Diabetes is a metabolic disturbance that gradually affects the function of various systems in the body. Poorly controlled blood glucose is believed to be the most important factor in the development of diabetic complications in both type 1 and type 2 diabetes (1). Individuals affected by diabetes are prone to the long-term complications such as retinopathy, cataract, neuropathy, atherosclerosis, nephropathy, embryopathy, and delayed healing of wounds (2).

A worldwide survey reported that diabetes affects nearly 10% of the world population (3). According to a projection of the International Diabetes Federation, 194 million people had diabetes in 2003, which will increase to 333 million by 2025 (4). It is likely to remain a significant threat to public health in the years to come. In the absence of effective and affordable interventions for either type of diabetes, the frequency of the disease will escalate worldwide, with a major impact on the populations of developing countries (5). In modern medicine, the beneficial effects of standard medications on glycemic levels are well documented; the preventive activity of medications against the progressive nature of diabetes and its complications was modest and not always effective. Insulin therapy affords effective glycemic control, yet its shortcomings, such as ineffectiveness on oral administration, short shelf-life; the requirement of constant refrigeration, and in the event of excess dosage, fatal hypoglycemia limits its usage (6).

In spite of the fact that insulin has become one of the most important therapeutic agents known to medicine, researchers have been making efforts to find insulin substitutes from synthetic or plant sources for the treatment of diabetes (7). Herbs and spices have a traditional history of use, with strong roles in cultural heritage, and in the appreciation of food and its links to health (8).

Medicinal plants continue to provide valuable therapeutic agents, in both modern medicine and in traditional system. The doubts about the efficacy and safety of the oral hypoglycemic agents have promoted a search for safer and more effective drugs for the treatment of diabetes (9).

Garlic (Allium sativum L.) -a common food spice, belongs to the Alliaceae family, which is consumed all over the world as a food flavoring agent and in traditional medicine to enhance physical and mental health (10).

Garlic and its constituents prepared by various means have been shown to have diverse biological activities, including anticarcionogenic, antiatherosclerotic, antithrombotic, antidiabetic, and various other biological actions (11, 12).

In the 1970s, Jain et al. (13) and Jain and Vyas, (14) showed that the ingestion of garlic juice resulted in better utilization of glucose in glucose tolerance test performed in rabbits. The ethyl alcohol, petroleum ether and ethyl ether extracts of garlic produced a significant fall in blood sugar levels in rabbits. Augusti and Sheela, (15) and Sheela and Augusti, (16) consistently showed that S-allyl cysteine sulfuxide (alliin), a sulfur containing amino acid in garlic has a potential to reduce diabetic condition in rat almost to the same extent as did glibenclamide and insulin.

Thus, the antidiabetic action of garlic established in animal studies provided a background for further investigations concerning possible clinical implications for garlic-based preparations. Since all of the pervious studies have focused on the therapeutic role of garlic and garlic preparations in diabetes mellitus, we investigated the preventive effect of oral administration of garlic juice on the changes of biochemical factors and histopathological alterations in pancreatic and hepatic tissue caused by diabetes.