Health Effects of Fats: Rheumatoid Arthritis

Rheumatoid arthritis is a chronic and progressive autoimmune disease characterized by painful inflammation of the tissue around the joints. The disease can affect other organs, such as skin, lungs and heart, as well. In advanced disease, the cartilage in the joints is destroyed, causing joints to become deformed. The bones themselves can be eroded. About 2 million people in the U.S. have this type of arthritis and it is three times more common in women than men.

Obtaining effective treatment for rheumatoid arthritis in the early stages of the disease is important for slowing its progression, reducing the risk of long-term disability and lowering heart disease risk. People with rheumatoid arthritis are more likely to die prematurely from heart disease. However, most people can expect to have their disease well controlled and avoid severe disability. Current treatment includes disease-modifying drugs and anti-inflammatory agents such as marine omega-3 fatty acids (fish oil). Treatment is usually life-long.

In rheumatoid arthritis, there is an over-production of substances that trigger and sustain inflammation. Many of these agents derive from the polyunsaturated fatty acid (PUFA) arachidonic acid. Western diets facilitate the abundance of this fatty acid because they are rich in its precursor, linoleic acid, an omega-6 PUFA. Further, western diets are low in the long-chain omega-3 fatty acids EPA and DHA, which counteract the inflammatory effects of arachidonic acid. Our diet likely makes rheumatoid arthritis worse, and may contribute to the frequency of its occurrence. Most anti-inflammatory drugs (e.g., diclofenac) work by blocking the conversion of arachidonic acid to inflammatory compounds. However, these drugs can have serious side effects and may increase the risk of heart disease. EPA and DHA block the same pathways and reduce cardiovascular risk without harmful side effects.


Many controlled clinical studies have reported that consuming substantial amounts of fish oil leads to significant improvements in the pain, stiffness and swelling of arthritic joints. Small amounts of EPA and DHA, such as would be obtained by eating fatty fish every day, appear to have little effect. Doses of EPA and DHA in the range of 3 to 6 gm/day—about 9 to 18 “common” fish oil capsules†—have been beneficial in many arthritic patients over the course of 3 years or longer. There is usually a delay of 2 to 3 months before improvements are noticed.

Liquid fish oil may be easier to consume and more readily tolerated than taking many fish oil capsules. The gelatin coating of the capsules taken in anti-inflammatory doses can cause unwanted effects such as abdominal pain and repeating taste. For this reason, taking liquid fish oil before a meal by layering it on a small amount of juice, swallowing it unstirred, and following with a juice chaser is recommended where liquid fish oil is available.

Increased consumption of fish oil reduces the production of several inflammatory substances and the enzymes that degrade cartilage. Fish oils affect more inflammatory mediators than non-steroidal anti-inflammatory drugs because they affect several enzymes. Unlike these drugs, EPA and DHA reduce rather than increase the risk of cardiovascular disease. Another advantage of fish oil is that a person may need less of other suppressive medications, thereby reducing unwanted side effects.


The effectiveness of EPA and DHA is increased if foods rich in omega-6 PUFAs are kept to a minimum. Most vegetable oils, salad dressings and many prepared foods are high in linoleic acid, which is readily converted to arachidonic acid in the body. Linoleic is the main fatty acid in corn, sunflower, safflower and soybean oil. In contrast, canola and olive oils are rich in the monounsaturates—mainly oleic acid—and comparatively low in linoleic acid, making these the oils of choice. High oleic acid versions of sunflower and soybean oils have less linoleic acid too. Choosing foods rich in monounsaturates and omega-3s and low in omega-6 polyunsaturates will improve the fatty acid balance of the typical western diet.


Should you choose to take an anti-inflammatory dose of fish oil, it may be important inform your doctor, especially if you are taking certain medications, such as anti-coagulants, where the dose is determined according to test results. Fish oils can enhance the effectiveness of some medications related to heart disease and arthritis. With appropriate monitoring, fish oil does not increase hemorrhagic events associated with warfarin and aspirin therapy. Many physicians may be unaware of the potential benefits to patients of large doses of fish oil. If you wish to take a referenced version of this article to your doctor, please request a copy from the editor.

† Over-the-counter fish body oil capsules commonly have about 300 mg of EPA + DHA per 1-gram capsule. Concentrated fish oil capsules contain ethyl esters and about 600 mg of EPA + DHA per capsule.

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