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By William C. Haas, III, MD, MBA
Carolinas Medical Center, Department of Family Medicine, Charlotte, NC
Dr. Haas reports no financial relationships relevant to this field of study.
SYNOPSIS: Ginger supplementation exhibits a promising effect on glycemic control, triglyceride levels, and systemic inflammation in type 2 diabetics.
SOURCE: Arablou T, et al. The effect of ginger consumption on glycemic status, lipid profile, and some inflammatory markers in patients with type 2 diabetes mellitus. Int J Food Sci Nutr 2014;65:515-520.
Traditionally, the management of type 2 diabetes mellitus involves achieving enhanced glucose control as a result of increasing insulin resistance. However, mounting evidence suggests that insulin resistance, and its associated defects in glucose and lipid metabolism, is just one of the many consequences of chronic, low-grade systemic inflammation.1 As a result, reducing levels of chronic systemic inflammation has become a growing interest among researchers, especially as it relates to insulin resistance and metabolic syndrome.
Botanicals with strong anti-inflammatory properties routinely generate attention for a possible role in the management of diabetes mellitus. Ginger (Zingiber officinale), a spice used in Chinese and Ayurvedic traditions to treat diseases ranging from gingivitis to asthma,2 contains many antioxidant compounds believed to exert strong anti-inflammatory effects through the inhibition of cyclooxygenase, inducible nitric oxide synthase, and lipoxygenase, as well as through the suppression of prostaglandin synthesis.3 To assess both the anti-inflammatory properties and clinical outcomes of ginger supplementation among diabetic patients, researchers in this study developed a randomized, double-blind, placebo-controlled trial to analyze changes in inflammatory markers, glycemic indices, and lipid profiles.
Diabetic patients treated with oral hypoglycemic agents who had a hemoglobin A1c (HbA1c) between 7-10%, as well as a body mass index (BMI) between 20-35 kg/m2, were recruited for study participation. Exclusion criteria included current pregnancy or lactation, active infection, history of cancer, current tobacco or alcohol use, and/or a renal, liver, thyroid, or parathyroid disorder. Seventy patients initially were enrolled and randomized to consume either 1600 mg capsules of powdered ginger rhizomes or wheat flower placebo daily for 12 weeks (one 800 mg capsule before lunch and one 800 mg capsule before dinner). Ginger was sourced from a local market and both sets of capsules were prepared by the research group. Patients were instructed not to change their diet or activity patterns during the study period and were assessed using a 24-hour recall questionnaire at the beginning and end of the study. Fasting blood samples were also collected at the beginning and end of the intervention and analyzed for blood glucose levels, insulin levels, HbA1c, triglycerides, total cholesterol, and HDL as well as prostaglandin E2 (PGE2), tumor necrosis factor-alpha (TNFα), and C-reactive protein (CRP).
A total of 63 patients completed the study (33 in the ginger group and 30 in the placebo group). Several dropouts occurred due to unwillingness to participate, along with one developed pregnancy and one insulin start. Results were analyzed from those completing the study with no reported intent-to-treat analysis. Baseline characteristics, including age, body weight, duration of diabetes, gender, and physical activity, did not differ between the intervention and placebo groups. Analysis of caloric consumption, macronutrients, micronutrients, and dose of oral diabetic medication did not differ before or after the intervention between or among the treatment and placebo groups.
