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Topic hub — 2026-09-19

Getting used to bitterness

People often say they came to like bitter things. What that sentence claims is undetermined until a measurement is chosen. Did the liking rating go up, did the perceived intensity go down, or did the amount consumed rise? The three look like rewordings of each other and move separately once measured.

This page keeps them apart. Repeated exposure raises liking. Frequent drinkers, however, rate bitterness as stronger. The learning starts before birth, while the measured effect fades under follow-up. What follows places each claim on the measurement it actually rides on.

What this page establishes

• Repeated exposure raises liking for vegetables. A meta-analysis of 43 papers and 117 comparisons gives SMD 0.35, about 0.6 points on a 9-point liking scale and about 10 g of intake: a small difference.
• It moves in adults too. After drinking a commercial bittersweet beverage once a day for 7 days at home, pleasantness ratings for that drink rose by 68%, while a control tasted only in the laboratory did not change.
• Perception does not move the same way. Frequent drinkers of canned coffee are reported to rate bitterness more intensely than infrequent ones, while after two weeks of repeated EGCG intake the same solution was rated less bitter.
• It starts before birth. Among 12 children whose mothers repeatedly consumed kale flavour in late pregnancy, negative facial expressions to that odour at age 3 were significantly fewer.
• It does not necessarily last. At the longest follow-up in the same meta-analysis, no effect on liking for novel vegetables remained (SMD 0.15, P = 0.41).

The liking side moves

Start with the largest body of evidence. Across 43 papers and 117 comparisons, repeated exposure raised post-intervention liking against no exposure (SMD 0.35, 17 comparisons, 820 participants) and raised intake as well (SMD 0.23, 21 comparisons, 1130 participants). That is about 0.6 points on a 9-point liking scale and about 10 g for vegetables. The authors themselves write that the effect sizes are small.

That analysis centres on infants and young children, and its vegetables are not stratified by bitterness. It cannot be read straight across as evidence about getting used to bitterness. The adult experiment below gives a result in the same direction with a drink that is bitter.

After a commercial bittersweet beverage was drunk once a day for 7 days at home, pleasantness ratings for it rose by 68%. Ratings for a control stimulus tasted only in the laboratory over the same period did not change. Drinking something inside daily life and tasting it in a booth gave different outcomes.

The perception side does not move the same way

If liking rises, it is tempting to conclude that the bitterness is felt less. That is where the measurements stop agreeing.

Frequent consumers of canned coffee beverages are reported to rate bitterness and retronasal aroma more intensely than less frequent consumers. This comes second-hand through a review, and the participant numbers and statistics could not be confirmed, but the direction is the opposite one.

Meanwhile, after two weeks of repeatedly drinking EGCG, a tea catechin, dissolved in water, the same solution was rated lower for bitterness than after repeating water alone. This is a short study of one compound in water and does not extend to cooking or to food in general.

With cheese, what moved was the vocabulary rather than the perception. Korean consumers initially unfamiliar with Emmental, Gorgonzola and Parmigiano Reggiano selected negative terms such as bitterness, off-flavours and lack of balance strongly, and after repeated exposure selected them less often. Whether the bitterness fell or stopped being called a fault is not separated by this measurement.

Put side by side, getting used to something is not one phenomenon. Rising sensitivity, falling ratings, and changing vocabulary have each been observed, in different studies.

When does it start

The learning begins before anyone sits at a table. Mothers who drank 300 mL of carrot juice 4 days a week for 3 weeks, either in late pregnancy or during the first 2 months of lactation, had infants who at weaning showed fewer negative facial expressions to carrot-flavoured cereal than to plain cereal (prenatal P =.01, via breast milk P =.03). The interactions for intake and feeding time were not significant, and the paper does not characterise carrot as bitter.

A follow-up using bitterness itself also exists. From single flavour stimuli to fetuses at 32 and 36 weeks through to 3 weeks and 3 years after birth, the bitter kale flavour showed a general tendency to produce more negative facial expressions than the non-bitter carrot flavour (p<0.001). Bitterness is distinguished from other flavours before birth.

Repetition still works. Among 12 children whose mothers repeatedly consumed either kale or carrot flavour in late pregnancy, presenting both odours at age 3 gave significantly fewer negative expressions, within the same child, to the flavour they had been exposed to in utero (p<0.001). That only 12 children were followed to that point cannot be dropped from the reading.

Is exposure enough

Here the claim itself is divided. The claim that acquiring a liking for bitterness requires not mere exposure but an association between the flavour and a post-ingestive reward carries three pieces of evidence pointing in different directions.

The caffeine evidence supports the association. In 20 moderate caffeine consumers, pleasantness ratings for a novel flavoured drink paired with caffeine rose steadily across 8 conditioning trials, while ratings for the drink paired with placebo did not change. The vegetable evidence runs the other way: simple repeated exposure without contingent reward raised liking (SMD 0.35), and flavour-nutrient conditioning produced lower intake than repeated exposure (SMD -0.45, P = 0.04, 3 comparisons, 101 participants).

