Zinc supplements for treating thalassaemia and sickle cell disease

Antioxidant supplementation for sickle cell disease

BACKGROUND

Sickle cell disease (SCD) refers to a group of genetic disorders characterized by the presence of an abnormal haemoglobin molecule called haemoglobin S (HbS). When subjected to oxidative stress from low oxygen concentrations, HbS molecules form rigid polymers, giving the red cell the typical sickle shape. Antioxidants have been shown to reduce oxidative stress and improve outcomes in other diseases associated with oxidative stress. Therefore, it is important to review and synthesize the available evidence on the effect of antioxidants on the clinical outcomes of people with SCD.

OBJECTIVES

To assess the effectiveness and safety of antioxidant supplementation for improving health outcomes in people with SCD.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was 15 August 2023.

SELECTION CRITERIA

We included randomized and quasi-randomized controlled trials comparing antioxidant supplementation to placebo, other antioxidants, or different doses of antioxidants, in people with SCD.

DATA COLLECTION AND ANALYSIS

Two authors independently extracted data, assessed the risk of bias and certainty of the evidence, and reported according to Cochrane methodological procedures.

MAIN RESULTS

The review included 1609 participants in 26 studies, with 17 comparisons. We rated 13 studies as having a high risk of bias overall, and 13 studies as having an unclear risk of bias overall due to study limitations. We used GRADE to rate the certainty of evidence. Only eight studies reported on our important outcomes at six months. Vitamin C (1400 mg) plus vitamin E (800 mg) versus placebo Based on evidence from one study in 83 participants, vitamin C (1400 mg) plus vitamin E (800 mg) may not be better than placebo at reducing the frequency of crisis (risk ratio (RR) 1.18, 95% confidence interval (CI) 0.64 to 2.18), the severity of pain (RR 1.33, 95% CI 0.40 to 4.37), or adverse effects (AE), of which the most common were headache, nausea, fatigue, diarrhoea, and epigastric pain (RR 0.56, 95% CI 0.31 to 1.00). Vitamin C plus vitamin E may increase the risk of SCD-related complications (acute chest syndrome: RR 2.66, 95% CI 0.77 to 9.13; 1 study, 83 participants), and increase haemoglobin level (median (interquartile range) 90 (81 to 96) g/L versus 93.5 (84 to 105) g/L) (1 study, 83 participants) compared to placebo. However, the evidence for all the above effects is very uncertain. The study did not report on quality of life (QoL) of participants and their caregivers, nor on frequency of hospitalization. Zinc versus placebo Zinc may not be better than placebo at reducing the frequency of crisis at six months (rate ratio 0.62, 95% CI 0.17 to 2.29; 1 study, 36 participants; low-certainty evidence). We are uncertain whether zinc is better than placebo at improving sickle cell-related complications (complete healing of leg ulcers at six months: RR 2.00, 95% CI 0.60 to 6.72; 1 study, 34 participants; very low-certainty evidence). Zinc may be better than placebo at increasing haemoglobin level (g/dL) (MD 1.26, 95% CI 0.44 to 1.26; 1 study, 36 participants; low-certainty evidence). The study did not report on severity of pain, QoL, AE, and frequency of hospitalization. N-acetylcysteine versus placebo N-acetylcysteine (NAC) 1200 mg may not be better than placebo at reducing the frequency of crisis in SCD, reported as pain days (rate ratio 0.99 days, 95% CI 0.53 to 1.84; 1 study, 96 participants; low-certainty evidence). Low-certainty evidence from one study (96 participants) suggests NAC (1200 mg) may not be better than placebo at reducing the severity of pain (MD 0.17, 95% CI -0.53 to 0.87). Compared to placebo, NAC (1200 mg) may not be better at improving physical QoL (MD -1.80, 95% CI -5.01 to 1.41) and mental QoL (MD 2.00, 95% CI -1.45 to 5.45; very low-certainty evidence), reducing the risk of adverse effects (gastrointestinal complaints, pruritus, or rash) (RR 0.92, 95% CI 0.75 to 1.14; low-certainty evidence), reducing the frequency of hospitalizations (rate ratio 0.98, 95% CI 0.41 to 2.38; low-certainty evidence), and sickle cell-related complications (RR 5.00, 95% CI 0.25 to 101.48; very low-certainty evidence), or increasing haemoglobin level (MD -0.18 g/dL, 95% CI -0.40 to 0.04; low-certainty evidence). L-arginine versus placebo L-arginine may not be better than placebo at reducing the frequency of crisis (monthly pain) (RR 0.71, 95% CI 0.26 to 1.95; 1 study, 50 participants; low-certainty evidence). However, L-arginine may be better than placebo at reducing the severity of pain (MD -1.41, 95% CI -1.65 to -1.18; 2 studies, 125 participants; low-certainty evidence). One participant allocated to L-arginine developed hives during infusion of L-arginine, another experienced acute clinical deterioration, and a participant in the placebo group had clinically relevant increases in liver function enzymes. The evidence is very uncertain whether L-arginine is better at reducing the mean number of days in hospital compared to placebo (MD -0.85 days, 95% CI -1.87 to 0.17; 2 studies, 125 participants; very low-certainty evidence). Also, L-arginine may not be better than placebo at increasing haemoglobin level (MD 0.4 g/dL, 95% CI -0.50 to 1.3; 2 studies, 106 participants; low-certainty evidence). No study in this comparison reported on QoL and sickle cell-related complications. Omega-3 versus placebo Very low-certainty evidence shows no evidence of a difference in the risk of adverse effects of omega-3 compared to placebo (RR 1.05, 95% CI 0.74 to 1.48; 1 study, 67 participants). Very low-certainty evidence suggests that omega-3 may not be better than placebo at increasing haemoglobin level (MD 0.36 g/L, 95% CI -0.21 to 0.93; 1 study, 67 participants). The study did not report on frequency of crisis, severity of pain, QoL, frequency of hospitalization, and sickle cell-related complications.

