Supplements for Psoriasis and Psoriatic Arthritis: Fish Oil, Vitamin D, Folic Acid and What the Trials Show

Psoriasis is an immune condition that speeds up skin-cell turnover, leaving thick, scaly, inflamed patches; in psoriatic arthritis the same process inflames joints and the places where tendons attach to bone (MedlinePlus). Creams, light therapy and prescription medicines (methotrexate, ciclosporin, acitretin, apremilast and biologic injections) are the treatments (MedlinePlus), and for psoriatic arthritis a rheumatologist chooses among disease-modifying medicines (Gossec 2024). No supplement replaces them. Keep using what your dermatologist or rheumatologist prescribed; don't stop or swap a medicine for a supplement. This guide covers adults.

The short version

• Folic acid with methotrexate is prescribed to cut methotrexate's side effects: across 6 trials (648 people, mostly with rheumatoid arthritis), it meant about a third fewer liver side effects. Your clinician sets the dose. B Grade B (Prey 2009; DailyMed methotrexate).
• Losing weight if you carry extra weight improved psoriasis in 6 pooled trials of diet or exercise. B Grade B (Mahil 2019).
• Fish oil (omega-3) for psoriasis: small oral trials, mixed results; the largest (145 people) found no change. C Grade C (Søyland 1993; Bittiner 1988).
• Fish oil for psoriatic arthritis: one trial (145 people) found no clear change in disease activity, though painkiller use fell. C Grade C (Kristensen 2018).
• Vitamin D pills: no clear benefit for psoriasis in trials against a dummy pill. Vitamin D-like creams (such as calcipotriol) are prescription drugs applied to the skin, a different thing. B Grade B (Dai 2023; Jenssen 2023).
• Probiotics and curcumin: small trials added to standard treatment found modest gains. C Grade C (Zhu 2024; Antiga 2015).
• Watch the interactions: vitamin A supplements with acitretin, and St John's wort with ciclosporin or with the birth control acitretin requires (DailyMed acitretin; DailyMed ciclosporin).

Does fish oil help psoriasis?

C Grade C: small oral trials, mixed results. The largest double-blind trial gave 145 people with moderate to severe psoriasis 6 g of fish oil a day (5 g of EPA plus DHA) or corn oil for 4 months; severity scores did not change in either group or differ between them (Søyland 1993). A smaller double-blind trial in 28 people found less itching, redness and scaling after 8 weeks of fish oil capsules than with olive oil capsules (Bittiner 1988).

The pooled analyses don't settle it, because their pools are small or mixed. One found severity about 1.6 points lower, but that figure came from just 3 small trials: two added capsules to creams or medicines, and one was a weight-loss diet rich in omega-3 (Clark 2019). A 2020 review of 18 trials found no change from fish oil or omega-3 on its own but lower scores, by about 3.9 points, when it was added to standard treatment; which trials sit in each pool can't be checked, and its trial list includes fish oil given by drip and as a cream (Chen 2020). A review of alternative treatments noted that most randomized fish oil trials found no clear improvement (Gamret 2018).

Fish oil pills can make atrial fibrillation, a common irregular heart rhythm, more likely: across 7 heart trials (81,210 people), the risk was 25% higher, and higher still above 1 g a day (Gencer 2021). There is no official upper limit; the FDA has concluded that supplements giving no more than 5 g a day of EPA and DHA are safe when used as recommended (NIH ODS). At high doses fish oil can make blood clot more slowly and may raise the INR (a clotting test) with warfarin, although most studies at 3 to 6 g a day found no meaningful change (NIH ODS). On any blood thinner, ask your prescriber before adding it; see can I take fish oil with Eliquis?.

Does fish oil help psoriatic arthritis?

C Grade C: one trial, no clear effect on disease activity. In a double-blind trial, 145 people with psoriatic arthritis took 3 g of omega-3 or 3 g of olive oil a day for 24 weeks. Disease activity, tender joints and skin scores all dropped on omega-3, yet the gap against olive oil was not statistically clear; people on omega-3 did cut their use of anti-inflammatory painkillers and paracetamol more (Kristensen 2018). In another trial of 97 people with psoriatic arthritis, a lower-calorie diet improved disease activity, and adding 3 g of omega-3 a day to it brought no extra improvement (Leite 2022). Few other supplements have been tested in psoriatic arthritis itself: a multi-strain probiotic in 66 people did no better than a dummy pill (Bosch 2026).

Do vitamin D pills help psoriasis?

