Improving Taste and Smell After COVID-19 Recovery

January 2022 Issue

Herbs + Spices: Improving Taste and Smell After COVID-19 Recovery
By Carrie Dennett, MPH, RDN, CD
Today’s Dietitian
Vol. 24, No. 1, P. 16

One of the more bizarre symptoms of COVID-19 is loss of taste and smell, and for many people this sensory deprivation lasts for several months—or longer. What’s behind this phenomenon, and how does it impact not just food pleasure but also food choices and nutrition status?

Smell, or olfaction, is the ability to sense trillions of odors via the nose. Taste, or gustation, is the capacity to perceive the five taste qualities—sweet, salty, sour, bitter, and umami—on the tongue. Chemesthesis is the ability to discern sensations in the mouth, as from eating chili peppers, chewing mint gum, or drinking carbonated water.1,2 Finally, flavor is the combination of all these senses.2

Our sense of smell begins through the nostrils, but as we chew and swallow food, we sense odors and aromatic compounds via the nasal cavity, which lies above the bone that forms the roof of the mouth and curves down at the back to join the throat. In both of these phases, tissues and nerves send neurological signals to the olfactory bulb in the brain. This plays a dominant role in food enjoyment, quality of life, and nutrition-related health outcomes.

Research suggests that COVID-19 infects cells that support sensory neurons in the nose, known as sustentacular cells.3 Inflammation also may play a role in both olfactory and gustatory impairment, although it’s less clear what causes other chemosensory distortions, such as impaired chemesthesis.4 Smell loss has become particularly prominent as a COVID-19 symptom. This includes hyposmia (reduced sense of smell), parosmia (smell distortion—things don’t smell like you remember them), and anosmia (complete loss of smell).

“Smell loss can happen in the presence or absence of other symptoms. For some people, smell loss is the only symptom they have,” says Stephanie Hunter, PhD, a postdoctoral fellow at Monell Chemical Senses Center in Philadelphia. “Since loss of smell, especially in the absence of nasal congestion, is a unique symptom of COVID—as opposed to fever or cough, which could occur for many other reasons—it’s a better predictor of COVID-19 than other symptoms.”

Hunter says a recent Monell study found that about 77% of people with COVID-19 experience smell loss when measured by an actual smell test. But when asked if they have smell loss, only 44% of people report smell loss from COVID-19. “Actually measuring people’s sense of smell can identify a lot more people with smell loss from COVID, because a lot of people just aren’t aware of changes in their taste and smell sometimes.” Hunter says the trajectory and duration of smell disruptions depend on how the person lost their sense of smell. For example, those with postviral smell loss from COVID-19 or a cold typically recover quicker—within about a month—than someone who lost their sense of smell from head trauma, which can be more permanent. “Postviral parosmia typically resolves within a year for most people,” Hunter says. “Recovery also can differ depending on whether someone did any interventions to get their sense of smell back, such as smell training, which could improve recovery from postviral smell loss.”

Results of an ongoing Virginia Commonwealth University study published online in September found that sense of smell or taste returns within six months for about 80% of COVID-19 survivors who reported losing these senses, with patients younger than 40 more likely to recover their sense of smell than older patients.5

Impact on Nutrition and Quality of Life
Hunter says that while many people quickly recover from COVID-19–related smell loss, what’s troubling is that about 10% to 15% of people will suffer long-term smell loss from the disease. “This can really alter their life in terms of quality of life, diet and nutrition, and safety from toxins.” She says many people report compensating for lack of flavor by adding sugar, salt, or spices to their foods—and excess sugar and salt could have adverse effects on nutrition status and health. “On the other hand, others may find food just not very enjoyable, or even unpleasant to eat, and don’t have much of an appetite, and don’t eat as much as they used to.”

In early 2020, Chef Michele Redmond, MS, RDN, who provides culinary nutrition and gastronomy education and consulting services at The Taste Workshop in Scottsdale, Arizona, contracted COVID-19. She experienced reduced flavor perception but also increased taste sensitivity, or hypergeusia, to bitter foods for more than four months. She says she easily could taste salt and sweet and, for the first time, frequently desired ice cream. “Despite these treats, I experienced long-term appetite loss for the first time. Foods I normally loved tasted flat, and I lost interest in eating them,” she says. “However, it was a good professional experience for me to consider how the impact of loss of appetite can affect mood and mealtimes.”

Use of Herbs and Spices
Depending on the level and type of chemosensory impairment, using herbs and spices may help increase interest in eating, although which herbs and spices do so will vary from person to person.

“Our lifetime eating experiences, genetic makeup, and exposure to herbs and spices uniquely shape how the brain interprets them,” Redmond says, adding that when a client frequently has been exposed to herbs and spices, such as by cooking with them, this increases their odds of enjoying and recognizing individual ones when they’re struggling to make food smell or taste good.

