Why Some People Hate Broccoli: The TAS2R38 Bitter Taste Gene

In 1931, a chemist named Arthur Fox spilled a powder called PTC in his laboratory. A colleague nearby complained about a bitter taste in the air. Fox, standing closer, tasted nothing. That accident started one of the longest-running stories in human genetics: some people taste certain bitter compounds strongly and others hardly at all, and much of the difference comes down to one gene, TAS2R38.

What TAS2R38 does

Your tongue has about 25 different bitter taste receptors. TAS2R38 is the one that detects a family of compounds containing a particular chemical group, including PTC and PROP, the two substances used in taste tests. Related compounds form in vegetables of the cabbage family, such as broccoli, Brussels sprouts, kale, cabbage, watercress and turnips.

The gene was identified in 2003 (Kim et al.). Three common variants change three amino acids in the receptor, and they are inherited together as two main versions:

• PAV: the taster version. The receptor responds strongly to PTC and PROP.
• AVI: the non-taster version. The receptor barely responds (Bufe et al., 2005).

Since you have two copies, three combinations are possible. PAV/PAV people find these compounds very bitter, AVI/AVI people taste little or nothing, and PAV/AVI people are in between. Roughly a quarter to a third of people of European ancestry are AVI/AVI non-tasters. Raw DNA files usually contain rs713598, the first of the three variants, and often the other two (rs1726866 and rs10246939).

Is this the same as being a supertaster?

Not quite. Supertasters are people who perceive many tastes intensely. TAS2R38 explains a large part of who tastes PROP strongly, but supertasting also depends on other genes and on how many taste buds you have. A PAV/PAV result means you are very likely a PROP taster, not automatically a supertaster in every respect.

What it means for vegetables

In a taste study, people with two taster copies rated cabbage-family vegetables containing these compounds as clearly more bitter than people with two non-taster copies (Sandell and Breslin, 2006). In college-aged adults, tasters reported eating fewer vegetables (Duffy et al., 2010).

Other studies found smaller or no differences in what people actually eat. That makes sense: cooking, habit, culture and price shape vegetable intake at least as much as one taste receptor. The gene can explain why you dislike raw kale; it does not decide whether you eat enough vegetables.

Beyond vegetables: coffee, alcohol and your nose

Bitterness genes also show up in drinks. In a large genetic study, people who perceived PROP as more bitter tended to drink a little less coffee and alcohol, while people more sensitive to the bitterness of caffeine itself drank more coffee (Ong et al., 2018). Taste is learned as well as inherited.

TAS2R38 receptors are also found in the nose and sinuses, where they help detect bacteria. In one study, people with two taster copies were less prone to some sinus infections (Lee et al., 2012). An interesting finding, but not a reason to test your sinuses with broccoli.

Six ways to make bitter greens taste better

1. A pinch of salt. Salt suppresses bitterness more than it adds saltiness at low levels (Breslin and Beauchamp, 1997).
2. Add fat. Olive oil, a little cheese, nuts or tahini soften bitterness and help you absorb fat-soluble vitamins.
3. Roast instead of boiling. Browning brings out sweet, nutty flavors that mask bitterness. Brief steaming keeps more nutrients than long boiling.
4. Add acid. A squeeze of lemon or a dash of vinegar changes how bitterness is perceived.
5. Pair and choose. Mix greens with sweeter vegetables such as carrots, peppers or squash, and start with milder cabbage-family vegetables: cauliflower, bok choy, young leaves.
6. Keep tasting. In children, offering a vegetable repeatedly increases liking (Wardle et al., 2003); adults adapt too.

If you are a strong taster, the goal is not to force yourself to love Brussels sprouts. It is to find the vegetables and preparations you enjoy, so that variety and quantity stay high.

How to check yours

Look up rs713598 in your raw file from 23andMe, AncestryDNA or MyHeritage, or see the TAS2R38 gene page for what each genotype means. Our Complete report reads it in its food intolerances section, next to lactase.

References

1. Fox AL. The relationship between chemical constitution and taste. Proc Natl Acad Sci USA. 1932;18(1):115-120.
2. Kim UK, Jorgenson E, Coon H, Leppert M, Risch N, Drayna D. Positional cloning of the human quantitative trait locus underlying taste sensitivity to phenylthiocarbamide. Science. 2003;299(5610):1221-1225.
3. Bufe B, Breslin PA, Kuhn C, et al. The molecular basis of individual differences in phenylthiocarbamide and propylthiouracil bitterness perception. Curr Biol. 2005;15(4):322-327.
4. Sandell MA, Breslin PA. Variability in a taste-receptor gene determines whether we taste toxins in food. Curr Biol. 2006;16(18):R792-R794.
5. Duffy VB, Hayes JE, Davidson AC, Kidd JR, Kidd KK, Bartoshuk LM. Vegetable intake in college-aged adults is explained by oral sensory phenotypes and TAS2R38 genotype. Chemosens Percept. 2010;3(3-4):137-148.
6. Ong JS, Hwang DL, Zhong VW, et al. Understanding the role of bitter taste perception in coffee, tea and alcohol consumption through Mendelian randomization. Sci Rep. 2018;8(1):16414.
7. Lee RJ, Xiong G, Kofonow JM, et al. T2R38 taste receptor polymorphisms underlie susceptibility to upper respiratory infection. J Clin Invest. 2012;122(11):4145-4159.
8. Breslin PA, Beauchamp GK. Salt enhances flavour by suppressing bitterness. Nature. 1997;387(6633):563.
9. Wardle J, Cooke LJ, Gibson EL, Sapochnik M, Sheiham A, Lawson M. Increasing children's acceptance of vegetables; a randomized trial of parent-led exposure. Appetite. 2003;40(2):155-162.