By Charla Corbin, MBBS, and Nancy Selfridge, MD
Dr. Corbin is Clinical Skills Instructor, Clinical Foundations Department, Ross University School of Medicine, Barbados West Indies.
Dr. Selfridge is Professor, Clinical Foundations Department, Ross University School of Medicine, Barbados, West Indies.
• Chamomile, a plant that is rich in polyphenols, flavonoids, and other antioxidant and anti-inflammatory chemicals, has a long history of medicinal use worldwide and across healing traditions and practices.
• In this systematic review, results from various research studies suggest that chamomile may improve glycemic control, improve lipid metabolism, and reduce oxidative stress in diabetes.
• Some weaker evidence suggests that chamomile use may affect diabetic complications positively.
SYNOPSIS: A systematic review of recent studies of the effects of chamomile on metabolic profiles suggests a positive effect on glycemic control, lipid profiles, and diabetic complications.
SOURCE: Hajizadeh-Sharafabad F, Varshosaz P, Jafari-Vayghan H, et al. Chamomile (Matricaria recutita L.) and diabetes mellitus, current knowledge and the way forward: A systematic review. Complement Ther Med 2020;48:102284.
Diabetes mellitus is one of humankind’s top 10 leading causes of death and disability.1 Affecting more than 400 million people worldwide, including more than 30 million Americans, diabetes prevalence continues to rise — disproportionately more rapidly in low- and middle-income countries.1,2
Despite breakthroughs in pharmacotherapy and strong evidence of efficacy for lifestyle interventions, diabetes remains a major cause of blindness, amputations, chronic kidney disease, and cardiovascular events, such as myocardial infarction and stroke.2 Oxidative stress and systemic inflammation appear to be the common pathophysiologic conditions linking diabetic macrovascular and microvascular complications. Chamomile has been used as an herbal medication for thousands of years in many healing traditions and still is included in the natural pharmacopoeia of many countries.3 The plant has been found to contain sesquiterpenes, terpenoids, flavonoids, coumarins, and polyphenols, many of which have been shown to demonstrate anti-inflammatory, antioxidant, antiseptic, and antihyperglycemic effects.3
The authors of this systematic review wished to review, analyze, and report evidence of chamomile’s effects on metabolic markers and complications of diabetes from animal and human studies. After a broad literature search of common electronic databases, including PubMed, Scopus, Embase, ProQuest, and Google Scholar, the authors applied the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol.4 Of 208 initial articles retrieved in the literature search, nine animal studies and six human clinical trials met inclusion criteria for review. In eight of the animal studies, diabetes was induced by streptozotocin or alloxan. A variety of chamomile preparations were used in the animal trials, including ethanolic extract (n = 3) and aqueous extract (n = 4), both at doses between 20 mg/kg to 500 mg/kg for two to 14 weeks, and chamomile tea (n = 2) at a dose of 500 mg/kg for four weeks or 1 g for eight weeks. Studies also varied in the part of the chamomile plant used for the aqueous and ethanolic extracts. All human trials employed chamomile tea, 2.5 g to 10 g for four to 12 weeks.
Outcome measures varied by trial but included blood glucose and insulin, hemoglobin A1C levels (HbA1c), lipid profiles, liver enzymes and liver function, renal function, measures of oxidative stress and inflammation, and body weight fluctuations. Animal studies typically employed gavage or gastric cannula to deliver doses; one study administered the chamomile in the rat’s drinking water. All animal studies showed improvement in various measures of glycemic control and glucose intolerance, sustained over time. Improvements in plasma glucose levels in rats with diabetes ranged from 14% to 59% and was dose-dependent in studies that included different dosing regimens. Where measured, insulin levels and insulin sensitivity increased.
In one study, histopathologic assessment of sacrificed animals showed that rats with diabetes treated with chamomile demonstrated increased insulin positive B cells in pancreatic islets compared to untreated controls. Animal studies also demonstrated positive results of chamomile on lipid profiles in two studies, with statistically significant reductions in total cholesterol, triglycerides, low-density lipoproteins (LDL), and very-low-density lipoproteins, as well as increases in high-density lipoproteins in rats with diabetes.
