Humans have different levels of sensitivity to sweetness. What you think is too sweet, your friend may think is just right—or vice versa. Genetics may explain part of this difference. An AncestryDNA® test can tell you how the DNA it looks at might affect your sweet tooth.

Humans Love a Sweet Taste

Humans seem wired to love foods that leave a sweet taste in their mouths. This preference probably dates back to prehistoric times, when humans discovered eating naturally sweet foods like fruit or honey gave them energy. Sweet foods also helped their bodies store fat—very handy when they had long stretches between meals.

Over the millennia many human cultures have enjoyed creating sweet things. The Egyptians and Greeks for instance combined ingredients like honey and fruits to make sweet treats.

And now there's evidence humans don't just learn to crave sweets: Studies have found even newborn babies are partial to sweet flavors.

Genetics of Sweetness Sensitivity

Your sensitivity to sweetness is influenced by many factors. One of them is genetics.

While the exact impact of genetics is not yet known, a study of twins found that your genes are responsible for about 30% of the variation in perception of sweetness from one person to the next.

DNA differences that control how people experience flavors may mean that some of us are just more sensitive to sweets than others.

In other words people who have a more sensitive "sweet tooth" may taste sweet flavors more intensely than people who are less sensitive. And this sensitivity to sweetness can be passed on from parent to child.

The Science of Sweet Sensitivity

A cluster of three genes called the TAS1R family, found on chromosome 1, are responsible for both sweet and savory taste perception.

Scientists have discovered that certain DNA differences in one of the three genes—TAS1R3—can make you more (or less) sensitive to tasting sweet.

You inherit a copy of the TAS1R3 gene from each of your parents. So you can have either zero, one, or two copies of the DNA difference that makes you perceive sweetness more intensely.

If you have just one copy of this DNA difference, you will taste sweet flavors more strongly than if you have none—but not as strongly as if you had two copies.

Fun Facts about Sweet Sensitivity

In the past people thought different parts of the tongue taste different flavors, but scientists discovered this was not the case. Rather than having “sweet taste buds" on a single area of your tongue, all of your taste buds have receptors for different kinds of flavors.

There are some people who can't detect sweetness in foods. This extremely rare condition is called aglycogeusia. To those who have this condition, sweet foods taste either bitter or sour.

Some research suggests people who are less sensitive to sweet may eat more sugary foods to compensate for not being able to taste them as strongly.

References

Fushan AA, Simons CT, Slack JP, Manichaikul A, Drayna D. Allelic Polymorphism within the TAS1R3 promoter is associated with human taste sensitivity to sucrose. Current Biology. 2009;19(15):1288–1293. doi:10.1016/j.cub.2009.06.015.

The gene for sweet: why we don’t all taste sugar the same way. NPR. July 24, 2015. https://www.npr.org/sections/thesalt/2015/07/24/425609156/the-gene-for-sweet-why-we-dont-all-taste-sugar-the-same-way.

How much is too much? The growing concern over too much added sugar in our diets. Sugar Science at UCSF. https://sugarscience.ucsf.edu/the-growing-concern-of-overconsumption.html#.Wv86WmbMza4 Accessed May 17, 2018.

The human sweet tooth. BMC Oral Health. June 15, 2006. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2147592/.

Insatiable sweet tooth? Blame genetics. Genetic Literacy Project. July 22, 2015. https://geneticliteracyproject.org/2015/07/22/insatiable-sweet-tooth-blame-genetics/.

Keskitalo K, Knaapila A, Kallela M, et al. Sweet taste preferences are partly genetically determined: identification of a trait locus on chromosome 16. The American Journal of Clinical Nutrition. 2007;86(1):55–63. doi:10.1093/ajcn/86.1.55.

Mainland JD, Matsunami H. Taste perception: how sweet it is (to be transcribed by you). Current Biology. 2009;19(15). doi:10.1016/j.cub.2009.06.050.

Some like it sweet, others not so much: It’s partly in the genes. Monell Chemical Senses Center. July 17, 2015. https://www.monell.org/news/news_releases/sweet_genes.

Sugar: Should we eliminate it from our diet? Medical News Today. January 11, 2016. https://www.medicalnewstoday.com/articles/288088.php.

Why is sugar so addictive? BBC Science. March 22, 2013. https://www.bbc.co.uk/science/0/21835302.