Some people have a much keener sense of taste than others and, on average, women are much better tasters than men. I am very fond of hot, spicy food - curries, chilies etc. I don't know whether my partiality to hot and spicy food reflects a genuine fondness for this taste or is simply a consequence of a poor basic sense of taste which must be vigorously assaulted in order to gain its close attention.
Taste is one of the five special senses (the others are sight, smell, hearing and touch). The basic taste qualities experienced by humans are sweet, salty, sour, and bitter. Taste is determined by the taste buds that are located on the surface and sides of the tongue, the roof of the mouth, and the entrance to the pharynx.
Some people have a much more intense sense of taste than others. Tasting ability directly correlates with the number of taste buds on the tongue.
About 20 per cent of people have a very high number of taste buds and a highly-developed sense of taste. Another 20 per cent have few taste buds and a correspondingly dull sense of taste. The remaining 60 per cent of people fall in between.
Women are much more sensitive to taste than men. Obesity and eating disorders are more common in women than in men. These conditions may well be connected to tasting ability, and further research is indicated in this area to see if there is any connection.
What is the evolutionary benefit of taste, and why are some people better at it than others?
Food and drink enter through the mouth and the taste buds are the guards that examine them for security reasons. This is a brief initial examination. The full flavour of food is largely detected only subsequently, when its olfactory labels are examined by smell receptors in the nose.
The four basic flavours detected by the taste buds give certain fundamental information. A sweet flavour indicates calories and energy. Breast milk is sweet, and this flavour may play a role in suckling.
Salt is of vital importance to the body. For example, you must take in salt and water to survive if you are wounded.
Most poisons in the plant kingdom are bitter, so the ability to detect this flavour is an important protection. The ability to detect sour may have arisen in order to identify unripeness in fruit.
If the ability to taste was selected during evolution because it provides data essential for survival, why is it that poor tasters and champion tasters are equally represented in the population? The answer could be that each have their own advantages.
For example, in a region where all food is safe, poor tasters would thrive as they would be unlikely to take a dislike to any particular food on the basis of its taste. On the other hand, champion tasters would have a distinct advantage in a region where the food quality was very variable.
Thinking in evolutionary terms easily explains why women are better tasters than men. A champion sense of taste can be very valuable to a pregnant or a nursing mother.
In these circumstances, women can obviously benefit from a keen ability to identify sources of energy and to avoid poison, both for their own sakes and for the health of the baby.
The value of taste in allowing an animal to select nutritious or necessary ingredients of the diet can be readily demonstrated. In these experiments the animal is given a free choice of food distributed among individual containers, each with a necessary nutrient in pure form.
Animals are often seen to make compensatory changes in their choice of nutrients when they suffer from physiological stresses, such as glandular imbalances. For example, if rats have their adrenal glands removed their salt balance goes awry, usually with a fatal outcome in the absence of salt replacement therapy.
However, in the experiment as described, such rats usually show a significant increase in intake of sodium chloride, sufficient to counteract a fatal outcome.
Observations of the eating habits of children have noted similar effects. However, in adults, automatic physiological factors controlling eating behaviour can be over-ridden by complex psychological factors.
The hottest of all foods, the chili pepper, is a traditional ingredient of cooking in Mexico, where it has been used for at least 9,000 years. The native Indians of the region have many stories in which chili plays a part.
In one story, Narama, the first man, leaped onto a table on which a feast was laid out, whereupon his testes turned to chili pods. One might have thought that this unexpected development would cause Narama to walk away for a spot of quiet reflection. But Narama was having none of that.
Instead, he enthusiastically shook his new belongings over the feast and thereby forever conferred warmth and distinction on the local food.
Eating chili peppers produces a unique burning sensation in the mouth. Most of this effect is caused by a chemical called capsaicin, but chemically-related compounds called capsaicinoids add additional heat and flavour. Each variety of chili has a distinctive mixture of capsaicinoids. Sophisticated Mexican cooks blend different chilies and achieve a remarkable variety and subtlety of flavour.
Mexicans often complain that spicy foods from other cultures are all burn and no subtlety. The hottest chili of all is the habanero pepper. In the mouths of the uninitiated, or the unwary, it will cause an unbelievable sensation, described by one writer as `thermonuclear'. Why are so many people addicted to the sensation of the chili burn?
A psychologist has explained this by pointing out that capsaicin can cause pain without doing damage. People who eat chili feel the thrill of risk-taking, without taking any real risks.
Birds are indifferent to capsaicin, but mammals other than people hate the burn. Underground cables are sometimes coated with chili seeds to deter burrowing rodents.
It has been shown that chili can desensitise pain nerves. Some commercial creams now make use of capsaicin's painnumbing power and it has also been used successfully to treat acute clinical pain.
(William Reville is a senior lecturer in Biochemistry in UCC.)
