Effect of Malaria on Blood Levels of Vitamin E: A Systematic Review and Meta-Analysis

Abstract

Vitamin E has an antioxidant property and is associated with protection against malaria. The current study used systematic review and meta-analysis approaches examining the variance in blood levels of vitamin E in malaria patients as compared with uninfected individuals. The protocol for the systematic review was registered with PROSPERO (CRD4202341481). Searches for pertinent studies were carried out on Embase, MEDLINE, Ovid, PubMed, Scopus, ProQuest, and Google Scholar. The combined effect estimate (Cohen's d) of the difference in vitamin E levels in malaria patients as compared with uninfected individuals was estimated using the random effects model. The searches yielded 2009 records, and 23 studies were included in the systematic review. The majority of the studies (80%) found that vitamin E levels were significantly lower in malaria patients than those who were not infected. Overall, the results revealed a significant reduction in blood levels of vitamin E in malaria patients when compared with uninfected individuals (p < 0.01, Cohen's d: -2.74, 95% CI: -3.72-(-1.76), I²: 98.69%, 21 studies). There was a significant reduction in blood levels of vitamin E in patients suffering from severe malaria, in comparison with those experiencing less severe forms of the disease (p < 0.01, Cohen's d: -0.56, 95% CI: -0.85-(-0.26), I²: 0%, 2 studies), but no variation in blood levels of vitamin E among patients suffering from either P. falciparum or P. vivax malaria (p = 0.13, Cohen's d: -1.15, 95% CI: -2.62-0.33, I²: 93.22%, 3 studies). In summary, the present study strongly suggests that vitamin E levels are significantly reduced in malaria patients, with a more pronounced decrease observed in cases of severe malaria. However, the type of malaria parasite, specifically P. falciparum or P. vivax, did not appear to influence the levels of vitamin E. This study highlights the potential role of vitamin E in the pathogenesis of malaria and suggests that improved vitamin E status might be beneficial for improving disease outcomes.

Keywords: Plasmodium; antioxidant; malaria; meta-analysis; systematic review; tocopherol; vitamin E.

Figure 1

Study flow diagram.

Figure 2

The forest plot illustrates the variation in blood vitamin E levels between malaria patients and uninfected controls. Explanations for symbols: blue square, Cohen’s d for each study; green diamond, pooled Cohen’s d. Abbreviations: CI stands for confidence interval; N represents the number of populations enrolled; SD represents the standard deviation. References: [26,27,28,29,30,31,32,33,35,36,37,38,39,40,41,42,43,44,45,47,48].

Figure 3

The variation in blood vitamin E levels between patients with severe malaria and those experiencing less severe forms of the disease is illustrated by the forest plot. Explanations for symbols: blue square, Cohen’s d for each study; green diamond, pooled Cohen’s d. Abbreviations: CI stands for confidence interval; N represents the number of patients enrolled; SD represents the standard deviation. References: [32,44].

Figure 4

The fluctuation in blood vitamin E levels among patients infected with either P. falciparum or P. vivax malaria is illustrated by the forest plot. Explanations for symbols: blue square, Cohen’s d for each study; green diamond, pooled Cohen’s d. Abbreviations: CI represents confidence interval; N represents the number of patients enrolled; SD represents the standard deviation. References: [37,41,43].

Figure 5

The leave-one-out meta-analysis showing a significant reduction in vitamin E levels in patients with malaria as compared with uninfected controls in each rerun analysis (p < 0.05). Explanations for symbols: green circle, pooled Cohen’s d for each re-run analysis; red vertical line, overall Cohen’s d estimated from all re-run analyses. Abbreviation: CI stands for confidence interval. References: [26,27,28,29,30,31,32,33,35,36,37,38,39,40,41,42,43,44,45,47,48].

Figure 6

An asymmetrical spread of the effect estimate (SMD) from the middle line (red). The funnel plot was generated using the meta-analysis data from blood vitamin E levels between malaria patients and uninfected individuals. Abbreviation: CI, confidence interval.