Metallic taste is a common symptom reported by cancer patients. Also known as dysgeusia, this distortion of taste perception can present as a persistent bitter, sour, or chemical flavor in the mouth. While not life-threatening, metallic taste can negatively impact quality of life by making eating unappealing. Understanding the causes of metallic dysgeusia and available management strategies can help patients cope with this troublesome symptom.
In this article, we will explore the leading theories behind metallic taste in cancer, which types are most associated with taste changes, methods for diagnosis, and evidence-based approaches to reduce its severity. By equipping patients with knowledge on the science and treatment of metallic taste, we aim to demystify this challenging side effect and empower patients to advocate for interventions that improve their nutritional intake and meal enjoyment. Let us examine the current state of research on metallic dysgeusia in cancer patients.
A variety of factors can cause taste changes like a metal mouth sensation. Common causes include:
Medications – Certain medications like antibiotics, hypertension drugs, and antimalarial drugs are frequent culprits. Cancer drugs also often lead to taste problems.
Morning sickness – Hormonal changes during pregnancy can cause dysgeusia. It’s especially common with morning sickness early in pregnancy.
Dry mouth – Saliva helps neutralize and wash away taste sensations. A dry mouth allows tastes to linger.
Smoking – Chemicals in cigarettes and vaping can alter taste buds. Quitting smoking often helps taste return to normal.
Dental problems – Oral hygiene issues like gingivitis, oral thrush, and abscesses can cause a foul, metallic taste.
Radiation therapy – Head and neck radiation can damage taste buds and salivary glands, leading to long-term taste changes.
Zinc deficiency – Low zinc levels have been associated with dysgeusia. Zinc is needed for taste bud function.
Sinus congestion – Stuffed sinuses from colds or allergies can distort smell and taste perceptions.
Neurological damage – Injuries, tumors, or diseases affecting the taste nerves or brain centers may cause an abnormal taste.
Let’s look specifically at how certain cancers and cancer treatments can be culprits.
Read: What Deficiency Causes A Metallic Taste In Your Mouth?
Many cancer therapies work by targeting and killing rapidly dividing cancer cells. But they can also damage healthy cells, including the taste receptor cells in the mouth and tongue.
This “chemo taste” or “radiation taste” is thought to stem from the turnover and shedding of taste buds as they become damaged by cancer treatment. The result is a persistent odd taste, even when no food or drink is present.
Some cancer treatment-related causes of metal mouth include:
Many chemotherapy drugs are associated with metallic tastes, including:
For some people, this side effect is mild and tolerable. But a severe metal dysgeusia can make eating a miserable chore when you most need nutrition.
The taste alteration can begin with the first dose of chemo but tends to worsen over subsequent treatment cycles. It may take months after finishing chemo for taste to fully recover.
Radiation aimed at the head, neck, or chest areas can inadvertently deliver toxic doses to the taste buds and salivary glands. This can damage both the taste sensation and the natural flushing of the mouth. The result is often a persistent metallic or chemical taste.
Moreover, radiation to the neck and throat also increases risk of dry mouth from reduced saliva. This compounds any direct taste damage. Just as with chemo, the metal taste usually worsens as radiation treatments accumulate. It then gradually improves in the months following therapy.
Newer cancer drugs that target specific molecules can also cause dysgeusia. Examples include:
Compared to chemo drugs, these agents tend to cause milder taste problems that are tolerated well. But the metallic taste can still be bothersome.
High-dose chemo given prior to transplants is very intensive. So severe metal mouth is common and can last for months.
The pre-transplant conditioning aims to ablate the bone marrow and suppress the immune system. So it’s a necessarily toxic process.
Extended struggles with metallic taste are a trade-off for the treatment’s curative potential.
In some cases, cancers themselves, rather than just the treatments, can distort taste.
Cancers in the nasal cavity, sinuses, mouth, and airway can directly invade or compress the nerves that convey taste signals.
And cancers farther from the mouth may sometimes secrete substances that circulate and interact with taste receptors.
Types of cancers where the tumor itself may contribute to metal mouth include:
Cancers of the tongue, gums, sinuses, throat, voicebox, and other structures in the head and neck area are prone to causing taste changes like a metal mouth.
The growing tumor can damage nerves, blood vessels, and lymphatics that are critical for normal taste sensations.
For example, Beckwith says a quarter of patients with nasopharyngeal cancer and 20% with sinonasal cancers had severe dysgeusia even before treatment.
Taste problems are unfortunately common and likely multifactorial for people with oral, pharyngeal, laryngeal, and similar cancers.
Lung cancer may sometimes secrete particular substances that can circulate and bind with taste receptors.
One example is production of argpyrimidine by tumor cells. Researchers hypothesize this may interact with the tongue to cause a metallic taste in the mouth.
Of course, the chemo and radiation used to treat lung cancer can worsen any pre-existing dysgeusia.
There are a few theories on how breast cancer could contribute to metallic taste even before treatments begin.
One is that estrogen receptors on breast cancer cells may also exist in the taste buds. Tumor metabolites could bind here and distort taste.
And breast cancer, especially late stage, sometimes increases blood calcium levels. Some researchers speculate calcium may interact with the tongue to cause an abnormal sensation.
The kidneys filter and remove waste products from the bloodstream. When kidney cancer affects this process, buildup of toxins and chemicals can occur.
It’s hypothesised some of these circulating substances may alter how the taste buds respond and signal to the brain, causing phenomena like metal mouth.
Again, kidney cancer treatments like immunotherapy and chemotherapy certainly add to the problem as well.
That persistent metallic, chemical, bitter, or foul taste is not only annoying but can make eating a miserable experience. Here are some tips to help cope:
Let your oncology team know about taste changes. They may have nutritional drinks and tips to help maintain your diet and weight during cancer treatment.
The metallic mouth struggle is temporary. Stay positive knowing your taste will likely bounce back after treatment ends. Pay attention as sensory changes are an important indicator your body is healing.