A randomized, placebo controlled trial of oral zinc for chemotherapy-related taste and smell disorders

The role of metals in mammalian olfaction of low molecular weight organosulfur compounds

Covering: up to the end of 2017While suggestions concerning the possible role of metals in olfaction and taste date back 50 years, only recently has it been possible to confirm these proposals with experiments involving individual olfactory receptors (ORs). A detailed discussion of recent experimental results demonstrating the key role of metals in enhancing the response of human and other vertebrate ORs to specific odorants is presented against the backdrop of our knowledge of how the sense of smell functions both at the molecular and whole animal levels. This review emphasizes the role of metals in the detection of low molecular weight thiols, sulfides, and other organosulfur compounds, including those found in strong-smelling animal excretions and plant volatiles, and those used in gas odorization. Alternative theories of olfaction are described, with evidence favoring the modified "shape" theory. The use of quantum mechanical/molecular modeling (QM/MM), site-directed mutagenesis and saturation-transfer-difference (STD) NMR is discussed, providing support for biological studies of mouse and human receptors, MOR244-3 and OR OR2T11, respectively. Copper is bound at the active site of MOR244-3 by cysteine and histidine, while cysteine, histidine and methionine are involved with OR2T11. The binding pockets of these two receptors are found in different locations in the three-dimensional seven transmembrane models. Another recently deorphaned human olfactory receptor, OR2M3, highly selective for a thiol from onions, and a broadly-tuned thiol receptor, OR1A1, are also discussed. Other topics covered include the effects of nanoparticles and heavy metal toxicants on vertebrate and fish ORs, intranasal zinc products and the loss of smell (anosmia).

Olfactory Development, Part 1: Function, From Fetal Perception to Adult Wine-Tasting

Discrimination of odorous molecules in amniotic fluid occur after 30 weeks' gestation; fetuses exhibit differential responses to maternal diet. Olfactory reflexes enable reliable neonatal testing. Olfactory bulbs can be demonstrated reliably by MRI after 30 weeks' gestation, and their hypoplasia or aplasia also documented by late prenatal and postnatal MRI. Olfactory axons project from nasal epithelium to telencephalon before olfactory bulbs form. Fetal olfactory maturation remains incomplete at term for neuronal differentiation, synaptogenesis, myelination, and persistence of the transitory fetal ventricular recess. Immaturity does not signify nonfunction. Olfaction is the only sensory system without thalamic projection because of its own intrinsic thalamic equivalent. Diverse malformations of the olfactory bulb can be diagnosed by clinical examination, imaging, and neuropathology. Some epileptic auras might be primarily generated in the olfactory bulb. Cranial nerve 1 should be tested in all neonates and especially in patients with brain malformations, endocrinopathies, chromosomopathies, and genetic/metabolic diseases.

Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage

OBJECTIVE

To compare the efficacy of zinc acetate lozenges with zinc gluconate lozenges in common cold treatment and to examine the dose-dependency of the effect.

DESIGN

Meta-analysis.

SETTING

Placebo-controlled zinc lozenge trials, in which the zinc dose was > 75 mg/day. The pooled effect of zinc lozenges on common cold duration was calculated by using inverse-variance random-effects method.

PARTICIPANTS

Seven randomised trials with 575 participants with naturally acquired common colds.

MAIN OUTCOME MEASURE

Duration of the common cold.

RESULTS

The mean common cold duration was 33% (95% CI 21% to 45%) shorter for the zinc groups of the seven included trials. Three trials that used lozenges composed of zinc acetate found that colds were shortened by 40% and four trials that used zinc gluconate by 28%. The difference between the two salts was not significant: 12 percentage points (95% CI: -12 to + 36). Five trials used zinc doses of 80-92 mg/day, common cold duration was reduced by 33%, and two trials used zinc doses of 192-207 mg/day and found an effect of 35%. The difference between the high-dose and low-dose zinc trials was not significant: 2 percentage points (95% CI: -29 to + 32).

CONCLUSIONS

Properly composed zinc gluconate lozenges may be as effective as zinc acetate lozenges. There is no evidence that zinc doses over 100 mg/day might lead to greater efficacy in the treatment of the common cold. Common cold patients may be encouraged to try zinc lozenges for treating their colds. The optimal lozenge composition and dosage scheme need to be investigated further.

