"Men and women live in different taste worlds".

Differences in our sense of taste may have major public health implications. So believes Linda Bartoshuk of Yale University School of Medicine, who has discovered that some people's hereditary sensitivity to bitter taste leads them to avoid cancer-protective fruit and vegetables such as brussel sprouts and spinach.

The fully sequenced human genome will probably yield a simple blood test for taste sensitivity that could help people pay closer attention to their diets, Bartoshuk told the annual meeting of the American Association for the Advancement of Science this week in San Francisco.

Far more women than men are 'super-tasters', as the 25% of people who are especially sensitive to bitterness are formally known. Female super-tasters are less keen on sugar and fat than other women -- they are "indifferent to mayonnaise, something I, as a non-taster cannot comprehend", comments Bartoshuk. And they are, on average, the thinnest group. Male super-tasters, on the other hand, prefer fatty, sugary foods.

Whatever their preferences, "men and women live in different taste worlds", remarks Bartoshuk.

The Yale team use a technique called 'cross modality matching' to compare one person's subjective taste experience with another's. Subjects compare what they feel about a taste with what they feel about a tone they hear.

For example, super-tasters rate a trace of the bitter chemical 6-n-propylthiouracil on the tip of their tongue as "like a shout, medium tasters say it is like a conversation and non-tasters liken it to a whisper", Bartoshuk explains.

Having two copies of some as-yet unknown variation on chromosome 5 gives super-tasters more 'fungiform papillae' on their toungues. These tiny, button-mushroom shaped bobbles contain some taste buds.

Having a lot of them puts super-tasters "in a much larger taste world than others", says Bartoshuk. It also makes them more susceptible to the capsiacin in chili pepper: pain receptors cluster round taste buds.

The fact that the majority of bitter-tasting substances are to some degree toxic hints that bitterness-sensitivity may have evolved to protect us from being poisoned. This possibility is underlined by evidence now emerging that in women, sensitivity ramps up at puberty, cycles with menstruation, increases during pregnancy, and tails off at the menopause.

One notable consequence of this is that postmenopausal women, and men of similar age, often develop a taste for black coffee and dark chocolate. Their bitterness threshold rises, allowing them to consume more of it than they could when they were younger.