The clustering of metabolic abnormalities defined as metabolic syndrome does occur in one quarter of the world’s adults. People with metabolic syndrome are three times as likely to have a heart attack or stroke compared with people without the syndrome and have a five-fold greater risk of developing type 2 diabetes .
While metabolic syndrome causes the two global epidemics of type 2 diabetes and cardiovascular disease (CVD), it overpowers any effort to identify and treat those individuals with metabolic syndrome early, so that new and effective treatment methods may prevent the development of diabetes and/or CVD .
Although, complementary and alternative therapies have long been used in the Eastern world, interest to herbal medicine along with the isolation and standardization of herbal constituents has greatly increased worldwide and would open a new approach for novel therapeutic and more effective agents to treat or prevent diseases such as diabetes mellitus .
Anethum graveolens L. known as dill is a sparse looking plant with feathery leaves and tiny yellow flowers growing in the Mediterranean region, Europe, central and southern Asia and is widely cultured in south eastern region of Iran . The metabolic syndrome is a complex of interrelated risk factors for CVD and diabetes . In an urban population of Tehran MONICA project using the Adult Treatment Panel III (ATPIII) criteria showed that the crude prevalence rate of the metabolic syndrome was 29.9 %, meaning that more than one fourth of the population are at risk of CVD and diabetes . As a result, the metabolic syndrome is now both a public health and a clinical problem urging investigations on new methods for its treatment.
While the use of herbal medicine is gaining considerable recognition and popularity worldwide, a lack of medical evidence to support its therapeutic efficacy does exist and a few herbs have been clinically studied . As a folk remedy Anethum graveolens or dill is considered for some gastrointestinal ailments such as flatulence, indigestion, stomachache  and in traditional Iranian medicine (TIM) has been used as carminative, antispasmodic, sedative, lactagogue, diuretic and for hyperlipidemia .
Pharmacological effects of dill such as anti-inflammatory , antimicrobial [10–12] or antibacterial [13, 14] , antihyperlipidaemic , antihypercholesterolaemic [15–17] , antioxidative and hypoglycemic [16–18] activities have been shown. To date, the role of dill extract in the improvement of metabolic syndrome parameters has not been investigated. However there have been two human randomized clinical trials evaluating the lipid lowering effect of dill extract. Unlike most studies carried on animals, a few human studies showed this herbal treatment has no significant reducing effect in hyperlipidemic patients [19, 20].
It is worth mentioning that in human studies, hyperlipidemic patients have received a patented compound named Anthum which consists mostly of Anethum graveolens (68%) and less of Cichorium intybus, Fumaria parviflora and Citrus sp.
Due to the not existence enough human studies, we designed a double blind randomized, placebo-controlled trial to evaluate whether purred extracted dill could safely improve metabolic parameters in patients with metabolic syndrome.