Anosmia: Differential diagnosis, evaluation, and management

The ability to scrutinize our surroundings remains heavily dependent on the sense of smell. From the ability to detect dangerous situations such as fires to the recollection of a fond memory triggered by an odor, the advantages of an intact olfactory system cannot be overstated. Outcomes studies have highlighted the profound negative impact of anosmia and parosmia on the overall quality of life. The National Institute on Deafness and Other Communication Disorders estimates that ∼1.4% of the United States population experiences chronic olfactory dysfunction and smell loss. Efforts have focused on improving both the diagnosis of olfactory dysfunction through olfactory testing and improved reporting of treatment outcomes of olfactory training. The purpose of this article was to review the differential diagnosis, workup, and current treatment strategies of anosmia and smell disorders.

Zinc acetate lozenges for treating the common cold: an individual patient data meta-analysis

AIMS

The aim of this study was to determine whether the allergy status and other characteristics of common cold patients modify the effects of zinc acetate lozenges.

METHODS

We had available individual patient data for three randomized placebo-controlled trials in which zinc acetate lozenges were administered to common cold patients. We used both one stage and two stage meta-analysis to estimate the effects of zinc lozenges.

RESULTS

The total number of common cold patients was 199, the majority being females. Eighty percent of them fell into the age range 20-50 years. One third of the patients had allergies. The one stage meta-analysis gave an overall estimate of 2.73 days (95% CI 1.8, 3.3 days) shorter colds by zinc acetate lozenge usage. The two stage meta-analysis gave an estimate of 2.94 days (95% CI 2.1, 3.8 days) reduction in common cold duration. These estimates are to be compared with the 7 day average duration of colds in the three trials. The effect of zinc lozenges was not modified by allergy status, smoking, baseline severity of the common cold, age, gender or ethnic group.

CONCLUSION

Since the effects of zinc acetate lozenges were consistent between the compared subgroups, the overall estimates for effect seemed applicable over a wide range of common cold patients. While the optimal composition of zinc lozenges and the best frequency of their administration should be further investigated, given the current evidence of efficacy, common cold patients may be encouraged to try zinc lozenges for treating their colds.

ESPEN guidelines on nutrition in cancer patients

Cancers are among the leading causes of morbidity and mortality worldwide, and the number of new cases is expected to rise significantly over the next decades. At the same time, all types of cancer treatment, such as surgery, radiation therapy, and pharmacological therapies are improving in sophistication, precision and in the power to target specific characteristics of individual cancers. Thus, while many cancers may still not be cured they may be converted to chronic diseases. All of these treatments, however, are impeded or precluded by the frequent development of malnutrition and metabolic derangements in cancer patients, induced by the tumor or by its treatment. These evidence-based guidelines were developed to translate current best evidence and expert opinion into recommendations for multi-disciplinary teams responsible for identification, prevention, and treatment of reversible elements of malnutrition in adult cancer patients. The guidelines were commissioned and financially supported by ESPEN and by the European Partnership for Action Against Cancer (EPAAC), an EU level initiative. Members of the guideline group were selected by ESPEN to include a range of professions and fields of expertise. We searched for meta-analyses, systematic reviews and comparative studies based on clinical questions according to the PICO format. The evidence was evaluated and merged to develop clinical recommendations using the GRADE method. Due to the deficits in the available evidence, relevant still open questions were listed and should be addressed by future studies. Malnutrition and a loss of muscle mass are frequent in cancer patients and have a negative effect on clinical outcome. They may be driven by inadequate food intake, decreased physical activity and catabolic metabolic derangements. To screen for, prevent, assess in detail, monitor and treat malnutrition standard operating procedures, responsibilities and a quality control process should be established at each institution involved in treating cancer patients. All cancer patients should be screened regularly for the risk or the presence of malnutrition. In all patients - with the exception of end of life care - energy and substrate requirements should be met by offering in a step-wise manner nutritional interventions from counseling to parenteral nutrition. However, benefits and risks of nutritional interventions have to be balanced with special consideration in patients with advanced disease. Nutritional care should always be accompanied by exercise training. To counter malnutrition in patients with advanced cancer there are few pharmacological agents and pharmaconutrients with only limited effects. Cancer survivors should engage in regular physical activity and adopt a prudent diet.

