Frequencies of the haemochromatosis gene (HFE) variants C282Y, H63D and S65C in 6,020 ethnic Danish men

Hereditary hemochromatosis: data from a single center Copenhagen cohort

OBJECTIVES

We aimed to describe a cohort of hereditary hemochromatosis (HH) patients from a single urban center in Copenhagen.

METHODS

Retrospectively, data from patients with HH from the years 2009-2020 were collected.

RESULTS

A total of 203 patients was recorded. Males constituted 65.0% of the patients. Homozygous HH (HHH)/compound heterozygous HH (CHH) accounted for 69.4%/30.6%. HHH patients had significantly higher ferritin and transferrin saturation (TS) levels at debut than CHH patients. Fifty-five HHH patients (39.0%) had ferritin >1000 ug/L versus 9 (14.5%) in the CHH group (p < .001). Age at debut did not differ between female and male patients. Ferritin (but not TS) levels were significantly higher in male patients. The proportion of patients with ferritin >1000 did not differ between males and females. One-hundred patients (49.3%) had one or more symptoms at the time of diagnosis; arthralgias of the metacarpophalangeal joints and/or ankles (n = 46 (22.7%)), fatigue (n = 67 (33.0%)) and decreased libido (n = 20 (9.9%)). The proportion of patients with symptoms did not differ between HHH and CHH or between male and female patients. Severe organ complications (cardiomyopathy, late onset type 1 diabetes or cirrhosis) were present in 14 patients (6.9%).

CONCLUSIONS

We report a high proportion of compound HH, constituting almost one-third of patients. We found that the proportion of patients with symptoms did not differ between HHH and CHH and recommend that CHH should be treated and examined in the same way as HHH.

Investigation of correlation between H63D and C282Y mutations in HFE gene and serum Ferritin level in beta-thalassemia major patients

INTRODUCTION

Mutations in the HFE gene have been shown to be associated with hemochromatosis which is observed in beta-thalassemia major. In this study, we determined the HFE gene mutations (C282Y and H63D) among b-thalassemia major patients to investigate the effect of these mutations on serum Ferritin levels.

MATERIAL AND METHODS

In this cross-sectional study, a total of 105 b-thalassemia subjects with a history of regular blood transfusion were selected. They divided into two distinct groups according cut off 1000ng/ml of serum Ferritin levels. The HFE gene mutant allele detected by RFLP-PCR.

RESULTS

Of 105 thalassemia patients, 29 patients (14 male and 15 female) were heterozygote for H63D mutation, and just one male was homozygote, but for C282Y mutation just one heterozygote and one homozygote was detected, and overall 31% had coexistence of b-thal and HFE gene mutations. As expected, Ferritin levels significantly differed between groups (P=0.001).

CONCLUSION

The impact of detection of HFE mutations could prognosis the likelihood of iron overload in multi-transfused patients, and allowing early diagnosis and proper management to overcome complications of iron overload in beta-thalassemia patients.

Iron status in pregnant women and women of reproductive age in Europe

Understanding the iron status in pregnant women in Europe provides a foundation for considering the role of iron screening and supplementation. However, available reports and studies have used different approaches that challenge the devising of overall summaries. Moreover, data on pregnant women are limited, and thus, data on women of reproductive age provide useful background information including baseline iron stores in pregnant women. This review considered data that are available from >15 European countries including national surveys and relevant clinical studies. In European women of reproductive age, median or geometric mean serum ferritin (SF) concentrations were estimated at 26-38 μg/L. Approximately 40-55% of this population had small or depleted iron stores (i.e., SF concentration ≤30 μg/L), and 45-60% of this population had apparently replete iron stores. The prevalence of iron deficiency (ID) and iron deficiency anemia (IDA) was 10-32% and 2-5%, respectively, depending on the cutoffs used. Approximately 20-35% of European women of reproductive age had sufficient iron stores (SF concentration >70 μg/L) to complete a pregnancy without supplementary iron. During pregnancy, European women in controlled supplementation trials who were not receiving iron supplements displayed increasing prevalences of ID and IDA during pregnancy, which peaked in the middle to late third trimester. Available evidence has suggested that, in gestational weeks 32-39, the median or geometric mean SF concentrations were 6-21 μg/L, and prevalences of ID and IDA were 28-85% and 21-35%, respectively. Women who were taking iron supplements had higher iron status and lower prevalences of ID and IDA, which were dependent on the dose of iron and compliance. The data suggest that, in Europe, the iron status of reproductive-aged women varies by region and worsens in pregnancy without iron supplementation.

