Q&A with Donald D. Kasarda,
PhD, Collaborator, Agricultural Research Service, U.S. Department of Agriculture, and NFCA Scientific/Medical Advisory Council Member
There is no denying that the prevalence of celiac disease is on the rise. What remains a mystery, however, is the cause of the increase in the autoimmune disease.
Both researchers and people living with celiac disease have speculated the possible reasons for the increase. Some have hinted that the “hygiene theory” plays a role, in that westernized society has limited exposure to the bacteria that can help to strengthen the immune system. Still other theories focus on gluten, with specific suggestions that the increase is due to an increase in gluten ingestion in the modern diet or the rise of wheat breeding. Donald D. Kasarda, PhD, Collaborator, Agricultural Research Service, U.S. Department of Agriculture, and NFCA Scientific/Medical Advisory Council Member, recently conducted a study that leads him to believe that the latter is most likely not the cause for increased rates of celiac disease.
To get a better understanding of his study and what it means for people with celiac disease, the National Foundation for Celiac Awareness (NFCA) asked Dr. Kasarda to explain the study results.
Q. Can you explain what “wheat breeding” and “vital gluten” are? Why are they sometimes believed to play a part in the increased rates of celiac disease?
A. Wheat breeding is essentially the practice of crossing wheat lines that may have traits of interest (by pollen transfer to pistils) and then screening the offspring of the cross for lines that combine desirable traits. For instance, one might screen potential crosses for higher levels of protein (and most protein in wheat is gluten protein) in the offspring. Thus, if wheat breeding had resulted in an average increase in the gluten content of wheat over the years, this might be a factor in an observed increase in celiac disease. My survey of protein content in wheat in the U.S. over approximately the past 100 years did not support such an increase on the basis of historical data in comparison with recent data.
Concentrated gluten protein from wheat (sometimes called “vital gluten’) can be obtained by separating the protein from the starch (starch being the major component of white flour). This concentrated, separated gluten can be added to bread doughs to increase the elasticity. For example, as I mentioned in my paper, because whole wheat contains factors that decrease the loaf volume of breads made from whole wheat flour and because adding extra gluten can mitigate these negative effects on loaf volume, this separated gluten is often added to whole wheat flour intended for bread baking. Vital gluten may also be used as a thickener in food products or to change texture in products other than bread. The use of vital gluten seems to be increasing rapidly in recent decades in the U.S. Although the vital gluten intake is definitely increasing, it still is not a major part of the average total gluten intake resulting from intake of wheat flour-based products.
It is the gluten proteins of wheat that trigger celiac disease. Furthermore, certain segments of the gluten proteins are responsible. Perhaps the more of these proteins that a (potentially susceptible) person consumes, the more likely it might be that that person would develop celiac disease. There are a great number of these celiac-active segments produced from wheat during digestion. It is not known if changing the total amounts ingested by small percentages, say by about 10% of the total gluten intake (assuming a total gluten intake of about 11 pounds per year), would have an effect on celiac disease incidence (incidence being the number of people diagnosed with a disease within an interval of time, such as a year). This question could in theory be researched, but it would be very difficult. Do not expect answers soon.
Q. Your research suggests there is not an increase in gluten in wheat grain, but rather an increase in people’s consumption of wheat. What does that mean for the general population? Does this research suggest limiting wheat in the diet?
A. I do not think that limiting wheat in the diet of people who do not have celiac disease or wheat allergy is justified. Both consumption of wheat products and the use of vital gluten as an additive in food products have increased over a period of time that coincides with the time frame during which an apparent increase in celiac disease incidence in the U.S. has occurred. Such correlations could be investigated in the future for a causative effect on celiac disease incidence. At present, there is no evidence for such a causative effect. It may not exist.
Q. What implications do your study findings have for people living with celiac disease?
A. None. People with celiac disease need to avoid wheat, rye, and barley in their diets because the proteins of these grains cause harm to them and my study has no effect on that long established proscription.
We now know that there is a whole spectrum of gluten-related disorders, with celiac disease being on one end. What do you suggest your study’s implications are for the non-celiac gluten sensitive population?
A. Again, I would say none. Most, but not all, investigators have concluded that there is such a thing as non-celiac gluten sensitivity. However, not all that much is known about this condition. It may have different manifestations in different people and these may result from different mechanisms of interaction between ingested gluten and various processes in humans (immune or otherwise). What is not known is vast and my comments are highly speculative. Only further research will sort out the questions. At present, however, I suspect that the higher estimates of non-celiac gluten sensitivity (such as 6% of the population) are not likely to be correct.
Q. How will this study impact future research on celiac disease?
A. I think it will suggest to researchers that other bases for the apparent increase in celiac disease incidence beyond increased gluten content in wheat varieties should be investigated. These might include a causative connection to the levels of wheat consumption and the practice of using vital wheat gluten in food products. I emphasize, however, that there is currently no evidence that such causative effects exists. The question of whether or not total gluten intake (and perhaps the type of gluten being consumed) affects the incidence of celiac disease would be of interest for future research, but such research would be difficult (maybe even impossible) to carry out.
Based on your research, do you think a person who is at risk for celiac disease but does not yet have the condition (such as individuals with a family history of celiac disease) should monitor their consumption of wheat?”
A. No. I do not think there is sufficient scientific information at present to justify such monitoring.