There are three types of prostaglandins: PG₁, PG₂, and PG₃.

PG₁ have many beneficial effects, including reducing inflammation, inhibiting blood clotting, and maintaining various regulatory states in the body. The strong anti-inflammatory properties help the body recover from injury by reducing pain, swelling and redness.

PG₂ have the opposite effects of PG₁. They have been found to strongly increase inflammation, constrict blood vessels, and encourage blood clotting. These properties come into play when the body suffers a wound or injury, for without these prostaglandins, a person could bleed to death from the slightest of cuts. However, in excess, these prostaglandins may be harmful.

PG₃ have a mixture of functions in the body. In general, they are important in protecting the body from various modes of injury. One of their most important functions however, is their role in decreasing the rate at which PG₂ are formed. Because of their role in reducing inflammation caused by PG₂, PG₃ are often described as having anti-inflammatory properties.

In people with Heart Disease (HD), inhibition of PG₂ is desirable due to the role of inflammation in the progression of the disease. Studies have found that high omega-3 intake can decrease the production of PG₂. To understand how omega-3 inhibits inflammation due to PG₂, we need to go over the pathways by which the omega-3 and omega-6 fatty acids are processed in the body.