Iron absorption in the thalassemia syndromes and its inhibition by tea

Tannin complexation with metal ions and its implication on human health, environment and industry: An overview

Tannins, also known as plant polyphenols (PPs), are secondary metabolites widely existing in higher plants and are a kind of natural renewable resource with wide distribution, variety and quantity. Tannin has become an important class of fine chemicals due to the easily modified molecular structure and the properties of antibacterial and antioxidant, combining with protein and complexing with metal ion. Besides being used for tanning leather, tannins are also widely used in wood adhesive, concrete water-reducing agents, oil drilling fluid viscosity-reducing agents, pharmaceutical, mineral processing, water treatment, gas desulfurization, metal anticorrosion, wood anticorrosion, printing and dyeing, liquor clarification, oil antioxidant, daily chemical products and other products preparation. There are two groups of tannins: condensed tannins (CTs) (flavonoid-derived proanthocyanidins) and hydrolysable tannins (HTs) (gallic acid ester-derived). Tannins can form complexes with metals through the ortho-dihydroxyphenolic group(s), especially with transition metals. The structure-activity relationships, stoichiometry, and origin of the insolubility of which were emphasized. Furthermore, this paper proposed an in-depth discussion of the associations of tannins-metal complexes in human health, environment and industries.

The effect of food and nutrients on iron overload: what do we know so far?

There has been no established food and nutrition guidance for diseases characterized by the presence of iron overload (IOL) yet. Hepcidin is a hormone that diminishes iron bioavailability. Its levels increase in response to increased iron stores. Hence, IOL conditions could hypothetically trigger a self-regulatory mechanism for the reduction of the intestinal absorption of iron. In addition, some food substances may modulate intestinal iron absorption and may be useful in the dietary management of patients with IOL. This scoping review aimed to systematize studies that support dietary prescriptions for IOL patients. It was carried out according to the method proposed by the Joanna Briggs Institute and the preferred reporting items for systematic reviews and meta-analyses (PRISMA). Although the need to restrict iron in the diet of individuals with hemochromatosis is quite clear, there is a consensus that IOL diminishes the rate of iron absorption. Reduced iron absorption is also present and has been reported in some diseases with transfusion IOL, in which serum hepcidin is usually high. The consumption of polyphenols and 6-shogaol seems to reduce iron absorption or serum ferritin concentration, while procyanidins do not cause any changes. Vitamin C deficiency is often found in IOL patients. However, vitamin C supplementation and alcohol consumption should be avoided not only because they increase iron absorption, but also because they provoke toxic oxidative reactions when the iron is excessive. Dietary approaches must consider the differences in the pathophysiology and treatment of IOL diseases.

Recent Progress in Gene Therapy and Other Targeted Therapeutic Approaches for Beta Thalassemia

Beta-thalassemia is a genetic disorder characterized by the impaired synthesis of the betaglobin chain of adult hemoglobin. The disorder has a complex pathophysiology that affects multiple organ systems. The main complications of beta thalassemia are ineffective erythropoiesis, chronic hemolytic anemia and hemosiderosis-induced organ dysfunction. Regular blood transfusions are the main therapy for beta thalassemia major; however, this treatment can cause cardiac and hepatic hemosiderosis - the most common cause of death in these patients. This review focuses on unique future therapeutic interventions for thalassemia that reverse splenomegaly, reduce transfusion frequency, decrease iron toxicity in organs, and correct chronic anemia. The targeted effective protocols include hemoglobin fetal inducers, ineffective erythropoiesis correctors, antioxidants, vitamins, and natural products. Resveratrol is a new herbal therapeutic approach which serves as fetal Hb inducer in beta thalassemia. Hematopoietic stem cell transplantation (HSCT) is the only curative therapy for beta thalassemia major and is preferred over iron chelation and blood transfusion for ensuring long life in these patients. Meanwhile, several molecular therapies, such as ActRIIB/IgG1 Fc recombinant protein, have emerged to address complications of beta thalassemia or the adverse effects of current drugs. Regarding gene correction strategies, a phase III trial called HGB-207 (Northstar-2; NCT02906202) is evaluating the efficacy and safety of autologous cell transplantation with LentiGlobin. Advanced gene-editing approaches aim to cut DNA at a targeted site and convert HbF to HbA during infancy, such as the suppression of BCL11A (B cell lymphoma 11A), HPFH (hereditary persistence of fetal hemoglobin) and zinc-finger nucleases. Gene therapy is progressing rapidly, with multiple clinical trials being conducted in many countries and the promise of commercial products to be available in the near future.

