If you’re allergic to steak, eating a meat-heavy diet may be harmful.
We’ve all heard it a million times: too much red meat is bad for your heart.
Now researchers are starting to pay closer attention to a specific allergy to red meat caused by a tick bite that could play a prominent role in developing heart disease.
What makes you allergic to red meat?
In a new study published this week in the journal Arteriosclerosis, Thrombosis, and Vascular Biology — a peer-reviewed journal of the American Heart Association — scientists claim to have for the first time identified this link.
Galactose-alpha-1,3-galactose, generally referred to as simply alpha-gal, is an oligosaccharide (a form of carbohydrate) found in the cells of non-primate mammals including cows, sheep, and pigs — aka, the animals humans tend to eat.
Alpha-gal was previously identified by doctors as the cause of allergic reactions, including potentially fatal anaphylactic shock in humans. Now they are pointing their finger at it for its role heart disease.
“This study brings to light that inflammation can cause injury to the inner lining of the heart vessels and lead to heart attacks,” said Dr. Satjit Bhusri, cardiologist at Lenox Hill Hospital, New York City. “Those that are allergic to alpha-Gel have an increased propensity for heart disease, likely due to inflammation, however this is likely not the only underlying factor in those who have heart disease and this allergy.”
Bhusri was not directly involved with the study itself.
In the study, researchers conducted intravascular ultrasounds of 118 subjects to observe atheroma, the buildup of plaque, inside the arteries of the heart. They also tested for the presence of alpha-gal allergy.
Alpha-gal allergy was detected in roughly one-quarter (26.3 percent) of the participants, and researchers discovered a “significant association of atheroma burden and volume” in those patients with the alpha-gal allergy. In some cases, individuals with the allergy had 30 percent more plaque accumulation than those who did not.
“Previous studies have shown that non-specific markers of allergic disease were associated with atherosclerosis, but this never included a specific allergen. Identification of a specific allergen is intriguing because it suggests that dietary avoidance of the specific allergen may be beneficial,” said first author Dr. Jeff Wilson, a researcher at the University of Virginia School of Medicine.
How a tick bite revealed the red meat allergy
Alpha-gal allergy is a relatively new discovery and is not always easy to identify.
In 2002 it was first discovered by Dr. Thomas Platts-Mills, also at the University of Virginia, that the allergy was likely from an unexpected source: a breed of tick common to certain areas of the United States known as the lone star tick (Ambylomma americanum). It is primarily found in the Southeastern United States, as well as parts of New York, New Jersey, and New England.
Platts-Mills was investigating why some individuals were having allergic reactions to the cancer drug cetuximab, which contains alpha-gal. He found that those with a history of lone star tick bites were prone to allergic reactions while using the drug.
It’s still not understood how lone star tick bites trigger alpha-gal sensitivity, but they’re recognized as the primary culprit.
When a tick bite causes alpha-gal sensitivity in a human, it modifies their immunological response to eating meat. For these individuals, when meat is ingested, the body has an allergic reaction. Among other mechanisms, the body produces immunoglobulin E (IgE) as a response to the perceived threat of alpha-gal entering the body.
This reaction has previously been observed as the cause of allergy symptoms, such as hives, nausea, stuffy or runny nose, sneezing, asthma, and headaches.
In prior research, it has also been identified as the cause anaphylaxis in otherwise apparently healthy individuals.
However, unlike most allergies in which symptoms present almost immediately, alpha-gal allergy may not show signs for up to six hours after eating meat. This makes it harder to identify and treat.
“The best way find out if you are sensitized to alpha-gal is to get the blood test. We currently only recommend it for people who notice allergic symptoms after eating red meat. In the future it is possible the blood test could be used to screen for individuals, particularly those with histories of tick bites and who live where lone star ticks are common, who could be at heightened cardiovascular risk because of the sensitivity,” said Wilson.
Researchers believe that identifying the association between tick bites, alpha-gal sensitivity, and heart disease could have important implications for future care. Among those affected by the allergy, specialized care and guidelines may need to be developed.
However, third-party experts contacted by Healthline agreed that the results, while interesting, certainly require more research, with a larger pool of patients.
“The study does raise interesting questions, as any good study does. It provides some answers, but I don’t think we can definitively say whether there’s a causation here or not. At this point it’s strictly an association study,” said Dr. Brian Silver, vice chair of neurology at Massachusetts Medical School, speaking on behalf of the American Heart Association.
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