In the four animal studies that addressed chamomile’s effects on oxidative stress markers in both normal rats and rats with diabetes, the levels of various antioxidant enzymes were increased consistently. In three studies of the effects of chamomile on diabetic complications, statistically significant positive effects on renal profiles, reductions in hepatic enzymes (alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase), and weight reduction were noted. Human study results were less consistent. Only three of the six human studies included in the review examined the effects of chamomile in patients with diabetes. One study using chamomile tea (10 g/100 mL boiling water) twice daily for four weeks in both patients with diabetes and controls demonstrated reductions in fasting and post-prandial blood glucose of 8% and 7%, respectively, although the changes were not statistically different between the treatment and control groups.
In another trial, 64 patients with type 2 diabetes received three cups daily of chamomile tea (3 g/150 mL of hot water) or placebo for eight weeks. The chamomile tea group demonstrated significant decreases in HbA1c, insulin levels, and insulin resistance, as well as an 11% reduction in serum glucose levels compared to the placebo group. A third study of 64 depressed patients with diabetes receiving three cups daily of chamomile or black tea for 12 weeks demonstrated significant reduction in HbA1c in the chamomile users compared to the black tea group. Again, three of the six human studies investigated the effects of chamomile supplementation on dyslipidemia.
All of these studies demonstrated significant reductions in total cholesterol, triglycerides, and LDL. In the chamomile vs. black tea study mentioned previously, there were no between-group differences in the post-treatment lipid profiles of the patients with diabetes in the study. Only three human trials included measures of oxidative stress and inflammation. Two of the trials yielded inconclusive results. However, one trial noted significant increases in antioxidant enzymes and reductions in malondialdehyde (MDA — a marker of oxidative stress) levels, as well as decreases in tumor necrosis factor and C-reactive protein measures of systemic inflammation. The single clinical trial that evaluated the effects of chamomile on diabetic complications demonstrated significant decreases in serum creatinine over the four-week treatment period.
Chamomile tea appears to have positive effects on glycemic control and hyperlipidemia, based on the human clinical trials included in this systematic review. Animal studies of different extracts of chamomile more strongly support chamomile’s positive effects on insulin resistance, blood glucose, dyslipidemia, and disease complications in rats with diabetes. A major strength of this systematic review is the application of the PRISMA protocol, a standardized checklist for systematic reviews and meta-analyses that aligns with Cochrane Collaboration standards and procedures and helps minimize bias in reporting.
A significant weakness is that the streptozotocin- and alloxan-induced diabetes in rats in the animal studies may be a poor model for human type 2 diabetes mellitus. These chemicals destroy pancreatic islet cells within a short timeframe after exposure, unlike the lengthy evolution of type 2 diabetes mellitus involving predisposing increased adiposity, insulin resistance associated with elevated insulin levels, and multiple associated metabolic disturbances long before reduction of pancreatic islet cells occurs.
Nonetheless, preliminary results from small human trials is encouraging, and chamomile tea is accessible and has no known adverse effects, although patients who are allergic to the Asteraceae/Compositae family of plants (e.g., dandelions, daisies, asters, ragweed, and goldenrod) may need to exercise caution in using chamomile.In one report, 3.1% of a general population of subjects developed Asteraceae-related allergic reactions, and of those subjects, more than 50% demonstrated an allergic response to chamomile.5 Chamomile is contraindicated in patients taking warfarin because of an increased risk of bleeding mediated through cytochrome P450 enzyme inhibition, although case-based evidence for this drug-herb interaction is not strong.6 Because of its effects on P450 enzymes, chamomile should be used with caution in patients taking aspirin and platelet inhibitors, cyclosporine, tricyclic antidepressants, some antipsychotics, propranolol, theophylline, and tacrine. Use in patients taking insulin may place the patient at an increased risk of hypoglycemic episodes.
However, outside of these caveats, and while awaiting larger human randomized controlled clinical trials of chamomile for the management of type 2 diabetes, physicians can recommend daily use of chamomile tea for patients with type 2 diabetes because of its known anti-inflammatory and antioxidant effects and for its potential value in improving the disease’s glycemic control, lipid profiles, and renal and hepatic consequences.
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