Carrageenan

Carrageenan has been used as a food additive for decades. It is a red sea-weed derived high molecular weight hydrocolloid that is used as a stabilizer and thickener in food to make it more gel-like ^[1]. It is mainly used in dairy and meat products because of strong binding properties. There are multiple varieties of carrageenan, but they are fairly similar. All are considered vegetarian or vegan alternatives to gelatin. Carrageenan is not degraded very much in the gastrointestinal tract and is not absorbed, at least from the species in which it's been studied. When systemically administered, carrageenan has been reported to have a variety of effects on the immune system, but these don't necessarily mean that the same thing is occurring when it is consumed orally.

Online sources and the media have taken the extreme stance that carrageenan is dangerous and should be avoided. Carrageenan has not been found to be carcinogenic, genotoxic, or tumor-promoting ^[1]. Many of the toxicological studies that have been conducted have used doses far in excess of standards in human consumption. The Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives have recommended an allowable daily intake of 'not specified', meaning it is not dangerous. As a result of the various types, differing naming systems, basic chemistry differences, and types of carrageenan tested, there has been a lot of confusion about the human safety of carrageenan consumption ^[2]. The other aspect to examine is that there is data from in vitro experiments that have been translated to be equivalent to how humans process carrageenan, but this is not appropriate. This leads to information being taken out of context and being reported as factual. Many cell-based models have been able to provide key information regarding safety of various drugs or chemicals. These can be useful, but care must be taken when extrapolating findings to mean they are equivalent in humans ^[2]. Issues such as identity, purity, dosing, solubility, binding, and use of cell models are overlooked. In these types of circumstances, in vitro data can be misleading. There have not been many comprehensive literature reviews of carrageenan. This article will identify claims being made online and recommend an evidence-based approach.

 Online Claims

One popular blogger posted an article called "Carrageenan: The chemical hiding in your organic foods!" ^[3]. The title arouses suspicion in carrageenan. The article states that carrageenan is not digestible and has no nutritional value. But this is not the purpose of using it as a food additive; it is not meant to be nutritional or digestible. Humans eat many things that are not nutritional or digestible all the time. The article then says that carrageenan causes inflammation, which can lead to ulceration and bleeding ^[3]. This is a very strong claim to make and requires strong evidence to back it up. The blogger cites the work of Joanne Tobacman, who has done research on carrageenan. According to Tobacman, exposure to all forms of carrageenan are capable of causing inflammation. Inflammation is the root of many serious diseases, including heart disease, Alzheimer's, and cancer. Make the link and carrageenan is playing a role in the pathogenesis of these diseases. This is a large extrapolation of rats who were being administered supra-physiological doses. It is not appropriate to translate this to mean the same thing will happen in human consumption. The blogger concludes by saying that carrageenan may not be as bad as some sources portray, but that there is evidence that it can be harmful, especially if consumed regularly, with some citing it causes digestive trouble, skin rashes, and other health problems. This conclusion is a bit more tame, but is nevertheless not founded on strong evidence.

Another popular blogger wrote a post about whether carrageenan was helpful or harmful ^[4]. This blogger identifies that the evidence published in 2001 actually used poligeenan instead of carrageenan. Poligeenan is a breakdown product of carrageenan. Poligeenan was implicated in carcinogenesis in animal data. However, the conversion from carrageenan to poligeenan does not happen in the human body, as the human body cannot replicate the high temperatures and strong acids required to create poligeenan. The blogger also identifies that many of the studies conducted on carrageenan show conflicting results based on the species being studied. In some species, it is possibly harmful, while in others it is safe. Overall, this blogger presents a much more reasonable view, based on the fact that in animal studies of diets that consisted of 1-3% of carrageenan showed no changes to the colonic cells ^[5]. The other thing to note is that the concentration of carrageenan in food is between 0.01% and 1%. And then that food will only be a small percentage of a human's overall diet. This means that the final amount of carrageenan actually ingested by a human would be extremely small.

Actual Evidence of Harm?

There is some evidence that carrageenan can induce cell cycle arrest in human intestinal cells in vitro ^[6]. In this particular study, human intestinal epithelial cells were exposed to low concentrations of carrageenan. The results showed that there was increased cell death, reduced cell proliferation, and cell cycle arrest compared with the unexposed control cells. However, these concentrations of carrageenan are more than the anticipated exposure of the human colon to carrageenan from the standard Western diet and thus must be interpreted appropriately. This data does not mean that carrageenan causes ulcerative colitis or other chronic diseases, for example. This data only indicates that at most, further research should be conducted. A recent review on the safety of carrageenan in food found that it is excreted in the feces ^[1]. It is not degraded by stomach acid or by microflora in the GI tract. It is not significantly absorbed or metabolized, nor does it significantly affect the absorption of nutrients. The author states that reviews of several studies from numerous species indicates that food grade carrageenan does not produce intestinal ulceration at doses up to 5% in the diet ^[1], which are doses that are orders of magnitude beyond what a typical human might consume. Carrageenan has not been found to affect the immune system (as judged by multiple appropriate measures). Even in infant formula, it has been shown to be safe in infant baboons and in an epidemiological study on human infants. Overall, it is safe.

Conclusion

Carrageenan is a food additive found in desserts, ice creams, salad dressings, sauces, beer, toothpaste, and many other products. It has been reported by many online sources and the media that carrageenan may be unsafe. These statements are not founded on appropriate evidence. Carrageenan has not been found to be carcinogenic, genotoxic, or tumor-promoting. Furthermore, the experiments in which carrageenan was found to be unsafe either used a different item such as poligeenan, or used doses and methods that would far exceed what a human would consume. Many inappropriate extrapolations have been made from in vitro and animal data. There is sparse published human data on the consumption of carageenan, but all of the currently available evidence points to it being safe for human consumption.