Carrageenan: A Common Food Additive That May Cause Intestinal Inflammation
Like maltodextrin and carboxymethyl cellulose, carrageenan is a thickener commonly used in processed foods. And similar to maltodextrin and carboxymethyl cellulose, carrageenan appears to come with some concerns for its potential negative effects on the gastrointestinal tract.
Carrageenan is a polysaccharide—a chain of sugar molecules—found in edible red seaweeds (Necas 2013). It comes in three main varieties depending on the number of attached sulfate groups. As a food additive, carrageenan is commonly found in ice cream, yogurt, milk products, cured meat, fruit fillings, powdered beverages, soups and sauces.
For fifty years carrageenan has been controversial, with some researchers claiming it is harmless (Weiner 2014), while others show evidence linking carrageenan to inflammatory bowel disease (Borsani 2021). Considering its widespread use, it is worth reviewing the potential safety concerns related to carrageenan consumption.
Potential Safety Concerns
Injectable Carrageenan Produces Inflammation
In animal research, carrageenan is used as a standard approach for inducing inflammation. When injected, carrageenan reliably produces a strong inflammatory response, including redness, swelling and pain (Morris 2003). In some cases, depending on the type and level of exposure, inflammation from carrageenan can become chronic, even after exposure is discontinued (Hansra 2000, Petryk 2020).
While injecting carrageenan is different from ingesting carrageenan, the strength of the inflammatory response and its potential chronicity still raise some valid concerns. It’s also been shown that small amounts of carrageenan can pass from the digestive tract into the body with mostly unknown consequences (Nicklin 1989).
Ingested Carrageenan in Animal Studies
One of the factors that has led to some of the conflicting results on carrageenan has to do with the size of the carrageenan molecule. Animal research suggests that “degraded” carrageenan, or carrageenan with a smaller particle size, is more inflammatory and toxic than larger or “undegraded” carrageenan. However, even undegraded carrageenan can break down into smaller particles during digestion (Pittman 1976). Food grade carrageenan is typically considered to be undegraded, although testing still shows around 8% of food grade carrageenan is the more inflammatory, degraded variety (Spichtig 2008).
An older review of the animal research on ingesting carrageenan of different sizes outlines a number of concerns (Tobacman 2001). In guinea pigs, degraded carrageenan was shown to rapidly cause gastrointestinal ulcerations (Marcus 1989). A study in rats on undegraded carrageenan found increased cancer tumors, with one combination treatment showing an almost eight-fold higher tumor count with carrageenan as compared to without (Watanabe 1978). In rabbits, degraded carrageenan added to drinking water caused bloody diarrhea and gastrointestinal ulcerations by one week (Marcus 1970).
Primate Studies
However, some of the primate studies appear to indicate less harmful effects with undegraded carrageenan. A study in monkeys found no gastrointestinal side effects from undegraded carrageenan, but serious gastrointestinal ulceration and blood loss from degraded carrageenan (Benitz 1973). A study on infant baboons fed formula containing undegraded carrageenan at levels similar and higher than human baby formula did not find adverse gastrointestinal effects (McGill 1977)..
Overall, the evidence is pretty clear that degraded carrageenan causes inflammation and ulceration of the digestive tract similar to inflammatory bowel disease. For undegraded carrageenan, the studies are mixed, with the monkey and baboon studies suggesting safety, although the increased tumors seen in rats should not be dismissed.
While more research is needed, the human studies below also provide additional evidence of potential concern.
Carrageenan in Humans
A study in cultured human intestinal cells found that carrageenan in low concentrations caused increased necrotic cell death (Bhattacharyya 2008). A similar human intestinal cell study showed that undegraded carrageenan activated an inflammatory pathway that may be relevant for the initiation of inflammatory bowel disease (Borthakur 2007). Further studies showed that these inflammatory changes could be long standing based on the underlying mechanism upregulating the inflammatory pathway (Borthakur 2012).
A clinical trial in adults with prediabetes gave participants a normal diet or an equivalent diet free of carrageenan. The individuals on the carrageenan-free diet had improved blood sugar parameters and decreased inflammation (Feferman 2020). A similar study in patients with ulcerative colitis, a form of inflammatory bowel disease, found increased relapses in patients given a diet containing carrageenan, as compared to a diet without (Bhattacharyya 2017). While small, these human studies provide the best evidence that food grade carrageenan can lead to adverse effects in at least certain individuals.
Conclusion
Carrageenan is a common food additive found in numerous processed foods. While the degraded form is of obvious concern, the non-degraded form typically used in processed food products may also be problematic. For individuals with blood sugar problems or gastrointestinal conditions it may be worth considering avoidance. For others, the data is still somewhat unclear. However, reducing processed foods in general, which would reduce carrageenan intake overall, is a reasonable recommendation to support or improve overall health for any individual regardless of health status.
