There is ample medical research that shows that fatty fish is healthy for the heart. Researchers discovered that it may also help prevent conditions such as arthritis. According to a study in the Annals of the Rheumatic Diseases, you can help cut your risk of developing rheumatoid arthritis by eating as little as one serving of salmon a week, or four servings a week of a leaner fish such as cod.

Rheumatoid arthritis is a chronic condition in which the immune system attacks the body’s joints, causing pain and eventually destroying the cartilage and bone. This condition affects more women than men. People who are affected by this disease often lose function in their joints -- usually in their hands and feet. 

A study of 32,000 Swedish women who consistently ate at least one serving of fatty fish each week for a period of about 10 years tests this diet. Researchers followed the women for nearly eight years to see the progress of the diet. They found that the women who ate at least one serving of fatty fish once a week were 29 percent less likely to develop rheumatoid arthritis than other women who did not include fatty fish in their diet.

Researchers believe that the omega-3 fatty acids contained in fatty fish such as salmon, mackerel and herring have protective anti-inflammatory effects on the immune systems. Omega-3 fatty acids are believed to act upon the immune system, normalizing itself and reducing inflammation. 

As for which fish are the best to eat, researchers found that salmon and mackerel have the greatest effect, reducing the risk of developing the disease by up to 52 percent. This is because they have the greatest concentration of omega-3 fatty acids. 

Experts recommend that people eat at least two servings of seafood, fish or shellfish each week to help prevent rheumatoid arthritis.