B Grade B: no clear benefit in trials against a dummy pill. Pooling 4 trials (333 people), oral vitamin D did not change severity scores at 3 months or at the end of follow-up (Dai 2023), and another review of 4 trials found no difference at 3, 6 or 12 months (Formisano 2023). In a trial of 122 adults whose vitamin D was on the low side, vitamin D supplements lifted blood levels without changing psoriasis severity or quality of life against a dummy pill (Jenssen 2023). A 2025 network analysis did report lower severity scores, but it compared vitamin D with standard treatment, including trials that added it to light therapy and trials of calcitriol, a prescription form of vitamin D, its results varied widely, and its certainty was low to moderate (Chen 2025).

People with psoriasis tend to have lower blood vitamin D (Formisano 2023). If a test shows you are low, your clinician can treat that, as for anyone. Creams containing vitamin D-like drugs (calcipotriol, calcitriol) are prescribed treatments applied to the skin; their results don't carry over to pills.

Do probiotics or curcumin help psoriasis?

Probiotics, grade C: small gains as an add-on. In a review of 7 small trials of probiotic capsules or drinks, mostly added to usual treatment, severity scores were about 3 points lower than with a dummy pill in the 5 trials that reported them, though results varied and the largest, 6-month trial found no change; CRP, a blood marker of inflammation, fell in the 3 trials that measured it; the share of people whose psoriasis improved by 75% was not clearly higher, and quality of life did not change. Most products mixed several strains, and one also contained a prebiotic fibre (Zhu 2024).

Curcumin, grade C: one small trial as an add-on. In 63 people with mild to moderate psoriasis using steroid creams, adding 2 g a day of a lecithin-based curcumin product by mouth for 12 weeks lowered severity scores more than the creams alone (Antiga 2015). Curcumin has no official upper limit, but NCCIH warns that liver damage has been reported with curcumin products made to absorb better, like this one (NCCIH). That matters more if you take methotrexate, which can also harm the liver (DailyMed methotrexate). Curcumin may also raise bleeding risk alongside blood thinners: one case report found a raised INR (a clotting test) when turmeric was taken with a warfarin-type medicine (Daveluy 2014), though a 10-day study of a lecithin-based curcumin in people on warfarin, dabigatran or antiplatelet drugs found no change in INR or bleeding time (Hu 2018). On a blood thinner, ask your prescriber first; see can I take turmeric with Eliquis?. Turmeric gels and creams are a different route; their trials don't support pills.

Should you take folic acid with methotrexate?

B Grade B: yes, as prescribed. The methotrexate label tells prescribers to give folic acid or folinic acid to people with psoriasis or rheumatoid arthritis to lower the risk of side effects (DailyMed methotrexate). In a review of 6 trials (648 people, mostly with rheumatoid arthritis and at most one trial in psoriasis), folic or folinic acid cut liver side effects by about 36%, with a trend toward fewer mouth and stomach side effects (Prey 2009). Your clinician sets the dose and the day you take it; don't add other folic acid products on top without asking.

Does diet or weight loss help psoriasis?

B Grade B for weight loss. Pooling 6 trials, weight loss from diet or exercise lowered severity scores by about 2.6 points, and in one trial in psoriatic arthritis, diet-led weight loss gave about 4 times the odds of reaching minimal disease activity (Mahil 2019).

C Grade C for a Mediterranean diet. In a 16-week trial of 38 adults with mild to moderate psoriasis on stable creams, a Mediterranean diet lowered severity scores by 3.4 points more than standard low-fat diet advice, in an open-label trial, and 9 of 19 reached a 75% improvement against none given the advice (Perez-Bootello 2025).

A gluten-free diet only makes sense if blood tests show gluten antibodies or coeliac disease. The supporting study looked only at people with those antibodies and had no control group (Michaëlsson 2003).

What we'd skip

• Selenium. Two small trials of selenium as an add-on, one alongside light therapy, found no benefit (Serwin 2006; Serwin 2003).
• Zinc. A double-blind trial in 25 people with plaque psoriasis found no improvement over 12 weeks (Burrows 1994).
• Vitamin D pills to treat psoriasis when your level is normal, for the reasons above.
• "Immune" or skin blends that contain St John's wort, vitamin A or concentrated turmeric, because of the medicine interactions below.

