cooked potatoes can trigger an anaphylactic reaction. In the case of a food that contains isolated potato protein — depending on how well cooked the food is — the proteins may be present in their native (raw) or partially/fully denatured (cooked) state. Therefore, people who are allergic to cooked or raw potatoes should avoid consuming the Impossible Burger.
Yeast extract is derived from Saccharomyces cerevisiae, a yeast commonly used in baking and brewing, and as the source of nutritional yeast. Yeast extract is commonly used to provide flavor to food, and is also a rich natural source of B vitamins. People with allergies to yeast most often have skin (atopic dermatitis) or respiratory (rhinitis or asthma) symptoms from environmental exposure to yeasts and molds. More serious generalized allergic reactions to ingested yeast are rare, but have been reported. Anyone with known sensitivity to yeast-containing foods should not consume our burger.
The Impossible Burger’s fat comes primarily from two sources: refined coconut oil and refined sunflower oil. While coconut is classified as a tree nut by the FDA, and coconut is a known allergen, refined coconut oil is free of coconut protein and is not allergenic. For this reason, the FDA does not require coconut to be listed as an allergen if it is present only in the form of a refined oil. Seed proteins can also be allergens, and allergic reactions to sunflower seeds have been reported. However, like our coconut oil, the sunflower oil we use is highly refined, and therefore not allergenic.
Other ingredients in the Impossible Burger, such as methylcellulose, starch, cultured dextrose, and our natural flavors, are not known to be allergenic. However, individuals with specific food allergy concerns are encouraged to contact us with their questions.
For individuals who are allergic to wheat or have celiac disease or another form of gluten sensitivity or intolerance, the good news is that the Impossible Burger now has gluten-free certification. This means that our products are allergen tested on a regular basis and that our manufacturing facilities are audited and inspected by the certifying organization each year.
We strive to make food that is completely sustainable and at least as nutritious and wholesome as their animal-derived counterparts. Our rigorous safety testing and commitment to transparency comes amidst overwhelming evidence that moving toward a plant-based diet yields both huge benefits for the health of our planet and huge public health benefits.
We’re creating new products in a new category of food, and people naturally have a lot of questions about what we do. We’re committed to answering them, and provide details about our ingredients, processes and science on our website — on our FAQ page and in our media kit.