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Oat Cereals and Fungal Toxin OTA -- bowl of oat cereal


Yes, unfortunately. In fact, a study of oat-based cereals purchased in the U.S. found that 70% were contaminated the fungal toxin ochratoxin A. Ochratoxin A is a potential human carcinogen. It is a kidney toxin in all animal species studied and is most likely toxic to humans -- who have the longest half-life for its elimination of any species. It may also have immunosuppressive effects and cause reproductive harm. Unlike some other fungal toxins, the effects will not necessarily cause immediate symptoms (such a vomiting). However, excessive urination has been reported -- possibly due to effects on the kidney (Bennett, Clin Microbio Rev 2003)

Researchers at the University of Idaho purchased breakfast cereals from local supermarkets in various U.S. cities between 2012 and 2014, testing 489 samples. Overall 42% had contamination with ochratoxin A, with the highest percentage being among oat-based cereals (70%, or 142 out of 203 products), followed by cereals made from wheat (32%), corn (15%), and rice (15%). Most were below the limit of 3 ng/g (established by the European Union for processed cereal products — the U.S. has no established limit), except for 16 samples of oat-based cereals which exceeded the limit. There was no statistical difference between organic and conventional products. Unfortunately, the researchers did not name products (Lee, J Ag Food Chem 2015). Studies conducted in other countries have generally found similarly high levels of ochratoxin A contamination in breakfast cereals.

UPDATE: Due to the concern about ochratoxin A in oat-based cereals, purchased and tested popular oat-based cereals (and one buckwheat cereal) for contamination with this toxin (as well as for contamination with gluten and heavy metals) in 2016. Fortunately, it found that most did not exceed contamination limits for ochratoxin A (although it may be best to limit use of one of the products if it is to be given to small children). also tested the oat cereals for gluten, finding surprisingly high amounts in certain products. For the results, see the Oats Cereal Review >>

Ochratoxin A has become increasingly regulated by many countries, including the European Union where, as noted above, the maximum limit is 3 ng per gram in processed cereal products (which includes breakfast products ranging from steel-cut oats to more processed cereals).

Ochratoxin A is produced by fungi (mold) which grow on grains when exposed to moisture and heat in the field and at various stages of production, storage, and transport. Unfortunately, the toxin is difficult to destroy under normal food-processing or cooking conditions (it is relatively stable even when heated to 392 degrees Fahrenheit). 

It is likely that higher concentrations of ochratoxin A will occur in less-processed products, like steel-cut oats and rolled oats, than in highly processed products, like Cheerios, that contain additional ingredients which reduce the percentage of oats in the product. It may potentially occur in higher concentrations in oat bran because fungal toxins tend to occur on the external layers of grains, such as the bran, rather than on the on the starchy inner portion or the germ (Vidal, Food and Chem Tox, 2013). Whole grain oat flour (which, by definition, includes the bran) may also be contaminated with ochratoxin A.

The European Union has proposed a strict tolerable daily intake level for ochratoxin A of 5 ng per kilogram of body weight, which works out to 227 ng of ochratoxin A per 100 lbs of body weight. The amount of ochratoxin A in the most contaminated oat-based cereal in the U.S. study above contained 9.3 ng per gram. A single 30 gram serving of this cereal would, therefore, contain 279 ng of ochratoxin A. What this means is that a very small percentage of oat-based breakfast cereals seem capable, on their own, of causing a person to exceed the tolerable daily intake level for ochratoxin A. The risk, however, is greater for those who consume multiple servings of oat-based cereal per day, weigh less -- such as children, and/or have significant exposure to ochratoxin A from other sources.  

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