UK study to assess vitamin A drops for reversing COVID-19 smell loss
29 Sep 2021 --- Vitamin A nasal drops might help people regain their sense of smell after viral infections, including COVID-19.
This is the hypothesis of UK researchers, who will embark on a two-year study to help improve the lives of millions around the world who suffer from smell loss. Sensory deficit can have a significant impact on nutrition, triggering unhealthy eating habits, for example.
“If we can provide better evidence for an effective treatment for viral smell disorders, this will be a major step forward as high-quality clinical studies have been lacking in this field to date,” Carl Philpott, professor at University of East Anglia and James Paget University Hospitals NHS Trust, tells NutritionInsight.
He adds that if this is found to be effective, treated beneficiaries will be better able to regulate their nutritional intake.
The study has landed £250,000 (US$338,000) from the National Institute for Health Research (NIHR), which is the UK’s largest funder of research. 
Philpott theorizes that topical vitamin A treatment will encourage regeneration of the olfactory epithelium.
A “big problem”
Even before the COVID-19 pandemic hit, smell loss was thought to affect an estimated 5% of people, with viruses accounting for one in ten of those. However, the pandemic has created an “unprecedented” worldwide demand for treatment.
According to Philpott, around one in ten people who experience smell loss as a result of COVID-19 report that their sense of smell has not returned to normal four weeks after falling ill.
“It’s a big problem, and our previous research has shown the impact of smell loss – including depression, anxiety and isolation, as well as risk of danger from hazards such as gas and spoiled food, and changes in weight due to reduced appetite.”
He notes that around a third of people with smell loss lose weight, while a third gain weight. “Ironically, some people will eat more take-out foods, trying to get some stimulation of flavor.”
Why vitamin A?
Philpott’s team is inspired by a German study from four years ago that showed people treated with vitamin A nasal drops improved twice as much as those in the untreated group.
“We want to find out whether there is an increase in the size and activity of damaged smell pathways in patients’ brains when they are treated with vitamin A nasal drops. This would show recovery of the damage caused by common viral infections, including COVID-19, in the nose,” says Philpott.
He theorizes that topical vitamin A treatment will encourage regeneration of the olfactory epithelium – which is damaged by respiratory viruses responsible for the common cold – and help restore the sense of smell in sufferers.
Recruitment is expected to begin in December 2021.
Smelling distinctive odors
The researchers aim to recruit 57 participants who have lost their sense of smell due to a viral infection. They will either receive a 12-week course of nasal vitamin A drops or inactive equivalent drops.
Commenting on the potential for other delivery formats, Philpott explains that evidence points to nasal drops being the most beneficial.
The participants will then have their brains scanned before and after treatment. “They will be smelling distinctive odors – roses and rotten eggs – while special MRI brain scans are taken,” details Philpott.
The researchers will look for changes in the size of the olfactory bulb – an area above the nose where the smell nerves join together and connect to the brain. They’ll also look at activity in areas of the brain linked to recognizing smells.
Earlier this month, Nutricia urged nutrition to be integrated into medical care to improve COVID-19 patient recovery in hospital and after discharge. It noted that loss of smell and taste can contribute to further worsening of nutritional issues.
In June, a survey of UK consumers found that nearly two-thirds had made changes during the pandemic to improve their health.
By Katherine Durrell