A 1-h time interval between a meal containing iron and consumption of tea attenuates the inhibitory effects on iron absorption: a controlled trial in a cohort of healthy UK women using a stable iron isotope

Background: Tea has been shown to be a potent inhibitor of nonheme iron absorption, but it remains unclear whether the timing of tea consumption relative to a meal influences iron bioavailability.Objective: The aim of the study was to investigate the effect of a 1-h time interval of tea consumption on nonheme iron absorption in an iron-containing meal in a cohort of iron-replete, nonanemic female subjects with the use of a stable isotope (⁵⁷Fe).Design: Twelve women (mean ± SD age: 24.8 ± 6.9 y) were administered a standardized porridge meal extrinsically labeled with 4 mg ⁵⁷Fe as FeSO₄ on 3 separate occasions, with a 14-d time interval between each test meal (TM). The TM was administered with water (TM-1), with tea administered simultaneously (TM-2), and with tea administered 1 h postmeal (TM-3). Fasted venous blood samples were collected for iron isotopic analysis and measurement of iron status biomarkers. Fractional iron absorption was estimated by the erythrocyte iron incorporation method.Results: Iron absorption was 5.7% ± 8.5% (TM-1), 3.6% ± 4.2% (TM-2), and 5.7% ± 5.4% (TM-3). Mean fractional iron absorption was found to be significantly higher (2.2%) when tea was administered 1 h postmeal (TM-3) than when tea was administered simultaneously with the meal (TM-2) (P = 0.046). An ∼50% reduction in the inhibitory effect of tea (relative to water) was observed, from 37.2% (TM-2) to 18.1% (TM-3).Conclusions: This study shows that tea consumed simultaneously with an iron-containing porridge meal leads to decreased nonheme iron absorption and that a 1-h time interval between a meal and tea consumption attenuates the inhibitory effect, resulting in increased nonheme iron absorption. These findings are not only important in relation to the management of iron deficiency but should also inform dietary advice, especially that given to those at risk of deficiency. This trial was registered at clinicaltrials.gov as NCT02365103.

Iron deficiency anemia due to excessive green tea drinking

Tea interferes with iron absorption and can lead to iron deficiency anemia when consumed in large quantities. The rechallenge effect of green tea on anemia in a middle‐aged man emphasizes the potential causal role of this beverage. Lifestyle and dietary habits are important diagnostic considerations in diseases of this type.

Effect of Mentha piperita (Labiatae) and Mentha spicata (Labiatae) on iron absorption in rats

Aim: The effect of Mentha piperita (Labiatae) and Mentha spicata (Labiatae) teas, which contain different phenol compounds, on iron metabolism was studied. These teas grow in different areas of the city of Isparta, Turkey. These herbals were given to the rats in tea. Methods: Forty-eight male Wistar albino rats weighing 200-250 g were used for this study. The rats were divided into four groups of 12 animals: Group I received no herbal tea (control group); Group II received 20 g/L M. piperita tea; Group III received 20 g/L M. spicata tea; Group IV received 40 g/L M. spicata tea. Herbal teas were prepared daily and provided at all times to the rats over 30 days as drinking water. Results: M. piperita tea caused a decrease in serum iron and ferritin levels P <0.05), and caused an increase in unsaturated iron-binding capacity (UIBC) P <0.01). M. spicata tea caused no significant change in serum iron, ferritin levels and UIBC P <0.05). Conclusion: Both herbal teas inhibited Fe absorption. Inhibition caused by M. spicata tea was dose dependent. Therefore, when drinking these teas, their effect should be considered, especially for children and anemic patients.

