Taste preferences of infants and children
by Prof Adam Drewnowski
Why do infants and young children prefer bananas to broccoli and
sweets to spinach? Is taste genetically determined or is it cultivated through early
exposures to food? To expound on this interesting field of the development of infants'
taste preferences is Professor Adam Drewnowski, Professor of Epidemiology, School
of Public Health and Community Medicine and Director of Nutritional Sciences Program
at the University of Washington, USA.
by Prof Adam Drewnowski
The following are some questions and his answers
on this subject:
1. Are babies born with a mature taste bud? Please elaborate
on the development of the sensory system.
The sensory system is pretty much complete by the time of birth. Taste buds mature
by the last trimester of pregnancy. Newly- born babies react to sweet, sour, and
bitter tastes - but not so much to salt. Some researchers believe that prenatal
exposure to food odors, derived from foods consumed by the mother in the course
of pregnancy, can influence future food preferences and eating habits. It is never
too early to surround the infant with positive and rewarding taste experiences.
2. What are the taste preferences of infants? Why are
infants born with an innate liking for sweetness?
Infants like sweet and dislike bitter tastes. This can be read from their facial
expressions. A drop of sweet taste on the tongue makes the infant smile and relax.
Sweetness is nature's way of announcing that the food is rich in calories and good
to eat. The infants' feeding response is driven by sweetness and infants quickly
learn to consume sugar solutions in preference to plain water. Sweeter sugars such
as sucrose are preferred over less sweet sugars, and intensely sweet solutions are
liked the best.
3. It is a known fact that the preferred level of sweetness
in food differs across cultures. Why is that so?
Taste preferences for sweetness are maximal in infancy and childhood and progressively
drop during adolescence and adult life. Children adore foods that would be much
too sweet for adults. Children also select foods that are more energy-dense than
do adults, and hence their passion for candy and chocolate.
So the basic liking for sweetness is an innate human trait. The preferred level
of sweetness is determined first by age and only then by culture. Those cultures
that did not have cane, beet, or corn sugar in their staple diet are only now getting
used to increasing level of sweetness in food. I believe that the amount of sugars
in the diet is likely to increase; it is an inexpensive source of energy.
4. Why do humans naturally reject the bitter taste of
food ?
Humans equate bitter taste with dietary danger, and rightly so. Plant poisons, toxic
metals, spoiled proteins, and rancid fats all have an unpleasant bitter taste. The
real puzzle is why so many unrelated compounds can give rise to a single taste sensation
- bitter. This is probably nature's way of making sure that bitter is the main alarm
signal. It turns out that we may have as many as 80 different taste receptors for
bitter, as compared with only 2 or 3 for sweet. From the evolutionary standpoint,
avoiding bitter toxins is the most important thing of all.
5. What are the factors that determine our taste preference
from young? Do genes play a part as well?
Sensitivity to some bitter compounds - and there are so many - is a heritable trait.
We have done studies with a compound called 6-n-propylthiouracil or PROP that is
extremely bitter to some people but is tasteless to others. Sensitivity to PROP
correlates well with sensitivity to some, but not all, bitter tastes. People who
dislike PROP also dislike caffeine and grapefruit juice, but may not be bothered
by other bitter foods.
6. Does taste sensation alter at different stages of life?
If so, is it due to hormonal or other causes?
Sensitivity to bitter is highest at two critical life stages: pregnancy and early
life. Infants and pregnant women are most vulnerable to bitter toxins and are most
likely to avoid bitter foods. In the US, aversions to coffee are very common among
pregnant women. And as we all know, infants and young children dislike bitter vegetables
and even bitter chocolate. Preferences for bitter and bittersweet chocolate are
very much related to age.
7. Please elaborate why most children dislike vegetables,
particularly those that do not taste sweet, such as broccoli. How can we overcome
this natural dislike for such vegetables?
Vegetables strike out on two counts. They are bitter and they do not provide sufficient
calories per unit volume to make them attractive to children. Remember that growing
and active children have higher energy needs than do adults and must consume energy-dense
foods. There is just no way to pack enough calories into a dish of broccoli.
Here is where gastronomy comes to the rescue. Vegetables are usually prepared with
fat, sugar or salt. They are sauteed, stir-fried, baked or braised. Adding fat,
sugar or salt is a very effective way of minimizing bitter taste. Scientists are
still figuring out how some tastes suppress each other and how bitter is suppressed
by sweet. Of course, adding sugar or fat also increases energy density. But the
major thing is that vegetables ought to taste good - bitter glucosinolates in broccoli
can be neutralized by the addition of sauce.
8. Some young children tend to be very selective in their
choice of food and eat only those that they are familiar with. Is this normal or
should it be a concern for mothers?
The infants' taste world is driven by only two things: bitter and sweet. In addition,
foods that are familiar are preferred over those that are not. The introduction
of new foods, whether liquid or solid, should increase the range of food preferences.
Some studies tried to expose young infants to the taste of garlic. However, in practice
it is perfectly normal for infants and young children to stay with foods that are
both familiar and sweet.
9. How does zinc play a role in taste acuity?
Some studies have linked zinc deficiency to taste abnormalities. Clinical studies
showed that ageusia (no taste) and dysgeusia (persistent bad taste) could be treated
with zinc supplementation. However, most zinc deficient patients are also elderly,
and zinc deficiency is often the outcome of drug-drug interactions. So it is not
always clear if taste deficits are the result of aging, disease or drug treatment.
Among healthy older adults, few taste deficits are observed. For the most part they
involve bitter taste - we get to like broccoli as we get older.