Miss a day, miss a lot. Subscribe to The Defender's Top News of the Day. It's free.
Editor’s note: This article is part 1 in a three-part series on alpha-gal syndrome, more commonly known as red meat allergy.
Mainstream news outlets have been reporting on a new, mysterious health threat with no treatment or cure: alpha-gal syndrome (AGS), or red meat allergy.
Individuals with AGS experience mild-to-severe symptoms several hours after eating red meat. AGS has no cure and the only “treatment” is to avoid certain meats and animal products.
According to the latest consensus, the lone star tick is the main transmission vector for AGS. This creature previously was known to transmit several rare bacterial and viral infections, including such exotic-sounding ailments as southern tick-associated rash illness, ehrlichiosis, tularemia, heartland virus and Bourbon virus disease.
The tick-AGS connection
When ticks latch onto a host they may remain embedded for up to several days. During that time, the creatures keep the wound open and their food source — blood — flowing by injecting saliva into their host.
Tick saliva contains proteins that prevent blood from coagulating. Victims get sick when the saliva also contains viruses and bacteria associated with tick-borne illnesses.
But unlike Lyme disease, AGS is not caused by a microbe. Tick saliva also contains trace quantities of a sugar, alpha-gal (chemical name: galactose-alpha-1,3-galactose), a known human irritant that many researchers and clinicians believe induces the dangerous allergic responses that are the hallmark of AGS.
Alpha-gal is found mostly in red meats, including pork, beef, rabbit, lamb, goat, buffalo and venison, and in other animal products such as gelatin, and cow’s milk.
It also can be found in some personal care and household products containing animal-derived ingredients — and in the cancer drug cetuximab.
People with AGS may also have bad reactions to products containing carrageenan, a thickening additive found in many foods and drinks. Carrageenan is composed of many different types of sugar, including alpha-gal. The additive also has been implicated in other serious digestive problems.
AGS-type reactions have also been reported in patients receiving heart valves, gelatin-based plasma expanders and pancreatic enzyme treatments.
Depending on the study, as many as 46% of Americans carry antibodies to alpha-gal — meaning they have been exposed in some manner to the sugar. However, only a tiny fraction of those who have the antibodies are allergic to meat.
Symptoms range from barely noticeable to life-threatening
People with AGS who consume red meat or products containing alpha-gal develop typical allergy symptoms ranging from barely noticeable to life-threatening.
Mild symptoms include hives or itchy rash, nausea or vomiting, indigestion and diarrhea. Serious reactions may include difficulty breathing, a big drop in blood pressure leading to fainting or heart conditions, and swelling of the lips and tongue.
The worst manifestations of AGS, including life-threatening anaphylaxis, do not generally occur soon after eating like other food allergies but may be delayed for as long as six hours.
According to the Centers for Disease Control and Prevention (CDC), about 34,000 cases of AGS were reported in the U.S. between 2010 and 2018 — or just under 4,000 cases per year.
Given the U.S. population of about 320 million during that time period, one would expect fewer than 1 in 100,000 people to develop AGS in any given year.
Since AGS was only discovered in 2009, many healthcare providers are unaware of the condition. And because healthcare systems are not required to report AGS cases to the CDC, the incidence of meat allergy is probably somewhat higher than the CDC stats indicate.
When choosing foods, read the labels
Although no treatments exist for AGS, those who suffer from the disorder can, with some effort, avoid its worst consequences.
According to the CDC, not all individuals with AGS react to every food product containing alpha-gal. But to be safe, patients should eliminate meats and other food products derived from mammals. Fish, chicken, vegetables and grains are OK to eat.
Those affected should also read food product labels carefully, as animal-derived products can show up in almost any processed or prepared food.
And since some non-obvious food choices and even some medicines may also trigger AGS or a similar allergic response, people with severe AGS should make sure their prescribers are aware of their condition.
People with AGS may be tempted to work around their food restrictions by incorporating lab-produced meat into their diets. These products are made from either plant or fungal (e.g. mushroom) extracts or cultured animal cells.
In either case, manufacturers add numerous artificial or highly processed ingredients to make the products palatable and visually appealing.
In his expose of the “fake meat” industry, Dr. Joseph Mercola concluded in 2022 that:
“Ultimately, fake food contributes to the rising number of people who suffer from health conditions related to the foods they eat, such as diabetes, heart disease and obesity.
“For health reasons, ecological reasons and your future, I recommend skipping meat alternatives and opting for real beef.”
It’s real, but is it overhyped?
It’s common for health reports of “new” health risks to go viral, which has been true of late for tick-induced meat allergies. An internet news search returned more than 13,000 page hits for “alpha-gal syndrome” in the 30 days prior to this writing — nearly as many as a search on “breast cancer.”
Is this level of concern over alpha-gal syndrome justified?
Current epidemiologic and predictive models rely on a test for antibodies to alpha-gal. But that model is flawed because, as recent studies reviewed below show, close to one-third of U.S. residents have the antibody — but the overwhelming majority do not have AGS.