However, if a client is unfamiliar with using herbs and spices, Redmond suggests listing foods, beverages, and ingredients they previously enjoyed. “Make a note of those that also evoke positive memories and experiences since the olfactory bulb connects to the brain’s limbic system involved in processing memory, mood and emotions, and learning,” she says. “Then identify any herbs, spices, and flavorful ingredients fitting these criteria and individually incorporate them into a food at varying quantities.” For patients who are frustrated with loss of smell, Redmond suggests trying a smell training kit (see sidebar) from a reputable sensory organization and considering repeated exposure to aromas they’re most familiar with, especially ones that are pungent and connect to positive memories and emotions.

When flavor perception is compromised or illusive, Redmond says spicy ingredients can stimulate the eating experience. “That’s because we feel ingredients like chili flakes, chili powder, or peppercorns as a physical sensation,” she says. Redmond also says dry or liquid flavor extracts have been shown to help improve flavor and taste perception by adding aroma or flavor, increasing salivary output, heightening appetite, and masking bad or “off” flavors. “Flavor extracts are available for a variety of flavorful plants, including basil, garlic, thyme, anise, bergamot, mint, and peppermint.” Many of these extracts are available in grocery stores, while others may be available only online.

Ginger Hultin, MS, RDN, owner of Champagne Nutrition in Seattle and author of Anti-Inflammatory Diet Meal Prep, suggests clients start by using lemon as a flavor. “It’s not an herb or spice, but it can be an effective way to stimulate the taste buds,” she says. “Next, I might suggest strong flavors from foods like onion and garlic. Finally, try fresh herbs, which are often a little more potent-flavored, and start with more familiar options like basil, oregano, mint, and cilantro.”

Of course, loss of taste and smell is one thing; distorted taste and smell is another. Hunter says people will experience parosmia when their olfactory sensory neurons are recovering. She says this can be a very troubling time and has profound negative impacts on their quality of life. “This is when people experience foods tasting like sewage or spoiled even though they aren’t, and this can especially disrupt someone’s diet,” she says. “It’s hard to have an appetite or want to eat if everything tastes bad, and constantly smelling sewage all day can be very troubling.”

Hultin says fruity and salty flavors may be better tolerated in this case and that patients may find they’re averse to protein foods such as meat. “Aim for plant-based proteins such as tofu, tempeh, beans, and lentils, or use a marinade on meat to change the flavor,” she says. “It’s important to keep trying—not to give up—and to try a food more than once. People with food aversions or distorted smell or taste may find that they can’t tolerate a food one day, but on another, it’s better.”

However, if distorted taste and odor perception continues to create feelings of disgust for and aversion to previously enjoyed foods, affecting appetite, nutrient and calorie intake, and mental health, Redmond says, “It’s important to seek support from health professionals skilled in sensory diagnosis and assessment.” Rhinologists and otolaryngologists (ear, nose, and throat doctors) who specialize in nose and sinus problems, are the specialists for clients to contact.

— Carrie Dennett, MPH, RDN, CD, is the nutrition columnist for The Seattle Times, owner of Nutrition by Carrie, and author of Healthy for Your Life: A Holistic Guide to Optimal Wellness.

References
1. Bussière N, Mei J, Lévesque-Boissonneault C, et al. Chemosensory dysfunctions induced by COVID-19 can persist up to 7 months: a study of over 700 healthcare workers. Chem Senses. 2021;46:bjab038.

2. Maheswaran T, Abikshyeet P, Sitra G, Gokulanathan S, Vaithiyanadane V, Jeelani S. Gustatory dysfunction. J Pharm Bioallied Sci. 2014;6(Suppl 1):S30-S33.

3. Brann DH, Tsukahara T, Weinreb C, et al. Non-neuronal expression of SARS-CoV-2 entry genes in the olfactory system suggests mechanisms underlying COVID-19-associated anosmia. Sci Adv. 2020;6(31):eabc5801.

4. Cazzolla AP, Lovero R, Lo Muzio L, et al. Taste and smell disorders in COVID-19 patients: role of interleukin-6. ACS Chem Neurosci. 2020;11(17):2774-2781.

5. Coelho DH, Reiter ER, Budd SG, Shin Y, Kons ZA, Costanzo RM. Predictors of smell recovery in a nationwide prospective cohort of patients with COVID-19. Am J Otolaryngol. 2022;43(1):103239.

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Resources
• Abscent.org: AbScent is a United Kingdom–registered charity that funds research to end smell disorders and supports individuals experiencing the effects of smell loss. This organization sells smell training kits and provides instructions for creating your own kit. It also offers other information on smell loss.

• Thestana.org: The Smell and Taste Association of North America is a patient advocacy group that seeks to improve the quality of life for people with smell and taste disorders.

• Monell.org: The Monell Center website offers information on the Monell Chemical Senses Center’s research, including research on smell loss.

• American-rhinologic.org: The American Rhinologic Society serves, represents, and advances the science of rhinology. The website includes a “find a rhinologist” feature and other information in the rhinology field.