A possible correlation between vitamin D deficiency and loss of smell: 2 case reports

Vitamin D and smell impairment: a systematic literature review

OBJECTIVE

Smell impairment affects 60-80 per cent of individuals aged over 80 years. This review aimed to identify any association between vitamin D deficiency and smell impairment, and determine the efficacy of vitamin D to treat smell impairment.

METHODS

A literature search was conducted across four databases between the years 2000 and 2022. The literature screen was performed by two independent reviewers.

RESULTS

Seven articles were included in this review. Four studies examined the association between vitamin D deficiency and smell impairment, with three studies identifying a significant relationship. Three studies investigated the use of vitamin D as treatment for smell impairment, which found complete resolution or significant symptom improvement after vitamin D deficiency was treated.

CONCLUSION

This review identified limited studies on this topic. As vitamin D supplementation is relatively cost-efficient, further large-scale studies should be carried out to investigate the efficacy of vitamin D for treating anosmia.

Smell Regions in Patients with Vitamin D Deficiency: An MRI Evaluation

Objective  We investigated the effects of vitamin D deficiency in the peripheral and central smell regions by magnetic resonance imaging (MRI). Methods  This retrospective study included 29 patients (12 males, 17 females) with 25-dihydroxy vitamin D3 [25(OH) ₂ D ₃ ] deficiency (group 1) and 34 subjects without 25(OH) ₂ D ₃ deficiency (14 males, 20 females) (group 2). Using cranial MRIs, the peripheral (olfactory bulb [OB] volume and olfactory sulcus [OS] depth) and central (insular gyrus and corpus amygdala) smell regions were evaluated. Results  The OB volume and OS depth values of the 25(OH) ₂ D3 deficiency group were significantly lower than those of the control group ( p  < 0.05). For the central smell regions, the insular gyrus and corpus amygdala areas of the 25(OH) ₂ D3 deficiency group were nonsignificantly lower than those in the control group ( p  > 0.05). There were positive correlations between OB volumes, OS depths, and insular gyrus and corpus amygdala areas bilaterally in the 25(OH) ₂ D3 deficiency group separately and in all subjects (groups 1 and 2) ( p  < 0.05). In the 25(OH) ₂ D3 deficiency group, as the 25(OH) ₂ D3 values became lower, the insular gyrus area values decreased bilaterally ( p  < 0.05). In females, the corpus amygdala area values were lower than in males ( p  < 0.05). Conclusion  Since vitamin D3 deficiency affected the peripheral and central smell regions negatively, we recommend evaluating patients' vitamin D levels as a health policy to prevent vitamin D3 deficiency-related cranial smell region problems. Moreover, sunlight exposure is very important to increase vitamin D levels, and the public should be informed about this topic.

Association of 25-hydroxyvitamin D status with brain volume changes

Vitamin D is critical to brain function and its deficiency accelerates cognitive impairment. There is limited understanding of the brain-specific areas that undergo volume change in relation to blood vitamin D levels. The objective of this study was to evaluate the association between blood 25-hydroxyvitamin D (25(OH)D) concentration and structural changes in the brain. We analyzed structural three-dimensional T1 MRI images of 201 elderly individuals (mean age = 74.91 ± 9.21 years; 68.1% female; mean 25(OH)D = 18.05 nmol/L), with 10 community-based normal healthy subjects, 33 with subjective cognitive decline, 97 with mild cognitive impairment, and 61 with Alzheimer's disease (AD). To analyze the structural changes in the brain respective to blood 25(OH)D, multiple regression analyses were performed using voxel-based morphometry with age and total intracranial volume as covariates. Lower 25(OH)D level were associated with reduced brain volume in right olfactory, rectus GM regions (FWE-corr, p < .05) for entire subjects. For AD subjects, left parahippocampal, fusiform, and hippocampal areas were positively associated with 25(OH)D (FWE-corr, p < .05). Low blood 25(OH)D was associated with reduced volumes in olfactory and hippocampal regions in elderly patients with cognitive decline. Our results may provide insight into the neurological pathophysiology of vitamin D.

Serum vitamin D level is associated with smell dysfunction independently of aeroallergen sensitization, nasal obstruction, and the presence of allergic rhinitis in children

BACKGROUND

Smell dysfunction is highly prevalent worldwide and has adverse effects on quality of life. Smell loss in rhinitis subjects is mainly caused by mechanical obstruction of odorant transmission due to mucosal type 2 inflammation. We determined the association of 25-hydroxyvitamin D (25[OH]D) levels with the severity of smell dysfunction in children.

METHODS

We measured the olfactory threshold score in a total of 518 children (10-12 years old, 264 boys) using the Sniffin' Sticks kit, and the children were divided into tertiles according to olfactory threshold score. We also assessed serum 25[OH]D level, common aeroallergen-specific immunoglobulin E, rhinitis severity with visual analog scale, and the Total Four Symptom Score, and pre- and post-decongestant nasal patency with acoustic rhinometry.

