Table 2.
Study characteristics of the 13 studies included in the systematic review sorted by vitamin type.
| Study | Design | Population | Intervention | Controls | Outcome | Outcome Measurement | ||
|---|---|---|---|---|---|---|---|---|
| Type | N | Type | N | |||||
| Vitamin E | ||||||||
| Aryaeian, 2008 [14] | Double blind RCT | 102 randomized in 4 groups * incl. 51 in vitamin E or placebo groups → 43 completed | Vitamin E 400 mg/day for 12 weeks |
21 | Placebo for 12 weeks | 22 | DAS-28, VAS pain, SJC, TJC, Morning stiffness | 12 weeks |
| Edmonds, 1997 [15] | Double blind RCT | 42 randomized → 39 completed | Vitamin E 600 mg twice daily for 12 weeks | 20 | Placebo for 12 weeks |
19 | Ritchie articular index, morning stiffness, SJC, VAS pain | 12 weeks |
| Vitamin K | ||||||||
| Shishavan, 2016 [16] | Double blind RCT | 64 randomized → 58 completed | Vitamin K 10 mg/day for 8 weeks |
30 | Placebo for 8 weeks |
28 | DAS-28 | 8 weeks |
| Folic acid | ||||||||
| Stamp, 2018 [17] | Double blind RCT | 40 randomized and completed | Folic acid 5 mg/day for 24 weeks | 22 | Folic acid 0.8 mg/day for 24 weeks | 18 | DAS-28 | 24 weeks |
| Morgan, 1994 [18] | Double blind RCT | 94 randomized → 79 completed the study in three groups | Folic acid 5 mg/day or 27.5 mg/day for 1 year |
25 + 26 |
Placebo | 28 | Ritchie articular index, Joint indices for tenderness and swelling, HAQ |
1 year |
| Vitamin D | ||||||||
| Soubrier, 2018 [19] | Double blind RCT | 59 randomized → 59 completed | Cholecalciferol 100,000 IU (frequency depending on the baseline vitamin D dosage) for 24 weeks |
30 | Placebo | 29 | HAQ, DAS-28, VAS pain | 24 weeks |
| Li, 2018 [20] | Double blind RCT | 369 randomized → 369 completed | 22-Oxa-Calcitriol 50,000 IU/week for 6 weeks or Calcitriol 50,000 IU/week for 6 weeks |
123 + 123 |
Placebo | 123 | SJC, VAS pain, HAQ | 6 weeks |
| Dehghan, 2014 [21] | Double blind RCT | 80 randomized → 80 completed | Cholecalciferol 50,000 IU/week for 6 months | 40 | Placebo | 40 | Number of flares | 6 months |
| Salesi 2012 [22] | Double blind RCT | 117 eligible → 98 | Cholecalciferol 50,000 IU/week for 12 weeks | 50 | Placebo | 48 | DAS-28, TJC, SJC, VAS pain | 12 weeks |
| Gopinat, 2011 [23] | Open label RCT | 204 identified → 121 randomized → 110 completed | Calcitriol 500 IU + Calcium 1000 mg per day for 12 weeks | 59 | Calcium 1000 mg per day | 62 | Time to achieve pain relief, number of patients with VAS pain reduction | 12 weeks |
| Hansen, 2014 [24] | Double blind RCT | 711 contacted → 98 eligible → 22 randomized | Ergocalciferol 50,000 IU 3 times/week for one month then twice a month for 8 weeks | 11 | Placebo | 11 | HAQ, DAS-28, VAS pain | 1 year |
| Brohult, 1973 [25] | Double blind RCT | 49 | Calciferol 100,000 IU per day for one year | 24 | Placebo | 25 | Objective and subjective symptom reduction | 1 year |
| Yang, 2015 [26] | Open-label RCT | 340 included→ 172 with vitamin D deficiency | Alfacalcidol 0.25 mcg twice a day for 24 weeks | 84 | Placebo | 88 | RA flare (DAS-28 > 3.2) | 6 months |
* Aryaeian et al. assessed four groups: linoleic acid, linoleic acid with vitamin E, vitamin E alone, and placebo. For this review, we only included the two following groups: vitamin E and placebo. RA: rheumatoid arthritis; RCT: randomized controlled trial; incl.: including; DAS-28: disease activity score—28; VAS pain: visual analog scale for pain; EULAR: European League Against Rheumatism; HAQ: Health Assessment Questionnaire; TJC: tender joint count; SJC: swollen joint count; IU: international units.