Eating the 3 Macronutrients of Life

Every day, we eat multiple times to provide fuel that will sustain all our planned work and activities. How do our bodies break down something like a peanut butter sandwich into the nutrients they can utilize to support normal daily needs?

The food we eat is broken down into one or a combination of 3 key macronutrients known as carbohydrates, protein and/or fats. Each of these nutrients is digested in a slightly different way, using different enzymes at different rates . Let’s walk through the process!

1. Mouth: Active chewing begins the mechanical digestion of our food. Some digestive enzymes are released directly into your mouth through saliva, and thus begins the digestion of carbohydrates and fat.
2. Stomach: After swallowing, the (bolus) of food passes down into the stomach. The food is combined with a mixture of stomach acid and digestive enzymes. The acid and digestive enzymes break down the protein in our food into amino acids, and the other digestive enzymes work to break down the fats into fatty acids.
3. Small intestine: From the stomach, the partially digested food (chyme) enters the small intestine, which is the main site of digestion and absorption. Other organs like the pancreas and liver secrete digestive enzymes into the small intestine to aid in the further breakdown of each of the macronutrients. After they are broken down into their simplest forms, the small intestine can absorb these macronutrients to be used by the body.
4. Large intestine: Finally, the large intestine is the main site of water absorption. After water is absorbed, what is left, the body gets rid of. 

Each person's body digests and absorbs food somewhat differently, which may affect things such as an individual's blood glucose level. On average, it take 6-8 hours for food to pass through the stomach and small intestine. It then takes nearly 36 hours for undigested material to pass through the large intestine. 

Eating a well-balanced variety of foods that include all macronutrients aids in optimal nutrition. Besides ensuring adequate vitamin and mineral intake (e.g., proteins boast zinc and iron while carbohydrates can provide fiber and energy), pairing foods increases satisfaction, slows digestion and aid in increasing absorption of nutrients.