A Link Between Bitter Taste and Body Weight (TAS2R38)

TAS2R38, short for taste receptor type 2 member 38, encodes one of the 25 taste receptors that detect bitterness. It is responsible for tasting the bitterness of foods like cabbage and raw broccoli or drinks like coffee and dark beers [R, R].

Bitter taste is one of the major reasons for accepting or rejecting different foods. So it’s not surprising that mutations in this gene have been linked to higher or lower intakes of cruciferous vegetables, coffee, beer and wine. Some studies also suggest TAS2R38 may account for one’s preference for sweet foods over bitter ones [R, R, R, R, R, R, R].

Interestingly, researchers found that these receptors are also found in the brain, lungs, gut, and thyroid, where they probably play roles unrelated to diet [R, R].

TAS2R38 encodes a bitter taste receptor. Variations in this gene have been linked to preference or avoidance of bitter foods and drinks, such as cruciferous vegetables, coffee, and beer.

Our food preferences influence what we eat and in what amounts, which in turn affects our body weight. That’s what drove scientists to look into a possible link between the TAS2R38 gene and obesity.

In a Spanish study with over 1.3k people, obesity and BMI were linked to having a specific genotype in three SNPs in the TAS2R38 gene, which are often linked and inherited together [R]:

• rs713598  ‘CC’ 
• rs1726866 ‘AA’
• rs10246939 ‘TT’

In this study, the link with obesity was stronger in younger people (<40), which may be because the sense of taste in general tends to get weaker with age [R].

In a Japanese study of 84 female college students, the same genotypes for these 3 SNPs were linked to higher energy and carb intake, and higher body weight. However, there was no difference in BMI, which means that these students also tended to be taller as well as heavier [R].

In a Korean study with over 3.5k people, the ‘TT’ genotype of rs10246939, was associated with a 1.75 higher risk of being obese, but this link was found only in women, not men [R]. 

Finally, in a study with over 700 Amish, women with the ‘A’ allele for rs1726866 were more likely to overeat. Interestingly, this too was not  true for men [R].

Three linked SNPs have been associated with body weight and obesity in several studies, but this association may be less relevant in men. One of these variants has also been linked to overeating in women. 

Have you ever wondered why foods that tasted bitter to others tasted just fine to you? Or vice versa?

There are three main variants in the TAS2R38 gene that are “linked”, which means they are often inherited together:

• rs713598: where ‘G’ is the “taster” and ‘C’ is the “non-taster”
• rs1726866: where ‘G’ is the “taster” and ‘A’ is the “non-taster”
• rs10246939: where ‘C’ is the “taster” and ‘T’ is the “non-taster”

These variants account for up to 85% of individual differences in the perception of bitterness [R]! 

People who have two copies of the “taster” variant in each of these SNPs are considered “super-tasters” [R, R, R].

People with two copies of the “non-taster” variant for each SNP are considered “non-tasters” and are about 80% likely not to taste bitterness of specific foods [R, R, R]. This doesn’t mean they don’t taste bitterness at all, but it means they have a lower sensitivity to it.

You may fall somewhere in between, in which case you have intermediate sensitivity to bitterness [R].

There are 3 linked variants in the TAS2R38 gene that together account for up to 85% individual differences in sensing bitterness. Non-tasters may find that certain foods that taste bitter to others don’t taste bitter to them.

Because sensitivity to bitter taste is only a small part of the equation when it comes to body weight, take the studies above with a grain of salt. There are several other studies that failed to find a significant link between the above mentioned SNPs and body weight [R, R, R, R, R, R].

In addition, although there does seem to be a link between people’s sensitivity to bitter taste and body weight, TAS2R38 genotypes don’t always align with this sensitivity (phenotype) [R].

In one genome-wide association study of 381 people, a higher total taste score (for bitter, salt, sweet, umami, and sour) was associated with lower body weight, BMI, and waist circumference. Which means the more people could taste, the less likely they were to be overweight. However, TAS2R38 SNPs independently explained only a low percentage of total taste variability [R].

Bitterness accounts for only a part of total taste variability, and there are a lot of other factors that influence a person’s eating habits and body weight. Several studies have failed to find a link between TAS2R38 and BMI. 

TAS2R38 rs713598:

• ‘G’ = the major “tasting” allele. People who carry this allele are “tasters” 
• ‘C’ = the minor “non-tasting” allele. People with two copies of this allele are “non-tasters”

TAS2R38 rs1726866:

• ‘G’ = the major “tasting” allele, People who carry it have bitter tasting ability
• ‘A’ = the minor allele. People with two copies are “non-tasters”. Women with this allele may be more likely to overeat [R].

TAS2R38 rs10246939:

• ‘C’ = the major “tasting” allele, People who carry it have bitter tasting ability
• ‘T’ = the minor allele. People with two copies are “non-tasters”. They may be at a higher risk of obesity [R].

Around 27% of people are non-tasters for rs713598 (‘CC’ genotype), 20% for rs1726866 (‘AA’ genotype), and 25% for rs10246939 (‘TT’ genotype).

As already mentioned, these 3 SNPs are often inherited together. People who are non-tasters for each of the three SNPs have an 80% chance of not being able to taste bitterness in certain foods, and they may have a higher risk of obesity [R, R].