key: cord-0776226-36w41hov
authors: Beran, Azizullah; Mhanna, Mohammed; Srour, Omar; Ayesh, Hazem; Stewart, Jamie M.; Hjouj, Majdal; Khokher, Waleed; Mhanna, Asmaa S.; Ghazaleh, Dana; Khader, Yasmin; Sayeh, Wasef; Assaly, Ragheb
title: Clinical Significance of Micronutrient Supplements in Patients with Coronavirus Disease 2019: A Comprehensive Systematic Review and Meta-Analysis
date: 2022-01-13
journal: Clin Nutr ESPEN
DOI: 10.1016/j.clnesp.2021.12.033
sha: 2b8663560145a0fac5cd153d5cf02b5035bebf3e
doc_id: 776226
cord_uid: 36w41hov

Background and aims Micronutrient supplements such as vitamin D, vitamin C, and zinc have been used in managing viral illnesses. However, the clinical significance of these individual micronutrients in patients with Coronavirus disease 2019 (COVID-19) remains unclear. We conducted this meta-analysis to provide a quantitative assessment of the clinical significance of these individual micronutrients in COVID-19. Methods We performed a comprehensive literature search using MEDLINE, Embase, and Cochrane databases through December 5th, 2021. All individual micronutrients reported by ≥3 studies and compared with standard-of-care (SOC) were included. The primary outcome was mortality. The secondary outcomes were intubation rate and length of hospital stay (LOS). Pooled risk ratios (RR) and mean difference (MD) with corresponding 95% confidence intervals (CI) were calculated using the random-effects model. Results We identified 26 studies (10 randomized controlled trials and 16 observational studies) involving 5633 COVID-19 patients that compared three individual micronutrient supplements (vitamin C, vitamin D, and zinc) with SOC. Nine studies evaluated vitamin C in 1488 patients (605 in vitamin C and 883 in SOC). Vitamin C supplementation had no significant effect on mortality (RR 1.00, 95% CI 0.62-1.62, P=1.00), intubation rate (RR 1.77, 95% CI 0.56-5.56, P=0.33), or LOS (MD 0.64; 95% CI -1.70, 2.99; P=0.59). Fourteen studies assessed the impact of vitamin D on mortality among 3497 patients (927 in vitamin D and 2570 in SOC). Vitamin D did not reduce mortality (RR 0.75, 95% CI 0.49-1.17, P=0.21) but reduced intubation rate (RR 0.55, 95% CI 0.32-0.97, P=0.04) and LOS (MD -1.26; 95% CI -2.27, -0.25; P=0.01). Subgroup analysis showed that vitamin D supplementation was not associated with a mortality benefit in patients receiving vitamin D pre or post COVID-19 diagnosis. Five studies, including 738 patients, compared zinc intake with SOC (447 in zinc and 291 in SOC). Zinc supplementation was not associated with a significant reduction of mortality (RR 0.79, 95% CI 0.60-1.03, P=0.08). Conclusions Individual micronutrient supplementations, including vitamin C, vitamin D, and zinc, were not associated with a mortality benefit in COVID-19. Vitamin D may be associated with lower intubation rate and shorter LOS, but vitamin C did not reduce intubation rate or LOS. Further research is needed to validate our findings.

The titles and abstracts of identified studies were screened, and full texts were examined. We included all published RCTs and observational studies (prospective and retrospective) that all compared individual micronutrients versus standard-of-care (SOC) in adult patients with and examined the impact of individual micronutrient supplementation on clinical outcomes of COVID-19. Only individual micronutrients reported in ≥3 studies were included in the final analysis. We excluded single-arm studies, case reports, reviews, commentaries, abstracts, studies with no clear outcomes, and preprint studies. We also excluded studies that examined micronutrient supplements as a combination. A study by Carlucci et al. (16) that evaluated zinc supplements' role in patients with COVID-19 was excluded because the mortality rate was reported as a composite outcome as death/hospice.

Data on study design, patients' demographics, study characteristics, follow-up duration, route of administration and dosage, and outcome measures were extracted from the included studies. Two investigators (AB and MM) finished the data extraction independently. Discrepancies were resolved by a third reviewer (HA).

The primary outcome of our study was mortality between the micronutrient and SOC groups. The secondary outcomes were intubation rate and length of hospital stay (LOS).

We performed a meta-analysis of the included studies using Review Manager 5. 3 

Cochrane Centre) and Comprehensive Meta-Analysis (Biostat, Englewood, USA). The median and interquartile range were converted to mean and SD where applicable (17) . The random-effects model was used to calculate the weighted pooled risk ratio (RR) and mean difference (MD) with the corresponding 95% confidence intervals (CI) of our desired outcome. A P-value <0.05 was considered statistically significant. The heterogeneity of the effect size estimates across the studies was quantified using the Q statistic and I 2 (P < 0.10 was considered significant). A value of I 2 <50%

indicates low heterogeneity, and ≥50% indicates substantial heterogeneity (18) .