Major flavonoid constituents and short-term effects of Chun Mee tea in rats

Chun Mee tea is a kind of green tea produced in China mainly for export purposes. Foam quantity is usually used as an index for evaluating the quality of Chun Mee tea. In the current study, we compared the concentrations of total saponin and flavonoids between foamy and low-foam Chun Mee tea. Our research confirmed that the total saponin and O-glycosylated flavonoid concentrations were related to the foam quantity of Chun Mee teas. We also studied the short-term safety effects of extract supplementation with foamy and low-foam Chun Mee tea in rats by routine blood tests and analysis of liver and kidney function, and blood lipids. Our results showed that both types of tea extract supplementations did not cause any observable adverse effects or impair either liver or kidney function. Additionally, this study confirmed the beneficial effects of Chun Mee tea extract supplementation on the decrease of total plasma cholesterol.

Polyphenols in brown algaeFucus vesiculosus andAscophyllum nodosum: Chemical defenses against the marine herbivorous snail,Littorina littorea

Polyphenols from two brown algae,Fucus vesiculosus (L.) andAscophyllum nodosum (L.) Le Jolis, inhibited feeding by the herbivorous snail,Littorina littorea. The active compounds were characterized as phloroglucinol polymers with a wide molecular weight range (mol wt <30,000 to >300,000) by spectroscopic, Ultrafiltration, thin-layer chromatographic, and chemical degradation data. As little as 1% (dry wt) polyphenol in food reduced feeding by more than 50%, and polyphenolic extracts inhibited feeding entirely when present in concentrations of 2-5% (dry wt). Commercially available phloroglucinol dihydrate and gallotannin, which are known herbivore feeding deterrents in terrestrial plants, inhibitedL. littorea feeding when added to food media in concentrations similar to those above. We conclude that polyphenols inF. vesiculosus andA. nodosum are functionally similar to terrestrial plant polyphenols (tannins) in providing chemical defenses against herbivores. This research is the first demonstration that chemical compounds defend these two dominant, perennial marine algae from the major herbivore found in their community.

Inadequate dietary intake in patients with thalassemia

BACKGROUND

Patients with thalassemia have low circulating levels of many nutrients, but the contribution of dietary intake has not been assessed.

OBJECTIVE

Our objective was to assess dietary intake in a large contemporary sample of subjects with thalassemia.

DESIGN

A prospective, longitudinal cohort study using a validated food frequency questionnaire was conducted.

PARTICIPANTS/SETTING

Two hundred and twenty-one subjects (19.7±11.3 years, 106 were female) were categorized into the following age groups: young children (3 to 7.9 years), older children/adolescents (8 to 18.9 years), and adults (19 years or older); 78.8% had β-thalassemia and 90% were chronically transfused. This study took place at 10 hematology outpatient clinics in the United States and Canada.

MAIN OUTCOME MEASURES

We conducted a comparison of intake with US Dietary Reference Intakes and correlated dietary intake of vitamin D with serum 25-OH vitamin D and dietary iron with total body iron stores.

STATISTICAL ANALYSES PERFORMED

Intake was defined as inadequate if it was less than the estimated average requirement. χ(2), Fisher's exact, and Student's t test were used to compare intake between age categories and logistic regression analysis to test the relationship between intake and outcomes, controlling for age, sex, and race.

RESULTS

More than 30% of subjects consumed inadequate levels of vitamin A, D, E, K, folate, calcium, and magnesium. The only nutrients for which >90% of subjects consumed adequate amounts were riboflavin, vitamin B-12, and selenium. Dietary inadequacy increased with increasing age group (P<0.01) for vitamins A, C, E, B-6, folate, thiamin, calcium, magnesium, and zinc. More than half of the sample took additional supplements of calcium and vitamin D, although circulating levels of 25-OH vitamin D remained insufficient in 61% of subjects. Dietary iron intake was not related to total body iron stores.