News reports nevertheless continue to conflate positive antibody tests with confirmed, symptomatic AGS.
STAT, a for-profit healthcare information provider, noted that cases are “on the rise.” However, the basis of this claim was not actual AGS diagnoses but positive antibody tests, the vast majority of which were from asymptomatic individuals.
Another site simply and erroneously defines ASG as a positive antibody test.
Even CBS News has referred to antibody assays as “blood tests for alpha-gal syndrome.”
Yet the CDC defines AGS as the presence of:
“One or more of the [listed] allergic and/or gastrointestinal symptoms that occur 2–10 hours after ingestion of pork, beef, lamb, any other mammalian meat, or any mammalian-derived product (e.g. gelatin), OR within two hours after intramuscular, intravenous, or subcutaneous administration of alpha-gal-containing vaccination or medication.”
What does a positive antibody test mean?
A positive antibody test can mean many things. Our understanding of AGS tells us that a person has been exposed to alpha-gal and that their immune system produces antibodies to alpha-gal.
Specifically, antibodies are of the IgE type, which is normally associated with allergies. However, the presence of IgE antibodies only means that someone has been exposed to an irritant, a process known as sensitization. It does not mean they will definitely experience allergic symptoms when they encounter that substance.
In a paper published in July, Dr. Sarah McGill and co-workers at the University of North Carolina School of Medicine reported that of 404 patients undergoing colonoscopy, 127 (31%) had elevated IgE alpha-gal antibodies.
A survey querying subjects about gastrointestinal symptoms and diet found that patients with and without the antibodies experienced statistically similar levels of GI distress, and ate about the same amount of red meat.
No differences were seen in patients with elevated IgE levels either. Patients with the very highest levels of antibodies tended to eat less meat but were not overrepresented among those with GI symptoms.
McGill et al. concluded that:
“Elevated alpha-gal IgE antibodies were common and not associated with a reduced mammalian meat intake, abdominal pain, or diarrhea. Seropositivity did not predict symptomatic alpha-gal sensitization in this general screening population.
“Other host factors likely contribute to the phenotypic expression of alpha-gal syndrome.”
McGill et al.’s report echoed population-based results from a much larger study, also published in July in the CDC’s Morbidity and Mortality Weekly Report. That paper also found that about 31% of people in the U.S. tested between 2017 and 2021 carried anti-alpha-gal IgE antibodies.
This study, whose author affiliations included the CDC, Eurofins Viracor (a medical testing company), and the University of North Carolina (including a co-author on the McGill study), confirmed that most antibody-positive results came from U.S. regions where ticks are plentiful.
But they did not discuss how antibody positivity might progress to full-blown AGS. They referred to positive test results as “suspected cases” without elaborating.
But in an interview with The Defender, McGill, lead author on the smaller IgE study, provided an interesting clinical perspective on this point: “Most of the individuals who tested positive for IgEs were referred to testing because they’d already shown symptoms, which justifies labeling them as ‘suspected’ cases.”
Danger of over-diagnosing is real
A 2017 article, published on Healthy Debate before concern over alpha-gal hit current levels, questioned the value of antibody tests in the context of food allergy, referring to them as “science-ish” as opposed to “science” and questioning whether diet modifications based on results from flawed tests might do more harm than good.
Perhaps more germane is the position of the Canadian Society of Allergy and Clinical Immunology (CSACI), which in 2012 warned against misusing antibody tests to diagnose food allergies.
The Society was:
“very concerned about the increased marketing of food-specific immunoglobulin G (IgG) testing towards the general public over the past few years, supposedly as a simple means by which to identify ‘food sensitivity,’ food intolerance or food allergies. …
“There is no body of research that supports the use of this test to diagnose adverse reactions to food or to predict future adverse reactions.”
Unique risks warrant caution
While very few people with elevated antibodies to alpha-gal develop a meat allergy, antibody positivity carries some unique risks for certain individuals.
“I’m concerned that some people who are positive for antibodies but don’t show typical allergy symptoms after eating meat could experience a catastrophic reaction to common medications, like heparin, or to the cancer drug cetuximab,” McGill told The Defender.
Heparin is a common blood thinner administered by injection and is associated with serious but extremely rare adverse reactions in patients with confirmed AGS.
“Another potential issue is that alpha-gal sensitization and ensuing inflammation may worsen coronary artery disease,” McGill said.
This possibility, like the ability to predict which “suspected” (based on an antibody test) AGS cases will convert to confirmed, symptomatic cases, will require additional study.
For now at least, very few people have to worry about AGS. To those alarmed by the news blitz surrounding this topic, Dr. Robert Shmerling, senior faculty editor at Harvard Health Publishing, shared this advice in a 2021 post:
“Beware the spectacular medical news story. More often than not, it’s an exceptional situation that may not have much relevance to you. And it might even lead you away from what’s most important to your health.”
