Tracing the Digestion of a Cookie

Cookies require a variety of enzymes to be digested.

Cookies require a variety of enzymes to be digested.

Almost everyone likes to snack on a cookie from time to time, but have you ever stopped to consider how it’s digested by your body? Most cookies contain a wide variety of nutrients that require numerous enzymes to break down before your body can absorb them. Carbohydrates or sugars are the dominant ingredient in cookies, but they typically also contain a variety of fats, protein and dietary fiber. Carbohydrates digest the quickest, whereas protein and fat take longer to break down.

Carbohydrate Digestion

Carbohydrates are sugars and starches. Cookie dough, dairy products, raisins and other dried fruit contain quite a bit of sugar, among other things, and sugar digestion starts in your mouth. An enzyme called alpha-amylase is in your saliva, and it starts to reduce the long chains of sugar, called polysaccharides, into smaller chains of sugar. Some gastric amylase in your stomach continues to break down the sugars, although the majority of carbohydrate digestion takes place in your small intestine with the release of enzymes from the intestinal wall and pancreas. Intestinal and pancreatic amylases fully reduce carbohydrates into maltose, which is then cleaved by maltase enzyme to produce two molecules of glucose. Glucose, the simplest sugar, is quickly absorbed by the small intestine and deposited into your blood, which is why it’s called blood sugar. All cells use glucose for energy purposes.

Fat Digestion

Cookie dough, butter, lard, dairy products and nuts also contain saturated and unsaturated fats. The digestion of fat also begins in your mouth because an enzyme called lingual lipase is secreted when you chew food that contains fat. However, the majority of fat digestion occurs in the small intestine with enzymes secreted by the pancreas and bile secreted from your gallbladder. Pancreatic lipase enzymes reduce the fat into smaller units called fatty acids and triglycerides, which are absorbed into the bloodstream and either used for energy or stored. Some fat is needed to absorb fat-soluble vitamins, such as A, D, E and K, in the small intestines. Other vitamins and minerals are absorbed throughout the gastrointestinal system.

Protein Digestion

The grains, nuts and butter in cookies also contain some protein, which begins its metabolism in the stomach with the help of an enzyme called pepsinogen. Pepsinogen is quickly converted into pepsin by stomach acidity and starts to digest protein into smaller building blocks called amino acid chains and peptide fragments. The partially digested protein then moves into the small intestine where pancreatic proteases fully reduce it into single amino acids. Amino acids are absorbed in the small intestine and used to make and repair muscles tissue, skin, fingernails, hair and other protein-based structures.

Digestion Time

The digestion and absorption time of cookies depend on the ingredients. The protein and fat in cookies take longer than the carbohydrates to digest and absorb. A chewed-up cookie stays in the stomach long enough to process the most difficult compounds, then the partially digested nutrients move into the small intestine and begin separating, with the sugars being absorbed first, the protein and fat requiring more digestion with specific enzymes and the fiber moving on virtually untouched to the large intestine. Overall, a cookie will spend less than an hour in your stomach, but it may spend up to a day or so in your intestines as different parts of it are absorbed at different rates.

 

References

  • Encyclopedia of Human Nutrition; Benjamin Caballero et al.
  • Human Metabolism: Functional Diversity and Integration; J. Ramsey Bronk

About the Author

Sirah Dubois is currently a PhD student in food science after having completed her master's degree in nutrition at the University of Alberta. She has worked in private practice as a dietitian in Edmonton, Canada and her nutrition-related articles have appeared in The Edmonton Journal newspaper.

Photo Credits

  • Ablestock.com/AbleStock.com/Getty Images