Expression analysis of zinc-metabolizing enzymes in the saliva as a new method of evaluating zinc content in the body: two case reports and a review of the literature.

BACKGROUND: The activity level of alkaline phosphatase, a zinc-requiring enzyme in the serum, is used to indicate zinc nutritional status; however, it does not correlate with serum zinc levels or subjective symptoms of taste disorder in many cases. Hence, this study focused on the total activity of alkaline phosphatase, a zinc-requiring enzyme. The total alkaline phosphatasa activity level in the saliva was measured before and after zinc supplementation, and the results were compared with serum zinc levels. CASE PRESENTATION: This study included patients with hypozincemia, specifically a patient with zinc-deficient taste disorder (patient 1: a 69-year-old Japanese woman) and a patient with glossodynia with zinc deficiency (patient 2: an 82-year-old Japanese woman). Saliva samples were collected, and blood tests were performed before and after zinc supplementation. Subjective symptoms and serum zinc levels were simultaneously evaluated. Zinc supplementation was performed using zinc acetate hydrate or Polaprezinc. CONCLUSIONS: Total alkaline phosphatase activity levels were found to be associated with serum zinc levels and subjective symptoms. A further study with a higher number of patients is necessary to confirm whether total alkaline phosphatase activity levels more accurately reflect the amounts of zinc in the body than serum zinc levels.

Diagnosis and treatment of taste disorders in Japan.

Though 270,000 patients with complaints of taste abnormalities visited medical institutions annually in 2019 survey, there are no drugs for the treatment of taste disorders that are covered by health insurance in Japan. In the survey, the number of patients with taste disorders was correlated with age, and the need for medical treatment for taste disorders is expected to increase in the future because of the super-aging society. The pathophysiology of taste disorders varies widely. There is an obvious need to decide the site and the causes of the disorder and understand the mechanism, by performing various examinations. It needs to first adjust the causative systemic diseases and medications in the treatment for taste disorder. Damage of taste cells due to zinc deficiency is the main pathophysiological mechanism of taste disorders, and zinc supplementation is a standard treatment in Japan. Oral zinc therapy is the treatment for taste disorders due to zinc deficiency or idiopathic taste disorder; though a double-blind study was conducted, it was considered low-level evidence in a clinical review. In Japan, the off-label use of polaprezinc for taste disorders was approved in 2011, and zinc acetate hydrate was approved for hypozincemia in March 2017, making it easier to use oral zinc therapy in general. In some cases, psychotherapy or herbal medicine therapy has been used with remarkable success, although its effectiveness has not been clearly tested. It might be expected to offer some help to patients. In the treatment of elderly patients with taste disorders, physicians need to consider the difference between "age-related changes in taste in healthy people" and "taste disorders in elderly persons", and they should separate them. Aggressive treatment is desirable regardless of age, because no significant difference in the efficacy of various treatments was found between patients older and younger than 65 years.

Part Two: Perspectives on Olfactory and Gustatory Dysfunction Pathophysiology, Management, and Relevance to COVID-19: Current Approaches.

Context: The phenomena of olfactory and gustatory dysfunction disorders (OGD) are hardly unique to COVID-19. However, the widespread incidence of OGD as sequelae of COVID-19 has provoked rejuvenated interest in these long existing, but poorly studied maladies. Objective: This second of a three-part review discusses past and current approaches for treatment of OGD, not restricted to those that COVID-19 has caused, with the intention to lay a foundation for consideration of new paradigms for evaluation and management of OGD. Design: The researcher performed a narrative review by searching databases including PubMed, Sciencedirect, Google Scholar, Old Dominion University Libraries, and the websites of various medical journals. Searches included numerous combinations of keywords accompanied by the phrases, loss of sense of smell and taste, olfactory and gustatory dysfunction disorders, as well as the terms anosmia, parosmia, ageusia, and parageusia. Such keywords included viruses, bacteria, fungi, protozoa, parasites, infection, COVID-19, treatments, medications, steroids, supplements, nutrients, alternative medicine, acupuncture, olfactory training, clinical trials, cranial nerves, pathogenesis, pathophysiology, and etiology. Setting: The Liebell Clinic, Virginia Beach, VA, USA. Conclusions: The epidemiology and hypotheses of pathophysiology of post-COVID OGD has been addressed via numerous studies and reviews. However, extremely limited evidence of effective treatment for chronic OGD, in general, exists, Global demand for any treatment capable of reducing or resolving it is unprecedented. Past and present treatment approaches and recently initiated clinical trials, since the onset of the pandemic, have yet to yield any significant results.

