Is Quinoa Gluten-Free? Yes, But Recent Research Raises Questions for Celiacs
By Peter Olins, PhD and Gillian Olins, PhD on July 5, 2012
Quinoa is a highly nutritious substitute for wheat-based foods, and normally has “gluten” levels that meet the common standard of less than 20 ppm. A research study published on July 3, 2012, investigated the immune properties of 15 different cultivars of quinoa. V.F. Zevallos and co-workers confirmed the lack of “gluten”, but found that two varieties had unexpectedly high levels of immune reactivity on celiac disease cells, comparable to the levels found in wheat. This work suggests that the current ELISA test for gluten may not always accurately predict the safety of a food product for celiacs.
What is Quinoa?
Quinoa (pronounced “KEEN-wa”) is not a grain (like wheat, barley or rye). Instead, this seed is only very distantly related to the grains, and is actually a closer relative of spinach, amaranth and rhubarb (also tumbleweed!).
Quinoa has been grown as a food crop in the Andes for over 5000 years. The nutritional composition of quinoa makes it an attractive alternative to wheat; in fact, the proteins in quinoa actually have a more balanced range of amino acids, and include all the essential amino acids required for human nutrition (Ref. 1). Quinoa makes a great, mild-tasting side-dish, and offers fiber, folic acid and minerals often lacking in other gluten-free foods that are a critical part of the diet of people with celiac. Currently, most quinoa is produced in Peru and Bolivia, but the increased interest in this nutritious seed has prompted an increase in cultivation in North America.
Ref. 1: Saturni, L, et al. Nutrients (2010) 2:16-43. doi:10.3390/nu2010016 The gluten-free diet: safety and nutritional quality
What is Gluten? How is It Measured?
This question is actually harder to answer than you might think. The “gluten” protein in wheat is actually a complex mixture of over 100 closely-related proteins, and these proteins differ between wheat varieties. When gluten is consumed and digested in the stomach and small intestine, many small “peptide” fragments are created. Some of these peptides activate the “innate” immune system, and some of them activate the “adaptive” immune system, which results in celiac disease. Currently, there is no simple way to measure the amount of all these proteins and peptides, but an estimate can be obtained using a diagnostic test called an ELISA. This ELISA is used for detecting traces of gluten in foods, and most countries require that foods labeled as “gluten-free” have no more than 20 parts per million of gluten. Last year we published a blog entitled “Proposed FDA Standard for Gluten-Free Foods (20 ppm) May Not Adequately Protect the Food Supply for Celiacs“, and followed up with a “Letter to FDA on Labeling of Gluten Free Foods for Celiac Disease“. A key point was that although an ELISA test might give a precise value for the “gluten” content of a food, celiac consumers are more interested in how safe a food actually is. The research paper we discuss in this blog provides the first clear evidence supporting the idea that “ppm of gluten” may not be an accurate measure of the safety of a food for celiacs.
Is Quinoa Gluten Free?
Since quinoa is not a grain like wheat, rye or barley, by definition, it does not contain “gluten”. In addition, diagnostic tests that measure gluten in foods show that quinoa typically gives a very low reading for “gluten” levels. (As with all gluten-free foods, there is always a small risk of cross-contamination with wheat, barley or rye, but this appears to be rare for quinoa).
Quinoa does, however, have seed storage proteins in the “prolamin” family that are distantly related to the gluten proteins present in wheat. The obvious question is: are these storage proteins sufficiently similar to wheat gluten that they could cause an immune reaction in celiacs?
Is Quinoa Safe for People With Celiac Disease?
This question has not been investigated rigorously, but most authorities recommend quinoa as a safe and nutritious alternative to wheat-based foods. One 2011 research study (Ref. 2) tested the biological activity of two cereals (teff and millet), and two pseudo cereals (quinoa and amaranth). The first test used cultured T-cells derived from a celiac patient; the second used biopsy tissue samples from a celiac patient; and the third tested the grains in a mouse model of celiac disease. In all three cases, no immune cross-reactivity was observed, and the authors concluded that these various seeds were safe in the diet of celiac patients.
Ref. 2: Bergamo, P, et al. Mol Nutr Food Res (2011) 8:1266-1270. Immunological evaluation of the alcohol-soluble protein fraction from gluten-free grains in relation to celiac disease
Latest Research Shows That Some Varieties of Quinoa are Very Potent in Activating the Immune System of Celiacs
In contrast to the work described above, a research paper published two days ago by V.F. Zevallos and co-workers examined 15 different cultivars of quinoa, to examine their safety for people with celiac disease (Ref. 3). First, they tested the quinoa samples using an ELISA to test for “gluten” content. As expected, protein samples from all 15 cultivars gave gluten readings below the typical cutoff of 20 ppm (four samples gave a very low, but detectable signal).
Next, the proteins were tested for their biological activity, either using cultured T-cells or using biopsy samples obtained from celiac disease patients. The biological responses were monitored by measuring the production of two immune-stimulating substances (“cytokines”), IFN-gamma and interleukin 15. These cytokines are critical for the human immune response to gluten, and for the development of celiac disease. Remarkably, 2 out of the 15 quinoa cultivars (“Ayacuchana” and “Pansakalla”) stimulated an immune response that was as potent as that observed for wheat gluten! This result suggests that the current ELISA test used for detecting gluten in food may not be sufficient to predict toxicity of all foods in celiac patients.
What about the earlier study (Ref. 2) showing that quinoa did not activate cells and tissues from celiac patients? Unfortunately, we don’t have enough detail about the specific variety of quinoa used for that study. Obviously, this research will need to be repeated in different laboratories and with different samples of quinoa. However, this study calls into question the assumption that all varieties of quinoa are safe for celiacs.
This is very reminiscent of recent work done with different varieties of oats, which had widely varying cross-reacting activities with antibodies specific for wheat gluten.
Ref. 3: Zevallos, VF, et al. Am J Clin Nutr (2012) 10.3945/ajcn.111.030684 Variable activation of immune response by quinoa (Chenopodium quinoa Willd.) prolamins in celiac disease
Conclusions About Gluten Free Quinoa
This blog is not meant to be alarmist, but is intended to provide an update on the potential safety of this important food. For now, quinoa remains an attractive and nutritious substitute for wheat.
Strictly-speaking, quinoa is indeed “gluten-free”. However, this latest research by Zevallos and co-workers provides the clearest evidence so far that the ELISA used for measuring “gluten” in foods may not be an accurate measure of the immune-stimulating activity of a given food, and therefore may underestimate the toxicity of “gluten-like” proteins in people with celiac disease.
Obviously, people differ widely in their response to gluten-containing foods: if you suspect that you might have had an adverse response to a given food, it’s important for you to discuss this with your dietitian or physician.
Finally, if you search the internet for the phrase “is quinoa gluten free“, you will find a strong consensus that this is a safe food for celiacs; but as in most aspects of science, the real world often turns out to be a bit more complicated than expected.