How many people's eating experience is being diminished as a consequence of long COVID? No one really knows.
We do know that many of those infected report loss of smell and taste – called anosmia – as a symptom (it is believed that 75-95% of what we taste is actually due to the smell). This can develop into parosmia: when the smell returns but is distorted. The smell and taste of certain things – or sometimes everything – is different, and usually unpleasant.
Parosmia is currently regarded as one of the symptoms of long COVID-19 syndrome or chronic COVID-19 syndrome. But the full extent of the problem is unclear. At the start of the year, the charity Fifth Sense reported that about 60% of those with COVID suffer smell and taste disturbances; of that 60%, about 10% have persistent problems beyond four weeks. Newer data from the Imperial College London-led REACT-2 study in June 2021 suggested that more than two million people in England may have been affected by persistent symptoms lasting for 12 weeks or more after COVID.
Many can shrug off smell and taste loss in less severe and short-lived cases. In others, it can greatly impact their enjoyment of food and life. Some experience nutrition problems by eating too little or too much (in an attempt to chase those lost flavours). There are implications for food safety too. A 2014 study found that people with anosmia were more than twice as likely to eat spoilt food.
Smell and taste: the ‘forgotten’ sense
Smell and taste disorders have always existed. But COVID put the problem firmly on the map. Speaking at a recent webinar organised by the Institute of Food Science and Technology, Dr Jane Parker from the Flavour Centre at the University of Reading, noted there was little awareness of olfactory dysfunction until COVID hit. She estimated it has since impacted a trillion olfactory sensory neurons across the globe.
"The nose as a human sensory instrument is really quite underestimated by the general public,” she said. “It's not until you lose your sense of smell that you realise how important it is to your general wellbeing and quality of life."
Parosmia can be quite a debilitating disease because familiar and usually enjoyed smells and tastes become distorted and unpleasant, she explained. Coffee is the big one. Parosmics no longer smell coffee’s magical aroma: they smell burnt rubber; sewage; petrol; dead meat; rotten food or garbage.
Other common ‘trigger’ foods that become terrible tasting and smelling have, like coffee, high levels of odour-active compounds. These include foods such as meat (some consumers have turned vegetarian), onions, garlic, peppers, chocolate, citrus and apples.
The Flavour Centre at the University of Reading estimate that 15% of all COVID cases will include a long-term smell disorder or parosmia -- that's 3 million people in Europe -- 20% of the UK public have smell disorders anyway.
The phenomenon is presenting opportunities for the food industry to formulate recipes and menus, according to observers. Tapping into the needs of those consumers who are experiencing long-term difficulties connecting with their food could further help address issues related to mental health and their nutritional requirements.
Scope to make up for lost flavour
A report from market researcher Spoonshot offers some suggestions.
“Menus that avoid ‘trigger ingredients’ and instead focus on other aspects to enhance appreciation of foods would likely to appeal to those recovering from the aftermath of the coronavirus,” its analysis said.
The foodservice sector has a chance to incorporate dishes with ingredients and flavours that can be appreciated by people suffering from diminished or lost sense of smell or taste, it said, adding the move could “prove extremely beneficial for restaurants and their customers”.
There also scope to play up elements of texture and taste to make up for lost flavour. Crunchy or crisp textures or contrasting ones like crunchy and chewy can help keep food in the mouth for longer and help extend taste.
Umami flavours can increase the taste of dishes. Trigeminal – or hot, cold, spicy, tingling and electric -- sensations could be used to enhance consumers’ enjoyment of foods and drinks.
These solutions are not just for post-COVID sufferers and could have wider appeal. An ageing population, for instance, means there may be a longer term place for food and drink, in foodservice and retail, that aids such consumers. CPG brands could therefore look to incorporate some of these elements into products.
By way as an example, Life Kitchen -- a not-for-profit cookery school for people whose taste has been affected by cancer – launched a ‘COVID cookbook’ placing strong emphasis on ‘aroma, umami, texture, layering and trigeminal food sensations’ designed to ‘reignite the joy of taste and flavour’.
The science is still out on smell training
Dr Parker suggested there is room for improvement in the smell training space. Studies by the Flavour Centre at the University of Reading have shown that smell training, where patients regularly smell different intense bottled odours (typically rose, eucalyptus, lemon and cloves) can improve their general olfactory function. However, smell training is designed not for parosmics, but to bring back smell for anosmia sufferers. What’s more, many parosmics find clove and lemon objectionable.
“We don't know if it definitely works for parosmia,” she said. “We still need to do the studies. Unfortunately, there's no current treatment for parosmia. People have tried all sorts of interventions.
We don't know yet if smell training improves parosmia but we do know that by smell training for four months twice a day you can increase your olfactory function score by 6 units – that’s something but not very much. It's a slow process.”
At the moment, all she can advise those with parosmia to do is to be patient. “It can take up to two years for people to get back to something that approaches normality and back to enjoying food. It's a slow process. The key thing is to smell ‘something’. Some people just shut themselves down and don’t want to think about it. They’re the ones that don’t recover.”