Perspectives on the Pathophysiology, Management, and Relevance of Olfactory and Gustatory Dysfunction to COVID-19, Part One.

Context: Amelioration of olfactory and gustatory dysfunction (OGD) disorders has become a common requirement due to COVID-19. Although it's hardly exclusive to COVID-19, OGD's prevalence requires exploration of therapeutic and restorative modalities, on the broadest scale possible. No specific medication or treatment of any noteworthy efficacy exists for OGD. Objective: As Part 1 of a three-part article, a narrative review intended to examine the known causes of OGD, not restricted to COVID-19, and frame their relevance for development of new treatments or the repurposing of existing ones. Design: The researcher performed a narrative review by searching databases including PubMed, Sciencedirect, Google Scholar, Old Dominion University Libraries, and the websites of various medical journals. Searches included numerous combinations of keywords accompanied by the phrases, loss of sense of smell and taste, olfactory and gustatory dysfunction disorders, as well as the terms anosmia, parosmia, ageusia, and parageusia. Such keywords included viruses, bacteria, fungi, protozoa, parasites, infection, COVID-19, treatments, medications, steroids, supplements, nutrients, alternative medicine, acupuncture, olfactory training, clinical trials, cranial nerves, pathogenesis, pathophysiology, and etiology. Setting: The Liebell Clinic, Virginia Beach, VA, USA. Results: Scientific investigation into mechanisms and treatment of OGD appears to be historically limited and unremarkable. Medical literature spanning decades reports a bleak clinical outlook with an abundance of speculation and hypotheses. Limited evidence of effective or reliable treatment exists, especially for chronic cases. Conclusions: With a dismal lack of medical support for a suddenly prevalent, but hardly novel set of maladies of taste and smell perception; the imperative for multifaceted and broad investigations across all medical disciplines is without question. Global urgency for the development of any treatment capable of reducing or resolving OGD triggered by COVID-19 is unprecedented. Part 2 of the current author's three-part series will address the details of current and past treatment approaches and clinical trials.

A Literature Review of Taste Change and Zinc Deficiency After Bariatric Surgery: Could There Be a Causal Link?

In this review, we collated evidence relating to taste change and zinc deficiency in relation to bariatric surgery (BS) and effects of zinc replacement on taste perception and speculate on the possible role of zinc deficiency to induce taste change after BS. A literature search was conducted (33 studies, N = 3264). We showed that taste change and zinc deficiency are frequent complications after BS, which both typically occurred at 6 months post-surgery. Our analysis did not support a causal link between the two, but similar onset of incidences indirectly indicates a link. Supplementation with 45-50 mg of zinc sulphate, higher than current recommendation, was effective in improving taste. Further studies are required to establish the causal link between the two in the context of BS.

Efficacy of Lentinula edodes Mycelia Extract on Chemotherapy-Related Tasted Disorders in Pancreatic Cancer Patients.

