The microbial metabolism of Blank______ produces short-chain fatty acids that can be used as fuel by the cells that line the large intestine. Multiple choice question. cholesterol amino acids fat-soluble vitamins dietary fiber
The correct answer and explanation is:
Correct Answer: Dietary fiber
Explanation (300 words):
The correct answer is dietary fiber because microbial metabolism in the large intestine (colon) primarily acts on undigested carbohydrates, particularly dietary fiber, leading to the production of short-chain fatty acids (SCFAs) such as acetate, propionate, and butyrate.
Dietary fiber refers to plant-based carbohydrates that cannot be fully broken down by human digestive enzymes in the small intestine. Instead of being absorbed earlier in the digestive process, dietary fiber travels intact to the colon, where it becomes food for gut microbes. These microbes ferment the fiber, producing beneficial byproducts.
Among the most important products of this fermentation are short-chain fatty acids (SCFAs). These SCFAs are not only an energy source for colon cells (especially butyrate), but they also play a role in:
- Maintaining the health and integrity of the intestinal lining
- Modulating inflammation
- Supporting immune function
- Promoting water and electrolyte absorption
- Regulating metabolism and potentially body weight
The epithelial cells of the colon, known as colonocytes, especially rely on butyrate as their primary energy source. A deficiency in SCFAs can lead to poor gut health and has been associated with conditions like inflammatory bowel disease (IBD).
The other answer choices—cholesterol, amino acids, and fat-soluble vitamins—are not major substrates for microbial fermentation in the colon:
- Cholesterol is mainly absorbed in the small intestine and does not contribute to SCFA production.
- Amino acids are absorbed earlier in digestion and are not typically fermented unless there is an excess or deficiency.
- Fat-soluble vitamins (A, D, E, K) are absorbed with dietary fat in the small intestine and are not significantly metabolized by gut bacteria for SCFA production.
Thus, dietary fiber is the key component fermented by gut microbes to produce SCFAs—an essential fuel for the colon.