Anethum graveolens L. (Dill) Effect on Human Lipid Profile: An Updated Systematic Review

Abstract

Dill is an aromatic edible herb, belongs to the genus Anethum in the celery family (Apiaceae or Umbelliferae) with a long history of cultivation from ancient times and two closely related cultivated species, European dill (Anethum graveolens) and Indian dill (Anethum Sowa). We wanted to do this systematic review on the effect of Anethum graveolens intake on lipid profile because the outcomes of multiple research and meta-analyses in this regard were inconsistent. A systematic search for English published randomized controlled trials (RCTs) covering PubMed, EMBASE, Scopus, and Coherence library. The pooled weighted mean difference (MD) and its 95% confidence interval (CI) were calculated and pooled using a random-effects model. Pooled data of 6 RCTs involving 171 intervention cases indicated that dill supplementation was associated with a significant reduction in mean serum total cholesterol (MD 95% CI= -3.71(-5.71,-1.70); P < 0.001), low-density lipoprotein cholesterol (LDL-C) (MD 95% CI= -1.51(-2.65,-0.47); P = 0.005), TG (triglycerides) (MD 95% CI= -2.48(-3.98,-0.98); P = 0.001) and interestingly high-density lipoprotein cholesterol level (HDL-C) (MD 95% CI= -2.19(-3.58,-0.81); P = 0.002). Subgroup analysis showed that dill use was more effective in lowering triglyceride in both hyperlipidemic patients, MD 95% CI= -3.54(-6.49,-0.60); P = 0.02) and type 2 diabetes (MD 95% CI= -3.64(-5.69,-1.58); P = 0.001). Dill use reduced the LDL levels more effectively in patients with type 2 diabetes (MD 95% CI= -3.54(-6.49,-0.60); P = 0.03). Dill supplementation significantly improved LDL-C, TG, and Total cholesterol (TC) levels but not HDL-C. Further high quality controlled clinical trials on human is needed for more accurate and confirm conclusion.

Introduction

Anethum graveolens L. (AG) or European dill is growing mostly in the Europe Mediterranean region, the central and southern part of Asia. The name of genus Anethum is derived from the Greek word, aneeton or aneeson that means strong-smelling. Dill is used in the preparations of more than 50 ayurvedic preparations.¹ India, Pakistan, USA, Mexico, Germany, and the Netherlands are the most producer countries dill.² In Iran, dill is called 'Shevid’ and is used mostly in foods such as rice known as ‘Shevid polo' and a special soup called 'aash'. It is used also in yogurt and salad and many other side dishes in Iran. Dill is used widely as an antihyperlipidemic food-based treatment in Iranian folk medicine. The growing condition in the south-eastern of Iran (where dill is cultivated mostly) is favorable and adequate for this plant since it prefers full sun and a pH range of 5.3-7.8.³ Dill has been used for a long time as a spice for the seasoning and flavoring of various foods such as rice, sauces, salads, side dishes, and soups in different countries. Dill oil is extracted from seeds, leaves, and stems, which contain an essential oil that is used as a flavoring in the food industry. In perfumery, it is used to perfume detergents and soaps and as an alternative to leek oil.⁴ A recent systematic review and meta-analysis on the effects of dill intake on glycemic indices and lipid profiles and in adults showed that dill improves insulin resistance and serum low-density lipoprotein (LDL) but no other lipid profile components,⁵ but another meta-analysis which also has been published recently assess AG supplementation's efficacy on lipid profile in adults with cardiovascular risk factors showed significant improvement of all lipid profile components Triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), Total cholesterol (TC) and high-density lipoprotein cholesterol level (HDL-C).⁶ Due to the inconsistency in the results of different studies and meta-analysis we aimed to perform this systematic review.

Each part of this plant including root, seed, and leaves was rich in tannins, cardiac glycosides, terpenoids, and flavonoids. The main constituents of dill are d-carvone (C10H14), d-limonene (C10H16), α- phellandrene (C10H16), β-phellandrene (C10H16), Myristicin (C11H12O3), Apiole (C12H14O4), Umbelliferone (C9H6O3), Anethole (C10H12O), and P- anisaldehyde (C8H8O2). Terpenes were the most abundant volatiles identified in dill.^3,7, 8, 9

The most common medical application of dill in Ayurveda/folk medicine is in decreasing abdominal irritations; relieve colic pain in babies and improving digestion.^4,10,11 A paste of flaxseed, castor seeds, and dill, which are beaten with milk, are effective for external applications in rheumatic swellings and other joints. They attributed this tonic and rejuvenating properties to the dill herb.¹¹ The seed is mildly diuretic, carminative, galactagogue, stomachic, and stimulant.^12,13 Dill has also been shown to increase and stimulate breast milk in lactating mothers and is therefore often given to cows.^10,14 The seed oil and aqueous extracts of this plant have antimicrobial and antifungal activity against different bacteria such as E. coli, Shigella flexneri, S. aureus, P.aeruginosa, S. typhimurium, and Salmonella typhi.15, 16, 17, 18

Many studies proved the antihypercholesterolemic /antihyperlipidemic activity for this herb^19,20; however, the results are not consistent.²¹ Herein we aimed to understand the significance of Anethum graveolens L. effect on lipid profile components; TG, TC, LDL-C,HDL-C.

Hyperlipidemia is a disorder defined by high levels of TG, (TC, and LDL-C and has been considered as one of the main risk factors of coronary heart disease (CHD); the leading cause of death worldwide [WHO].^22,23 Various lipid-lowering drugs such as statins have been applied to adjust the TC and LDL-C levels successfully. Studies show that statins are effective in ameliorating vascular function through an inhibitory effect on 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase. However, statins have side effects such as myopathy, rhabdomyolysis, myotoxicity, and myalgia.^24,25 In addition lipid guidelines of the European Society of Cardiology / European Atherosclerosis Association 2019, defined the LDL-C target for very high-risk patients to less than 55 mg / dL (1.4 mmol/L) and for those with a second cardiovascular event in 2 years to less than 40 mg/dL (1 mmol/L), which is very difficult to achieve with statin therapy alone.²⁶ The application of herbal medicine as complementary medicine for the adjustment of hyperlipidemia/dyslipidemia has attracted much more attention due to their cheaper price, fewer adverse effects, and their easier availability.^23,27