Patients undergoing chemotherapy suffer from taste disorders that affect the quality of life (QOL). In this study, a randomized, double-blind, placebo-controlled trial was conducted to explore the effectiveness of AHCC®, a standardized extract of cultured Lentinula edodes mycelia, for chemotherapy-related adverse events and taste disorders in patients with gastrointestinal cancer. Patients who received chemotherapy were randomized to receive either placebo or AHCC®. The study endpoints were the incidence of anemia and taste disorders assessed with changes in nutritional parameters. Ninety-eight patients with pancreatic ductal adenocarcinoma (PDAC) were enrolled in this study, with 55 patients randomly assigned to the AHCC® group and 43 to the placebo group. The incidence of grades 2-3 anemia in the AHCC® group who were receiving chemotherapy was not significantly different compared to that of the placebo group (Risk difference; -3.1% [95% confidence intervals (CI): -22.8% to 16.9%], p = 0.8392). In the AHCC® group, the occurrence of taste disorders during chemotherapy was significantly lower, and the nutritional parameters were significantly improved compared to those in the placebo group (Risk difference; 28.6% [95% CI: 7.5% to 47.8%], p = 0.0077). AHCC® appears to prevent taste disorders in patients with advanced PDAC who were receiving chemotherapy. AHCC® is expected to enable patients who need chemotherapy to improve nutritional status and their QOL.

The efficacy and safety of acupuncture in the treatment of taste disorders after rehabilitation from COVID-19: A protocol for systematic review and meta-analysis.

BACKGROUND: Since the outbreak of the new crown pneumonia epidemic, although it has had a serious impact on people's lives and health in itself, the sequelae that accompany coronavirus disease 2019 (COVID-19) have also had a serious impact on people's mental health and quality of life. Taste disorder (TD) is one of the sequelae of COVID-19. Patients may experience reduced or even absent taste sensation, which seriously affects their real life. The efficacy of acupuncture in the treatment of taste disorders has been well reported, but there is a lack of evidence-based medical evidence. Therefore, this study set out to systematically evaluate the efficacy and safety of acupuncture in the treatment of post-COVID-19 taste disorder. METHODS: According to the retrieval strategies, randomized controlled trials on the acupuncture for COVID-19 TD were obtained from Cochrane Central Register of Controlled Trials, Embase, PubMed, Web of Science, the Chinese National Knowledge Infrastructure, the Chinese Biomedical Literature Database, the Chinese Scientific Journal Database and the Wanfang Database, regardless of publication date, or language. Studies were screened based on inclusion and exclusion criteria, and the Cochrane risk bias assessment tool was used to evaluate the quality of the studies. The meta-analysis was performed using Review Manager (RevMan 5.4) and StataSE 15.0 software. Ultimately, the evidentiary grade for the results will be evaluated. This systematic evaluation protocol is registered in PROSPERO under the registration ID CRD42022364653. RESULTS: The results of this meta-analysis will be submitted to a peer-reviewed journal for publication. CONCLUSION: This meta-analysis will evaluate the effect of acupuncture and moxibustion on TD caused by sequelae of COVID-19, providing evidence as to the treatment in these patients.

COVID-19 Induced Taste Dysfunction and Recovery: Association with Smell Dysfunction and Oral Health Behaviour.

Background and Objectives: Disruption to taste and smell are common symptoms of COVID-19 infection. The current literature overlooks taste symptoms and tends to focus on the sense of smell. Persisting cases (>28 days) of taste dysfunction are increasingly recognised as a major future healthcare challenge. This study focuses on the severity and recovery of COVID-19 induced taste loss and association with olfactory symptoms, lifestyle and oral health factors. Materials and Methods: This study was a cross-sectional survey comparing 182 rapid taste recovery participants (≤28 days) with 47 participants with prolonged taste recovery >28 days. Analyses of taste loss in association with smell loss, age, sex, illness severity, diet, BMI, vitamin-D supplementation, antidepressants, alcohol use, smoking, brushing frequency, flossing, missing teeth, appliances and number of dental restorations were conducted. Differences in the severity of the loss of sour, sweet, salt, bitter and umami tastes were explored. Results: Both the severity and the duration of taste and smell loss were closely correlated (p < 0.001). Salt taste was significantly less affected than all other taste qualities (p < 0.001). Persisting taste loss was associated with older age (mean ± 95% CI = 31.73 ± 1.23 years vs. 36.66 ± 3.59 years, p < 0.001) and reduced likelihood of using floss (odds ratio ± 95% CI = 2.22 (1.15−4.25), p = 0.047). Conclusions: Smell and taste loss in COVID-19 are closely related, although a minority of individuals can experience taste or smell dysfunction in the absence of the other. The taste of salt may be less severely affected than other taste qualities and future work exploring this finding objectively is indicated. The association of flossing with rapid taste recovery adds to the growing evidence of a link between good periodontal health and favourable COVID-19 outcomes.

