The authors of a recent study, which appears in BMC Medicine, argue that at least part of the answer might lie in an immune interaction.
Nutrition and dietary habits play pivotal roles in a wide range of health conditions, including type 2 diabetes, obesity, cancer, hypertension, and cardiovascular disease.
Red meats and processed meats have each received a fair amount of attention in this regard. Both have been implicated in cancer risk, but how they exert their influence is up for debate. As the authors of the latest study explain:
“Although various mechanistic explanations have been proposed, [such as a] high energy/fat diet, N-nitroso, nitrates, nitrites, heme iron, [and] compounds produced by gut microbiome or during cooking, none seems to be specific to red meat or dairy.”
A role for antibodies?
The authors point to tentative evidence that N-glycolylneuraminic acid (Neu5Gc) might be a risk factor for colorectal cancer.
Neu5Gc is a carbohydrate, or sugar, present in foods derived from mammals, and it is abundant in red meat and dairy. It occurs at low levels in some fish but is absent from poultry.
Humans cannot synthesize Neu5Gc, but when we consume it, small amounts accumulate on cell surfaces. When immune cells encounter this nonhuman material, it triggers the production of anti-Neu5Gc antibodies. Studies have shown that humans have a wide range of these antibodies.
Scientists have also found evidence that long-term exposure to these antibodies promotes inflammation and cancer in animal models. However, they have yet to identify any clear effect of eating mammalian products on levels of these antibodies.
As these anti-Neu5Gc antibodies travel around the body, they bump into Neu5Gc on cell surfaces, sparking inflammation. Experts believe that this, in turn, exacerbates cancer, because cancer cells tend to have higher levels of Neu5Gc on their surfaces.
In one study, researchers demonstrated an association between levels of circulating Neu5Gc antibodies and colorectal cancer risk. However, the level of antibodies was not associated with red meat intake.
Now, the latest study has set out to unpick the relationship between a person’s diet and their levels of Neu5Gc once and for all.
“We found a significant correlation between high consumption of Neu5Gc from red meat and cheeses and increased development of those antibodies that heighten the risk of cancer,” explains corresponding author Dr. Veder Padler-Karavani, of Tel Aviv University.
“For years, there have been efforts to find such a connection, but no one did. Here, for the first time, we were able to find a molecular link thanks to the accuracy of the methods used to measure the antibodies in the blood and the detailed data from the French diet questionnaires.