Safety and interactions

• Acitretin: don't take vitamin A supplements with it, because the two add up to vitamin A poisoning. The label also warns against St John's wort, which may stop hormonal birth control from working, and acitretin can cause major birth defects (DailyMed acitretin). Check multivitamins for vitamin A.
• Ciclosporin: St John's wort lowers its blood level, which the label calls a serious interaction; grapefruit raises it. Ciclosporin can push potassium up, so potassium supplements need your prescriber's OK (DailyMed ciclosporin).
• Methotrexate: only the folic acid your prescriber sets; avoid adding liver-stressing products such as concentrated curcumin without asking (NCCIH).
• Biologics and apremilast: tell your team about every supplement you take.
• Fish oil: a higher chance of atrial fibrillation, and at high doses slower clotting, which matters with warfarin or other blood thinners (NIH ODS); ask your prescriber before combining them.
• Turmeric or curcumin with a blood thinner: a possible bleeding risk (one case report of a raised INR); ask your prescriber first (Daveluy 2014).
• Pregnancy: methotrexate and acitretin can cause birth defects, so plan any pregnancy with your dermatologist or rheumatologist first; these medicines need long gaps. The acitretin label says no pregnancy during treatment or for at least 3 years after stopping, and the methotrexate label advises birth control for 6 months after the last dose (3 months for men with a partner who could become pregnant) (DailyMed acitretin; DailyMed methotrexate). Supplements in pregnancy should be as advised by your midwife or obstetric team.
• Breastfeeding? Before adding a supplement, check with a clinician who knows about breast milk, such as your midwife, doctor or a lactation specialist.
• Under 18? Get a clinician's advice first.

When to see a doctor

• Go to the emergency room or call 911 if a severe flare covers all or most of your body. Tell your provider if flares come with joint pain or fever (MedlinePlus).
• Joint pain, swelling or morning stiffness with psoriasis: see your doctor, dermatologist or rheumatologist about psoriatic arthritis (MedlinePlus).
• On methotrexate: a new fever or signs of infection, easy bruising or bleeding, a new or worse rash, severe belly pain, vomiting blood or black stools need an urgent call, as the label advises (DailyMed methotrexate).
• On curcumin or turmeric: tiredness, nausea, dark urine or yellowing skin or eyes; stop it and call your doctor (NCCIH).

Keep taking your prescribed medicines unless your prescriber or pharmacist tells you otherwise.

FAQ

What is the best supplement for psoriasis? None replaces treatment. Fish oil has small oral trials with mixed results (grade C), and probiotics and curcumin have only small add-on trials (grade C). Losing extra weight has better evidence (grade B).

Does vitamin D help psoriasis? Vitamin D pills did not clearly improve psoriasis in trials against a dummy pill (grade B). Vitamin D-like creams such as calcipotriol are prescription drugs used on the skin, which is a different thing.

What supplements help psoriatic arthritis? Few supplements have been tested in psoriatic arthritis itself. Fish oil, in 145 people, did not clearly lower disease activity against olive oil, though they used fewer painkillers (grade C); added to a lower-calorie diet, it brought no extra gain; and a probiotic in 66 people did no better than a dummy pill. A rheumatologist's prescribed medicines are the treatment.

Should I take folic acid with methotrexate? Yes, if your prescriber gives it: it cut liver side effects in trials (grade B). Take only the dose and day they set, and don't add other folic acid products on your own.

Can I take St John's wort for low mood with psoriasis medicines? Not without asking. It lowers ciclosporin levels and may stop the hormonal birth control acitretin requires from working.

Related pages

• Psoriasis · Psoriatic arthritis protocol · Ankylosing spondylitis protocol
• Fish oil · Vitamin D · Curcumin · Probiotics · Folic acid
• Guides: fish oil supplements · supplements for inflammation · supplements for eczema · turmeric and curcumin · supplements for joint pain
• Check my stack · How we grade