Multisensory mental representation in covid-19 patients and the possibility of long-lasting gustatory and olfactory dysfunction in the CNS.

Gustatory (GD) and olfactory (OD) dysfunctions are the most frequent neurological manifestations of COVID-19. We used mental imagery as an experimental psychological paradigm to access olfactory and gustatory brain representations in 80 Italian COVID-19 adult patients (68.75% reported both OD and GD). COVID-19 patients with OD + GD have a significantly and selectively decreased vividness of odor and taste imagery, indicating that COVID-19 has an effect on their chemosensory mental representations. OD + GD length and type influenced the status of mental chemosensory representations. OD + GD were become all COVID-19 negative at the time of testing. Data suggest that patients are not explicitly aware of long-term altered chemosensory processing. However, differences emerge when their chemosensory function is implicitly assessed using self-ratings. Among patients developing OD + GD, self-ratings of chemosensory function (taste, flavor) were significantly lower as compared to those who did not. At the level of mental representation, such differences can be further detected, in terms of a reduced ability to mentally activate an odor or taste mental image. Our study shows that COVID-19 infection not only frequently causes hyposmia and dysgeusia, but that may also alter the mental representations responsible for olfactory and gustatory perception.

Photobiomodulation therapy for treatment olfactory and taste dysfunction COVID-19-related: A case report.

It is postulated that the inflammatory process resulting from SARS-CoV-2 infection is the main cause of smell and taste dysfunctions in patients. In view of this, photobiomodulation, due to its anti-inflammatory and antioxidant effects, may be a promising therapeutic modality to treat these disorders. In the present case report, we observed clinical improvement in the symptoms of anosmia and ageusia related to COVID-19 after treatment with photobiomodulation. Due to the inflammatory nature of COVID-19 and the anti-inflammatory effects, photobiomodulation antioxidants already proven in the literature make it a promising therapeutic modality, especially sequela COVID-related, including olfactory (anosmia) and taste (ageusia) dysfunction. In the present case report, the patient's olfactory and gustatory functions were re-established after 10 treatment sessions with photobiomodulation.

A Brazilian multicenter pilot case series on the efficacy of photobiomodulation therapy for COVID-19-related taste dysfunction.

BACKGROUND AND AIM: Among the most common symptoms of COVID-19 is taste dysfunction, which has a ranging clinical presentation. As well as its pathophysiology remains to be unclear, there is not enough information about the efficacy and safety of the available treatments. This study aims to report a series of cases using PBMT for the management of COVID-19-related taste impairment. CASE SERIES: 8 female and 2 male patients sought medical help for taste impairment (either partially or completely) after COVID-19 infection. Photobiomodulation therapy (PBMT) on the tongue mucosa was then proposed but with 3 different protocols. Taste perception at baseline and before every laser session was evaluated using a visual analog scale. Irrespective of the PBMT protocol, taste recovery was noted in all cases but with varying degrees of improvement. CONCLUSION: given the high prevalence rates of taste dysfunction in COVID-19 patients and the lack of information about the available treatments, PBMT seems to be a promising therapeutic modality but not dependent on the total number of laser sessions and the interval between them. The choice of the most suitable laser protocol as well as the knowledge of the exact photonic mechanisms, however, need to be better studied.

Therapeutic supplementation with zinc in the management of COVID-19-related diarrhea and ageusia/dysgeusia: mechanisms and clues for a personalized dosage regimen.