RESULTS

The children with 25(OH)D deficiency had significantly reduced mean olfactory threshold scores when compared to those with 25(OH)D levels of ≥20.0 ng/mL (6.56 ± 3.54 and 7.28 ± 3.87, respectively, P = .036). The proportion of loss of smell function and pre-decongestant nasal patency significantly associated with low 25(OH)D levels (chi-square trend test, P for trend = .007). Likewise, after adjustment for confounders, children with smell loss (third tertile) were significantly associated with low 25(OH)D level (aβ=-0.062, 95% CI=-0.064 to -0.060, P = .009) independent of aeroallergen sensitization, and a low pre-decongestant nasal patency.

CONCLUSIONS

25-Hydroxyvitamin D is significantly associated with smell dysfunction independent of aeroallergen sensitization, nasal obstruction, and the presence of allergic rhinitis. This finding may provide insight into the mechanisms involved in the development of olfactory dysfunction.

Age-related Smell and Taste Impairments and Vitamin D Associations in the U.S. Adults National Health and Nutrition Examination Survey

Smell and taste decline with aging, and markedly deteriorate when nutritional deficiencies occur. This study aims to examine the associations between Vitamin D (VD) deficiency and smell and taste impairments among adults. This paper details a cross-sectional study utilizing data from the US National Health and Nutrition Examination Survey (NHANES, 2013–2014.). Smell impairment was assessed by the Pocket Smell Test and defined as failing to correctly identify six or more of the eight odors. Taste impairment was defined as failing to correctly identify quinine or sodium chloride. VD was measured as serum 25-hydroxyvitamin. Multivariable weighted logistic regressions were utilized. Adjusted odds ratio (OR) and 95% confidence interval (CI) were presented. Overall, 2216 (smell sample) and 2636 (taste sample) participants were included, aged between 40 and 80 years old. Of those, 18.3% had taste impairment, 12.2% had smell impairment, and 20% had VD deficiency (<20 ng/mL). Compared to participants with sufficient VD (>30 ng/mL), those with VD deficiency were more likely by 39% to report a higher prevalence of smell impairment (OR = 1.39, 95%CI: 1.02–1.89); and only participants aged 70–80 years with VD inadequacy (20–30 ng/mL) were more likely by 96% to report a higher prevalence of taste impairment (OR = 1.96, 95%CI: 1.35–1.85). VD may have a significant role in age-related smell impairment in adults aged 40 years or older, and in age-related taste impairment in the elderly aged 70–80 years.

Remission of anosmia in a patient receiving chiropractic care: A case report

OBJECTIVE

To chronicle the remission of anosmia in a 79-year-old female receiving chiropractic care using the Activator Methods Chiropractic Technique (AMCT) protocol.

CLINICAL FEATURES

A 79-year-old white female with a 4-year history of medically diagnosed anosmia. Postural alterations, reduction in cervical ranges of motion (ROM), and absent cranial nerve I function were found in conjunction with vertebral subluxation throughout the spine and mild to severe degenerative changes throughout the spine present on radiographic studies.

INTERVENTION & OUTCOMES

Chiropractic care using AMCT was provided for the assessment and correction of vertebral subluxations. The patient reported subjective improvement in olfaction, physical functioning and life enjoyment, and demonstrated objective improvement in posture, cervical ROM, cranial nerve I function.

CONCLUSION

A course of chiropractic care, following the AMCT protocol, was associated with remission of anosmia.

Treatments for smell and taste disorders: A critical review

A key concern of both the patient and physician is whether treatment is available that will eliminate or quell a given chemosensory disturbance. In cases where obvious oral, nasal, or intracranial pathology is involved, rational straightforward approaches to treatment are often available. In cases where damage to the sensory pathways is secondary to chronic inflammatory disease, trauma, viral invasion, toxic exposure, or unknown causes, the direction for therapy is more challenging. Indeed, many chemosensory disorders, if present for any period of time, cannot be reversed, while others spontaneously remit without any therapeutic intervention. This review assesses the strengths and weaknesses of more than two dozen approaches to treatment that have been suggested for a wide range of taste and smell disorders.

Relationship of socioeconomic status to olfactory function

Socioeconomic status can significantly impact health. To what degree education and other socioeconomic factors influence the chemical sense of olfaction is not clear. Most studies that have assessed such influences come from countries lacking large disparities in education and income and generally view such measures as nuisance variables to be controlled for statistically. In this study, we evaluated the influences of education and income on odor identification in a diverse sample of subjects from Brazil, a society where large disparities in both income and education are present. The 40-item University of Pennsylvania Smell Identification Test (UPSIT) was administered to 1572 healthy Brazilian citizens with no self-reported olfactory or gustatory deficits and for whom detailed socioeconomic and educational status data were obtained. Univariate and multivariate models were employed to examine the influence of socioeconomic status on the test scores. After controlling for age, sex, ethnicity, and smoking behavior, income and educational level were positively and independently related to the olfactory test scores (respective ps < 0.001 & 0.01). Both linear and quadratic functions described the relationship between the UPSIT scores and the levels of education and socioeconomic status. Individuals of lower socioeconomic status performed significantly worse than those of higher socioeconomic status on 20 of the 40 odorant items. This study demonstrates socioeconomic status is significantly associated with influence the ability to identify odors. The degree to which this reflects differential exposures to xenobiotic agents, cultural differences, familiarity with odors or their names, cognitive development, or other factors requires further investigation.