We performed a subgroup analysis based on the study design (RCTs vs. observational studies) and route of administration (intravenous [IV] or oral) if at least three studies reported the outcome. We also conducted a subgroup analysis of studies reporting the supplementation of vitamin D before the diagnosis of COVID-19 and those reporting the supplementation of vitamin D post-COVID-19 diagnosis. To confirm the robustness of the results in the presence of significant heterogeneity, sensitivity analysis for mortality using leave-one-out meta-analysis was performed to see if it had a significant influence on the meta-analysis result (i.e., jack-knife sensitivity analysis).

The Jadad composite scale was used to assess the methodological quality of the clinical trials based on randomization, blinding, and withdrawals. The scale ranged from 0 to 5 points. Studies with total scores of ≥3 were considered to have a low risk of bias. The Newcastle Ottawa Quality Assessment Scale (NOS) was used to assess the quality of the observational studies based on the selection of the study groups, comparability of study groups, and ascertainment of exposure/outcome. Studies with total scores of ≥6 were considered to have a low risk of bias. For outcomes J o u r n a l P r e -p r o o f reported by ≥10 studies, publication bias was assessed qualitatively by visually assessing the funnel plot and quantitively using Egger's regression analysis. Two authors (AB and MM) independently assessed each study for bias. Discrepancies were resolved by a third reviewer (HA).

We identified a total of 1034 studies that examined the clinical significance of micronutrient supplements in patients with COVID-19. Based on full texts, we excluded 108 studies that had no control group, no appropriate outcome, or <3 studies reporting the individual micronutrient.

Eventually, 26 studies met our inclusion criteria and were included in the meta-analysis. These studies investigated three individual micronutrient supplements: vitamin C, D, and zinc. Figure 1 shows the PRISMA flow chart that illustrates how the final studies were selected.

Characteristics and patient demographics of the included studies for vitamin C supplementation are shown in Table 1 . Nine studies (8, 11, 13, 14, (19) (20) (21) (22) (23) (four RCTs and five retrospective cohort studies) that examined the effect of vitamin C on clinical outcomes of 1488 patients with COVD-19 (605 patients in the vitamin C group and 883 in SOC) were included. The mean age was 61.0±15.02, and 57.4% were males.

These studies were conducted in China (8, 14, 22) , Iran (13) , Pakistan (20) , Saudi Arabia(24), Turkey (25) , and United States (11, 21) . The studies provided daily doses alone (11, 13, 14, (20) (21) (22) 24, 25) or daily doses after a loading dose (8) . The studies provided IV (8, 13, 14, (20) (21) (22) 25) or oral (11, 24) vitamin C supplementations. Daily doses used were oral 1 gm(24) and 8 gm(11) daily, and IV 50 mg/kg/day (20) , 2 gm(25), 2-4 gm(22), 6 gm (8, 13, 21) , or 24 gm(14) daily. The loading dose was 6 gm IV infusion for 12 hours (8) . The duration of treatment varied from four to 18 days.

There was a low risk of bias for seven studies (8, 11, 14, 21, 22, 24, 25) , while the risk of bias for two studies was high (13, 20) , as shown in Supplementary   Table 2 .

Vitamin C (ascorbic acid) supplementation had no significant effect on mortality among COVID-19 patients (RR 1.00, 95% CI 0.62-1.62, P < .001, I 2 = 74%, Figure 2A ), intubation rate (RR 1.77, 95% CI 0.56-5.56, P = 0.33, I 2 = 67%, Figure 2B 

Characteristics and patient demographics of the included studies for vitamin D supplementation are shown in Tables 2 and 3 . Thirteen studies(9,10,15,26-35) (four RCTs and nine observational studies) that evaluated the effect of vitamin D on clinical outcomes of 3407 patients with COVID-19 (878 patients in the vitamin D group and 2529 in SOC) were included. Four studies (27, 28, 33, 35) assessed the use of vitamin D before the diagnosis of COVID-19, while eight studies (9, 15, 26, (29) (30) (31) (32) 34) reported the use of vitamin D after the diagnosis of COVID-19, and one study (10) reported the use of vitamin D pre and post COVID-19 diagnosis. The mean age was 65.25±18 years, and 49.9% were males. These J o u r n a l P r e -p r o o f studies were conducted in France(9,10), Spain (26, 28, 32, 33) , Brazil (15) , India (29, 31) , Italy (27, 35) , Turkey (34) , and United States (30) . All studies provided oral vitamin D supplementations with highly variable dosages and duration of treatment across the included studies. There was a low risk of bias for all studies (9, 10, 15, (26) (27) (28) (29) (30) (31) (32) (33) (34) (35) , as shown in Supplementary Table 3 .