With regard to the primary outcomes, all glycemic indices demonstrated a significant improvement in the ginger group (fasting plasma glucose [FPG], -9.1 ± 38.5 mg/dL, P = 0.02; HbA1c -1.0 ± 1.7%, P = 0.001; insulin -3.7 ± 8.2 μU/mL, P = 0.01) compared to the placebo group (FPG, 16.0 ± 48.5 mg/dL, P = 0.02; HbA1c 0.4 ± 1.4%, P = 0.001; insulin 0.1 ± 3.5 μU/mL, P = 0.01). Among lipid parameters, triglycerides, total cholesterol, and the HDL/total cholesterol ratio were the only measures to improve with ginger supplementation compared to baseline (-45.4 ± 69.6 mg/dL, -15.4 ± 34.3 mg/dL, and 0.2 ± 0.05, respectively). Placebo demonstrated no significant benefit with the lipid profiles. With regard to inflammatory markers, both CRP and PGE2 levels decreased significantly among ginger users compared to placebo (CRP: -2.5 ± 4.7 mg/L vs -0.7 ± 6.5 mg/L, P = 0.02; PGE2: -126.7 ± 231.6 pg/mL vs -21.4 ± 60.4 pg/mL, P = 0.009). No changes in weight or BMI were noted with either group.
Given the overall paucity of data pertaining to ginger in the management of type 2 diabetes, the authors of this study attempted to identify potential changes in inflammatory markers, glycemic indices, and lipid profiles after 12 weeks of supplementation. Improvements were most convincingly noticed in the areas of glycemic control and triglyceride lowering, with data supporting a possible anti-inflammatory effect. Both HBA1c and insulin levels decreased, suggesting ginger may decrease insulin resistance and decrease serum glucose levels. Ginger is speculated to decrease serum glucose levels through the activities of phenols, polyphenols, and flavonoids, which may inhibit intestinal glucosidase and amylase enzymes.4-5 The antioxidants within ginger, including paradol and zingerone, might increase insulin receptors and enhance ß-cell function,6 thereby decreasing insulin resistance. At the moment, the literature surrounding ginger and glycemic control is mixed; however, other studies also have demonstrated positive results when using higher ginger doses of 3 g/day.7-8
The effect of ginger on blood lipids is also mixed, as one study demonstrated a decrease in serum triglycerides without an effect on total cholesterol levels,6 but another study of diabetics with and without coronary artery disease found no significant change in lipid chemistries.9 A proposed mechanism for the triglyceride-lowering effect surrounds an increase in lipoprotein lipase enzyme activity.10 Finally, the current study demonstrated a potential anti-inflammatory effect of ginger, primarily through the reduction of CRP — reductions in TNFα were not statistically significant and the wide standard deviation in PGE2 reductions complicates conclusions. A more robust analysis of inflammatory markers could have enhanced the anti-inflammatory analysis of ginger supplementation. The potential anti-inflammatory effect of ginger should be explored further, given the implications for improving the many complications of metabolic syndrome.
Overall, the study was well-designed with only a few minor limitations that were not explicitly discussed. As previously indicated, an intent-to-treat analysis was not performed, which would have enhanced the validity of the results, as dropouts were not taken into account. Although the patients enrolled in the current study represent the average diabetic patient, those with diabetic nephropathy were excluded, which may limit the findings to patients with poorly controlled or long-standing diabetes. Another important group excluded were those taking insulin, which limits the current recommendations for ginger supplementation among this subset of diabetic patients. Unfortunately, the oral antidiabetic medications taken by the patients were not presented; however, no differences between the groups were reported, thereby reducing the chance that differences were attributable to pre-existing antidiabetic medications. Finally, the duration of this study, as well as others, currently does not extend beyond 3 months, limiting definitive recommendations for long-term use.
Despite its various limitations, the present study suggests that ginger may indeed have a role in the management of diabetes mellitus, particularly among non-insulin dependent diabetics. Although studies have not specifically evaluated harm among diabetic patients, ginger supplementation is generally regarded as safe by the FDA, with a theoretical risk of bleeding that may be amplified with concurrent use of anticoagulant and antiplatelet drugs.11 Supplementation with ginger root is relatively affordable, with the cost of a 90-day supply averaging about $6 based on a recent Web search. Perhaps the best advice for diabetic patients would be to use ginger several times per week when preparing food or adding it to water, as ¼ teaspoon is roughly equivalent to the dosage studied.