Rheumatoid arthritis (RA) affects about two million Americans … mostly middle-aged women.
RA is characterized by crippling inflammation in the lining of the joints, caused when the body's immune system attacks its own connective tissues.
It remains unclear why RA happens and why it afflicts more women than men, though genetic factors and environmental triggers – including diet – probably play key roles.
While there is no cure, it's possible to control RA with dietary changes, immune-modulating drugs (which can have serious side effects), exercise therapy, and joint-protection techniques.
Omega-3s and RA: The story so far
The results of numerous controlled clinical trials show that the long-chain omega-3 fatty acids in fish oil (EPA and DHA) can help ease the symptoms of rheumatoid arthritis.
Three years ago, the authors of an Australian evidence review came to an encouraging conclusion: “Meta- and mega-analysis of randomized controlled trials [in RA patients] indicate reduction[s] in tender joint counts and decreased use of non-steroidal anti-inflammatory drugs [e.g., aspirin, ibuprofen, naproxen] ...” (James M et al. 2010)
Last year, British scientists arrived at a similar conclusion: “Evidence is seen for a fairly consistent, but modest, benefit of marine n-3 PUFAs on joint swelling and pain, duration of morning stiffness, global assessments of pain and disease activity, and use of non-steroidal anti-inflammatory drugs.” (Miles EA Calder PC 2012)
Only the long-chain, seafood-source omega-3s called EPA and DHA – the kind found in fish oil – possess sufficient anti-inflammatory potency to deliver significant relief.
Details of the study
The Karolinska group collected information on the dietary habits of more than 32,000 women born between 1914 and 1948, whose health was tracked between 2003 and 2010 as part of the Swedish Mammography Cohort study.
The women, all of whom lived in two counties of Sweden, completed a questionnaire on dietary intake, height, weight, motherhood and educational attainment between 1987 and 1990.
In 1997, the 56,000 who were still alive were sent a second questionnaire to gather similar diet information, plus their answers about smoking, exercise, and use of dietary supplements and aspirin.
The participants detailed how often and how much they ate any of 67 (1987 survey) and 96 (1997 survey) foods, including a range of fatty and lean fish.
During the 10-year monitoring period, 205 women were diagnosed with rheumatoid arthritis. To enable the researcher to make statistical comparisons between omega-3 intake and risk of RA, the women were divided into fifths (“quintiles”), according to their average daily intake of long-chain omega-3s from fish or supplements.
Across the entire group, there was a fourfold difference in omega-3 consumption between the quintile who consumed the most omega-3s daily – 0.49 gram (4,900mg) or more – and the quintile who consumed the least omega-3s daily.
The women took part in two surveys, one in 1987 and one in 1997. The first gathered information on the women's diets, height, weight, parity, and education, while the second added smoking history, physical activity, and use of dietary supplements and aspirin.
The lowest-intake quintile had the highest proportion of smokers (24 percent) and the lowest proportion of alcohol drinkers (72.9 percent) and aspirin users (41.1 percent).
(The plant-source omega-3 called ALA – found in flax oil, canola oil, dark leafy greens, walnuts, and chia, flax, and hemp seeds – has been found ineffective for RA patients, though it still makes sense to favor these foods.)
Doctors typically recommend that RA patients take three grams of combined omega-3 EPA and DHA per day, and any symptomatic relief from fish oil can take three months to manifest fully.
The beneficial effects of seafood-source omega-3s on RA symptoms are plausibly attributed to the proven anti-inflammatory and inflammation-resolving effects of omega-3 EPA and DHA.
Swedish study links fishy diets to reduced RA risk
A population study from Stockholm's renowned Karolinska Institute suggests that eating fish frequently could halve the risk of developing rheumatoid arthritis (Di Giuseppe D et al. 2013).
This epidemiological study compared women's diets to their health status over time.
Accordingly, its results cannot prove a cause-effect relationship between fish diets and reduced risk of RA … but they align with most of the prior epidemiological evidence.
After comparing the women's self-reported diets to their health status 10 years later, the Swedish team can to three key conclusions:
The women whose intake of omega-3s exceeded 0.21 grams a day – equivalent to at least one serving of fatty fish or four servings of lean fish a week were 52 percent less likely to have developed RA within 10 years, compared with those who reported consuming less than 0.21 grams omega-3s daily.
Eating one or more servings of any types of fish every week for at least 10 years was linked to a 29 percent drop in the risk of developing RA, compared with eating less than one portion a week.
The incidence of RA among women in general would drop by 28 percent if all women consumed more than 0.21 grams (2,100mg) of long-chain omega-3s daily.
And as they wrote, “The inverse association between fish consumption and [risk of rheumatoid arthritis] can be attributed mainly to its content of long chain omega-3s.” (Di Giuseppe D et al. 2013)
Unsurprisingly, they wrote that their findings suggest omega-3s may help deter the debilitating, painful, potentially crippling (even fatal) disease.
Adam O, Beringer C, Kless T, Lemmen C, Adam A, Wiseman M, Adam P, Klimmek R, Forth W. Anti-inflammatory effects of a low arachidonic acid diet and fish oil in patients with rheumatoid arthritis. Rheumatol Int. 2003 Jan;23(1):27-36. Epub 2002 Sep 6.
Di Giuseppe D, Wallin A, Bottai M, Askling J, Wolk A. Long-term intake of dietary long-chain n-3 polyunsaturated fatty acids and risk of rheumatoid arthritis: a prospective cohort study of women. Ann Rheum Dis. 2013 Aug 12. doi: 10.1136/annrheumdis-2013-203338. [Epub ahead of print]
Rosell M, Wesley AM, Rydin K, Klareskog L, Alfredsson L; EIRA study group. Dietary fish and fish oil and the risk of rheumatoid arthritis.Epidemiology. 2009 Nov;20(6):896-901. doi: 10.1097/EDE.0b013e3181b5f0ce.
European League Against Rheumatism (EULAR). Oily fish can protect against RA, but smoking and psychosocial stress increase its risk Results from the EIRA study. June 13, 2008. Accessed at www.eurekalert.org /pub_releases /2008-06/elar-ofc061308.php
James M, Proudman S, Cleland L. Fish oil and rheumatoid arthritis: past, present and future. Proc Nutr Soc. 2010 Aug;69(3):316-23. doi: 10.1017/S0029665110001564. Epub 2010 May 28. Review.
Lindahl A, et al. Intake of oily fish decreases the risk of developing rheumatoid arthritis: results from the Swedish EIRA study. EULAR 2008; EULAR 2008, the Annual Congress of the European League Against Rheumatism Abstract SAT0129-AHP.
Miles EA, Calder PC. Influence of marine n-3 polyunsaturated fatty acids on immune function and a systematic review of their effects on clinical outcomes in rheumatoid arthritis. Br J Nutr. 2012 Jun;107 Suppl 2:S171-84. doi: 10.1017/S0007114512001560. Review.
Shapiro JA, Koepsell TD, Voigt LF, Dugowson CE, Kestin M, Nelson JL. Diet and rheumatoid arthritis in women: a possible protective effect of fish consumption. Epidemiology. 1996 May;7(3):256-63.