Fish oil may decrease cholesterol absorption from the gut and decrease cholesterol synthesis. There is evidence that fish and fish oil increase high-density lipoproteins (HDL or good cholesterol) and decrease low-density lipoproteins (LDL or bad cholesterol) by increasing the size of LDL particles. This causes a more buoyant LDL to be formed, which is less likely to form fatty deposits in arteries. Fish oil regulates immune function by reducing the production of compounds IL-1, IL-2, and TNF. DHA is thought to be important for normal neural function and might play a key role in the structural development of neurons. Furthermore, there is preliminary evidence that low levels of omega-3 fatty acids, especially DHA, might benefit retinal, visual, learning, and memory function.