For fatty acids longer than 10 carbon atoms, what is required for their digestion and absorption?

• A. Only pancreatic enzymes
• B. Acidic pH
• C. Bile salts are required for both digestion and micelle formation
• D. Direct diffusion across the intestinal epithelium

Answer: (C)

Long-chain fatty acids rely on bile salts to both break up fat into smaller droplets and to solubilize the digestion products so they can be absorbed. Bile salts emulsify dietary fats, dramatically increasing the surface area available to pancreatic lipase. The lipase then digests triglycerides into free fatty acids and monoglycerides, but these products are poorly soluble in the watery lumen. Bile salts form mixed micelles with these digestion products, keeping them in solution and delivering them to the brush border of enterocytes for uptake. Without bile salts, the digestion products wouldn’t be efficiently solubilized or absorbed, even though pancreatic enzymes are active. Direct diffusion of long-chain fatty acids is not sufficient due to their low solubility, and acidic pH isn’t the driving factor in this process. After absorption, the fatty acids are repackaged into triglycerides and enter the lymph via chylomicrons.