A reader asked me the
question “What happens to your taste buds as you age?” Well, I said (and
assumed) that they decline with age. I remember my grandmother sucking on mints
that were a bit too strong for some punk kid in his first decade. Anyway, I
said I would find out more. And indeed I did. Come with me and I’ll guarantee
you will learn something new.
Taste buds on the top of your tongue
My physiology text tells
me that there are 10,000 taste buds in your mouth, with most concentrated on
the top of your tongue. Each taste bud has a small opening called the taste
pore through which liquids can come into contact with the taste receptor cells (see pic). That means you can taste soup or ice cream instantly, but a dry food
will need the assistance of saliva. Most taste buds have a life span of just 8-12
days, so they are replaced three times a month.
You will have been taught
that we have taste buds that sense the sweet, sour, salty and bitter tastes in
food. You may also know that there is a 5th taste known as umami,
the savoury flavour. There is even a suggestion of a 6th taste, one
of a metallic sensation, partly because sometimes this is picked up in tasting
labs for new processed foods and we don’t like anything that tastes ‘metallic’.
The chemistry of taste
In general, the sweet taste
comes from sugars (obviously), alcohol and small proteins. The most famous
example of the latter is the sweetener aspartame, which is a very small protein
of two amino acids. Those two amino acids (aspartic acid and phenylalanine) are
abundant in nature but still people consider them to be “artificial” and the
downfall of western civilisation.
Salts, not just sodium
chloride (table salt), are salty, and acids tend to give an sour flavour (eg
citric acid in lemons, and compounds in spoiled foods). Many poisons in nature
taste bitter, so it is speculated that the bitter sensation is to help us avoid
becoming sick, as well as avoiding cabbage. Certain amino acids, like
glutamate, provide the umami or savoury flavour. They are abundant in
mushrooms, tomato paste and parmesan cheese.
Weird stuff
Taste receptors aren’t
just in the taste buds in your mouth. They are all through your digestive
system, your throat and lungs, and (if you have them) your testis. No, I’m not
kidding. OK, what is going on here?
There are proteins in
saliva that mediate the taste of bitter, sweet and umami. The compounds in food
that trigger the bitter taste also seem to trigger the process of expelling
things from the body. Give an infant a bitter food and it will be spat out.
Even if as an adult you can handle some bitterness, the taste can evoke
sneezing and coughing.
OK, that makes sense, but
taste receptors (not taste buds) in the testis and sperm? Look, I can’t say I fully understand, although it seems that
the receptors may sense a wholesome diet in Dad meaning there is abundant food,
or sense toxic substances in Mum, suggesting she may not be ready for pregnancy,
signalling sperm death. So, these receptors could be sensing the health of
prospective parents. Weird, but seriously cool if that be the truth. (Here, I
have taken artistic license; you read the paper and see if you can make better
sense of it. Warning: It contains sentences like this: “Odorants directly
activate CatSper without involving GPCRs or cAMP”).
Sweetness about bitter
The ability to taste
certain bitter compounds is genetically based. Now there is a strong suggestion
the bitter taste is also linked to longevity. The early evidence is that those
of you who enjoy bitter tasting vegetables may live longer, no just due to the
nutrition in a cabbage or Brussels sprouts. There are compounds in bitter
fruits and veg that could be defensive against cancer and that puts the life
odds in our favour. Some people have one specific gene for bitter tasting that
is strongly associated with a long life.
Taste buds & aging
And speaking of a long
life, let’s return to the original question: “What happens to taste
buds as you age?” Certainly there is agreement that taste sensitivity declines
as we age. A taste has to be stronger at age 75 than at age 25 before it is
detected or recognised. Most studies agree that the salty and bitter tastes
decline more than sour and sweet tastes over a lifetime.
As we age we seem to
have fewer taste buds and fewer taste cells in each taste bud, with the biggest
decline in the 74-85 year olds. Why this happens is not clear although there is
suspicion that age might affect the stem cells involved in taste bud
generation.
What does it all mean?
Discover your taste
buds. Eat a wide range of wholesome foods that take all your taste buds through
a full range of experiences. Beats me why so many people rely on a hard-working
teenager to cook them a predictable fare of fat, salt or sugar-laden
easy-to-chew fast foods.
This was going to be a
short article providing a simple answer to a simple question. But I learned so
much more, and I hope that you didn’t mind me sharing it with you.
References:
Sherwood L. Human Physiology,
6th edition p 221-225
Ross A et al. Modern
Nutrition in Health & Disease, 11th edition p 577-579
Feng P et al 2014. Chemical Senses
Kinnamon SC 2012. Acta Physiology
Campa D et al 2012. PLoS ONE