CONCLUSIONS

Subjects with thalassemia have reduced intake of many key nutrients. These preliminary findings of dietary inadequacy are concerning and support the need for nutritional monitoring to determine which subjects are at greatest risk for nutritional deficiency. Future research should focus on the effect of dietary quality and nutritional status on health outcomes in thalassemia.

Mechanisms of heme iron absorption: current questions and controversies

Iron is a critical micronutrient, and iron derived from heme contributes a large proportion of the total iron absorbed in a typical Western diet. Heme iron is absorbed by different mechanisms than non-heme iron, but despite considerable study over many years these mechanisms remain poorly understood. This review provides an overview of the importance of heme iron in the diet and discusses the two prevailing hypotheses of heme absorption; namely receptor mediated endocytosis of heme, and direct transport into the intestinal enterocyte by recently discovered heme transporters. A specific emphasis is placed on the questions surrounding the site of heme catabolism and the identity of the enzyme that performs this task. Additionally, we present the hypothesis that a non-heme iron transport protein may be required for heme iron absorption and discuss the experiences of our laboratory in examining this hypothesis.

Optimal management strategies for chronic iron overload

Iron overload is characterised by excessive iron deposition and consequent injury and dysfunction of target organs, especially the heart, liver, anterior pituitary, pancreas and joints. Iron overload disorders are common worldwide and occur in most major race/ethnicity groups. Physiological mechanisms to excrete iron are very limited. Thus, all patients with iron overload need safe and effective treatment that is compatible with their co-existing medical conditions. Treatments for iron overload include phlebotomy and erythrocytapheresis that remove iron predominantly as haemoglobin, and chelation therapy with drugs that bind excess iron selectively and increase its excretion. The most important potential benefits of therapy are preventing deaths due to cardiac siderosis and hepatic cirrhosis. Preventing iron-related injury to endocrine organs is critical in children. Successful treatment or prevention of iron overload increases quality of life and survival in many patients. This article characterises the major categories of iron overload disorders, tabulates methods to evaluate and treat iron overload, and describes treatment options for iron overload disorders. Research needed to advance knowledge about treatment of iron overload is proposed.

Effects of dietary iron reduction versus phlebotomy in patients with chronic hepatitis C: results from a randomized, controlled trial on 40 Japanese patients

BACKGROUND AND AIM

Iron may play an important role in the pathogenesis of hepatitis C. We conducted this randomized, controlled trial comparing phlebotomy with dietary iron reduction.

METHODS

Forty patients with chronic hepatitis C showing serum ferritin levels of over 150 ng/ml were randomized to either group A (low-iron diet for six months) or group B (phlebotomy biweekly). Phlebotomy was continued until serum ferritin had reached 20 ng/ml or less.

RESULTS

At enrollment the clinical characteristics of patients in the two groups were similar. Serum ALT levels were significantly reduced in both groups, but the percent change in alanine aminotransferase (ALT) was larger in group B (median, -47.1 [range, -69.1 to -16.7] %) than in group A (-24.2 [-72.6 to 15.9] %, p<0.001). In group A subjects, no correlation was detected between percent change in ALT and clinical parameters. In group B subjects, the baseline ALT activity was significantly correlated with percent change in ALT (p<0.05), but iron-related parameters were not correlated.

CONCLUSION

The efficacy of phlebotomy is superior to that of dietary iron reduction in chronic hepatitis C. Serum levels of transaminase activities were a better indicator for phlebotomy than conventional indices of iron overload.