Efficacy and Interaction of Antioxidant Supplements as Adjuvant Therapy in Cancer Treatment: A Systematic Review

Oxidative stress is a key component in carcinogenesis. Although radiation produces reactive oxygen species, some anticancer agents such as alkylating agents, platinum and antitumor antibiotics exert cytotoxicity by generating free radicals. Nonenzymatic exogenous antioxidants such as vitamins, minerals, and polyphenols can quench ROS activity. However, whether antioxidants alter antitumor effects during radiotherapy and some types of chemotherapy remains unclear. In the present study, we reviewed antioxidants as an adjuvant therapy for cancer patients during chemotherapy or radiotherapy. Electronic literature searches were performed to select all randomized controlled clinical trials (RCTs) in which antioxidants were administered to cancer patients along with chemotherapy or radiotherapy. Articles or abstracts written in English were included. In total, 399 reports received primary screening. Duplicated articles and those meeting the exclusion criteria (not RCT, not human, and no oral administration) were excluded. Finally, 49 reports matching the inclusion criteria were included. It was difficult to determine whether antioxidants affect treatment outcomes or whether antioxidants ameliorate adverse effects induced by chemotherapy and radiotherapy. It is desirable to use an evidence-based method to select supplements best suited to cancer patients. Although there are many opinions about risks or benefits of antioxidant supplementation, we could mostly conclude that the harm caused by antioxidant supplementation remains unclear for patients during cancer therapy, except for smokers undergoing radiotherapy.

Taste dysfunction in patients undergoing hematopoietic stem cell transplantation: Clinical evaluation in children

The aim of this study was to determine the variability of TD in children undergoing HSCT. Cases were identified as consecutively enrolled children in the period January 2011-January 2013 among patients attending the Paediatric Department of Spedali Civili of Brescia and all candidates to HSCT. The TST was conducted in two phases: identification of threshold values and identification of perceived stimulus intensity. Sixteen sapid solutions with four flavors (sucrose, sodium chloride, citric acid, and quinine hydrochloride) at four different concentrations were administered in a random sequence. The same protocol was administered at different time intervals: before starting the conditioning therapy (T0), during the conditioning therapy (T1) (two times), and every three months (two times) after engraftment post-HSCT (T2). A p-value < 0.05 was considered statistically significant. Fifty-one children (29 female and 22 male, mean age 5.2 ± 0.7 yr) were enrolled. Threshold value means for the four flavors increased during HSCT conditioning therapy (T1) (p < 0.01); intensity of perceived stimulus decreased during HSCT conditioning therapy (p < 0.01). At six months after engraftment (T2), both parameters had returned to starting values (T0). Changes in taste perception in children undergoing HSCT seem to occur especially during the conditioning therapy and resolve in about six months after engraftment post-HSCT.

Interventions for the management of taste disturbances

BACKGROUND

The sense of taste is very much essential to the overall health of the individual. It is a necessary component to enjoying one's food, which in turn provides nutrition to an individual. Any disturbance in taste perception can hamper the quality of life in such patients by influencing their appetite, body weight and psychological well-being. Taste disorders have been treated using different modalities of treatment and there is no consensus for the best intervention. Hence this Cochrane systematic review was undertaken.

OBJECTIVES

To assess the effects of interventions for the management of patients with taste disturbances.

SEARCH METHODS

We searched the Cochrane Oral Health Group Trials Register (to 5 March 2014), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 1, 2014), MEDLINE via OVID (1948 to 5 March 2014), EMBASE via OVID (1980 to 5 March 2014), CINAHL via EBSCO (1980 to 5 March 2014) and AMED via OVID (1985 to 5 March 2014). We also searched the relevant clinical trial registries and conference proceedings from the International Association of Dental Research/American Association of Dental Research (to 5 March 2014), Association for Research in Otolaryngology (to 5 March 2014), the US National Institutes of Health Trials Register (to 5 March 2014), metaRegister of Controlled Trials (mRCT) (to 5 March 2014), World Health Organization's International Clinical Trials Registry Platform (WHO ICTRP) (to 5 March 2014) and International Federation of Pharmaceutical Manufacturers and Associations (IFPMA) Clinical Trials Portal (to 5 March 2014).

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) comparing any pharmacological agent with a control intervention or any non-pharmacological agent with a control intervention. We also included cross-over trials in the review.