The evolutionary adaptation of the C282Y mutation to culture and climate during the European Neolithic

OBJECTIVES

The C282Y allele is the major cause of hemochromatosis as a result of excessive iron absorption. The mutation arose in continental Europe no earlier than 6,000 years ago, coinciding with the arrival of the Neolithic agricultural revolution. Here we hypothesize that this new Neolithic diet, which originated in the sunny warm and dry climates of the Middle East, was carried by migrating farmers into the chilly and damp environments of Europe where iron is a critical micronutrient for effective thermoregulation. We argue that the C282Y allele was an adaptation to this novel environment.

MATERIALS AND METHODS

To address our hypothesis, we compiled C282Y allele frequencies, known Neolithic sites in Europe and climatic data on temperature and rainfall for statistical analysis.

RESULTS

Our findings indicate that the geographic cline for C282Y frequency in Europe increases as average temperatures decrease below 16°C, a critical threshold for thermoregulation, with rainy days intensifying the trend.

DISCUSSION

The results indicate that the deleterious C282Y allele, responsible for most cases of hemochromatosis, may have evolved as a selective advantage to culture and climate during the European Neolithic.

EMQN best practice guidelines for the molecular genetic diagnosis of hereditary hemochromatosis (HH)

Molecular genetic testing for hereditary hemochromatosis (HH) is recognized as a reference test to confirm the diagnosis of suspected HH or to predict its risk. The vast majority (typically >90%) of patients with clinically characterized HH are homozygous for the p.C282Y variant in the HFE gene, referred to as HFE-related HH. Since 1996, HFE genotyping was implemented in diagnostic algorithms for suspected HH, allowing its early diagnosis and prevention. However, the penetrance of disease in p.C282Y homozygotes is incomplete. Hence, homozygosity for p.C282Y is not sufficient to diagnose HH. Neither is p.C282Y homozygosity required for diagnosis as other rare forms of HH exist, generally referred to as non-HFE-related HH. These pose significant challenges when defining criteria for referral, testing protocols, interpretation of test results and reporting practices. We present best practice guidelines for the molecular genetic diagnosis of HH where recommendations are classified, as far as possible, according to the level and strength of evidence. For clarification, the guidelines' recommendations are preceded by a detailed description of the methodology and results obtained with a series of actions taken in order to achieve a wide expert consensus, namely: (i) a survey on the current practices followed by laboratories offering molecular diagnosis of HH; (ii) a systematic literature search focused on some identified controversial topics; (iii) an expert Best Practice Workshop convened to achieve consensus on the practical recommendations included in the guidelines.

Quality of life utility values for hereditary haemochromatosis in Australia

Background

Hereditary hemochromatosis (HH) is a common autosomal recessive disorder amongst persons of northern European heritage. If untreated, iron accumulates in parenchymal tissues causing morbidity and mortality. As diagnosis often follows irreversible organ damage, screening programs have been suggested to increase early diagnosis. A lack of economic evidence has been cited as a barrier to establishing such a program. Previous analyses used poorly estimated utility values. This study sought to measure utilities directly from people with HH in Australia.

Methods

Volunteers with HH were recruited to complete a web-based survey. Utility was assessed using the Assessment of Quality of Life 4D (AQOL-4D) instrument. Severity of HH was graded into four categories. Multivariable regression analysis was performed to identify parameters associated with HSUV.