Iron-chelating and free-radical scavenging activities of microwave-processed green tea in iron overload

Secondary iron overload is found in beta-thalassemia (thal) patients because of increased dietary iron absorption and multiple blood transfusions. Excessive iron catalyzes free-radical generation, leading to oxidative damage and vital organ dysfunction. Non-transferrin-bound iron (NTBI) detected in thalassemic plasma is highly toxic and chelatable. Though used to treat iron overload, desferrioxamine (DFO) and deferiprone (L1) also have adverse effects. Green tea (GT) shows many pharmacological effects, particularly antioxidative and iron-chelating capacities. This study was performed to investigate the ability of GT extracts to reduce plasma NTBI concentration and oxidative stress in vitro. The Fe(3+) was found to bind to GT crude extract and form a complex. Green tea crude extract time- and dose-dependently decreased plasma NTBI concentration and counteracted the increase of oxidative stress in both Fe(2+)-EDTA-treated human plasma and erythrocytes. Green tea is a bifunctional natural product that could be relevant for management of iron overload and oxidative stress.

Use of hydroxyurea and recombinant erythropoietin in management of homozygous beta0 thalassemia

This report describes the sustained response of an Iranian girl with homozygous beta(0) thalassemia (IVS-II-1G-->A) to hydroxyurea (HU) and recombinant erythropoietin (rEPO). Since the start of this regimen 7 years ago, she has been transfusion-independent and her hemoglobin is maintained between 9.5-11.0 gm/dL. She is maintaining consistent growth around the 10th percentile for age and enjoys a good quality of life. She has not had any therapy-related adverse effects. This experience suggests that therapy with HU and rEPO may be useful long-term in some patients with beta thalassemia.

Assessment of iron stores in children with transfusion siderosis by biomagnetic liver susceptometry

To investigate the applicability of noninvasive Superconducting Quantum Interference Device (SQUID) biomagnetic liver susceptometry and its limitations in thalassemic children, 23 patients with beta-thalassemia major and other iron loading anemias (age: 4-16 years) and 16 age-related normal children were studied. Liver iron concentrations ranged from 600 to 11,000 microg/g(liver) for thalassemic patients and from 60 to 340 microg/g(liver) for normal patients. Measuring the respective organ volumes by sonography, liver and spleen iron stores, accounting for 80% of total body iron stores, were estimated. Nonliver contributions from the lung or intestine to the measured SQUID signals in the small-sized patients were not observed. Moreover, livers in thalassemia were found to be enlarged by 18% per 1,000 microg/g (r = 0.75, P < 10(-3)). Serum ferritin values correlate significantly with iron stores (r = 0.64, P < 10(-3)), but predict iron stores only within large error intervals of 4,000 microg/g(liver). Analyzing the experimental data from biomagnetometry and from related transfusion and chelation treatment data within the framework of a two-compartment model, we were able to derive additional information on total body iron elimination and chelation therapy efficacy. The exponential decline of iron stores allows forecast of steady-state conditions of the final iron load for a particular transfusion and chelation therapy regimen.

Abordagem ambulatorial do nutricionista em anemia hemolítica

Descreve a atuação do nutricionista em ambulatório de Hematologia Pediátrica em um hospital escola e relata as condutas dietéticas necessárias na abordagem de crianças com anemia hemolítica com e sem sobrecarga de ferro, e também as atitudes mais freqüentes dos familiares em relação à alimentação desses pacientes.

Long-term intraperitoneal deferoxamine for hemochromatosis

Intraperitoneal deferoxamine is a well established treatment for aluminum accumulation syndrome in patients with end-stage renal disease receiving peritoneal dialysis, but the use of intraperitoneal deferoxamine has not been described outside of the setting of chronic renal failure. We present here a case of secondary hemochromatosis, complicated by cirrhosis and cardiomyopathy, in which a chronic peritoneal dialysis catheter was used both to treat ascites and to deliver parenteral deferoxamine for iron overload. Daily urinary iron excretion was similar to that achieved when using standard routes of deferoxamine administration. Over a 2-year period, reversal of both the biochemical indicators and the clinical manifestations of iron overload was accomplished.

