Table 3.

Characteristics of participants within the studies included in the systematic review.

Refs.	First Author, Year Trial Name	Number of CIS/MS Participants	Age at Baseline	Inclusion and Exclusion Criteria
[22]	Dörr et al., 2020 EVIDIMS trial	53	41 ± 2.1	Inclusion: patients with CIS or RRMS; age 18–65 years (y); EDSS score 0–6; no relapse in the last 30 days; IFN-β1b treatment >3 months. Exclusion: pregnancy; history of sarcoidosis; hepatopathy or renal dysfunction; nephrolithiasis; pseudo-hypoparathyroidism; vitamin D supplementation with more than 500 IU/d in the last 6 months; hypercalcemia or urine calcium/creatinine ratio > 1; concomitant medication with hydrochlorothiazide, digitoxin, digoxin, barbiturates, phenytoin; incompatibility with MRI.
[21,43]	Hupperts et al., 2019 Rolf et al., 2017 SOLAR trial	229	34 ± 8.0	Inclusion: RRMS; age 18–55 y; adequate renal and hepatic function; early-stage MS on brain or spinal MRI; first clinical event in the last 5 years; EDSS score lower than 4.0; active disease with either one relapse or MRI new lesion within the last 18 months; no or low vitamin D supplementation (lower than 1000 IU/d). Exclusion: lactation or pregnancy; other disease than MS that could explain symptoms; relapse in the last 30 days before inclusion; use of corticosteroids within 30 days before inclusion; complete transverse myelitis or bilateral optic neuritis; abnormalities of vitamin D metabolism other than low dietary intake or decreased sun exposure; urinary calcium higher than 1.0 mmol/mmol of creatinine or hypercalcemia (11 mg/dL); hepatic impairment (alanine or aspartate aminotransferase higher than three times the upper limit of normal (ULN); bilirubin higher than 1.5 times ULN if associated with any elevation of alanine aminotransferase or alkaline phosphatase; or alkaline phosphatase higher than 2.5 times ULN); drugs other than corticosteroids that affect vitamin D metabolism; vitamin D supplementation higher than 400 IU/d; conditions with susceptibility to hypercalcemia (e.g., treatment with digitalis or hydrochlorothiazide, arrhythmia or heart disease, nephrolithiasis).
[23]	Camu et al., 2019 CHOLINE trial	129	38 ± 9.3	Inclusion: patients with RRMS; age 18–65 y; serum 25(OH)D < 75 nM; treatment with IFN-β1a for 4 ± 2 months prior to randomization; EDSS 0–5; ≥1 relapse during the previous 2 y; stable disease over the last 30 days. Exclusion: medications affecting vitamin D metabolism other than corticosteroids; previous or ongoing hypercalcemia; estimated glomerular filtration rate (eGFR) lower than 60 mL/min.
[31]	Kotb et al., 2019	35	27 ± 4	Inclusion: patients with RRMS; age ≥18 y; no exacerbations; regular treatment with IFN; no new MRI lesions. Exclusion: glucocorticoid treatment within 4 weeks prior to recruitment; disease-modifying drugs (DMD) other than IFN; vitamin D >1000 UI/d; use of glucocorticoid or relapse in the last 30 days; severe depression; pregnancy; serum creatinine >1.5 mg/dL; hypersensitivity to vitamin D; history of hyperparathyroidism, tuberculosis, nephrolithiasis, or sarcoidosis.
[32]	Darwish et al., 2017	88	34 ± 11	Inclusion: patients with RIS, CIS, RRMS, SPMS; age ≥16 y; 25(OH)D <250 nM. Exclusion: not reported.
[27]	O’Connell et al., 2017	67	37 ± 8.7 (group 10,000 UI/d) 33 ± 4.6 (group 5000 UI/d)	Inclusion: patients with CIS; age 18–55 y; symptom onset in the last 3 months; more than one asymptomatic T2 lesions on brain MRI; no treatment with corticosteroids in the last month; no other DMD. Exclusion: disease other than MS that could explain symptoms; exacerbation in the last six weeks; treatment with any immunomodulating therapy in the last three months; steroids in the last month or any previous treatment with other immunosuppressant or mitoxantrone; no hypercalcemia, renal impairment, intolerance to vitamin D, parathyroid dysfunction, sarcoidosis; pregnancy or lack of contraception; prior or current treatment with thiazide diuretics or vitamin D supplementation (≥1000 IU/d).
[28]	Laursen et al., 2016	134	41 (23–63)	Inclusion: RRMS patients with natalizumab treatment for at least 1 year prior to enrolment. Exclusion: pregnancy; development of SPMS, cancer, anti-natalizumab antibodies.
[39]	Sotirchos et al., 2016	40	41 ± 8.1	Inclusion: RRMS; age 18–55 y; serum 25(OH)D 50–125 nM. Exclusion: vitamin D supplementation >1000 IU; change of immunomodulatory therapy within the past 3 months; systemic glucocorticoid therapy or relapse in the last month; pregnancy; serum creatinine higher than 1.5 mg/dL; vitamin D intolerance; history of hyperparathyroidism, sarcoidosis, tuberculosis, or nephrolithiasis.
[35,44]	Farsani et al., 2015 Naghavi Gargari et al., 2015	32	31 ± 7.1	Inclusion: RRMS; remission period; serum 25(OH)D <50 nM; EDSS score 0–5. Exclusion: treatment with steroid or immunosuppressive drugs.
