Taste is the sensory modality that guides organisms to identify and consume nutrients while avoiding toxins and indigestible materials. For humans, this means recognizing and distinguishing sweet, umami, sour, salty, and bitter-the so called” basic” tastes. There are likely additional qualities such as fatty, metallic and others that might also be considered basic tastes. Each of these is believed to represent different nutritional or physiological requirements or pose potential dietary hazards. Thus sweet-tasting foods signal the presence of carbohydrates that serve as an energy source. Salty taste governs intake of sodium and other salts, essential for maintaining the body’s water balance and blood circulation. We generally surmise that umami, the taste of L-glutamate and a few other L-amino acids, reflects food’s protein content. These stable amino acids and nucleotide monophosphates are naturally produced by hydrolysis during curing. Bitter taste is innately aversion and is thought to guard against consuming poisons, many of which taste bitter to humans. Sour taste signals the presence of dietary acids. Because sour taste is generally aversion, we avoid ingesting excess acids and overloading the mechanisms that maintain acid-base balance in the body. Moreover, spoiled foods often are acidic and are thus avoided. Nonetheless, people learn to tolerate and even seek out certain bitter and sour-tasting compounds such as caffeine and citric acid, overcoming innate taste responses. Variations in taste preference may arise from genetic differences in taste receptors and may have important consequences for food selection, nutrition and health.

An important, unrecognized aspect of taste is that it serves ‘functions’ in addition to guiding dietary selection. Stimulating the taste buds initiates physiological reflexes that prepare the gut for absorption (releasing digestive enzymes, initiating peristalsis, increasing mesenteric flow) and other organs for metabolic adjustments (insulin release, sympathetic activation of brown adipose tissue, increased heart rate etc). Collectively, these reflexes are triggered by the sensory (sight, smell, taste) recognition of food are termed as cephalic phase responses [1].

The taste threshold alters by number of factors such as age, ethic backgrounds, drugs, local and systemic diseases, consumption of alcohol, smoking and tobacco chewing. One of the factors, which alter the physiological taste threshold, is diabetes mellitus (DM).The pathophysiology of taste alteration in DM may be related to a decreased rate of turnover of the receptors [2] also, an association between taste impairment and diabetic neuropathies has been described, but remains disputed [3].

Diabetes is a group of metabolic disorders, characterized by hyperglycemia resulting from defects in insulin secretion, insulin action or both. The chronic hyperglycemia in diabetes is associated with long-term damage, dysfunction and failure of different organs, especially the eyes, kidneys, nerves, heart and blood vessels.

Type 1 DM may be due to β-cell destruction, usually leading to absolute insulin deficiency. This form of diabetes, which accounts for only 5-10% of those with diabetes, previously encompassed by the terms insulin-dependent diabetes, type 1 diabetes or juvenile-onset diabetes, results from a cellular-mediated autoimmune destruction of the β-cells of the pancreas.

Type 2 DM (ranging from predominantly insulin resistance with relative insulin deficiency to predominantly an insulin secretary defect with insulin resistance) is a form of diabetes, which accounts for ~90-95% of those with diabetes, previously referred to as non-insulin dependent diabetes, type 2 diabetes or adult onset diabetes, encompasses individuals who have insulin resistance and usually have relative rather than absolute) insulin deficiency. At least initially, and often throughout their lifetime, these individuals do not need insulin treatment to survive. There are probably many different causes for this form of diabetes. Although the specific etiologies are not known, autoimmune destruction of β-cells does not occur. Most patients with this form of diabetes are obese and obesity itself causes some degree of insulin resistance [4].

Many studies have been done on alteration of taste sensations in type 1 or type 2 diabetes mellitus separately, mainly on four primary sensations of taste, without considering the umami taste in their study frame. Nevertheless, no comprehensive informations are available on alteration of physiological taste threshold for different taste modalities, including umami taste in both type 1 and type 2 diabetes mellitus. Thus, the present study was undertaken with the objectives; to compare the alteration in taste threshold for five primary sensations in type 1 and type 2 diabetes mellitus. Most of the previous studies have used electrogustometry as the principle tool of investigation. However, in the present study the chemical gustometry method was used. It is more feasible method for testing patients on outpatient basis and so aids in timely management of decreased taste sensation.