The senses of taste and smell are very closely related. Most people who go to the doctor because they think they have lost their sense of taste are surprised to learn that they have a smell disorder instead. To learn more about your sense of smell, read the NIDCD publication, Smell Disorders.
Your ability to taste comes from tiny molecules released when you chew, drink, or digest food; these molecules stimulate special sensory cells in the mouth and throat. These taste cells, or gustatory cells, are clustered within the taste buds of the tongue and roof of the mouth, and along the lining of the throat. Many of the small bumps on the tip of your tongue contain taste buds. At birth, you have about 10,000 taste buds, but after age 50, you may start to lose them.
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When the taste cells are stimulated, they send messages through three specialized taste nerves to the brain, where specific tastes are identified. Taste cells have receptors that respond to one of at least five basic taste qualities: sweet, sour, bitter, salty, and umami [oo-MOM-ee]. Umami, or savory, is the taste you get from glutamate, which is found in chicken broth, meat extracts, and some cheeses. A common misconception is that taste cells that respond to different tastes are found in separate regions of the tongue. In humans, the different types of taste cells are scattered throughout the tongue.
In other disorders of the chemical senses, an odor, a taste, or a flavor may be distorted. Dysgeusia [dis-GYOO-zee-a] is a condition in which a foul, salty, rancid, or metallic taste sensation persists in the mouth. Dysgeusia is sometimes accompanied by burning mouth syndrome, a condition in which a person experiences a painful burning sensation in the mouth. Although it can affect anyone, burning mouth syndrome is most common in middle-aged and older women.
An accurate assessment of your taste loss will include, among other things, a physical examination of your ears, nose, and throat; a dental examination and assessment of oral hygiene; a review of your health history; and a taste test supervised by a health care professional.
Loss of taste can create serious health issues. A distorted sense of taste can be a risk factor for heart disease, diabetes, stroke, and other illnesses that require sticking to a specific diet. When taste is impaired, a person may change his or her eating habits. Some people may eat too little and lose weight, while others may eat too much and gain weight.
Loss of taste can cause you to add too much sugar or salt to make food taste better. This can be a problem for people with certain medical conditions, such as diabetes or high blood pressure. In severe cases, loss of taste can lead to depression.
The National Institute on Deafness and Other Communication Disorders (NIDCD) supports basic and clinical investigations of smell and taste disorders at its laboratories in Bethesda, Maryland, and at universities and chemosensory research centers across the country. These chemosensory scientists are exploring how to:
NIDCD-funded researchers have shown that small variations in our genetic code can raise or lower our sensitivity to sweet tastes, which might influence our desire for sweets. Scientists are also working to find out why some medications and medical procedures can have a harmful effect on our senses of taste and smell. They hope to develop treatments to help restore the sense of taste to people who have lost it.
Scientists are gaining a better understanding of why the same receptor that helps your tongue detect sweet taste can also be found in the human gut. NIDCD-funded scientists have shown that the sweet receptor helps the intestine to sense and absorb sugar and turn up the production of blood sugar-regulation hormones, including the hormone that regulates insulin release. Further research may help scientists develop drugs targeting the gut taste receptors to treat obesity and diabetes.
Among three other studies using subjects who were not restricted to self-identified MSG sensitive subjects, a significant difference in the incidence of headache was found in two studies, both of which originated in the same laboratory in Denmark [13, 14]. In the first study reported by Baad-Hansen, 400 ml sugar-free soda containing MSG (75 or 150 mg/kg) or NaCl (24 mg/kg) was administered to 14 healthy men [14]. These doses correspond to 4.5 g (1.125 %) and 9.0 g (2.25 %) /400 ml60 kg b.w., respectively. A significant difference in the incidence of headache was observed at the 75 mg/kg dose of MSG, but not at the 150 mg/kg dose compared to the NaCl placebo. In the second study reported by Shimada, the protocol and the number of subjects were the same as in the first study, except that the number of days in one session was increased from 1 to 5 days to amplify the incidence and the MSG dose was 150 mg/kg, along with the placebo 24 mg/kg NaCl [13]. During one session, either of MSG or NaCl was administered. The 400 ml volume and the high dose of MSG, especially 150 mg/kg, are thought to be sufficient to cause gastrointestinal unpleasant sensation attributable to unfavorable taste and high osmotic pressure. The other issue of these studies are that the content of sodium in placebo (24 mg/kg) corresponds to 75 mg/kg MSG and half of 150 mg/kg MSG. It means that the saltiness and osmotic pressure caused by placebo solution was much less than MSG solution of 150 mg/kg dose. In addition, the number of 14 subjects is too small to permit any conclusion regarding large population.