AUTHORS' CONCLUSIONS

There was inconsistent evidence on all outcomes to draw conclusions on the beneficial and harmful effects of antioxidants. However, L-arginine may be better than placebo at reducing the severity of pain at six months, and zinc may be better than placebo at increasing haemoglobin level. We are uncertain whether other antioxidants are beneficial for SCD. Larger studies conducted on each comparison would reduce the current uncertainties.

Zinc for infection prevention in children with sickle cell anemia: a randomized double-blind placebo-controlled trial

Data from small clinical trials in the United States and India suggest zinc supplementation reduces infection in adolescents and adults with sickle cell anemia (SCA), but no studies of zinc supplementation for infection prevention have been conducted in children with SCA living in Africa. We conducted a randomized double-blind placebo-controlled trial to assess zinc supplementation for prevention of severe or invasive infections in Ugandan children 1.00-4.99 years with SCA. Of 252 enrolled participants, 124 were assigned zinc (10 mg) and 126 assigned placebo once daily for 12 months. The primary outcome was incidence of protocol-defined severe or invasive infections. Infection incidence did not differ between treatment arms (282 vs. 270 severe or invasive infections per 100 person-years, respectively, incidence rate ratio of 1.04 [95% confidence interval (CI), 0.81, 1.32, p=0.78]), adjusting for hydroxyurea treatment. There was also no difference between treatment arms in incidence of serious adverse events or SCA-related events. Children receiving zinc had increased serum levels after 12-months, but at study exit, 41% remained zinc deficient (<65 μg/dL). In post-hoc analysis, occurrence of stroke or death was lower in the zinc treatment arm (adjusted hazard ratio (95% CI), 0.22 (0.05, 1.00); p=0.05). Daily 10 mg zinc supplementation for 12 months did not prevent severe or invasive infections in Ugandan children with SCA, but many supplemented children remained zinc deficient. Optimal zinc dosing and the role of zinc in preventing stroke or death in SCA warrant further investigation. This trial was registered at clinicaltrials.gov as #NCT03528434.

