Impaired sense of smell may be linked to zinc deficiency

Ageing, overweight, and respiratory infections can impair your sense of smell. However, a sufficiently high zinc intake from dietary sources or supplements can support or even improve the sense of smell – especially in older people and those who are overweight. This was shown in a study that is published in Rhinology. Unfortunately, zinc deficiencies are common due to poor diets and the use of various medical drugs that impair the body’s utilization of zinc.

Humans possess approximately 40 million olfactory cells located in the upper part of the nasal cavity. When our sense of smell is stimulated, airborne molecules dissolve in the mucous membranes within the nasal cavity. These molecules then interact with the olfactory cells, which transmit signals to the brain for processing. Olfactory cells typically have a lifespan of 6–8 weeks before being replaced by new cells. If the mucous membranes are damaged, the sense of smell can usually recover.
Loss of smell is relatively common with aging and upper respiratory infections such as influenza, colds, and COVID-19, as inflammation can damage the olfactory cells. Our sense of smell is vital for quality of life because it is closely linked to taste, mood, and memory.
The new study explored the connection between daily zinc intake and various dysfunctions related to the sense of smell. Researchers utilized data from the large American NHANES study (National Health and Nutrition Examination Survey), which tracks dietary habits and health over extended periods. The study involved nearly 3,000 participants from diverse ethnic backgrounds and with varying BMI levels.
The scientists identified a significant link between zinc deficiency and an increased risk of impaired sense of smell across all population groups. In the subgroup with a high BMI (25-30), the relationship was particularly pronounced.
The same was true for people aged 60 or older, compared to those who were younger. Additionally, the researchers found that a daily zinc intake between 9.6 and 17.45 mg offered the highest level of protection against loss of smell. For those with a daily zinc intake either below 9.6 mg or above 17.75 mg, there was an increased risk of losing their sense of smell.
The researchers recommend that populations with insufficient zinc intake increase their zinc consumption to improve overall health and maintain their sense of smell. On the other hand, excessive zinc intake should be avoided, as it can interfere with iodine utilization over time.

Zinc Sources and Common Causes of Deficiency

Good sources of zinc include shellfish, organ meats, meat, eggs, and dairy products. Zinc can also be found in nuts, seeds, and beans, but animal-based sources are the most easily absorbed.
Common causes of zinc deficiency include one-sided diets, alcohol abuse, the aging process, celiac disease (gluten sensitivity), and diabetes. Additionally, excessive calcium intake from dairy products and supplements, antacid medications, diuretics, ACE inhibitors, corticosteroids, antibiotics, and birth control pills can hinder the absorption or utilization of zinc.

Facts about zinc’s role in immune defense and in our sense of taste and smell

• Zinc supports over 300 essential enzyme processes crucial for overall health.
• Zinc plays a key role in our sense of taste and smell.
• Zinc bolsters the immune defense by stabilizing cell membranes and protecting them from viral attacks.
• Zinc also aids the powerful SOD antioxidant (superoxide dismutase), which counteracts cellular damage caused by free radicals and oxidative stress.
• A zinc deficiency can weaken cell membranes and impair immune function, making the body more vulnerable to infections, inflammation, and localized cellular damage.
• Previous research has shown that zinc deficiencies are common among COVID-19 patients, increasing the risk of infection and loss of smell.

References:

Yifang Wang et al. Association between dietary zinc intake and olfactory dysfunction: a study based on the NHANES database. Rhinology 2024

Anne Sophie Thingsted. Mistet lugtesans er det sikreste symptom på COVID-19. Videnskab.dk 19. januar 2021

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