Olive Oil & Diet & Rheumatoid Arthritis

E Kaklamana MD PhD, Professor Emeritus, The Medical School of the University Athens
Original article: 17/11/2002
Reviewed: 28/10/2009
Next review due: 28/10/2012

Genes and environment in the cause of rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disorder which causes not only joint damage but also problems in other tissues and organs of the body. The cause of rheumatoid arthritis remains unknown although genetic, immune, hormonal, environmental and other factors have been implicated. The prevalence of the disease is 0.5-1% worldwide although there are wide variations in the prevalence and severity of the disease among different countries. Diet is an obvious environmental factor and it is an extremely tempting prospect if changes to diet could be used for therapy. However, the results of various studies have produced conflicting or inconclusive results in this area.

Rheumatoid arthritis and diet

In a study comparing rheumatoid arthritis between Greek and British patients it was found that the severity of the disease was significantly lower among Greek rheumatoid arthritis patients. Genetic or environmental factors may be responsible for these differences in disease severity. Although there are genetic differences between the British and Greek populations, these are not differences that can be altered for therapeutic purposes. On the other hand there are great differences in the dietary habits between British and Greek populations. Clearly, diet can be manipulated for therapeutic purposes. The Greek diet contains high quantities of monounsaturated fatty acids (shown to lower cholesterol) and antioxidant agents (molecules that can have protective qualities within the body), which are abundant in fruits and olive oil. Specifically, the traditional Greek diet is dominated by the consumption of olive oil, vegetables, fruit, fish rather than meat and animal products.

Altering the diet can alter arthritis

There is evidence some studies to suggest that supplementation of the diet with fish oil, evening primrose oil or olive oil improves the symptoms of rheumatoid arthritis. It was found that supplementing the diet with olive oil reduced the number of painful joints, improved the grip strength and reduced the length of time that the patients had stiff joints in the mornings. These are not truly objective measurements but there was, in addition, a reduction in the levels of C-reactive protein (CRP), a blood protein which is an objective laboratory measure of inflammation. This confirms the clinical findings that dietary intervention had altered disease activity in patients with rheumatoid arthritis.

We have carried out two retrospective studies in Greece on the role of diet and activity of rheumatoid arthritis. These studies were based on a questionnaire completed by patients with RA and by healthy controls (i.e. people that did not have RA) on the association between the consumption of more than 100 food items and the development of rheumatoid arthritis. The major food groups which were included in the questionnaire were olive oil, other fats and oils, meat, fish, shellfish, dairy products, raw and cooked vegetables, cereals, fruits, starchy roots, sugars or syrups, pulses and alcoholic/non-alcoholic beverages. We found that lifelong olive oil consumption and cooked vegetables seemed to protect people from the development of rheumatoid arthritis. Thus, people in the highest category of olive oil consumption had approximately 1/3 of the risk of developing RA compared to those in the lowest category of olive oil consumption. The same protective effect applied to the consumption of cooked vegetables, while eating raw vegetables did not protect. It should be stressed that olive oil is the main cooking oil for the Greeks. In the traditional Greek diet olive oil, vegetables (raw or cooked or eaten with olive oil) and fruits are consumed frequently, while meat and animal products are eaten considerabley less frequently. The differences from the typical British diet are obvious!

Diet, religion and rheumatoid arthritis in Greece

In Greece, diet has another dimension. In following the rules of the Greek Orthodox Church many people abstain from meat and animal products during periods of Lent. There are several periods during the year that the Church defines as Lent and these add up to a total of 180 days per year. During these fasts those adhering to these rules therefore consume mainly fish, fruits, cereals and vegetables often cooked with olive oil. In our studies we found that people adhering to the Greek Orthodox Lents have the lowest risk of developing rheumatoid arthritis.

Now for a bit of chemistry - I'm afraid

Olive oil is produced from the whole fruit of the olive tree (Olea europea), by physical pressure without the use of chemicals. Many of the oils that are usually used in the Western diet, such as vegetable oils from corn, sunflower seeds, safflower, cotton seeds and soy beans contain high amounts of omega 6 fatty acids. Such acids are converted into molecules that participate in the inflammation of the rheumatoid joint. Oleic acid on the other hand, the main fatty acid of olive oil, is an omega-9 monounsaturated fatty acid that is converted to molecules with a much lower inflammatory potential. Fish oils, green vegetables, flaxseed, rape-seed and walnuts contain high quantities of omega 3 fatty acid, which are thought to help to reduce levels of inflammation. Trials have shown that supplementation of the diet with fish oil can improve arthritic symptoms. The dietary benefit of virgin olive oil may also be attributed to the presence of natural antioxidants that are found in high quantities in the unrefined, unbleached and undeodorised olive oil that is mainly consumed by the Greeks.

Summary and conclusions

Olive oil has anti-inflammatory effects through a variety of mechanisms, some of which have not been reviewed here for reasons of clarity. Thus the consumption of virgin olive oil and the avoidance of animal fats and vegetable oils with high content in omega 6 fatty acids appears to have a beneficial effect on the disease activity of rheumatoid arthritis.