So, how are Supertasters diagnosed (see Appendix 3)? Most supertasters know from childhood that they have a strong sense of taste and smell. They just know that certain foods appeal to them while they voice a strong aversion to other foods. Confirming they are supertasters provides the person with information not only for themselves, but also for other family members or possibly future children as well because of the genetic component. Supertasters are tested for a bitter sensation and for bitter taste receptors (T2Rs). These receptors belong to a family of genes, the T2Rs, and they are needed to complete all our taste receptors. They are thought to protect against the ingestion of toxic compounds, including bacterial products from spoiled foods. It is believed this genetic trait was useful for survival and has been retained by some individuals while not in others such as the non-tasters (sub-tasters) and the general population (mid-tasters). Mid-tasters may be able to taste some bitter, but it is not on the same scale as the taste perception of supertasters who react substantially to bitter tastes. See Appendix 4 to view Using the Intraoral Camera to Educate Patients about Papillae. Several taste tests are used to diagnose the supertaster. A paper strip imbedded with the chemical known as PROP is placed on the anterior tongue region (Figures 13-14). A clinical assessment is also provided in the “Let Me See Your Tongue” video by Carol Perkins on supertasters.
And, a control strip is used prior to the PROP strip. A chemist named Fox discovered the origin of the supertaster quite by accident while transferring a white powder 6-n-propylthiouracil or PROP, from one container to another. When this product became airborne, his colleague, Noller, found the taste extremely bitter while Fox had no sense of taste from the powder. And, at this point, the quest was to discover the characteristics of the body’s reaction to the powder and why one person would react in such a way, yet another person would have no reaction.
The supertaster will find the PROP strip extremely bitter, while a non-taster will find no difference in the two strips. The non-taster will find the PROP strip taste like a piece of paper that has no flavour. A general taster, 50% of the population, will find the PROP strip to have a very mild bitter flavour. The PROP sensitivity test (6-n-prophylthioruacil (PROP) and phenylthiocarbamide (PTC) are used to detect the bitter taste. PROP is a medication that has a bitter taste and is used in the treatment of Graves' disease (hyperthyroidism) but can be tasted by supertasters in a very low and safe concentration. The general population and non-tasters (sub-tasters) will not be able to discern a specific taste in most cases and only slightly bitter in some individuals in the general population. However, not with a highly objectionable taste as is found in the case of the supertaster. A jellybean or peppermint is usually offered to the supertaster in order to diminish the taste after using the PROP strip (Figure 14). (See the “Let Me See Your Tongue” and “How to Know If You're a ‘Supertaster’” videos).
These individuals have a gene that allows them to taste the bitterness of the chemical immediately and there is no delay. It is thought by many researchers because of the numbers and density of the fungiform there are more taste receptors present for immediate pick up by the taste buds. Melis, et al. looked at Gustin and fungiform papilla density in groups of patients and found patients who perceived the highest PROP bitterness had higher papillae densities compared to those who perceived PROP at a lesser intensity. They also found a single A allele in the gustin gene produced small papillae with a regular morphology, but did not find this characteristic in the TAS2R38 genotypes.23 Recent studies by Garneau et al. 2014, found some conflicting information in their study. The researchers presented results citing “our population data provides no evidence to substantiate prior reports that the increase and density of fungiform papillae is predictive of PROP intensity rating and it contributes to super tasting.”12 In studies by Negri et al., conclusions were made and their findings suggest variation in PROP sensitivity and ultimately in the chemosensory ability of supertasters, may be influenced by taste bud density mediated by a functional gustin gene.26 The debate continues with varying information. The reason why supertasters so strongly react to bitter taste is debatable, but supertasters do react to the PROP strips and those tested do have the genetic trait (Figures 13-14).