Zinc supplementation is indicated for diarrhea and taste disorders, which are both features of COVID-19 . Nevertheless, this strategy has not been tested for the treatment of these secondary complications in the current pandemic. Through an updated review, a practical appraisal was considered as a means of providing a medical nexus of therapeutic zinc regimens as an adjunct in the management of COVID-19-related diarrhea and ageusia/dysgeusia. While diarrhea and taste disorders are consequences of COVID-19, zinc supplementation is useful for non-COVID-19 patients with these clinical problems. The overwhelming evidence for supplementing with zinc in diarrhea and pneumonia is associated with the treatment of children, while for taste disorders the use of supplementing with zinc is more examined in adults. Whereas COVID-19 is more prevalent in adults, precautions should be exercised not to translate the zinc dosage used for children with diarrhea and taste disorders into the current pandemic. Therapeutic doses of zinc used for adults (∼50-150 mg/day of elemental zinc) could be included in the treatment strategies for COVID-19, but this proposal should be examined through randomized studies.

Lactoferrin supplementation for taste and smell abnormalities among patients receiving cancer chemotherapy.

PURPOSE: Taste and smell abnormalities (TSA) are common in patients receiving chemotherapy and may lead to altered nutritional intake, treatment withdrawal, and impaired quality of life. Lipid peroxidation in the oral cavity is one cause of TSA. Lactoferrin (LFN), an iron-binding salivary protein, reduces production of lipid oxidation byproducts and has been shown to reduce perception of unpleasant flavors. To assess the feasibility of LFN as a treatment for TSA, we conducted pilot investigations among patients with cancer who self-reported TSA following onset of chemotherapy. The primary objective was to assess change in subjective taste and smell perception from baseline to completion of 30 days of LFN supplementation. METHODS: Patients were treated with 750 mg LFN daily for 30 days and followed for an additional 30 days without LFN. TSA was measured via the taste and smell questionnaire (TSQ) including taste (score 0-10), smell (score 0-6), and composite scores (0-16) (0 = no TSA) at baseline, day 30, and day 60. RESULTS: A total of 26 patients enrolled; 19 remained on study at day 30 and 17 at day 60. Baseline mean TSQ scores were 6.5 (taste), 3.1 (smell), and 9.6 (composite). By day 30, mean composite TSQ score improved by 1.7 (p = 0.018); taste and smell improved by 0.6 (p = 0.062) and 1.1 (p = 0.042), respectively. From baseline to day 60, mean composite TSQ score improved by 3.8 (p < 0.0001); taste and smell improved by 1.9 (p = 0.001) and 1.8 (p = 0.003). CONCLUSIONS: Further evaluation of LFN is warranted to determine its value for improving self-reported TSA among patients receiving chemotherapy.

Does the radioactive iodine dose affect smell, taste sensation and nose function?

OBJECTIVE: To detect whether the adverse effects of post-operative radioactive iodine therapy following differentiated thyroid cancer on smell, taste and nasal functions were associated with radioactive iodine dose. METHODS: Fifty-one patients who had undergone total thyroidectomy because of differentiated thyroid cancer were divided into two groups depending on the post-operative radioactive iodine therapy dose: low dose group (50 mCi; 21 patients) and high dose group (100-150 mCi; 30 patients). The Sniffin' Sticks smell test, the Taste Strips test and the 22-item Sino-Nasal Outcome Test were performed on all patients one week before therapy, and at two months and one year following therapy. RESULTS: Statistically significant differences were detected in the Sniffin' Sticks test results, total odour scores, total taste scores and Sino-Nasal Outcome Test results between the assessment time points. There was no statistically significant difference between the low and high dose groups in terms of odour, taste or Sino-Nasal Outcome Test scores either before or after therapy. CONCLUSION: Radioactive iodine therapy has some short- and long-term adverse effects on nasal functions and taste and odour sensations, which affect quality of life. These effects are not dose-dependent.

Taste Function in Adults Undergoing Cancer Radiotherapy or Chemotherapy, and Implications for Nutrition Management: A Systematic Review.

