Genetic Traits Ptc Testing

Have you ever wondered why something that tastes good to some people tastes pretty badly to others? Maybe you love broccoli but your kids cant stand it. Or you have a particular aversion to dark chocolate while it seems like its everyone elses favorite indulgence. The way people perceive taste can vary greatly from person to person, which is why you might like the taste of something while a friend avoids that particular food. This difference in taste perception has been of interest to scientists and others for quite some time, because the way things taste has a large impact on what we choose to eat. While much of this difference can be explained by our environment, scientists are finding that genetics also plays an important role.

About Bitter Taste Perception

Compounds, like PTC (or phenylthiocarbamide), cause humans to perceive bitterness in food. However, it appears that all people do not perceive the presence of PTC in the same manner. Bitter taste perception has received considerable attention from researchers, because the differences among humans are particularly pronounced. Some people have relatively little capacity to taste bitterness, while others either taste some bitterness or are particularly sensitive to it. Sensing bitterness in food or drink is actually linked to our evolution as humans. Toxins and other harmful chemicals often taste bitter, making bitter taste perception a genetic survival tactic (your body is essentially telling you that the food youre eating is toxic by making it taste unappealing). However, we cannot assume that a bitter taste means that something can harm us, because there are many foods (such as cabbage, broccoli and rapeseed) that have a bitter taste but are actually good for us.

Biology of Bitter Taste Perception

Taste buds, or tiny onion-shaped protrusions on the tongue, arent just around for our enjoyment; they have actually evolved in humans to become a critical survival tool. As humans, we use taste buds to recognize foods with a high enough caloric content to sustain us, as well as to recognize poisons and things that should not be eaten. Interestingly, many poisonous plants have an extremely bitter taste to them. Scientists have determined four basic tastes that we are able to recognize in varying degrees:

  • bitter
  • salty
  • sour
  • sweet.

Once food hits the tongue, taste receptors (there are about 100 on each bud) determine the taste of the food and carry that information to the brain via two different nerves (called the chorda tympani and the glossopharyngeal nerve). The taster will then be able to determine what the food is, and whether or not it is edible.

Genetics of Bitter Taste Perception

Scientists have found bitter taste perception is connected to human populations that share common genes. For example, the percentage of people who do not taste bitterness ranges from 3 percent in West Africa; 6 to 23 percent in China; 40 percent in India and approximately 30 percent in people of European decent.

Differences in bitter taste perception among people are believed to be about 20 percent gene-based. The most common gene cited as having an impact on bitter taste perception is the TAS2R38 gene on chromosome 7. People who are more sensitive to bitterness carry the C allele of the SNP rs1726866, while those who carry the T allele of this SNP on both copies of chromosome 7 are more likely to be less sensitive. There are other gene variants that may explain bitter taste perception, but not near to the degree as the TAS2R38 gene.

Interpreting Your Genetic Test Results

There is a way for people to find out if they are a bitterness non-taster, taster, or super-taster. It is difficult to make firm judgments based on the test results, but studies have found that the non-taster genotype can be a predictor of increased alcohol consumption in adults and lower preference for sweets in children. If you are a super-taster, you may not enjoy some foods such as grapefruit, cabbage, or coffee.

Frequently Asked Questions About Bitter Taste Perception

Q: If I taste a food that is new to me and it is bitter, should I leave it alone?

A: Not necessarily. There are many foods that have a bitter taste that are fine to eat. However, if you are trying something new and have no information on whether it is safe to eat or not, bitterness can possibly be an indication that you should not eat it.

Q: Why is the study of bitter taste perception important to researchers?

A: Research into bitter taste perception can be very useful because it provides information about the foods people may want to eat, depending on their sensitivity to bitterness. Over time, this research may be helpful in predicting how people respond to new food products and aid in the development of dietetic interventions.

Q: Do I need to be concerned if I am a non-taster or super-taster for bitterness?

A: Information that suggests that a person is prone to being a non-taster or super-taster of bitterness does not require any particular intervention, although it can be useful information in relation to why he or she likes certain foods. There is evidence that harmful chemicals often taste bitter, which could be an issue with non-tasters of bitterness. However, at this point, science has not evolved to the point of easily altering genes to enhance sensitivity to bitterness.

Recent News on Bitter Taste Perception

Researchers are looking at factors that contribute to children being overly sensitive to bitterness. Evidence shows that parents who are sensitive to bitterness have children who are often much more sensitive, suggesting that ability to accept bitterness may improve with age.

Scientists at the Monell Chemical Senses Center have discovered that bitter taste perception of vegetables is influenced by a combination of taste genes and the presence of naturally-occurring toxins in a given vegetable. It is believed that taste receptors are capable of detecting toxins in fruit and vegetable plants.

Resources

American Chemical Society staff. (2008). Helping the medicine go down. Retrieved June 28, 2009 from the Medical News Today Web site: http://www.medicalnewstoday.com/articles/118086.php.

Bio-Medicine staff. (2005). Individual taste receptor variations determine classic PTC bitterness perception. Retrieved on June 28, 2009 from the Bio-Medicine Web site: http://news.bio-medicine.org/biology-news-3/Individual-taste-receptor-variations-determine-classic-PTC-bitterness-perception-12885-1/.

Monell Chemical Senses Center staff. (2006). Bitter taste identifiers suggests toxins in foods. Retrieved June 28, 2009 from the Medical News Today Web site: http://www.medicalnewstoday.com/articles/52226.php.