This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Classification of carbohydrate, Subject name: Biochemistry
Which of the following fatty acids is produced by fermentation of dietary fiber by colonic flora? 
Select and explain. 
A. Palmitate, B. Butyrate, C. Oleate, D. Linoleate
B: Butyrate
Answer: B: Butyrate 
Explanation: Starch and non-starch polysaccharides are substrates for bacterial fermentation in the large intestine. They produce butyrate and other sho chain fatty acids. These fatty acids are a significant source of fuel for intestinal enterocytes. There is evidence that butyrate also has antiproliferative activity, and so provides protection against colorectal cancer.