You can’t benefit from the nutrients in the food you eat until you digest it. Digestion decreases the size of food particles until they are small enough to absorb into the cells of your intestine. Not all the food you eat is digestible, however. Some foods have a chemical structure incompatible with your digestive enzymes, while in other cases a gastrointestinal disorder may prevent you from completely breaking down the food you consume. Nonetheless, foods you can't digest can still benefit your health.
The important process of digestion
Digestion reduces proteins to amino acids, lipids to fatty acids and carbohydrates to sugars. It begins as you chew your food and continues in stages in your stomach and small intestine, where your food pieces get progressively smaller throughout the process. Digestion relies on the activity of digestive fluids, including digestive enzymes. These enzymes, produced by your salivary glands, stomach, pancreas and small intestine, are specific for different types of digestible foods. For example, some clip proteins into smaller fragments, others remove fatty acids from triglyceride molecules and some break down starches. Foods you can’t digest, on the other hand, pass through your gut without being reduced to their individual components.
Fibre, made up of various types of carbohydrates, contains chemical bonds that your digestive enzymes can’t break apart. Soluble fibre absorbs water in your gut and swells, slowing down the movement of food, while insoluble fibre adds bulk to your stool and helps keep your bowel movements regular. As fibre passes through your intestines undigested, bacteria in your gut which manufacture enzymes capable of digesting soluble fibre can break down this carbohydrate to some extent, which may result in intestinal gas. However, fibre in your diet can improve your digestive health, and it may reduce your risk of developing colon cancer, help manage diabetes and lessen your chance of becoming obese.
Resistant starch describes plant-based starches exhibiting a difference in their chemical bonds or undergoing chemical changes that prevent them from breaking down. Foods in this category include raw cornstarch, pasta that has been cooked and cooled, unripe bananas and sourdough bread. Because these starches pass through your gastrointestinal tract undigested, they can act similarly to dietary fibre. For example, resistant starches can help you feel full longer and can slow down the absorption of nutrients such as glucose. Unlike soluble fibre, however, resistant starches do not produce intestinal gas as they move through your system.
Sometimes the foods you eat do not undergo digestion because of a physiological disorder. In lactose intolerance, for instance, your intestinal cells either lack the ability to produce the digestive enzyme lactase or cannot synthesize enough of it. This enzyme digests the milk sugar lactose into single sugar units, and, if undigested lactose continues to your large intestine, bacteria break it down. As they do this, they release gas into your gut that can cause abdominal pain and bloating. Fortunately, in the case of lactose intolerance, you can supplement your diet with lactase to help you digest milk products and avoid unpleasant symptoms.
However humans do not always eat just because they are hungry. When we eat more food than our bodies need, the excess is stored as body fat. This can lead to problems of obesity which in turn can lead to a number of health problems including cardiovascular disease and type 2 diabetes.