DATA COLLECTION AND ANALYSIS

Two authors independently, and in duplicate, assessed the quality of trials and extracted data. Wherever possible, we contacted study authors for additional information. We collected adverse events information from the trials.

MAIN RESULTS

We included nine trials (seven parallel and two cross-over RCTs) with 566 participants. We assessed three trials (33.3%) as having a low risk of bias, four trials (44.5%) at high risk of bias and two trials (22.2%) as having an unclear risk of bias. We only included studies on taste disorders in this review that were either idiopathic, or resulting from zinc deficiency or chronic renal failure.Of these, eight trials with 529 people compared zinc supplements to placebo for patients with taste disorders. The participants in two trials were children and adolescents with respective mean ages of 10 and 11.2 years and the other six trials had adult participants. Out of these eight, two trials assessed the patient reported outcome for improvement in taste acuity using zinc supplements (RR 1.45, 95% CI 1.0 to 2.1; very low quality evidence). We included three trials in the meta-analysis for overall taste improvement (effect size 0.44, 95% CI 0.23 to 0.65; moderate quality evidence). Two other trials described the results as taste acuity improvement and we conducted subgroup analyses due to clinical heterogeneity. One trial described the results as taste recognition improvement for each taste sensation and we analysed this separately. We also analysed one cross-over trial separately using the first half of the results. None of the zinc trials tested taste discrimination. Only one trial tested taste discrimination using acupuncture (effect size 2.80, 95% CI -1.18 to 6.78; low quality evidence).Out of the eight trials using zinc supplementation, four reported adverse events like eczema, nausea, abdominal pain, diarrhoea, constipation, decrease in blood iron, increase in blood alkaline phosphatase, and minor increase in blood triglycerides. No adverse events were reported in the acupuncture trial.None of the included trials could be included in the meta-analysis for health-related quality of life in taste disorder patients.

AUTHORS' CONCLUSIONS

We found very low quality evidence that was insufficient to conclude on the role of zinc supplements to improve taste perception by patients, however we found moderate quality evidence that zinc supplements improve overall taste improvement in patients with zinc deficiency/idiopathic taste disorders. We also found low quality evidence that zinc supplements improve taste acuity in zinc deficient/idiopathic taste disorders and very low quality evidence for taste recognition improvement in children with taste disorders secondary to chronic renal failure. We did not find any evidence to conclude the role of zinc supplements for improving taste discrimination, or any evidence addressing health-related quality of life due to taste disorders.We found low quality evidence that is not sufficient to conclude on the role of acupuncture for improving taste discrimination in cases of idiopathic dysgeusia (distortion of taste) and hypogeusia (reduced ability to taste). We were unable to draw any conclusions regarding the superiority of zinc supplements or acupuncture as none of the trials compared these interventions.

Preventive effects of zinc sulfate on taste alterations in patients under irradiation for head and neck cancers: A randomized placebo-controlled trial

BACKGROUND

Taste abnormalities are common among cancer patients after starting radiotherapy or chemotherapy. Considering the role of zinc and reports on its beneficial effects in taste perception, we evaluated the preventive effects of zinc sulfate on radiation-induced taste alterations.

MATERIALS AND METHODS

In a randomized, placebo-controlled trial, adult patients with head and neck cancers who were on schedule for radiotherapy, with or without chemotherapy, were allocated to receive zinc sulfate (50 mg, three times a day) or placebo; started with beginning of radiotherapy and continued for one month later. Taste acuity was determined by measuring detection and recognition thresholds for four taste qualities at baseline, at the end of radiotherapy, and a month later using the Henkin method.

RESULTS

Thirty-five patients (mean age = 59.2 ± 16.5, 60% male) completed the trial. The two groups were similar at baseline. After radiotherapy, and one month later, there was a significant increase in taste perception threshold for bitter, salty, sweet, and sour tastes in the placebo group (P = 0.001). In those who received zinc, there was only slight increase in threshold for perception of the salty taste (P = 0.046). No relevant side effects due to zinc sulfate were reported.

CONCLUSION

Zinc supplementation in head/neck cancer patients under radiotherapy can prevent radiation-induced taste alterations. Further studies with longer follow-ups and with different doses of zinc supplementation are warranted in this regard.