Treatment for osteoporosis in people with beta-thalassaemia

BACKGROUND

Osteoporosis is characterized by low bone mass and micro-architectural deterioration of bone tissue leading to increased bone fragility. In people with beta-thalassaemia, osteoporosis represents an important cause of morbidity and is due to a number of factors. First, ineffective erythropoiesis causes bone marrow expansion, leading to reduced trabecular bone tissue with cortical thinning. Second, excessive iron loading causes endocrine dysfunction, leading to increased bone turnover. Lastly, disease complications can result in physical inactivity, with a subsequent reduction in optimal bone mineralization. Treatments for osteoporosis in people with beta-thalassaemia include bisphosphonates (e.g. clodronate, pamidronate, alendronate; with or without hormone replacement therapy (HRT)), calcitonin, calcium, zinc supplementation, hydroxyurea, and HRT alone (for preventing hypogonadism). Denosumab, a fully human monoclonal antibody, inhibits bone resorption and increases bone mineral density (BMD). Finally, strontium ranelate simultaneously promotes bone formation and inhibits bone resorption, thus contributing to a net gain in BMD, increased bone strength, and reduced fracture risk. This is an update of a previously published Cochrane Review.

OBJECTIVES

To review the evidence on the efficacy and safety of treatment for osteoporosis in people with beta-thalassaemia.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register, which includes references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. We also searched online trial registries. Date of most recent search: 4 August 2022.

SELECTION CRITERIA

Randomized controlled trials (RCTs) in people with beta-thalassaemia with: a BMD Z score below -2 standard deviations (SDs) for children aged under 15 years, adult males (aged 15 to 50 years) and premenopausal females aged over 15 years; or a BMD T score below -2.5 SDs for postmenopausal females and males aged over 50 years.

DATA COLLECTION AND ANALYSIS

Two review authors assessed the eligibility and risk of bias of the included RCTs, and extracted and analysed data. We assessed the certainty of the evidence using GRADE.

MAIN RESULTS

We included six RCTs (298 participants). Active interventions included bisphosphonates (3 trials, 169 participants), zinc supplementation (1 trial, 42 participants), denosumab (1 trial, 63 participants), and strontium ranelate (1 trial, 24 participants). The certainty of the evidence ranged from moderate to very low and was downgraded mainly due to concerns surrounding imprecision (low participant numbers), but also risk of bias issues related to randomization, allocation concealment, and blinding. Bisphosphonates versus placebo or no treatment Two RCTs compared bisphosphonates to placebo or no treatment. After two years, one trial (25 participants) found that alendronate and clodronate may increase BMD Z score compared to placebo at the femoral neck (mean difference (MD) 0.40, 95% confidence interval (CI) 0.22 to 0.58) and the lumbar spine (MD 0.14, 95% CI 0.05 to 0.23). One trial (118 participants) reported that neridronate compared to no treatment may increase BMD at the lumbar spine and total hip at six and 12 months; for the femoral neck, the study found increased BMD in the neridronate group at 12 months only. All results were of very low-certainty. There were no major adverse effects of treatment. Participants in the neridronate group reported less back pain; we considered this representative of improved quality of life (QoL), though the certainty of the evidence was very low. One participant in the neridronate trial (116 participants) sustained multiple fractures as a result of a traffic accident. No trials reported BMD at the wrist or mobility. Different doses of bisphosphonate compared One 12-month trial (26 participants) assessed different doses of pamidronate (60 mg versus 30 mg) and found a difference in BMD Z score favouring the 60 mg dose at the lumbar spine (MD 0.43, 95% CI 0.10 to 0.76) and forearm (MD 0.87, 95% CI 0.23 to 1.51), but no difference at the femoral neck (very low-certainty evidence). This trial did not report fracture incidence, mobility, QoL, or adverse effects of treatment. Zinc versus placebo One trial (42 participants) showed zinc supplementation probably increased BMD Z score compared to placebo at the lumbar spine after 12 months (MD 0.15, 95% CI 0.10 to 0.20; 37 participants) and 18 months (MD 0.34, 95% CI 0.28 to 0.40; 32 participants); the same was true for BMD at the hip after 12 months (MD 0.15, 95% CI 0.11 to 0.19; 37 participants) and 18 months (MD 0.26, 95% CI 0.21 to 0.31; 32 participants). The evidence for these results was of moderate certainty. The trial did not report BMD at the wrist, fracture incidence, mobility, QoL, or adverse effects of treatment. Denosumab versus placebo Based on one trial (63 participants), we are unsure about the effect of denosumab on BMD Z score at the lumbar spine, femoral neck, and wrist joint after 12 months compared to placebo (low-certainty evidence). This trial did not report fracture incidence, mobility, QoL, or adverse effects of treatment, but the investigators reported a reduction in bone pain measured on a visual analogue scale in the denosumab group after 12 months of treatment compared to placebo (MD -2.40 cm, 95% CI -3.80 to -1.00). Strontium ranelate One trial (24 participants) only narratively reported an increase in BMD Z score at the lumbar spine in the intervention group and no corresponding change in the control group (very low-certainty evidence). This trial also found a reduction in back pain measured on a visual analogue scale after 24 months in the strontium ranelate group compared to the placebo group (MD -0.70 cm (95% CI -1.30 to -0.10); we considered this measure representative of improved quality of life.