Overall, vitamin D supplementation did not reduce the risk of mortality among COVID-19 patients (RR 0.75, 95% CI 0.46-1.23, P = 0.25, Figure 3A ). However, vitamin D supplementation was associated with significant reduction in intubation rate (RR 0.55, 95% CI 0.32-0.97, P = 0.04, I 2 = 48%, Figure 3B ) and LOS (MD -1.26; 95% CI -2.27, -0.25; P = 0.01, I 2 = 0%, Figure 3C ). Subgroup analysis showed that vitamin D supplementation was not associated with a mortality benefit in patients receiving vitamin D pre or post COVID-19 ( Figure 3D ). 

Characteristics and patient demographics of the included studies for zinc supplementation are shown in Table 4 . A total of five studies (2, 11, 12, 24, 36) (three randomized controlled trials and two retrospective cohort studies), including 738 patients with COVID-19 (447 patients in zinc group and 291 in SOC group), were included. The mean age was 55±18.8 years, and 58.8% were males. The studies were conducted in Australia(36), Egypt(2), Saudi Arabia (24) , and the USA (11, 12) . The studies provided IV (36) or oral (2, 11, 12, 24) zinc supplementations in the form of zinc chloride(36), zinc gluconate(11), or zinc sulfate (2, 12, 24) . The duration of treatment varied from 7 to 15 days. There was a low risk of bias for four studies (11, 12, 24, 36) , while the risk of bias of one study (2) was high, as shown in Supplementary Table 4 .

Zinc supplementation was not associated with a significant reduction in mortality among COVID-19 patients (RR 0.79, 95% CI 0.60-1.03, P = 0.08, I 2 = 0%, Figure 4A ). The subgroup analysis for RCTs was consistent (RR 0.75, 95% CI 0.49-1.13, P = 0.16, I 2 = 0%, Figure 4B ).

To the best of our knowledge, this is the first comprehensive systematic review and meta-analysis that investigated the clinical significance of individual micronutrient supplements (e.g., vitamin C, vitamin D, and zinc) in patients with COVID-19, with more than 5600 patients from 26 articles. Our study findings indicate that all the three individual micronutrients, including vitamin C, vitamin D, zinc, were not associated with a mortality benefit in patients with COVID-19. While vitamin C was not associated with a reduction in intubation rate and length of hospital stay, vitamin D supplementation showed a lower intubation rate and shorter hospital stay length than SOC.

Vitamin C therapy is usually perceived as harmless, inexpensive, with potential benefits in various respiratory infections, so it is not surprising to be an attractive therapy in the current pandemic. It is thought that vitamin C improves the immune system through various mechanisms, such as increasing lymphocyte and phagocyte activity, enhancing the response of T-cells to infections, and augmenting interferon levels (37) . Some authors suggested that vitamin C could play a role in hastening the pro-inflammatory and pro-oxidant environment (the cytokine storm) that is believed to be the cornerstone in SARS-CoV2 infection and pathogenies(38). Vitamin C could also mediate the binding of SARS-CoV-2 with the angiotensin-converting enzyme 2 (ACE2) (39). Interestingly, certain populations (male, African American, older, diabetics, hypertensive, and COPD patients) at a higher risk of severe COVID-19 have also been found to have lower serum vitamin C levels (40). In a recent study, 94.4% of the 18 J o u r n a l P r e -p r o o f patients with COVID-19-induced ARDS had undetectable vitamin C levels, and one patient had low levels (4) . None of the studies included in our study reported the baseline vitamin C status.

The data regarding the value of ascorbic acid in the management of viral acute respiratory infections (ARIs) is inconsistent, with some studies showing that high doses of vitamin C may reduce the mortality among COVID-19 patients (8), while other studies have demonstrated no benefit (11, 13, 14) . Our meta-analysis demonstrated that vitamin D supplements had no significant effect on mortality, intubation rate, and LOS in COVID-19. Our findings were consistent with a recent meta-analysis by Rawat et al. (41), which showed no significant effect of vitamin C on the mortality of COVID-19 patients. However, the latter meta-analysis included studies that reported combined micronutrients(41). In our meta-analysis, we included only studies that reported the use of individual micronutrient supplements for a more accurate assessment of their clinical significance.

