NEW RESEARCH has shown that people with rheumatoid arthritis (RA) carry distinctly higher levels of certain monounsaturated fatty acids in their blood, with one fat in particular, oleic acid, tracking both how active the disease is and how much abdominal fat a person carries.
Monounsaturated Fatty Acids in Rheumatoid Arthritis
RA drives systemic inflammation and metabolic changes that can reshape blood lipids. Polyunsaturated fats have been studied at length, but far less is known about monounsaturated fatty acids (MUFAs), how the body makes them, and how they relate to disease activity and body fat.
Study Design and Fatty Acid Measurement
The cross-sectional study recruited 52 people with RA and 30 matched controls between 2017 and 2022. Disease activity was assessed using the 28-joint Disease Activity Score with C-reactive protein (DAS28-CRP), alongside body composition and metabolic parameters, with diet captured through a four-day food journal. Plasma fatty acids were measured by gas chromatography, and the stearoyl-CoA desaturase-1 (SCD-1) index estimated how much MUFA the body made itself.
Associations with Disease Activity and Adiposity
Compared with controls, people with RA had lower insulin sensitivity, higher triglycerides, and lower physical activity. Their plasma oleic and palmitoleic acids and SCD-1 index were higher, while linoleic and arachidonic acids were lower; saturated and omega-3 fats did not differ. After adjusting for age, sex, and diet, oleic acid was independently associated with RA status (β=1.4; 95% CI 0.33 to 2.5) and with waist-to-hip ratio (β=14; 95% CI 6.9 to 21). Within the RA group, higher oleic and gondoic acids tracked with DAS28-CRP disease activity, whereas palmitoleic acid was raised in women but showed no link to disease activity.
Implications for Endogenous Lipid Metabolism
The authors concluded that circulating monounsaturated fatty acids are associated with RA status, adiposity, and disease activity even after accounting for diet, pointing to the body’s own lipid metabolism, not food alone, as a driver. They noted the changes were selective rather than uniform, with oleic acid the most consistent marker, and that the cross-sectional design cannot prove cause. Larger studies could test whether these metabolic pathways might serve as treatment targets in rheumatoid arthritis.
Reference
Narayana Swamy S et al. Elevated plasma monounsaturated fatty acids and their associations with disease activity, adiposity and sex in patients with rheumatoid arthritis: a cross-sectional study. RMD Open. 2026;12:e006777.
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