Selected articles

Figure 1 depicts a flowchart of the research selection. The initial search resulted in a total of 567 articles, resulting in 541 non-duplicated publications after removing 26 articles. Following a review of titles and abstracts, 492 articles were eliminated. 6 studies were excluded due to the lack of inclusion criteria. Finally, the present review found 41 articles that meet the eligibility criteria. Table 1 summarizes the characteristics of chosen studies.

Fig. 1

Flowchart of the process for literature review and study selection

Table 1 characteristics of the included studies Characteristics of the included studies

In total, after screening and deleting duplicate articles, forty-one studies were selected for this systematic review. All studies assessed diabetic mice or rats. Ginger was used in different shapes in this study, including ginger powder, ginger oil, aqueous ginger extract, ethanolic ginger extract, and bioactive compounds such as zingerone and shogaol. Ginger and ginger extract treatment dosages ranged from 80 to 1000 mg/kg and bioactive compounds treatment dosages ranged from 5 to 100 mg/kg. Intervention duration ranged from 2 to 16 weeks. Location of studies performed as follows: 9 in Egypt [29, 30, 35, 37, 38, 47, 48, 54, 59], 8 in India [26, 36, 39, 41, 42, 49, 51, 56], 6 in Saudi Arabia[22, 23, 44, 45, 52, 61], 4 in Iran [31,32,33, 53], 3 in Kuwait [34, 57, 58], 3 in Pakistan [28, 46, 55], 2 in Nigeria [24, 43], 2 in China [21, 27], 1 in South Korea [25], Jordan [50], Iraq [60] and Malaysia [40]. Studies were done from 2006 to 2021.

Quality assessment

A summary of the results of the quality assessment is demonstrated in Fig. 2. In the majority of studies, performance bias, detection bias, and allocation concealment were found to be unclear risks of bias.

Fig. 2

Results of the SYRCLE’s tool for assessing the risk of bias

Ginger and glycemic control in DKD

Twenty-eight of 31 studies showed that ginger intake lowers blood glucose levels [24, 25, 27, 29, 30, 34,35,36,37,38,39,40,41,42,43, 47,48,49, 51,52,53, 55,56,57,58,59,60,61]. On the contrary, in 2 studies, blood glucose levels increased [22, 23]. One study did not show any meaningful changes [21]. 6 out of 7 studies reported that ginger increases serum insulin levels [24, 37, 38, 57, 59, 60], whereas in another study the result was reversed [27]. Ginger reduced hemoglobin A1c (HbA1c) and C peptide in all studies that examined these biomarkers [21, 26, 27, 29, 59]. Finally, to assess the impact of ginger consumption, a subgroup analysis was performed for ginger forms. In the bioactive compound subgroup of ginger, 6-shogaol had a better effect on blood sugar than zingerone. In the ginger powder subgroup, hypoglycemia’s effect increases with increasing dose intake. In the ginger extract subgroup with a dose of 500 mg/kg or less, hypoglycemia increases with increasing dose. However, by a dose of more than 500 mg/kg of ginger extract, hypoglycemia was reduced.

Ginger and dyslipidemia in DKD

Sixteen out of 41 articles examined the effect of ginger on the lipid profile. The reduction of TC and TG were also reported by 15 [21, 26, 29, 30, 34, 35, 38, 41, 44, 49, 52, 54, 56, 59, 60] and 14 [21, 26, 29, 30, 34, 35, 38, 41, 44, 49, 52, 56, 59, 60] studies respectively. Ginger has been shown to improve low-density lipoprotein-cholesterol (LDL-C) [26, 29, 30, 35, 38, 52, 54,