BACKGROUND: Taste changes are commonly reported by people with cancer undergoing radio- or chemotherapy. Taste changes may compromise dietary intake and nutritional status. OBJECTIVE: To understand whether or not taste change is associated with cancer diagnosis or treatment modality in adults. METHODS: A systematic literature search up to December 31, 2019, was conducted using PubMed, Embase, and PsycInfo (International Prospective Register of Systematic Reviews protocol no. CRD42019134005). Studies in adults with cancer objectively assessing the effect of a cancer diagnosis or chemotherapy and/or radiotherapy treatment on taste function compared with healthy controls or within participant changes were included. Additional outcomes were food liking, appetite, dietary intake, nutritional status, and body composition. Reference lists of relevant articles were searched to identify additional articles. Quality was assessed using the Academy of Nutrition and Dietetics quality criteria checklist. RESULTS: A total of 24 articles were included, one of which consisted of two studies that reported the effects of radiotherapy and chemotherapy separately. From the total 25 studies reported in 24 published articles, 14 studies examined effects of radiotherapy, and remaining 11 studies examined chemotherapy. There is limited evidence of a cancer diagnosis per se contributing to taste dysfunction. Impaired taste function was reported in almost all radiotherapy studies, occurring as early as Week 3 of treatment and lasting for 3 to 24 months posttreatment. During chemotherapy, impairment of taste function was less consistently reported, occurring as early as the first few days of chemotherapy, and persisting up to 6 months posttreatment. Taxane-based chemotherapy was reported to affect taste function more than other treatments. Several studies reported reduced liking for food, appetite, and dietary intake. Only one study reported nutritional status of participants, finding no association between taste function and nutritional status. No studies examined associations between taste changes and body composition. CONCLUSIONS: This review highlights the importance of considering treatment modality in practice. Research is required to identify factors contributing to taste alteration and to inform evidence-based interventions.

An Integrated Care Strategy for the Follow-up of Patients With COVID-19-Associated Chemosensory Dysfunction.

The proportion of patients with residual olfactory and gustatory dysfunction after COVID-19 is increasing, and practical health care strategies need to be developed to manage this novel situation in otolaryngology services worldwide. Starting from our experience in a large Italian hospital, we estimated that >1500 people will complain of some form of olfactory and gustatory dysfunction in the future months in our region. We want to share our logistical and clinical integrated pathway that is aimed to screen and refer each patient to the most appropriate level of care in order to optimize resources and avoid overwhelming the available clinics.

Taste and smell disturbances in cancer patients: a scoping review of available treatments.

PURPOSE: Taste and smell disturbances in patients affected by cancer are very common, but often under-recognized symptoms. If not addressed properly, they may impact nutritional status, food enjoyment, and quality of life. Treatment tools available for clinicians to manage chemosensory alterations are limited and are often based on personal clinical experiences. The aim of this study was to assess current oncological and palliative care literature through a scoping review, in order to identify available treatments for taste and smell alterations in cancer patients. METHODS: Medline, Embase, CINAHL, ProQuest Dissertations and Theses, and Google Scholar were searched from inception until January 2020, with subject headings relevant to the domains of chemosensory alterations, palliative, and cancer care. A total of 10,718 English and French language publications were reviewed, yielding 43 articles on the researched topic. RESULTS: The heterogeneity of selected articles led to difficulties in interpretation and analysis of the available evidence. Included publications differed in study design, population sample, anticancer treatments, and measures of assessment for taste and smell disturbances. A broad variety of treatment options were described including zinc and polaprezinc, radio-protectors, vitamins and supplements, anti-xerostomia agents, active swallowing exercises, nutritional interventions, delta-9-tetrahydrocannabinol, and photobiomodulation. CONCLUSION: This scoping review identifies the current state of knowledge regarding chemosensory alterations within supportive cancer care. Despite not reaching firm conclusions, this article offers therapeutic venues to further explore in larger and more methodologically sound studies.

Remote psychophysical evaluation of olfactory and gustatory functions in early-stage coronavirus disease 2019 patients: the Bologna experience of 300 cases.