AUTHORS' CONCLUSIONS

Bisphosphonates may increase BMD at the femoral neck, lumbar spine, and forearm compared to placebo after two years' therapy. Zinc supplementation probably increases BMD at the lumbar spine and hip after 12 months. Denosumab may make little or no difference to BMD, and we are uncertain about the effect of strontium on BMD. We recommend further long-term RCTs on different bisphosphonates and zinc supplementation therapies in people with beta-thalassaemia-associated osteoporosis.

Low-Molecular-Weight Synthetic Antioxidants: Classification, Pharmacological Profile, Effectiveness and Trends

Mounting research has been performed and published on natural antioxidants, more so than on synthetic ones, as key molecules that control oxidative damage and its pathway to disease. Since the discovery of vitamins, various fully synthetic or natural-identical compounds have been developed as stable small molecules translated into constantly active and completely controlled products which are widely exploited in the food and pharmaceutical industries. There is currently a debate within the literature about their mechanism of action, bioavailability, safety and real benefit for human health. Using a semiquantitative method and eligible criteria of selection, this review aimed to provide a very useful classification of antioxidants and a comprehensive cross-disciplinary description of 32 approved synthetic/natural-identical antioxidants, in terms of regulatory, antioxidant mechanism of action, safety issues, pharmacological properties, effectiveness in human health, timeline and future trends. Enriched interpretation of the data was obtained from summary bibliometrics, useful to portray the “good antioxidant” within the period 1966–2021 and, hopefully, to encourage further research.

Opioids and Sickle Cell Disease: From Opium to the Opioid Epidemic

Sickle cell disease (SCD) is an inherited disorder of hemoglobin structure. The clinical effects of the sickle gene are pleiotropic in nature causing multiple phenotypic expressions associated with the various complications of the disease. The hallmark of the disease is pain that could be acute, chronic, nociceptive, or neuropathic that could occur singly or in various combinations. The acute vaso-occlusive painful crisis (VOC) is the most common cause of admissions to the Emergency Department and/or the hospital. Although progress has been made in understanding the pathophysiology of SCD as well as in developing preventive and curative therapies, effective pain management continues to lag behind and depend mostly on the use of opioids. This review describes the history of opioids from the ancient times of opium to the current use of the many controversial opioids. In addition, the major cause of death of patients with SCD is the complications of the disease itself and not the use of opioids. The use of opioids by patients with SCD has been stable over the years. Judicious use of opioids to treat sickle cell pain according to available guidelines could minimize the unnecessary suffering experienced by patients with SCD.

