Protein slows the digestion of carbohydrates and the production of glucose, which can help to stabilize blood sugar levels. The faster your body can digest simple carbohydrates, the faster and higher your blood sugar levels rise. Both protein and fat slow the absorption of carbohydrates; eating a combination of fat, protein and carbohydrates at every meal helps regulate glucose and insulin levels in your body.
Carbohydrates and Glucose
Glucose is your body's primary energy source and is easily made from simple carbohydrates. Simple carbs are those with one or two sugars; complex carbohydrates have three or more sugars. Table sugar, maple syrup and honey are simple carbs, as is fructose, which occurs naturally in fruits, and lactose, a sugar in milk products. Simple carbs digest quickly -- usually in 15 to 30 minutes -- and have an immediate impact on blood sugar levels. Complex carbs such as fiber take more time to digest and have less of an affect on glucose production.
Glucose and Insulin Production
Protein slows digestion; eating protein and carbohydrates at the same time slows your body's ability to produce glucose. By keeping glucose and insulin production steady, you can avoid the dangerous cycle of high and low blood sugar that can lead to overeating, weight gain and insulin resistance. Eating a diet high in simple carbs can quickly raise glucose levels. Your pancreas responds by producing insulin; the faster glucose levels rise, the more insulin your pancreas releases into your bloodstream. Too much insulin can lead to low blood sugar, and your body is fooled into believing you need to eat again. Glucose not used right away for energy is stored as fat.
Digestion is both a physical and a chemical process. It starts in your mouth with the chewing and a digestive enzyme in your saliva called amylase that breaks down carbohydrates. Carbs, fats and proteins each need specific enzymes to break them down so your body can absorb their nutrients. These enzymes are located in different parts of your digestive system. One of the reasons carbs digest so quickly is that digestion starts in the mouth for sugar; but the enzymes that break down protein and fat are located further down your digestive tract.
The glycemic index, or GI, is a system that measures and scores carbohydrates based on how fast your body digests them and how quickly they can raise blood sugar. Carbohydrates with a high fat content have the slowest digestion times, because fat is broken down even more slowly than protein. Speed of digestion depends on the ratio of carbs, proteins and fat you eat. Foods that score low on the GI take a longer time to digest. You can slow the digestion of carbohydrates by adding protein and/or fat to your meal.
- National Digestive Diseases Information Clearinghouse; Your Digestive System and How it Works; April 2008
- Medline Plus: Carbohydrates
- SUNY Biology Department: Digestive System; Micheal Gregory
- Food and Agriculture Organization of the United Nations: Digestion, Absorption and the Energy Value of Carbohydrates