One of the many oft-repeated myths about the human body is that there are specific regions on the tongue which specialize in tasting certain aspects of food. This idea, however, has been completely discredited.
According to a review article in The Journal of Cell Biology in August 2010:
Although there are subtle regional differences in sensitivity to different compounds over the lingual surface, the oft-quoted concept of a ‘tongue map’ defining distinct zones for sweet, bitter, salty and sour has largely been discredited.
There are a couple of things wrong with the old “tongue map” model. First, it did not incorporate umami, which is a new taste region coming from the Japanese word for sensing rich and meaty protein flavors. Second, the model did not account for the fact that taste bud clusters have sensitivities in a number of different tastes in varying degrees, and that these clusters are distributed across the whole tongue.
Researchers believe the function of our taste receptors have specific evolutionary roots:
Recognizing bitterness is thought to protect against bitter poisons; sweet tastes signal sugars and carbohydrates; salty tastes signal sodium compounds and other salts; and sour tastes indicate organic acids. The tongue may also have specialized receptors for fatty flavors…
These all would help us determine which foods were needed to accomplish certain nutritional goals. However, the idea that these tastes are relegated to certain areas of the tongue and nowhere else is a myth.
[Via The New York Times]