How I Treat Acute and Persistent Sickle Cell Pain

Sickle pain is the hallmark of sickle cell disease (SCD). It could be acute, persistent/relapsing, chronic, or neuropathic. Although there is a general consensus that pain is a major manifestation of SCD, there is a controversy as to the types of pain and their interrelationship between acute, chronic, relapsing, persistent, etc. This report first reviews the general approach to the management of acute vaso-occlusive crisis (VOC) pain, including education, counseling, pharmacotherapy, non-pharmacotherapy, and fluid therapy. This is followed by the presentation of five patients that represent typical issues that are commonly encountered in the management of patients with SCD. These issues are: individualized treatment of pain, bilaterality of pain, use of illicit drugs, tolerance to opioids, opioid-induced hyperalgesia, and withdrawal syndrome. The clinical aspects and management of each of these issues are described. Moreover, such complications as tolerance and withdrawal may persist after discharge and may be mistaken as chronic pain rather than resolving, persistent or relapsing pain.

Leg Ulcers in Sickle-Cell Disease: Treatment Update

Significance: Sickle-cell leg ulcers (SCLUs) are a severe, chronic, and recurrent complication of sickle-cell disease (SCD). There are no official recommendations for treatment. Recent Advances: Only a few studies with a high level of evidence have been conducted to evaluate treatment of SCLUs. However, several studies have been conducted with a high level of evidence to evaluate the efficacy of treatments in venous leg ulcers, and SCLUs could benefit from these treatments, especially when a venous incompetence or an edema is associated. Pathophysiology of SCLUs includes a vasculopathy related to chronic hemolysis and an endothelial dysfunction, which could be therapeutic approaches to SCLU treatment. Critical Issues: Therapeutic approaches to SCLUs can target SCD on the one hand and skin healing and associated aggravating factors on the other. A review of the literature found only case series and six randomized controlled trials; some offered encouraging results, but most had serious biases. Clinical trials specifically targeting SCLUs are difficult to realize because of the small number of affected patients, in comparison with patients with leg ulcers from other causes. Future Direction: Treating SCLUs remains a challenge. Data in the literature are currently insufficient to offer clear treatment guidelines because of several biases in controlled studies. New studies are under way to assess the efficacy of topical treatments and describe the microbiome of SCLUs. Prevention of SCLU recurrence should be assessed in future clinical trials because the high risk of recurrence is an unsolved critical issue.

Inflammation Adjustment by Two Methods Decreases the Estimated Prevalence of Zinc Deficiency in Malawi

Serum zinc concentration (SZC) is used widely to assess population-level zinc status. Its concentration decreases during inflammatory responses, which can affect the interpretation of the results. This study aimed to re-estimate the prevalence of zinc deficiency in Malawi based on the 2015-2016 Malawi Micronutrient Survey (MNS) data, by adjusting SZC measures with markers of inflammation. SZC and inflammation data from 2760 participants were analysed. Adjustments were made using: (1) The Internal Correction Factor (ICF) method which used geometric means, and (2) The Biomarkers Reflecting Inflammation and Nutritional Determinants of Anemia (BRINDA) method, which used linear regression. Mean SZC values increased significantly when adjustments were made by either ICF or BRINDA (p < 0.001). The national prevalence of zinc deficiency decreased from 62% to 59%, after ICF adjustment, and to 52% after BRINDA adjustment. ICF and BRINDA values of SZC were highly correlated (p < 0.001, r = 0.99), but a Bland-Altman plot showed a lack of agreement between the two methods (bias of 2.07 µg/dL). There was no association between the adjusted SZC and stunting, which is a proxy indicator for zinc deficiency. Inflammation adjustment of SZC, using ICF or BRINDA, produces lower estimates of zinc deficiency prevalence, but the lack of agreement between the adjustment methods warrants further research. Furthermore, the lack of association between SZC and stunting highlights the need to explore other biomarkers and proxies of population zinc assessment. This study demonstrates the importance of considering inflammatory confounders when reporting SZC, to ensure accuracy and to support policy decision making.

