Our taste and smell can be destroyed by a lifetime of smoking or working in a “toxic” environment. Like all the other senses it is difficult to separate out the impact of healthy ageing from disease. However, there are some effects that appear to be causally related to ageing. The receptors will deteriorate with age like the other senses. Our taste buds and smell receptors have a remarkable capacity to regenerate themselves. The taste cells within the taste buds have an average lifespan of eight to twelve days. Our mouth is continuously regenerating them. As we age however the regeneration process slows and eventually stops leading to a decline in the number of buds and the smell receptors.
As we age the amount of saliva that we produce can decline resulting in “dry mouth” syndrome. This can inhibit our sense of taste or require us to chew for longer. Combined with any teeth problems, this can further reduce the pleasures that are usually associated with eating. All of this raises the thresholds of our sense of taste and smell, we need more stimulants.
The only thing that does not decay with age is the defensive mechanism within our mouths that prevents us from eating harmful food. It has separate sensors and a direct path to the brain. It is these sensors that detect the capsaicin in chillies. It can detect pain, stinging and irritation in our mouths. As we age it will still protect us from burning our mouths. We can still enjoy the stimulation of chillies or chilli sauces.
The Impact on What we Eat.
The prevalence of taste and smell problems varies with age but also dramatically across people. Smells can be correctly sensed until our seventies. Only about a fifth of Third Agers have problems. Issues with smell however, grow to sixty percent with the start of the Fourth Age. Men have worst problems with loss of smell. This is consistent with women having a better sense of smell throughout their lives. They outperformed the men by a third. As our sense of smell ages, not only do we need higher levels of scent to trigger the receptors, but we start to lose the ability to discriminate between smells.
The sense of taste is depressed by age as well. It is known that the sense of taste starts to deteriorate earlier than smell. It starts in one’s forties and fifties for women and fifties and sixties for men. Sweetness is preserved the longest with nearly ninety percent of Fourth Agers still recognizing it.
Left to their own devices the over sixties will enhance food with far more salt than their younger selves. We will add twice or even three times the amount of salt to a bowl of tomato soup to achieve the same perceived saltiness . We will add one and a half times as much lemon juice (acid) and nearly that much more sugar. The impact on bitter and umami tastes varies with the type of food. All of this to stimulate the senses whose sensitivity is declining.
Unfortunately, many of the drugs commonly taken by the “not so healthy” ageing magnifies this effect. For adults taking a cocktail of two or three medications the thresholds jump significantly depending on the taste. This has been shown for antihistamines, antibiotics, anti-inflammatories, asthma drugs and anti-depressants. All of these drugs are essential to “healthy aging” but the impact on diet can be huge.
With medication, salt can require twelve times the concentration to be detected. Bitter flavours need seven times and umami five times. Even sweeteners are often dosed three times more. These changes can have a profound effect on diet and health. They also increase the challenges for restaurants attracting Third and Fourth Agers. An added complexity is that the ability to detect changes in taste also declines. If the different foods on the plate are too similar, they may taste the same. A plate full of food without enough variety of taste can become very bland.
The effects on ageing on our sense of smell is just as profound and of the same scale. We only have five basic tastes. The sense of smell generates a huge sample of different odours that appear to be influenced differently by age. To date there appears to be no clear pattern to classify smells based on the impact of age.
Food Enjoyment for Third and Fourth Agers.
When we eat, we are introducing much higher concentrations of organic chemicals than needed to trigger our senses of taste and smell into our mouth. We can even surpass the raised thresholds of the Third Age. The evidence that increases in our thresholds can influence our enjoyment of food is therefore ambiguous. Understanding these changes is confounded by perceptual completion. We have a multitude of eating memories to draw on to “fill the gaps” in our senses. We are also creatures of habit and may adapt our choice of food to our changes senses of taste and smell.
We certainly have a lower preference for predominantly sour and pungent foods. We have an increased desire for sweets and fats. This is consistent with large-scale surveys which show that we preserve the sweet sense longest. The problem for a chef designing a menu is that not all senses and not all consumers are affected in the same way. Precisely because of this, attempts to enhance flavour in the kitchen for older people have shown mixed results in encouraging the enjoyment of food.
Since salt, enhancers and sauces can be added after the meal has left the kitchen, they can be “on the table”. Of course the chefs will have to be less precious about their work. Historically chefs seasoned their foods as part of the preparation. In many restaurants asking for salt produced a frown. With an ageing customer base this may become only the starting point, as customers personalize the flavours of their food! Italian chefs may be happy to see diners add Salsa Verde to their dishes. What will they do when the diners add Tabasco! Chefs in all kinds of restaurants will however have to learn to watch their older clients adding salt and Gentleman’s relish to their carefully prepared food in order to “taste” it.