The disagreement may come down to different subjects. Whether a pharmacologically active drink and a vegetable belong on one scale cannot be decided here. That is why the claim still carries the contested label.

Does it last

In the follow-up analysis of the same meta-analysis, no effect on liking for novel vegetables remained at the longest follow-up (SMD 0.15, P = 0.41), and where follow-up was measured the effect had generally diminished.

The same card carries evidence pointing the other way. In 95 infants at the start of complementary feeding, 10 repeated exposures to artichoke purée raised intake by 63% and liking by 21%, and the acceptance was stable up to 3 months after exposure. Whether this is a difference of age window or a genuine disagreement is not settled.

What was measured and did not move

Measurements that produced no difference are given the same weight as those that did.

Before and after 10 healthy women used a capsaicin oral gel for 14 days, there was no clear statistical change in their ability to identify salty, sweet, sour and bitter tastes or in the intensities they reported. This is a small pilot and is not proof of no effect at all.

The cultural record

Outside the laboratory, the learning is spoken of as a rule of cooking. In an ethnobotanical study of wild greens on Ikaria, Greece (semi-structured interviews, n=31), the researcher argues that developing a liking for bitterness requires a learning process, and older residents described adding lemon to bitter boiled greens as a culinary necessity. This is description rather than measurement, kept here as a record that getting used to bitterness does not happen only inside one person.

Questions people ask

Can an adult come to like bitter things?

Within the scope of this page there is one adult measurement that moved. After a commercial bittersweet beverage was drunk once a day for 7 days at home, pleasantness ratings rose by 68%, while a control tasted only in the laboratory did not change. The abstract gives neither the composition of the drink nor the sample size, and it is a single study.

Does getting used to bitterness mean feeling it less?

The direction depends on the measurement. After two weeks of repeated EGCG intake, bitterness ratings for the same solution fell. Frequent drinkers of canned coffee, on the other hand, are reported to rate bitterness more intensely than infrequent ones. With cheese, the frequency of selecting negative terms fell. Perceiving less, minding less, and naming it differently ride on different measurements on this page.

Will serving bitter vegetables to a child eventually work?

The meta-analytic effect exists and is small: across 43 papers and 117 comparisons, liking SMD 0.35, about 0.6 points on a 9-point scale and about 10 g of intake. At the longest follow-up no effect remained (SMD 0.15, P = 0.41). Yet in infants at the start of complementary feeding, the effect of 10 exposures was stable up to 3 months. Results differ by age and by vegetable, and this page cannot resolve them into one answer.

Are preferences settled before birth?

Not settled, but started. From 32 and 36 weeks of gestation to age 3, the bitter kale flavour tended to produce more negative facial expressions than the non-bitter carrot flavour (p<0.001). At the same time, negative expressions to the odour repeatedly experienced in utero were significantly fewer at age 3 (p<0.001, 12 children). The distinction before birth and the learning before birth sit inside the same study.

What is not known

• Which of liking, perceived intensity and intake has to move before the word "used to it" applies is not settled across the sources here. No study placed on this page measured all three at once.
• Whether exposure alone suffices, or an association with a post-ingestive reward is required, is unresolved. Caffeine drinks support the association; vegetables favour simple exposure. Whether the difference in subject explains it is also unknown.
• The vegetables in the meta-analysis are not stratified by bitterness. Whether the same effect size holds for strongly bitter vegetables alone is not known.
• Durability points both ways, in the meta-analytic follow-up and in the infant artichoke trial. Whether this is an age window or a genuine disagreement cannot be separated here.
• The report that frequent coffee drinkers rate bitterness more intensely is second-hand through a review; the original has not been read, and neither participant numbers nor statistics could be confirmed.
• The kale follow-up at age 3 covers only 12 children, and the numbers per exposure group are not given in the text.

Read in the encyclopedia

• Acquired liking — the phenomenon itself; the claim about its mechanism sits here under a contested label
• Repeated dietary exposure — eating something again and again; the vegetable, bittersweet drink, EGCG and capsaicin measurements gather here
• Perinatal flavor exposure — exposure in utero and through breast milk; the two follow-ups, carrot and kale

Go deeper in the research notes

• Learning to love bitter — the research on acquired liking, in the order of a human life
• Can a taste for bitterness be cultivated? — from the intervention studies: what moved, and by how much
• Taste is not addition — liking, intensity and vocabulary moving separately, from the side of taste interaction
• When bitter is a compliment — where getting used to bitterness ends up in the way people talk

Source ledger

The primary sources and limitations for the claims on this page can be checked from the source links inside each card. The full list is on the Japanesesource ledger.