BACKGROUND: An objective evaluation of coronavirus disease 2019 in the first days of infection is almost impossible, as affected individuals are generally in home quarantine, and there is limited accessibility for the operator who should perform the test. To overcome this limitation, a recently validated psychophysical self-administered test was used, which can be performed remotely in the assessment of early-stage coronavirus disease 2019 patients. METHODS: Olfactory and gustatory functions were objectively assessed in 300 patients in the first 7 days from coronavirus disease 2019 symptom onset. RESULTS: Seventy per cent of the patients presented olfactory and/or gustatory disorders. The dysfunctions detected were mainly complete anosmia (47 per cent) or ageusia (38 per cent). A significant correlation was found between taste dysfunction and female gender (odds ratio = 1.936, p = 0.014) and fever (odds ratio = 2.132, p = 0.003). CONCLUSION: The psychophysical evaluation protocol proposed is an effective tool for the fast and objective evaluation of patients in the early stages of coronavirus disease 2019. Chemosensitive disorders have been confirmed to be frequent and early symptoms of the coronavirus infection, and, in a significant number of cases, they are the first or only manifestation of coronavirus disease 2019.

Taste disorder's management: a systematic review.

BACKGROUND: Taste disorder is a frequent drug-induced or disease-related oral trouble. Various pharmacological, surgical, or physical treatments have previously been proposed for taste function recovery. OBJECTIVES: The aim of the present systematic review was to assess the effects of palliative and curative interventions on taste recovery in light of recent literature. MATERIALS AND METHODS: In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement, a search of the literature published up to June 2019 was conducted using MEDLINE via PubMed, EMBASE, and The US National Institutes of Health Trials Register (PROSPERO registration reference: CRD 42019139315). The methodological quality of the included trials was rated with the "Delphi list For Quality Assessment of Randomized Clinical Trials" and the Newcastle-Ottawa scale. RESULTS: From the 1842 titles first identified, 28 articles met the inclusion criteria. Interventions included zinc (aspartate, sulfate, gluconate, acetate, picolinate, and Polaprezinc®), esomeprazole, L-thyroxin, bethanechol, oral glutamine, delta-9-tetrahydrocannabinol, alpha-lipoic acid, Ginkgo biloba, artificial saliva, pilocarpine, local anesthesia, and improved oral hygiene. The quality of evidence ranged from poor to high. CONCLUSION: Improving oral hygiene may promote taste ability. Zinc may prevent and alleviate taste disorder in patients undergoing head and neck radiotherapy. CLINICAL RELEVANCE: The systematic review provided evidence about the clinical efficacy of oral procedures, zinc supplementation, and palliative cares in dysgeusic patients. Further research is needed to find effective treatments with low adverse effects.

Japan's Practical Guidelines for Zinc Deficiency with a Particular Focus on Taste Disorders, Inflammatory Bowel Disease, and Liver Cirrhosis.

Zinc deficiency is common in Japan, yet awareness on this disorder is lacking. The Japanese Society of Clinical Nutrition recently issued the Japan's Practical Guideline for Zinc Deficiency 2018 setting forth criteria for diagnosing zinc deficiency, i.e., (a) one or more symptoms of zinc deficiency or low serum alkaline phosphatase, (b) ruling out other diseases, (c) low serum zinc, and (d) alleviation of symptoms upon zinc administration. Serum zinc <60 µg/dL and 60-80 µg/dL indicate zinc deficiency and marginal deficiency, respectively. Zinc deficiency symptoms vary and include dermatitis and taste disorders among others. Zinc administration improves taste in 50-82% of patients suffering from taste disorders (a common symptom of zinc deficiency). Effects of zinc administration do not appear immediately, and therapy should be continued for at least three months. Zinc deficiency often accompanies various diseases and conditions. Here, we focus on inflammatory bowel diseases and liver cirrhosis. As zinc deficiency enhances intestinal inflammation via macrophage activation, we discuss the pathological mechanism for inflammation and zinc deficiency in the context of IBD. Zinc deficiency can also lead to a nitrogen metabolic disorder in patients with liver cirrhosis. Zinc supplementation can improve not only the ammonia metabolism, but also the protein metabolism. We also discuss directions for future studies of zinc deficiency.