Olestra (a sucrose polyester) is a man-made product that is used in products like snack chips as a fat-free and calorie-free substitute for regular fat. In that respect, it does an effective job. A critical difference between Olestra and most regular fats is that the latter are small enough to enter the bloodstream (with their fat and calories) through the intestinal walls. Olestra is too large and dense to do the same, so it passes through the digestive tract, with fat and calories intact. One issue with Olestra is that it reduces the bodily absorption of fat-soluble vitamins (A, D, E and K) from foods that are eaten during the same period with products containing Olestra. And some people who have consumed Olestra-added products have experienced diarrhea and other gastrointestinal side effects.