Impact of bone disease and pain in thalassemia

Conventional treatment of thalassemia, namely regular blood transfusion and iron chelation, improves perspectives and quality of life; however, successful treatment leads to more time in which long-term complications such as bone disease can develop. Thalassemia bone disease (TBD) is unique: all aspects, from bone anatomy and bone quality to mineral density, may be affected, with important morbidity including osteoporosis, fractures, spinal deformities, nerve compression, and pain. Clinical presentations include growth impairment, rickets-like features, back pain, spinal deformities, any sign of nerve compression, severe osteoporosis, and fragility fractures. Age, history, physical examination, and diagnostic tests support orientation on risk factors. These include bone marrow expansion, toxicity from iron overload and iron chelation, endocrine dysfunctions (hypogonadism, hypohyperparathyroidism, hypothyroidism, growth hormone deficiency, diabetes), and vitamin (D, C, K) and zinc deficiencies. Several of these may coexist in an individual for a long time and at different degrees, making clarification of the relative contribution and selection of the best therapeutic options a challenge. Milestones for prevention of TBD are early and full inhibition of bone marrow hyperplasia and iron toxicity. Empowering patients' positive resources is key for achieving long-term healthy habits with regard to diet, physical activity, sunlight exposure, and lifestyle. Pain, related or unrelated to bone disease, is frequent in thalassemia. The most important targets for the hematologist include having an expert orientation on disease-related causes of pain, driving differential diagnosis, providing effective pain relief and, where feasible, removing the cause.

Treatment for osteoporosis in people with ß-thalassaemia

BACKGROUND

Osteoporosis is a systemic skeletal disease characterized by low bone mass and micro-architectural deterioration of bone tissue with a consequent increase in bone fragility and susceptibility to fracture. Osteoporosis represents an important cause of morbidity in people with beta-thalassaemia and its pathogenesis is multifactorial. Factors include bone marrow expansion due to ineffective erythropoiesis, resulting in reduced trabecular bone tissue with cortical thinning; endocrine dysfunction secondary to excessive iron loading, leading to increased bone turnover; and lastly, a predisposition to physical inactivity due to disease complications with a subsequent reduction in optimal bone mineralization.A number of therapeutic strategies have been applied to treat osteoporosis in people with beta-thalassaemia, which include bisphosphonates, with or without, hormone replacement therapy. There are various forms of bisphosphonates, such as clodronate, pamidronate, alendronate and zoledronic acid. Other treatments include calcitonin, calcium, zinc supplementation, hydroxyurea and hormone replacement therapy for preventing hypogonadism.

OBJECTIVES

To review the evidence on the efficacy and safety of treatment for osteoporosis in people with beta-thalassaemia.

SEARCH METHODS

We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings.Date of most recent search: 04 February 2016.

SELECTION CRITERIA

Randomised, placebo-controlled trials in people with thalassaemia with a bone mineral density z score of less than -2 standard deviations for: children less than 15 years old; adult males (15 to 50 years old); and all pre-menopausal females above 15 years and a bone mineral density t score of less than -2.5 standard deviations for post-menopausal females and males above 50 years old.

DATA COLLECTION AND ANALYSIS

Two review authors assessed the eligibility and risk of bias of the included trials, extracted and analysed data and completed the review. We summarised results using risk ratios or rate ratios for dichotomous data and mean differences for continuous data. We combined trial results where appropriate.