Zinc bioavailability and tea consumption. Studies in healthy humans consuming self-selected and laboratory-controlled diets

One self-selected study (study A) and one laboratory-controlled study (study B) were conducted to investigate the effect of tea consumption on zinc bioavailability in healthy humans. The 14-day study A consisted of two 7-day experimental periods, while the 28-day study B consisted of two 14-day experimental periods. In study A eight subjects and in study B ten subjects were participated. Subjects of study A consumed self-selected diets and kept a record of foods eaten. In study B, subjects ate a constant and weighted laboratory controlled diet. In both studies, subjects consumed 8 g of instant tea during tea supplementation periods. Complete urine and fecal collections were made by subjects of both studies. Zinc contents of urine, fecal and food samples were determined by using Atomic Absorption Spectrophotometer. Mean zinc intakes of humans consuming self-selected diets were below the RDA. Mean urinary zinc excretion, fecal zinc excretion and zinc balance were unaffected by the tea consumption. Negative zinc balances in study A and positive zinc balances in study B were observed in both tea and no tea dietary treatments. Tea consumption showed a small but not statistically significant adverse affect on zinc bioavailability in humans.

Inhibition of iron absorption prolongs the life span of Drosophila

The life span of Drosophila melanogaster (Oregon R) males was found to be proportional to the logarithm of the iron content of the diet. Life span was also shown to be proportional to the rate of iron accumulation for Drosophila, mice and man. The total body iron content was found to correlate with the total calcium content of adult Drosophila. Iron content during the developmental stages, however, remained relatively constant and did not change with changes in the calcium concentrations. Dietary tea (Camellia sinensis) extracts were found to inhibit the ageing-related accumulation of iron and to prolong the life span of Drosophila by as much as 21.4%. It is concluded that iron accumulation is a significant factor contributing to senescence.

Beta-thalassaemia minor and porphyria cutanea tarda

A case of porphyria cutanea tarda occurring in association with beta-thalassaemia minor is reported in a 33-year-old Northern-Irish woman. Aetiological factors in this case included oral and parenteral iron therapy for refractory anaemia which was subsequently diagnosed as beta-thalassaemia minor, and the use of an oestrogen-containing oral contraceptive pill.

Reevaluation of iron absorption and serum ferritin in beta-thalassemia intermedia

In order to reassess the need for iron chelation therapy in nontransfused patients with beta-thalassemia intermedia, serum ferritin level and ferrous iron absorption from the gastrointestinal system were measured in 43 (23 male and 20 female) patients (mean age 13.4 +/- 7.5). The mean hemoglobin value was 8.6 +/- 1.3 g/dL and serum ferritin 303 +/- 207 ng/mL. Absorption of ferrous iron salt was determined in 21 patients by measuring serum iron before and 3 hours after giving ferrous salt orally at 1 mg/kg. The means of the increase in serum iron values were 39 +/- 45, 105 +/- 46, and 224 +/- 112 micrograms/dL in patients with beta-thalassemia intermedia, normal subjects, and patients with iron deficiency anemia respectively. Differences in the means in three groups were significant (p < 0.001). This study shows that iron absorption from the gastrointestinal system as ferrous salt is not accelerated in patients with beta-thalassemia intermedia. The serum ferritin level in these patients is not high enough to necessitate iron chelation therapy.

Should we set a place for diet in ethnopharmacology?

Ethnopharmacologic inquiry is most invincibly pursued by addressing "medicinals" across the divers contexts through which populations gain exposure to the material of their pharmacopoeia. Attention to multiple categories of use advances our comprehension of indigenous health care by providing a framework for laboratory investigations that explore the bioactive potential of the materia medica to influence the occurrence and expression of disease, and that determine how those physiologic outcomes may be further mediated by the context-specific vicissitudes of preparation, combination and consumption. Consideration of the dietary contexts of local "medicines" is central to this wider perspective.

Iron overload in Chinese patients with hemoglobin H disease

We examined the iron status of 23 adult patients with hemoglobin H (Hb H) disease. None of them had received multiple blood transfusions or prolonged iron therapy. Studies included serum iron and ferritin concentrations, transferrin saturation, a desferrioxamine test, computed tomography (CT) scan of the liver, and liver biopsy. Iron overload was found in 17 patients (73.9%), especially in males and in patients with splenomegaly (92.9% and 100%, respectively). Four patients with excessive alcohol consumption had clinical manifestations of severe iron overload. Idiopathic hemochromatosis associated HLA antigens, i.e., HLA-A3, -B7, or -B14, were not found in any of the 15 patients tested. These findings indicate that iron overload is common in adult patients with Hb H disease; such patients should abstain from alcohol and be considered for treatment with an iron chelating agent before irreversible organ damage occurs.

