What is the impact of both non-fiber and fructooligosaccharide (FOS) containing enteral formulas on stool?

• A. Both can decrease overall concentration of fecal bacteria compared with a normal diet
• B. They increase fecal bacteria concentrations
• C. They have no effect on stool
• D. They increase stool acidity

Answer: (A)

The main idea is how the type of substrates in enteral formulas shapes the gut microbiota that ends up in the stool. When a non-fiber formula is used, there is very little fermentable substrate reaching the colon, so bacterial growth is limited and the overall fecal bacterial concentration tends to be lower than what most people have with a normal mixed diet. With a formula containing fructooligosaccharides, you provide a fermentable prebiotic that can promote growth of specific beneficial bacteria, but the measured concentration of bacteria per unit of stool can still be lower than a normal diet because the stool becomes more bulky and hydrated, diluting the bacterial content, and the shift in the microbial community does not necessarily mean a higher total bacterial load per gram of stool. So, compared with a normal diet, both approaches can show a reduced fecal bacterial concentration, even though they influence the microbiota in different ways and can improve other stool characteristics.