MAIN RESULTS

Four trials (with 211 participants) were included; three trials investigated the effect of bisphosphonate therapies and one trial investigated the effect of zinc supplementation. Only one trial was judged to be of good quality (low risk of bias); the remaining trials had a high or unclear risk of bias in at least one key domain.One trial (data not available for analysis) assessing the effect of neridronate (118 participants) reported significant increases in favour of the bisphosphonate group for bone mineral density at the lumbar spine and hip at both six and 12 months. For the femoral neck, a significant difference was noted at 12 months only. A further trial (25 participants) assessed the effect of alendronate and clodronate and found that after two years, bone mineral density increased significantly in the alendronate and clodronate groups as compared to placebo at the lumbar spine, mean difference 0.14 g/cm(2) (95% confidence interval 0.05 to 0.22) and at the femoral neck, mean difference 0.40 g/cm(2) (95% confidence interval 0.22 to 0.57). One 12-month trial (26 participants) assessed the effects of different doses of pamidronate (30 mg versus 60 mg) and found a significant difference in bone mineral density in favour of the 60 mg dose at the lumbar spine and forearm, mean difference 0.43 g/cm(2) (95% CI 0.10 to 0.76), mean difference 0.87 g/cm(2) (95% CI 0.23 to 1.51), respectively, but not at the femoral neck.In a zinc sulphate supplementation trial (42 participants), bone mineral density increased significantly compared to placebo at the lumbar spine after 12 months (37 participants), mean difference 0.15 g/cm(2) (95% confidence interval 0.10 to 0.20) and after 18 months (32 participants), mean difference 0.34 g/cm(2) (95% confidence interval 0.28 to 0.40). The same was true for bone mineral density at the hip after 12 months, mean difference 0.15 g/cm(2) (95% confidence interval 0.11 to 0.19) and after 18 months, mean difference 0.26 g/cm(2) (95% confidence interval 0.21 to 0.31).Fractures were not observed in one trial and not reported in three trials. There were no major adverse effects reported in two of the bisphosphonate trials; in the neridronate trial there was a reduction noted in the use of analgesic drugs and in the reported back pain score in favour of bisphosphonate treatment. Adverse effects were not reported in the trial of different doses of pamidronate or the zinc supplementation trial.

AUTHORS' CONCLUSIONS

There is evidence to indicate an increase in bone mineral density at the femoral neck, lumbar spine and forearm after administration of bisphosphonates and at the lumbar spine and hip after zinc sulphate supplementation. The authors recommend that further long-term randomised control trials on different bisphosphonates and zinc supplementation therapies in people with beta-thalassaemia and osteoporosis are undertaken.

Biomarkers of Nutrition for Development (BOND)-Zinc Review

Zinc is required for multiple metabolic processes as a structural, regulatory, or catalytic ion. Cellular, tissue, and whole-body zinc homeostasis is tightly controlled to sustain metabolic functions over a wide range of zinc intakes, making it difficult to assess zinc insufficiency or excess. The BOND (Biomarkers of Nutrition for Development) Zinc Expert Panel recommends 3 measurements for estimating zinc status: dietary zinc intake, plasma zinc concentration (PZC), and height-for-age of growing infants and children. The amount of dietary zinc potentially available for absorption, which requires an estimate of dietary zinc and phytate, can be used to identify individuals and populations at risk of zinc deficiency. PZCs respond to severe dietary zinc restriction and to zinc supplementation; they also change with shifts in whole-body zinc balance and clinical signs of zinc deficiency. PZC cutoffs are available to identify individuals and populations at risk of zinc deficiency. However, there are limitations in using the PZC to assess zinc status. PZCs respond less to additional zinc provided in food than to a supplement administered between meals, there is considerable interindividual variability in PZCs with changes in dietary zinc, and PZCs are influenced by recent meal consumption, the time of day, inflammation, and certain drugs and hormones. Insufficient data are available on hair, urinary, nail, and blood cell zinc responses to changes in dietary zinc to recommend these biomarkers for assessing zinc status. Of the potential functional indicators of zinc, growth is the only one that is recommended. Because pharmacologic zinc doses are unlikely to enhance growth, a growth response to supplemental zinc is interpreted as indicating pre-existing zinc deficiency. Other functional indicators reviewed but not recommended for assessing zinc nutrition in clinical or field settings because of insufficient information are the activity or amounts of zinc-dependent enzymes and proteins and biomarkers of oxidative stress, inflammation, or DNA damage.