Losing one's sense of smell, or taste was not something we often heard of until 2020 when Covid-19 came into the picture. However this isn't the only illness that can have an effect on our senses, with many cancer patients reporting similar effects from undergoing chemo and radiation therapy. Losing these senses can have a detrimental effect on your health as it changes your relationship with food and contributes to a loss of appetite, leading to weight loss or malnutrition.

COVID almost seems a thing of the past for most of us, but some are still stuck with symptoms of Long Covid up to a year after contracting the virus. One of the more common side effects of Long Covid is the loss of one's taste or smell. 

Along with Covid-19, some cancer treatments can affect the way foods and drinks taste, taking away the joy eating is usually associated with, and reducing your appetite.

What cancer treatments can affect your taste and smell?

There are three main treatments that have been shown to affect our senses and damage nerves that send signals to the brain causing changes during and after treatment:

Chemotherapy: 

Can damage healthy cells such as taste buds and affect nerve endings, changing the way you feel hot and cold foods in your mouth.

Radiation therapy: 

Radiation to the head or neck area can damage taste buds and salivary glands.

Surgery: 

Surgery to the nose and mouth area affects part of the tongue, nose and salivary glands, altering your sense of smell and taste.

Chemotherapy is the most common cancer treatment and the majority of people (up to 70%) affected by cancer have reported taste and smell modification associated with loss of appetite, fatigue and decrease in energy intake. In several cases, loss of appetite has led to malnutrition. As a result, cancer patients are not only affected by taste and smell alteration, but also by nutritional deficiencies. The most common deficiencies are vitamin B1, B2, K, niacin, folic acid, and thiamine. For these reasons, it’s important to understand the importance of nutrition for recovery and how to include different ingredients to enhance flavours.

Eating the right foods in cancer recovery

For most, a healthy diet includes a mixture of fruit, vegetables and wholegrains, modest amounts of meat and milk products, with small amounts of fat, sugar and salt. 

However for cancer survivors, extra protein and calories are needed, since many patients experience loss of appetite and malnutrition. Protein is important for healing and for strengthening the immune system. Therefore, extra milk, cheese and eggs are recommended. A recovery diet for those who suffered from cancer consists of a higher amount of yoghurt, beans, chicken, eggs and protein-fortified milk. 

How to include more protein in your diet

There are different ways to increase the protein and calories in your diet. For example, you can add cheese or cream to your sandwich or soup, as well as nuts which are very caloric and good sources of fat. You can use fortified milk instead of water in porridge and protein powder in your milkshake. You can also add peanut butter or almond butter in porridges and fruit. A recovery diet can also consist of liquids that add calories including juices, soups as well as milk and soy-based soups with protein and powdered meal replacement such as “instant breakfast”.

Create dishes to target taste receptors

We have five taste receptors: sweet, sour, salty, bitter and umami. 

Umami, also known as monosodium glutamate, is a savoury, rich, base flavour that deepens flavour and comes from three compounds that are naturally found in plants and meat: glutamate, inosinate and guanylate. Technically, umami is the taste of glutamate, an amino acid that constitutes one of the building blocks of protein and is found in onions, garlic, marmite, miso paste, soy, cheese, lemon, mushrooms and dried porcini.

According to Ryan Riley, an expert cook and author on smell and taste loss, umami is the most powerful taste receptor in stimulating taste buds when the palate is dulled by chemotherapy. For this reason, he created recipes that enhance umami flavour specifically for people having taste and smell loss. Experts and researchers who worked with Ryan have noticed that umami helps individuals to better taste and smell the food. 

Examples of dishes recommended include spaghetti with porcini mushrooms cooked in a marmite and lemon sauce or fish tacos with kimchi and soy sauce. These dishes include ingredients such as kimchi, miso, soya, mushrooms that add extra base flavour and have been scientifically proven to trigger the trigeminal nerve which is responsible for sending pain, touch, cold and heat sensations.

Losing smell and taste with Covid-19

Research has shown that covid-19 can cause taste and smell loss due to the ability of the virus to interact with cells that support olfactory sensory neurons.  Taste changes related to covid break down into three categories: 

1. Those who lose the taste for a couple of weeks while they are ill, 
2. Those who lose their smell for a long period of time (called anosmia) and 
3. Those who have a distorted sense of smell for a long time (parosmia).

Although in both, cancer patients and covid-19 patients, people can lose their sense of taste and/or smell; people who lose taste and smell due to covid-19 often show different dietary preferences to those who lose their senses due to cancer treatment. For example, people who have parosmia often find foods like onions, garlic, meat, eggs and nuts repulsive. Therefore, there are different techniques used to increase flavour for people who are recovering from covid.

Eating well after losing your sense of taste or smell

Due to taste and smell loss, it can be challenging to eat, and even your favourite food can taste bland, salty, sweet or metallic. There are different ways to improve the taste of the food. For instance, adding strong flavour such as apple sauce, mint sauce, mustard, pickles and spices help to enhance the flavour. The best way to improve flavours for people that have lost their taste/smell due to covid-19, is to combine five elements: aroma, umami, texture, layering and trigeminal food sensations.

Eating well to recover from covid-19 is important, as our body needs energy, protein, vitamins and minerals to support rebuilding muscles, maintaining the immune system and increasing energy levels. Protein-rich and energy dense foods and drinks are recommended. 

For example, Greek yoghourt, milk-based drinks and cheese are great options to add to your meals for a good recovery. Furthermore, oral supplements are often recommended including vitamin D which can be suboptimal in covid patients, as they must stay at home, often confined indoors and are not exposed to much sun.

As with anything, recovery takes time. When recovering from a loss of taste or smell from illnesses or treatments, there are several important considerations to make: first of all, a recovery diet is essential, as the body is weak and needs extra protein and energy to fully recover. The changes your body and senses experience will take time to re-introduce flavours and smells. Cooking with strong flavours that enhance umami is the right way to help our senses to taste and smell the food again. Starting small and introducing bold flavours first, then building more flavour elements into a dish, the more appetising eating will become. .