It's not uncommon for picky eaters to trim the bread crust from a PB&J before eating it. But what these folks may not realize is that when they remove the crusts from sandwiches, they're also removing a powerhouse of antioxidants.
A study published in the American Chemical Society's Journal of Agricultural and Food Chemistry explains the various health benefits of eating bread crust. Bread crust not only contains powerful antioxidants that can combat cancer, it is also rich in dietary fiber, which can prevent colon cancer. Researchers at the German Research Center of Food Chemistry in Garching, Germany, experimented with an everyday sourdough bread mixture. Through analyzing the bread crust, bread crumbs from the paler inside of the bread and flour, researchers discovered that pronyl-lysine, an antixodant, was eight times more plentiful in the bread crust than in the other components of the bread. Pronyl-lysine was not at all present in the flour [source: Science Daily].
But what exactly does pronyl-lysine do? Researchers at the Institute of Human Nutrition and Food Science in Kiel, Germany, used human intestinal cells to study pronyl-lysine and found that it is effective at raising the levels of phase II enzymes -- enzymes that, according to previous studies, prevent cancer.
When you perform the seemingly simple act of popping some bread dough in the oven, you're actually beginning a complex set of chemical reactions that create powerful cancer-fighting molecules. What chemical reactions create the antioxidants that make bread crust so good for you?
The Science of Bread Baking
When you pop a slice of bread into the toaster, you're setting off a complicated set of chemical reactions. When you bake bread, the addition of heat causes carbon found in the carbohydrates of the bread to combine with the amino acids of the proteins, resulting in a browning of the surface of the bread. This process, known as the Maillard reaction, discovered by Louis-Camille Maillard in the early 1900s, was long credited by scientists for producing different flavor components and the brown color on the surface of baked breads. However, in recent years, researchers have credited the Maillard reaction with producing antioxidants that are beneficial to those who consume bread crust.
The antioxidant pronyl-lysine forms as a result of the Maillard reaction when starch and reducing sugars react with the protein-bound amino acid L-lysine. In a study published in the European Journal of Cancer Prevention, researchers found that rats that ingested pronyl-lysine experienced increased enzymic antioxidant activities [source: European Journal of Cancer Prevention].
Pronyl-lysine is more prevalent when bread is broken down into smaller pieces; that is, smaller loaves make for a bigger percentage of crust per slice. While pronyl-lysine is produced by both yeast-based and yeast-free bread, darker breads like wheat and pumpernickel contain higher levels of antioxidants than lighter breads like white.
But be careful of too much browning. Burning or overly browning bread can actually lower the level of antioxidants. In fact, burning bread flips from cancer-preventing to cancer-creating -- burning your bread can produce carcinogens [source: Health and Natural Lifestyles].
Related HowStuffWorks Articles
- Borelli, Rose C. and Vicenzo Fogliano. "Bread crust melanoidins as potential prebiotic ingredients." Molecular Nutrition and Food Research: 49.7. March 21, 2005.http://www3.interscience.wiley.com/journal/110550260/abstract?CRETRY=1&SRETRY=0
- "Bread Crust and Stuffing Rich in Healthy Antioxidants." Science Daily. Nov. 5, 2002.http://www.sciencedaily.com/releases/2002/11/021105080817.htm
- "Does eating bread crust make your hair go curly?". Heath and Well Being. June 2006.http://health.ninemsn.com.au/article.aspx?id=694037
- "Fun Facts: What's Good for Your Body?" St. Louis Science Center.http://www.slsc.org/uploadedFiles/move/Vitamins%20and%20Nutrients.pdf
- Horowitz, Janet, et. al. "Bread Goes Upper Crust." Time Magazine. May 7, 1990.http://www.time.com/time/magazine/article/0,9171,970017,00.html
- Panneerselvam, Jayabal, et. al."Inhibitory effect of bread crust antioxidant pronyl-lysine on two different categories of colonic premalignant lesions induced by 1,2-dimethylhydrazine." European Journal of Cancer Prevention. 18.4. August 2009.http://journals.lww.com/eurjcancerprev/Abstract/2009/08000/Inhibitory_effect_of_bread_crust_antioxidant.5.aspx