Does wheat starch belong in a gluten-free diet?
In Honor of Celiac Disease Awareness Month, Gluten Free Watchdog is writing a series of articles (the goal is one per day during the month of May) related to the gluten-free diet–currently the ONLY treatment for celiac disease.
First some background…
Under the FDA’s gluten-free labeling rule wheat starch is allowed in gluten-free foods as long as the final product contains less than 20 ppm of gluten. This is because wheat starch is considered by the FDA to be an ingredient processed to remove gluten.
Wheat starch is not wheat grain and it is not wheat protein. It is not intended to contain any gluten. BUT it is very difficult to completely separate the starch and protein components of wheat so small amounts of gluten remain in the wheat starch. Not all wheat starch is created equal. Depending on the extent of processing wheat starch will contain varying amounts of residual gluten. A recent study found wheat starch to contain from < 5 ppm of gluten to over 10,000 ppm of gluten (1). (wheat starch and wheat gluten are separated using water by first making dough).
Should folks with celiac disease eat wheat starch?
I have been writing about wheat starch since 2001 and the publication, “Wheat starch, gliadin, and the gluten-free diet.” My opinions are constantly evolving based on new information. In 2008 I wrote the following on wheat starch (from the Gluten Free Nutrition Guide, McGraw Hill):
“… If a manufacturer of wheat starch or products containing wheat starch demonstrates through testing that its products contain less than 20 parts per million of gluten, then in theory I support their consumption by people with celiac disease.”
BUT more is known today about testing wheat starch for gluten than was known 10 years ago.
For example, according to R-biopharm, wheat starch should be tested for gluten using a competitive ELISA (2) in addition to a sandwich ELISA. During the processing of wheat starch, residual gluten may be partially broken down (1). A sandwich ELISA detects intact or relatively intact gluten protein. A competitive ELISA detects gluten that has been broken down into smaller protein fragments.
In addition, the gluten content in wheat starch may be underestimated. The reason for this is complex. In brief, gluten is made up of prolamins and glutelins; in wheat the prolamin is gliadin and the glutelin is glutenin. When using the R5 ELISA, the gliadin value is multiplied by 2 to determine the level of gluten. In general, the gliadin to glutenin ratio is considered to be 1:1. However, in reality, this ratio is variable. In one recent study the ratio varied from 0.31 to 3.19 in wheat starch samples (1). The ratio was less than 1 in seven out of fifteen wheat starch samples (meaning that the gluten content was underestimated) (1).
Researchers concluded, “The considerable variation of gliadin to glutenin ratios confirmed the need for a reliable, non-immunochemical analytical method capable of accurately quantitating both gliadin and gluten in wheat starch samples to ensure the safety of gluten-free foods for coeliac disease patients.” (1)
Updated opinion on wheat starch…
Because of the current limitations associated with testing wheat starch for gluten, it is the opinion of Gluten Free Watchdog that products containing wheat starch are best avoided by individuals with celiac disease.
That said, if you have celiac disease or another gluten-related disorder and you would like to eat wheat-starch based foods, it is the recommendation of Gluten Free Watchdog that you do the following:
- Eat foods containing wheat starch only if the product is labeled gluten-free.
- Establish with the manufacturer that the final product is tested using both a sandwich and competitive ELISA.
Note: At Gluten Free Watchdog we have tested wheat starch labeled gluten-free and wheat starch not labeled gluten-free. As was expected, wheat starch not labeled gluten-free contained higher levels of gluten and gluten fragments than wheat starch labeled gluten-free. Nonetheless, wheat starch labeled gluten-free contained small levels of both intact and hydrolyzed gluten.
Note: While wheat starch is used in gluten-free foods in Europe, it is used in very few products in the US. The most well known product is likely Schar brand croissants. Schar provided Gluten Free Watchdog with a statement about their testing protocol for this product https://www.glutenfreewatchdog.org/news/using-wheat-starch-in-gluten-free-foods/
Tomorrow’s post: Happy wheat starch isn’t used in more gluten-free foods? You may have Ener-G Foods & Elaine Hartsook to thank
- Proceedings of the 27thMeeting Working Group on Prolamin Analysis and Toxicity. Analytical Research Reports. Katharina Konitzer, Herbert Wieser, Peter Koehler. German Research Centre for Food Chemistry, Leibniz Institute, Freising, Germany. Quantitation of gluten in wheat starch by gel permeation chromatography with fluorescence detection Available at: http://www.wgpat.com/proceeding_27th.html
- R-biopharm. Ridascreen Gliadin Competitive. Available at: https://food.r-biopharm.com/products/ridascreen-gliadin-competitive/