[36]	Etemadifar et al., 2015	15	27 ± 2.4	Inclusion: pregnant women with MS; age 20–40 y; stable neurological functioning for at least 1 month prior to study entry; EDSS score ≤ 6; serum 25(OH)D level < 50 nM. Exclusion: substantial disorders in psychiatric, hematologic, cardiac, endocrinological, renal, hepatic or metabolic functions; vitamin D3 supplement; any condition predisposing to hypercalcemia; nephrolithiasis; renal insufficiency.
[33]	Achiron et al., 2015	158	41 ± 9.8	Inclusion: fatigue severity scale score ≥ 40; age 18–55 years; EDSS score > 5.5. Exclusion: relapse within 30 days before the study; serum calcium level > 10.5 mg/dL; history of hypersensitivity or intolerance to 1α(OH)D3 or related substances; a life-threatening and/or unstable clinical condition and/or alcohol or drug abuse.
[34,45]	Golan et al., 2013a and 2013b	45	43 ± 12	Inclusion: age ≥ 18 y; patients who continued to suffer from flu-like symptoms after 4 months of treatment with IFN-β; 25(OH)D blood levels lower than 75 nM; EDSS score lower than 7. Exclusion: intestinal malabsorption, cirrhosis, nephrotic syndrome, hyperthyroidism, eGFR less than 40 mL/min, rickets, hypoparathyroidism, hypercalcemia at baseline, known malignancy, granulomatous disorders and lymphomas; treatment with orlistat, anticonvulsants, rifampin, isoniazide, ketoconazole, leucovorin, 5FU, hydrochlorothiazide; arrhythmia; heart disease; nephrolithiasis; pregnancy.
[29,46]	Soilu-Hänninen et al., 2012 Hänninen et al., 2020 Finnish Vitamin D Study	66	39 (range 22–53)	Inclusion: RRMS with IFN-β1b for at least 1 month; age 18–55 y; EDSS score ≤ 5.5; use of a contraceptive method. Exclusion: calcemia > 2.6 mM; serum 25(OH)D > 85 nM; primary hyperparathyroidism; pregnancy or lack of contraception; alcohol or drug abuse; immunomodulatory treatment other than IFN-β1b; intolerance to cholecalciferol or peanuts; treatment with digitalis, vitamin D3 analogs or vitamin D, calcitonin; any condition predisposing to hypercalcemia, sarcoidosis, nephrolithiasis or renal impairment; significant hypertension (higher than 180/110 mmHg); hyper- or hypothyroidism in the last year; a history of nephrolithiasis in the last 5 years; cardiac insufficiency or dysrhythmia; unstable ischemic heart disease; depression.
[30]	Kampman et al., 2012	68	40 ± 8	Inclusion: RRMS; age 18–50 y; EDSS score ≤ 4.5. Exclusion: inability to walk more than 500 m; history of conditions affecting bone; lactation or pregnancy in the last 6 months; use of bone-active drugs other than intravenous methylprednisolone for the treatment of relapse; nephrolithiasis in the last 5 years; menopause; unwillingness to use appropriate contraception.
[37]	Shaygannejad et al. 2012	50	39 ± 8.4	Inclusion: RRMS; age 15–60 y; EDSS score ≤ 6; stable neurological condition for more than 4 weeks prior to study; circulating 25(OH)D level higher than 100 nM. Exclusion: substantial disorders in psychiatric, neurological, cardiac, endocrinological, hematologic, hepatic, renal, or metabolic systems; treatment with digitalis, vitamin D supplementation; any condition predisposing to hypercalcemia, renal insufficiency nephrolithiasis; pregnancy.
[42]	Stein et al., 2011	23	34 [inter-quartile range (IQR) 30–49]	Inclusion: RRMS; age > 18 y; relapse in the last 2 years despite immunomodulatory treatment. Exclusion: primary or SPMS; pregnancy; clinical relapse or use of systemic glucocorticoid within the prior month; EDSS higher than 5; current DMD other than IFN or glatiramer acetate; elevated calcemia; creatinine higher than 0.2 mM; elevated serum uric acid; eGFR < 60 mL/min;
[38]	Mosayebi et al., 2011	59	34 ± 9	Inclusion: MS; age 18–60 y; at least one relapse in the 12 months; more than three lesions on spinal or brain MRI; baseline EDSS score lower than 4.0. Exclusion: patients with CIS or progressive MS; clinical relapses during the study; use of digitalis; vitamin D supplementation; drug abuse; any condition pre-disposing to hypercalcemia; nephrolithiasis or renal impairment; pregnancy or lack of contraception; refusal to restrict dietary calcium.
[40,47]	Kimball et al., 2007 Burton et al., 2010	49	41 (range 22–54)	Inclusion: MS; age 18–55 y; EDSS score lower than 7.0. Exclusion: use of steroids within 30 days; relapse within 60 days; chemotherapy within 12 months; pregnancy/inadequate contraception; vitamin D intake higher than 4000 IU daily; serum 25(OH)D level > 150 nM; lymphoma or granulomatous disease; cardiac arrhythmia; kidney impairment; altered calcium metabolism.
[41]	Wingerchuk et al., 2005	15	36 (range 22–44)	Inclusion: RRMS; age 18–65 y; EDSS score 0–5.0; at least one clinical exacerbation in the previous year; contraindication to or patient’s desire against treatment with IFN-β and glatiramer acetate. Exclusion: progressive MS; use of glatiramer acetate, IFN-β, corticosteroid or immunosuppressive treatment within the previous two months; use of vitamin D supplementation or digitalis; any condition predisposing to hypercalcemia; nephrolithiasis or renal insufficiency; pregnancy or lack of contraception method; and refusal to restrict dietary calcium.