Sources

1. Gossec L, et al. EULAR recommendations for the management of psoriatic arthritis with pharmacological therapies: 2023 update. Ann Rheum Dis. 2024. PubMed 38499325 · doi:10.1136/ard-2024-225531
2. Prey S, et al. Effect of folic or folinic acid supplementation on methotrexate-associated safety and efficacy in inflammatory disease: a systematic review. Br J Dermatol. 2009. PubMed 18945303 · doi:10.1111/j.1365-2133.2008.08876.x
3. Mahil SK, et al. Does weight loss reduce the severity and incidence of psoriasis or psoriatic arthritis? A Critically Appraised Topic. Br J Dermatol. 2019. PubMed 30729517 · doi:10.1111/bjd.17741
4. Søyland E, et al. Effect of dietary supplementation with very-long-chain n-3 fatty acids in patients with psoriasis. N Engl J Med. 1993. PubMed 8502270 · doi:10.1056/NEJM199306243282504
5. Bittiner SB, et al. A double-blind, randomised, placebo-controlled trial of fish oil in psoriasis. Lancet. 1988. PubMed 2893189 · doi:10.1016/s0140-6736(88)91181-6
6. Kristensen S, et al. Beneficial effect of n-3 polyunsaturated fatty acids on inflammation and analgesic use in psoriatic arthritis: a randomized, double blind, placebo-controlled trial. Scand J Rheumatol. 2018. PubMed 28303758 · doi:10.1080/03009742.2017.1287304
7. Dai Q, et al. Efficacy and safety of vitamin D supplementation on psoriasis: A systematic review and meta-analysis. PLoS One. 2023. PubMed 37967075 · doi:10.1371/journal.pone.0294239
8. Jenssen M, et al. Effect of Vitamin D Supplementation on Psoriasis Severity in Patients With Lower-Range Serum 25-Hydroxyvitamin D Levels: A Randomized Clinical Trial. JAMA Dermatol. 2023. PubMed 36988936 · doi:10.1001/jamadermatol.2023.0357
9. Zhu Y, et al. The efficacy and safety of probiotics in the adjuvant treatment of psoriasis: a systematic review and meta-analysis of randomized controlled trials. Front Med (Lausanne). 2024. PubMed 39328313 · doi:10.3389/fmed.2024.1448626
10. Antiga E, et al. Oral Curcumin (Meriva) Is Effective as an Adjuvant Treatment and Is Able to Reduce IL-22 Serum Levels in Patients with Psoriasis Vulgaris. Biomed Res Int. 2015. PubMed 26090395 · doi:10.1155/2015/283634
11. Clark CCT, et al. Efficacy of ω-3 supplementation in patients with psoriasis: a meta-analysis of randomized controlled trials. Clin Rheumatol. 2019. PubMed 30778861 · doi:10.1007/s10067-019-04456-x
12. Chen X, et al. Efficacy of fish oil and its components in the management of psoriasis: a systematic review of 18 randomized controlled trials. Nutr Rev. 2020. PubMed 31995220 · doi:10.1093/nutrit/nuz098
13. Gamret AC, et al. Complementary and Alternative Medicine Therapies for Psoriasis: A Systematic Review. JAMA Dermatol. 2018. PubMed 30193251 · doi:10.1001/jamadermatol.2018.2972
14. Gencer B, et al. Effect of Long-Term Marine ɷ-3 Fatty Acids Supplementation on the Risk of Atrial Fibrillation in Randomized Controlled Trials of Cardiovascular Outcomes: A Systematic Review and Meta-Analysis. Circulation. 2021. PubMed 34612056 · doi:10.1161/CIRCULATIONAHA.121.055654
15. Leite BF, et al. Dietetic intervention in psoriatic arthritis: the DIETA trial. Adv Rheumatol. 2022. PubMed 35387686 · doi:10.1186/s42358-022-00243-6
16. Bosch P, et al. Efficacy and safety of probiotic supplementation in PsA-a randomized controlled trial. Rheumatology (Oxford). 2026. PubMed 42832303 · doi:10.1093/rheumatology/keag547
17. Formisano E, et al. Psoriasis and Vitamin D: A Systematic Review and Meta-Analysis. Nutrients. 2023. PubMed 37571324 · doi:10.3390/nu15153387
18. Chen D, et al. Effectiveness and safety of dietary supplements in the adjunctive treatment of psoriasis: a systematic review and network meta-analysis. Front Nutr. 2025. PubMed 41459063 · doi:10.3389/fnut.2025.1718828
19. Daveluy A, et al. Probable interaction between an oral vitamin K antagonist and turmeric (Curcuma longa). Therapie. 2014. PubMed 25230280 · doi:10.2515/therapie/2014062
20. Hu S, et al. Interaction study between antiplatelet agents, anticoagulants, thyroid replacement therapy and a bioavailable formulation of curcumin (Meriva®). Eur Rev Med Pharmacol Sci. 2018. PubMed 30070343 · doi:10.26355/eurrev_201808_15647
21. Perez-Bootello J, et al. Mediterranean Diet and Patients With Psoriasis: The MEDIPSO Randomized Clinical Trial. JAMA Dermatol. 2025. PubMed 40991259 · doi:10.1001/jamadermatol.2025.3410
22. Michaëlsson G, et al. Gluten-free diet in psoriasis patients with antibodies to gliadin results in decreased expression of tissue transglutaminase and fewer Ki67+ cells in the dermis. Acta Derm Venereol. 2003. PubMed 14690336 · doi:10.1080/00015550310015022
23. Serwin AB, et al. Selenium supplementation, soluble tumor necrosis factor-alpha receptor type 1, and C-reactive protein during psoriasis therapy with narrowband ultraviolet B. Nutrition. 2006. PubMed 16829029 · doi:10.1016/j.nut.2006.05.011
24. Serwin AB, et al. Soluble tumor necrosis factor-alpha receptor type 1 during selenium supplementation in psoriasis patients. Nutrition. 2003. PubMed 14559319 · doi:10.1016/s0899-9007(03)00165-5
25. Burrows NP, et al. A trial of oral zinc supplementation in psoriasis. Cutis. 1994. PubMed 7956335