A matter of taste: the problem with losing our fifth sense

Compensating for missing tastes can throw diets out of whack.

If your child were diagnosed with a taste disorder, you’d be forgiven for welcoming an impending disinterest in sweets and salty chips.

But for the one in ten Australian children who can’t perceive sweet, sour, salty or bitter tastes in foods and drinks, this is a serious problem with long-term health implications.

Taste disorders are still widely undiagnosed but our recent study found 12% of Indigenous children and 8% of non-Indigenous children can’t perceive the full spectrum of tastes.

These levels are substantially higher than the World Health Organisation’s 4% marker, which indicates the point at which action is required by health authorities to reduce the occurrence of a disease or disorder.

The importance of taste

If we lose one sense of taste, we are more likely to compensate by consuming higher levels of another taste.

Sweet taste loss, for example, can cause a child to eat only savoury foods loaded with salt and carbohydrates.

Around two thirds of taste disorders involve sweet taste loss. This may be because humans have a higher proportion of sweet taste nerve fibres than any other taste.

Studies of chimpanzees, the closest animal related to humans, indicate that 50% of taste nerve fibres respond to sweet stimuli but substantially fewer fibres respond to other tastes.

In comparison, domesticated cats have few sweet nerves fibres and cannot distinguish water from sweetened water.

Depending on how a person tries to compensate for loss of taste, unmanaged taste disorders can lead to obesity, malnourishment or anorexia.

Potential indicators of a taste disorder include a child being overweight, underweight or a fussy eater. Not all children exhibiting one or more of these indicators will have a taste disorder, but clearly some will.

Recovery from taste loss, whatever the cause, generally occurs within 2 to 3 years. Otherwise the loss is permanent.

How taste is lost

Loss of taste has been linked to chronic kidney disease, diabetes, disorders of the oral cavity and salivary glands, and chemo- and radiotherapy during cancer treatment.

But the major cause of taste disorders in children seems to be inner ear infection, caused by upper respiratory infections.

Inner ear infections can severely damage the major taste nerve as it passes from the tongue through the inner ear to the brainstem.

Up to 90% of Indigenous children and 40% of non-Indigenous children will develop at least one inner ear infection in the first six years of life.

The higher prevalence of taste loss in Indigenous children may be linked to their greater frequency of experiences with the infection.

Inner ear infection is the most common reason a child visits a general practitioner in the Western world. But it is still unproven whether the inner ear infection itself, or the subsequent medication, leads to the development of a taste disorder.

Prevention

Without medication to cure taste loss, we need to focus on prevention and management.

The first priority should be reducing the rate of inner ear infections among Indigenous children, to levels seen in non-Indigenous children.

This is certainly an achievable aim, and is likely to reduce taste disorders in Indigenous communities.

Once a taste loss has been identified, it can be managed by consulting a dietician. For example, if a sweet taste is lost, development of a diet that controls salt intake is important.

Management by a dietician will ensure a healthy weight and nutrient levels are maintained.

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