Vitamin D is postulated to regulate innate and adaptative immune responses, and antigen-presenting cells can synthesize 1,25-dihydroxy vitamin D from 25-hydroxy vitamin D (42). Since cytokine storm plays an important role in COVID-19, vitamin D may also inhibit pro-inflammatory cytokine production in monocytes/macrophages (43). A recent meta-analysis by Pereira et al. (7) showed a positive association between vitamin D deficiency and the severity of COVID-19. However, there is conflicting data regarding the value of vitamin D supplements in the management of COVID-19. Some studies (9, 10) showed that vitamin D supplements might reduce the severity and mortality of COVID-19 patients, while other studies have shown no differences in mortality (15, 28) . Our meta-analysis demonstrated no significant reduction in mortality with vitamin D supplementation in COVID-19 patients, with consistent results on subgroup analysis of studies supplemented vitamin D pre or post COVID-19 diagnosis. Our study findings align with the most recent trial's results which showed no significant difference between the vitamin D and placebo groups in mortality risk (15) . The RCT showed no significant difference in terms of intubation rate or LOS between vitamin D and placebo groups J o u r n a l P r e -p r o o f (15) . Elamir et al.(30) demonstrated shorter LOS in the vitamin D group compared to SOC group (mean 5.5 vs. 9.2 days, respectively), but it did not reach statistical significance (P = 0.14). However, our study showed a significant reduction in intubation rate and LOS in patients who received vitamin D supplementation after COVID-19 diagnosis. This discrepancy could be explained by the small sample size of these studies as they were likely underpowered to detect the difference.

Zinc is a trace element that has been shown to play an important role in both innate and adaptive immune systems and cytokine production (44). Zinc also has antioxidant effect, and it inhibits viral replication because it is hypothesized that zinc has shown an inhibitory effect on the RNAdependent RNA polymerase of SARS-CoV in cell culture studies (45). Zinc deficiency appears to be common in COVID-19 patients, with an incidence ranging from 31% up to 57% (5, 6) . Although some studies have shown that zinc deficiency was associated with more risks of complications, hospital stay, and increased mortality (6) , there is no clear data yet about the effect of zinc supplements on the clinical outcomes of COVID-19 patients. A report on four patients suggested that oral zinc (not exceeding 200 mg) was well tolerated and was associated with better recovery from COVID-19 infections (46). However, Yao et al. (12) showed that the use of zinc sulfate was not significantly associated with a change in the risk of in-hospital mortality (adjusted hazard ratio 0.66; 95% CI, 0.41-1.07; P = 0.09). Our meta-analysis showed no mortality benefit from adding zinc supplements to COVID-19 patients. Our findings were consistent with the recently published clinical trial by Thomas et al.(11) , which demonstrated no significant reduction in mortality risk between the patients who received zinc and those who did not.

J o u r n a l P r e -p r o o f There are several registered clinical trials still in the recruitment stage evaluating the effect of different micronutrient supplements on the clinical outcomes of COVID-19, including selenium (NCT04869579), vitamin C (NCT04357782 and NCT04264533), vitamin D, and zinc (NCT04641195). The pending results of these trials are expected to provide more solid evidence regarding the role of micronutrients in the management of COVID-19 patients.

Our study has certain limitations. First, this meta-analysis is limited by the small number of studies with a small sample size and low event rate for zinc supplementation. Therefore, our findings should be interpreted with caution. Second, observational studies were included, which could be affected by confounding variables. In addition, some included trials were open-label trials. Therefore, double-blinded RCTs are needed to evaluate the clinical effectiveness of these supplements. Third, significant heterogeneity was found in the measurement of vitamin C and D. This could be explained by variation in the patient population, disease severity, co-administered medications used for COVID-19, and lack of standardization across the studies in medication dosage, duration of treatment. Fourth, lack of information on micronutrient deficiencies of individuals in both the treated and control groups. The patient's nutritional status and oxidative scavenging capacity could provide fundamental data to predict the severity of disease following SARS-CoV2 infection (47). Fifth, we could not assess the impact of these supplements on the duration of symptoms and recovery time for the micronutrients and the effect of zinc on intubation rate and LOS due to limited studies that reported these outcomes. Lastly, we could not assess the effect of other micronutrients such as magnesium and selenium on COVID-19 due to the limited number of studies.

Despite these limitations, our study has significant strengths. First, we included a total of 26 studies that evaluated three different micronutrients (vitamin C, D, and zinc) with over 5600 patients with COVID-19. To our knowledge, this is the first comprehensive meta-analysis J o u r n a l P r e -p r o o f to investigate the clinical significance of individual micronutrient supplements in patients with COVID-19. Although substantial heterogeneity was noted in the measurement of mortality for vitamin C and D, we performed sensitivity analysis and subgroup analysis to evaluate the robustness of our results. Consistent results were observed on sensitivity analysis and subgroup analysis of RCTs and studies that reported the use of vitamin D pre and post COVID-19 diagnosis. Lastly, most of the studies in our meta-analysis had a low risk of bias based on quality assessment. 

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Author contributions: AB, MM, and OS conceived and designed the study. AB, HA, WK, ASM, and DG collected, analyzed, and interpreted the data, and drafted the manuscript. YK, WS, JMS, and MH collected the data and reviewed the literature. AB and RA critically revised the manuscript. All authors read and approved the final manuscript.Grants and Funding: None.

All authors declare no conflicts of interest.