When it comes to arthritis, there is currently no clear evidence to support making specific dietary changes to improve symptoms or protect joints. While certain foods and beverages, such as organ meats and alcohol, may predispose individuals to gout or exacerbate its symptoms, most forms of arthritis do not have well-established dietary recommendations.
However, emerging research suggests that the microbiome, the community of microorganisms within our bodies, may play a role. Diet has been shown to influence the composition of the microbiome, potentially impacting immune function and disease activity. As a result, researchers are actively investigating the connection between the microbiome, diet, and autoimmune diseases to develop better strategies for managing inflammation based conditions like arthritis. The short answer is: Most studies agree that omega 3 supplementation can be good for inflammation, and fish is generally high in omega 3. As a result most studies on high fish diets have shown some correlation to lowered inflammation, but there are a few studies that suggest no effect. Although, these are in the minority.
Fish and Omega-3 Fatty Acids: Potential Benefits for Inflammation
Numerous studies have explored the potential benefits of fish and fish oil supplements, which are rich in omega-3 fatty acids, for controlling inflammation in conditions like rheumatoid arthritis. Omega-3 fatty acids have been found to possess anti-inflammatory properties, and their consumption has been associated with improved inflammation control and reduced disease risk.
A study published in the medical journal Arthritis Care and Research analyzed data from 176 individuals with arthritis  to investigate the relationship between fish consumption and arthritis control. The findings revealed a dose-dependent effect, with higher fish intake associated with better arthritis control. However, it is important to note that this study only found an association and not a causative link between fish intake and arthritis improvement.
The International Journal of Molecular Sciences further supports  the link between omega-3 fatty acids and reduced inflammation. The study found that DHA and EPA, the two omega-3s associated with lowering inflammation, not only reduce the risk of cardiovascular disease but also coronary heart disease and cardiovascular mortality.
The Impact of Fish on Rheumatoid Arthritis
Fish oil, which contains significant amounts of omega-3 fatty acids, has been the subject of numerous studies investigating its effects on rheumatoid arthritis. Some studies have suggested that fish oil supplementation or a diet rich in fish oils may help reduce inflammation and improve disease control. Interestingly, regions with higher fish consumption have been found to have lower rates of rheumatoid arthritis. There are also some theories around fish consumption, the gut microbiome and autoimmune conditions, which would mean a high fish diet could have further benefits beyond it's omega 3 content, but more research is needed.
Another study examined the impact of fish consumption on rheumatoid arthritis control specifically, the results showed that individuals who consumed more than two servings of fish per week had better control of their arthritis.  This finding persisted even after accounting for other factors that could potentially affect arthritis control. While the improvement in arthritis control was modest, even small effects from natural remedies that pose minimal risks are worth considering.
Studies on Eating Fish and Inflammation in General
There have also been several studies on inflammation markers in healthy populations,  which suggest that consuming a diet high in fish results in lower markers of inflammation, this was also true of other inflamatory conditions. 
Studies That Show A High Fish Diet Does Not Effect Arthritis
Not all studies showed a positive connection, one study aimed to determine the effects of consuming four servings of mixed fish per week on markers of inflammation in healthy older adults. The participants were randomly assigned to either the fish group or the control group, which consumed their usual diet along with four servings of red meat per week. The study found that after eight weeks, there was no significant difference in levels of inflammatory markers, such as CRP, IL-1β, and IL-6, between the fish group and the control group. This suggests that increasing fish intake may not have a significant impact on inflammation in healthy older adults. 
Which Fish Has The Most Omega 3?
Mackerel is the winner, among fatty fish, mackerel stands out for its exceptional content of omega-3 fatty acids. A 3-ounce serving of mackerel contains approximately 2.5 to 2.6 grams of omega-3 fat, making it an excellent choice for reducing chronic inflammation and mitigating the risk of serious diseases.
The Highest Omega Per 3 Ounce Portion of Fish
- Atlantic Mackerel: 2500mg
- Lake Trout: 1600mg
- Salmon: 1200 - 1800mg
- Herring: 1100 - 1700mg
- Anchovy: 1400mg
- Sablefish/Black Cod: 1400mg
- Albacore Tuna: 1300mg
- Sardines, canned: 1000mg
The above list is of average DHA and EPA, which is the type of omega 3 that is usable by humans.
Incorporating Fish into a Balanced Diet
While the evidence supporting the benefits of fish consumption for inflammation control is promising, it is important to approach dietary changes holistically. Incorporating fish into a balanced diet can offer numerous health benefits beyond potential anti-inflammatory effects. Fish is an excellent source of high-quality protein, essential nutrients, and healthy fats.
When considering fish consumption, it is important to prioritize varieties that are low in mercury and other contaminants. Opt for fatty fish such as salmon, mackerel, sardines, and trout, as they tend to be rich in omega-3 fatty acids. Aim to include fish in your diet at least twice a week to reap the potential benefits associated with inflammation control and overall health.
Other Considerations and Future Research
While fish consumption and fish oil supplementation show promise in managing inflammation, it is crucial to approach these potential benefits with realistic expectations. The effects of fish intake on arthritis control are typically modest, and medications remain the mainstay of treatment for rheumatoid arthritis.
Further research is necessary to explore the mechanisms underlying the potential anti-inflammatory effects of fish and fish oil. Larger, long-term studies are needed to provide more definitive evidence and better understand the role of diet in managing rheumatoid arthritis and other types of joint diseases.
Is Eating Fish Good For Arthritis?
While the precise role of diet in managing arthritis remains unclear for most types of the condition, emerging research suggests that fish consumption, particularly varieties rich in omega-3 fatty acids, may offer potential benefits for controlling inflammation. Fish and fish oil supplements have shown promise in improving arthritis control, although the effects are generally modest compared to medications.
1 - https://pubmed.ncbi.nlm.nih.gov/15992645/
2 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5751248/
3 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8199776/
4 - https://pubmed.ncbi.nlm.nih.gov/15992645/
5 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7468748/
6 - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3895208/