Scientists from Karolinska Institutet found that eating a Mediterranean diet frequently may be linked to a lower risk of rheumatoid arthritis.
Rheumatoid arthritis, or RA, is an autoimmune and inflammatory disease, which means that your immune system attacks healthy cells in your body by mistake, causing inflammation (painful swelling) in the affected parts of the body.
Rheumatoid arthritis mainly attacks the joints, usually many joints at once.
The Mediterranean diet is a plant-based diet including high amounts of fruit, vegetables, whole grains, and legumes, moderate amounts of fish, white meat, and alcohol, and low amounts of red meat and sugar.
The Mediterranean diet has been linked to a lower death risk and lower risks of heart disease and cancer by many studies.
Because the diet has presumed anti-inflammatory properties, it might reduce the risk of inflammatory conditions, such as rheumatoid arthritis.
However, only one study has specifically examined the link between the Mediterranean diet and the risk of rheumatoid arthritis, and it reported no association.
In the study, researchers examined 1721 patients with rheumatoid arthritis and 3667 healthy people.
They calculated the Mediterranean diet score, ranging from 0 to 9, from a 124-item food questionnaire.
The team found that about 24% of the arthritis patients and 28% of healthy people ate the Mediterranean diet frequently (high adherence, a diet score between 6 and 9).
High adherence to the Mediterranean diet reduced the risks of developing rheumatoid arthritis by 21% as compared to low adherence (a score between 0 and 2).
This benefit of the Mediterranean diet was only strong in men, but not in women.
In addition, the strong effect of the Mediterranean diet was only found in people with a positive rheumatoid factor, but not in people with a negative rheumatoid factor.
A positive rheumatoid factor test result indicates that a high level of rheumatoid factor was detected in the blood.
A higher level of rheumatoid factor in the blood is closely linked to autoimmune disease, particularly rheumatoid arthritis.
People who have negative rheumatoid factors are diagnosed with rheumatoid arthritis which means they have seronegative rheumatoid arthritis.
Occasionally, seronegative rheumatoid arthritis patients may develop antibodies and become seropositive at a later date — but this does not occur in most cases.
Based on the results, the researchers conclude that eating frequently is linked to a lower risk of rheumatoid arthritis in men and people with a positive rheumatoid factor.
They suggest that bioactive compounds that are rich in the Mediterranean diet, including antioxidants, monounsaturated and omega-3 fatty acids, phytosterols, and fiber, may play a role in the health benefits of the diet.
Future work needs to test this to see why the Mediterranean diet could help reduce rheumatoid arthritis risk in some people.
The research was published in Arthritis Research & Therapy and was conducted by Kari Johansson et al.
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