When food stops tasting of anything: smell loss and what to do about it

The tongue detects five qualities: sweet, salty, sour, bitter and umami. Everything else — the difference between a strawberry and a raspberry, between chicken and pork, between fresh and stale — is smell, delivered retronasally as air passes from the mouth up into the nasal cavity while chewing.

Which is why food tastes of nothing during a heavy cold, and why smell loss is experienced as taste loss by nearly everyone who has it.

How common it is

Measured olfactory impairment affects a substantial proportion of older adults — studies using validated smell tests typically find impairment in more than half of those over 65 and the large majority over 80. Self-reported rates are far lower, because the decline is gradual and people do not notice a sense they are losing.

Taste itself declines more modestly, with bitter and salt perception affected earlier than sweet.

Causes worth distinguishing

Normal ageing — reduced olfactory receptor neurons, reduced regenerative capacity, cumulative damage to the olfactory epithelium.

Nasal obstruction — chronic rhinosinusitis and nasal polyps are among the commonest causes and are treatable. This one is worth pursuing, because it is reversible.

Post-viral, including but not limited to COVID-19. Recovery is common but can take months and is sometimes incomplete, and can involve parosmia — distorted smells, often unpleasant.

Medication — a long list, including some antibiotics, antihypertensives, statins, and chemotherapy agents.

Neurodegenerative disease. Smell loss is an early feature of Parkinson's disease and of Alzheimer's, often preceding other symptoms by years. On its own it is far too common to be alarming; in combination with other prodromal features it is informative.

Head injury, which can shear the olfactory nerve fibres.

Zinc deficiency, uncommon but correctable, and worth checking in unexplained cases.

The nutritional consequences

Food that tastes of nothing is not worth eating, and this is one of the underlying drivers of the anorexia of ageing. Reduced enjoyment leads to reduced intake, reduced variety, and a drift toward the two things still perceptible — sweet and salty.

That drift has consequences. Over-salting is common in people with smell loss and matters in anyone with hypertension. Increased sugar intake matters in diabetes. And loss of variety reduces micronutrient intake.

Weight loss in an older adult with unrecognised smell loss is a recognisable pattern and one that is rarely connected.

Making food work anyway

The strategy is to lean on the senses that remain: the tongue's five tastes, plus texture, temperature and trigeminal stimulation — the physical sensations of chilli heat, mustard, ginger, carbonation and menthol, which are carried by a different nerve entirely and are usually preserved.

• Acid. Lemon, lime, vinegar, tamarind, pickles. Sourness is well perceived and lifts almost anything.
• Umami. Parmesan, mushrooms, tomato purée, soy sauce, anchovies, miso, stock. This is the single most useful lever, because umami depth reads as savouriness rather than as saltiness.
• Texture contrast. Something crunchy against something soft makes a dish interesting when flavour cannot. Toasted nuts, seeds, crisp breadcrumbs, raw vegetables alongside cooked.
• Temperature contrast within a meal.
• Trigeminal stimulation — black pepper, chilli, ginger, horseradish, mustard, fresh mint.
• Bitterness, which many older adults tolerate better than they used to — rocket, chicory, dark chocolate, coffee.

Note what is not on that list: more salt. Salt addresses one taste channel and does not compensate for the loss of aroma, which is why people who over-salt for this reason are rarely satisfied by it.

Smell training

The one intervention with reasonable evidence. Developed for post-viral and post-traumatic smell loss, it involves deliberately sniffing four distinct odours — classically rose, eucalyptus, lemon and clove — for around twenty seconds each, twice daily, for at least twelve weeks, while concentrating on the memory of that smell.

Trials show modest but real improvement in olfactory function, likely reflecting the regenerative capacity of the olfactory epithelium. It is free, harmless and requires only essential oils. The evidence in age-related decline is thinner than in post-viral loss, but the intervention carries no downside.

Worth mentioning to a doctor

Sudden smell loss, one-sided loss, loss with nasal obstruction or discharge, or loss accompanied by neurological symptoms all warrant assessment. Gradual bilateral decline over years is usually age-related, and even then a check for treatable nasal disease is reasonable.

It is a sense people mourn quietly and rarely mention. It is worth raising.