We should pay attention to the blind integrity of the human studies where high dose of MSG was administered in solution, especially focusing on the distinguishable and unpleasant taste of MSG solutions at 1.3 % (2 g/150 ml) or more and the gastrointestinal discomfort caused by high dose of MSG. These events may influence the occurrence of headache quite strongly especially in case of migrainers and the subjects who believe they are MSG-sensitive.
As you age, the way your senses (hearing, vision, taste, smell, touch) give you information about the world changes. Your senses become less sharp, and this can make it harder for you to notice details.
Your senses receive information from your environment. This information can be in the form of sound, light, smells, tastes, and touch. Sensory information is converted into nerve signals that are carried to the brain. There, the signals are turned into meaningful sensations.
You have about 10,000 taste buds. Your taste buds sense sweet, salty, sour, bitter, and umami flavors. Umami is a taste linked with foods that contain glutamate, such as the seasoning monosodium glutamate (MSG).
Smell and taste play a role in food enjoyment and safety. A delicious meal or pleasant aroma can improve social interaction and enjoyment of life. Smell and taste also allow you to detect danger, such as spoiled food, gases, and smoke.
The number of taste buds decreases as you age. Each remaining taste bud also begins to shrink. Sensitivity to the five tastes often declines after age 60. In addition, your mouth produces less saliva as you age. This can cause dry mouth, which can affect your sense of taste.
"And he thought, 'Why is it that my taste buds taste something meaty in this, but there's no meat in it?' " Geiling says. "He decided to go into his lab and try to isolate whatever gave it this meaty flavor."
The tongue is a muscular organ in the mouth. The tongue is covered with moist, pink tissue called mucosa. Tiny bumps called papillae give the tongue its rough texture. Thousands of taste buds cover the surfaces of the papillae. Taste buds are collections of nerve-like cells that connect to nerves running into the brain.
One of the main side effects of head and neck (H&N) radiation therapy (RT) is alteration in taste sensation. It causes significant morbidity and has a major effect on quality of life (QoL). The aim of this study was to prospectively define the effect of RT on taste sensation (general, and four basic tastes) and correlate these findings with changes in saliva secretion and QoL questionnaires.
We found a significant immediate reduction in taste sensation due to RT in H&N cancer patients with taste recovery 1 month after treatment completion. There were strong trends to a correlation with saliva production that requires further exploration.
Most previous studies of taste changes in oncology were limited to specific modalities, i.e., RT and CT, with few studies including patients who underwent surgery as treatment for tongue cancer. Moreover, mainly short-term follow-ups of taste loss recovery were documented (generally a few weeks). Finally, previous studies used non-validated techniques usually prepared by the research group itself or a related laboratory [24, 25].
We hypothesized that a significant difference in taste test scores would be found at the end of treatment compared to baseline and at 1- and 3-months follow-ups post treatment. We also hypothesized that a significant correlation would be found between saliva volume and changes in taste sensation, and that a significant correlation would be revealed between QoL score and changes in taste sensation. We believed the mean dose to the oral cavity could be associated with a chronic effect on taste.
We did not find any significant correlation between the maximum or mean dose to the oral cavity and overall taste sensation. There was also no significant correlation between doses to different areas of the tongue, and overall or specific tastes (Table 2).
Previously published reports on variations in taste acuity have had conflicting results. For example, several studies have found that bitter and salty tastes were affected early and more severely [6, 7, 10, 14]. Another study found that sour taste was significantly impaired after radiation, while bitter, salty, and sweet tastes were not [3]. The reason for these discrepancies is unknown. The use of citric acid in sialometry in our study could potentially mask alterations in sour taste. However, patients had to rinse with distilled water between sialometry and the taste strip test and wait several minutes. Patients also had to rinse after each specific taste strip. As sour was the second taste tested, the patient has already rinsed at least three times before the first exposure (between sialometry and taste strips, after a control strip and a sweet strip). Thus, we do not believe stimulated sialometry affected our results. 2ff7e9595c
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