Understanding Digestion: Process, Enzymes, and Nutrient Conversion

Author: Yean Toh | Published date: June 29, 2023 | Category: Nutrition

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Finally, after your semi-digested food is well acidified, it leaves the stomach and enters the small intestines, where the core of digestion takes place. But the partially digested food must first be alkalinised to enable the alkaline-linked enzymes to work well.
As the stomach contents enter the duodenum, its acidic pH triggers the release of digestive enzymes and two alkaline chemicals - bicarbonate from the pancreas and bile from the gall bladder- to neutralise the acidity. Bile, in addition, emulsifies the fats into smaller globules for easier digestion and assimilation.

Understanding Digestion: Converting Food into Absorbable Molecules

At this juncture, we might want to consider what, exactly, is digestion? What happens when food is digested?
Digestion is actually the process of converting food into smaller and simpler molecules that can be readily absorbed into the bloodstream. During digestion, the three macronutrients, along with other substances, are converted into their simpler forms:

  • Starches or polysaccharides, which are made up of three or more sugar molecules, are converted into maltose (two sugar molecules) and eventually into glucose (single sugar molecule);
  • Proteins are converted into peptides (which are smaller and simpler molecules) and eventually into amino acids, the basic building blocks of protein;
  • Oils and fats (triglycerides, which have three fatty-acid molecules and one glycerol molecule) are converted into single fatty acid molecules (monoglycerides);
  • The digestion of animal cell membranes releases two important fat ingredients: cholesterol and phospholipids;
  • The digestion of nucleic acid, which includes DNA and RNA, breaks it down into basic molecules called nucleotides,

During this process, vitamins, minerals and phytonutrients are also released so that they, too, can be absorbed into the bloodstream and transported to nourish cells.

Enzymes: Catalysts for Breaking Down Food

The job of breaking down food is performed by enzymes, which are proteins that speed up chemical reactions. Some enzyme activity takes place in the mouth and stomach. In the small intestines, however, your food is acted upon by many different enzymes secreted by the pancreas, gall bladder and the small intestines itself. To ensure that these enzymes function optimally, you need to avoid elements that might damage them, including:

  • Harmful bacteria, viruses, fungi and parasites;
  • Allergens and toxins;
  • Antibiotics that destroy both harmful and friendly bacteria;
  • Drugs that reduce stomach acidity;
  • Chemicals that make your intestinal mucus membrane more permeable, such as alcohol, caffeine and non-steroidal anti-inflammatory drugs like brufen, volteran and salicylate.

For those whose digestive systems are particularly weak, it may be helpful to take supplements of digestive enzymes as well as probiotics and prebiotics.

This content is adapted, with permission, from Book 1 of 2 : The Wonders of Nutrition by Dr Ang Poon Liat. MBBS, M.MED (PAED), MRCP (UK PAED), FAMS, MD.



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