In the 19th and early 20th centuries, mothers often fed their children a spoonful of cod liver oil. Her reasons were based on hundreds of years of folk medicine.

Rickets, a disease caused by a lack of vitamin D in the body, was common prior to the mid 1950s. The disease struck very young children, softening and deforming their bones. They’d outgrow it within a few years, but by then, the damage was already permanent. As folk medicine proved later through medical science, deriving important nutrients from certain foods is a useful complementary treatment method.

Cod liver oil’s connection with rickets wasn’t scientifically proven until the 1930s. It is also rich in Vitamin A (very good for bones, teeth and eyes) and omega-3 fatty acids.

Toward the end of the 20th Century, researchers began studying fish oil. Unlike cod liver oil, fish oil doesn’t contain vitamins A and D. But it’s much richer in omega-3 fatty acids than its predecessor. Omega-3s are excellent for heart health — and, as it turns out, for arthritis.

The two types of omega-3 fatty acids found in fish oil are DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid). EPA and DHA can reduce inflammation, which causes swelling and pain. Some studies have shown that the acids might also suppress the body’s immune system. Together, these factors can make fish oil a potential weapon against arthritis.

EPA and DHA can also help prevent heart attacks by making it harder for the blood to clot. They help lower blood triglyceride levels and blood pressure, too.

Cod liver oil is an excellent supplement as it contains omega-3s and vitamins A and D. It’s made from cod livers that are cooked and then pressed for the oil.

Fish oil supplements are made from a variety of oily-fleshed, coldwater fish, including mackerel, tuna, herring, salmon, and cod liver. They may also contain whale or seal blubber in them. Fish oil has only a small combination of vitamins and minerals, such as iron, calcium, B-vitamins, and vitamins A and D.

The term “arthritis” is derived from two Greek words: “arthro,” meaning “joint,” and “itis,” which means “inflammation.” There are 100 different types of arthritis, and all of them affect the joints. The most common is osteoarthritis. It attacks the tough, flexible cartilage in and around the joint. Caused mainly by wear-and-tear, osteoarthritis generally affects older people.

The second most common form of arthritis is rheumatoid arthritis (RA). RA is a chronic autoimmune disease that causes the immune system to attack the joint’s synovial capsule and other soft tissues. Both types of arthritis cause inflammation and pain in the joints.

In order for the omega-3 fatty acids in fish oil to work against arthritis, it’s necessary for an arthritis patient to consume a fairly large quantity of it each day. Fish oil (or cod liver oil) that’s enclosed in capsules makes this fairly easy.

But taking too much vitamin A and D, which are found in such high amounts in cod liver oil, can be toxic. For the purpose of treating arthritis, fish oil is the safer choice.

Most people can take fish oil—even large doses—without trouble. But some do report some mild side effects. These include:

  • belching, bad taste in the mouth
  • bad breath
  • heartburn
  • nausea
  • loose stools

Most of these side effects can be decreased or stopped by taking fish oil immediately before a meal, so the oil mixes well with the food. Or, you can freeze the capsules before taking them.

Talk with your doctor before you take fish oil for arthritis, especially in high doses. It’s especially important to speak with your doctor even if you’re already taking non-steroidal anti-inflammatory drugs (NSAIDs) that suppress the immune system, blood thinning, or blood pressure drugs.

Use care and check with your doctor before taking fish oil with any other alternative or complimentary remedies as well. There might be interactions to watch out for.