Iron balances in infant nutrition

Iron balance studies were performed in 17 full term male infants from their 3rd until their 17th week of life. The balance studies were made in the infant's home and comprised 5 periods with an interval of 3-4 weeks, each consisting of three 24-hour collections. Ten infants were breast-fed, 3 received an adapted infant formula (P1, iron content 1.1 mg/l) and 4 were given the same formula enriched with iron, copper and zinc (P2, iron content 10.35 mg/l). From the 3rd to the 17th week of life the breast-fed infants got a mean iron intake of 0.2 mg/kg body weight X 3 days and they retained 0.09 mg/kg b.w. X 3 days. The P1 group received 0.48 and 0.47 mg/kg b.w. X 3 days and retained -0.01 and -0.5 mg iron/kg b.w. X 3 days, while the P2 group had an intake from 5.04 to 6.38 mg b.w. X 3 days and retained between 1.13 and 3.66 mg iron/kg b.w. X 3 days. Comparing the 3 groups it can be concluded that the P1 group retained definitely less iron than the breast-fed group, whereas the P2 group retained 12 to 40 times more iron than the breast-fed babies.

Iron accumulation during development and ageing of Drosophila

We examined Drosophila melanogaster fruit flies to determine whether iron accumulates with ageing as it does in mice. Iron concentrations were measured by atomic absorption for flies maintained at 11, 20, 25 and 30 degrees C where the average lifespans were 152, 81, 62 and 25 days, respectively. Iron was found to accumulate with ageing during both the adult and developmental stages with an overall increase of 186% at 25 degrees C. A similar increase was found at 20 degrees C and 30 degrees C. At 11 degrees C the increase was less than half that at 25 degrees C. The rate of iron accumulation also varied with environmental temperature with the logarithm of the rate proportional to temperature (log R = 0.0509T-0.384). The rate of iron accumulation with ageing was, thus, found to be proportional to the rate of ageing, suggesting that excess dietary iron may be an initiator of senescence.

Iron deficiency and iron overload

An up to date review of our knowledge of human iron metabolism is given including problems of iron balance, internal transport, and intracellular mechanisms. Current knowledge of the iron proteins is summarized and this background is used in discussing the pathophysiology of iron deficiency and overload, together with the internal derangements such as sideroblastic anemia which form much of the clinical practice associated with disorders of iron metabolism. The therapeutic approach to these problems will be described.

Crossover and self-controlled designs in clinical research

Crossover studies (clinical trials in which each patient receives two or more treatments in sequence) and self-controlled studies (in which each patient serves as his or her own control) can produce results that are statistically and clinically valid with far fewer patients than would otherwise be required. We investigated the use of the crossover design in the 13 crossover studies that appeared in the Journal during 1978 and 1979. We considered the following important features of design and analysis as they applied to these studies: the method by which patients were assigned to initial treatment (only 7 of 13 studies used random assignment); the determination of when to switch treatments (10 of the 13 used a time-dependent rule, and 3 a less appropriate disease-state-dependent rule); blinding of the crossover point (in only 3 of the 13 studies was the crossover point concealed, but in 4 of the remaining 10 concealment was impossible); assessment of the effects of the order of treatments (included in only 1 of the 13 studies); and the use of at least minimally acceptable statistical analysis (11 of the 13 studies had such an analysis). We also report briefly on 28 additional studies of a single treatment each, in which each patient served as his or her own control before or after treatment or both. The scientific issues were much the same as in crossover studies except that self-controlled comparisons of treatments tended to be less precisely designed and conducted and to focus on clinical problems and patient groups that are especially difficult to study.