Results

Between November 2013 and November 2014, 221 people completed the survey. Increasing severity of HH was negatively associated with utility. Mean (standard deviation) utilities were 0.76 (0.21), 0.81 (0.18), 0.60 (0.27), and 0.50 (0.27) for categories 1–4 HH respectively. Lower mean utility was found for symptomatic participants (categories 3 and 4) compared with asymptomatic participants (0.583 v. 0.796). Self-reported HH-related symptoms were negatively associated with HSUV (r = −0.685).

Conclusions

Symptomatic stages of HH and presence of multiple self-reported symptoms were associated with decreasing utility. Previous economic analyses have used higher utilities which likely resulted in underestimates of the cost effectiveness of HH interventions. The utilities reported in this paper are the most robust available, and will contribute to improving the validity of future economic models for HH.

Carriers of the Complex Allele HFE c.[187C>G;340+4T>C] Have Increased Risk of Iron Overload in São Miguel Island Population (Azores, Portugal)

Iron overload is associated with acquired and genetic conditions, the most common being hereditary hemochromatosis (HH) type-I, caused by HFE mutations. Here, we conducted a hospital-based case-control study of 41 patients from the São Miguel Island (Azores, Portugal), six belonging to a family with HH type-I pseudodominant inheritance, and 35 unrelated individuals fulfilling the biochemical criteria of iron overload compatible with HH type-I. For this purpose, we analyzed the most common HFE mutations– c.845G>A [p.Cys282Tyr], c.187C>G [p.His63Asp], and c.193A>T [p.Ser65Cys]. Results revealed that the family’s HH pseudodominant pattern is due to consanguineous marriage of HFE-c.845G>A carriers, and to marriage with a genetically unrelated spouse that is a -c.187G carrier. Regarding unrelated patients, six were homozygous for c.845A, and three were c.845A/c.187G compound heterozygous. We then performed sequencing of HFE exons 2, 4, 5 and their intron-flanking regions. No other mutations were observed, but we identified the -c.340+4C [IVS2+4C] splice variant in 26 (74.3%) patients. Functionally, the c.340+4C may generate alternative splicing by HFE exon 2 skipping and consequently, a protein missing the α1-domain essential for HFE/ transferrin receptor-1 interactions. Finally, we investigated HFE mutations configuration with iron overload by determining haplotypes and genotypic profiles. Results evidenced that carriers of HFE-c.187G allele also carry -c.340+4C, suggesting in-cis configuration. This data is corroborated by the association analysis where carriers of the complex allele HFE-c.[187C>G;340+4T>C] have an increased iron overload risk (RR = 2.08, 95% CI = 1.40−2.94, p<0.001). Therefore, homozygous for this complex allele are at risk of having iron overload because they will produce two altered proteins—the p.63Asp [c.187G], and the protein lacking 88 amino acids encoded by exon 2. In summary, we provide evidence that the complex allele HFE-c.[187C>G;340+4T>C] has a role, as genetic predisposition factor, on iron overload in the São Miguel population. Independent replication studies in other populations are needed to confirm this association.

A Systematic Review and Narrative Synthesis of Health Economic Studies Conducted for Hereditary Haemochromatosis

BACKGROUND

Hereditary haemochromatosis (HH) is a common genetic condition amongst people of northern European heritage. HH is associated with increased iron absorption leading to parenchymal organ damage and multiple arthropathies. Early diagnosis and treatment prevents complications. Population screening may increase early diagnosis, but no programmes have been introduced internationally: a paucity of health economic data is often cited as a barrier.

OBJECTIVE

To conduct a systematic review of all health economic studies in HH.

METHODS

Studies were identified through electronic searching of economic/biomedical databases. Any study on HH with original economic component was included. Study quality was formally assessed. Health economic data were extracted and analysed through narrative synthesis.

RESULTS

Thirty-eight studies met the inclusion criteria. The majority of papers reported on costs or cost effectiveness of screening programmes. Whilst most concluded screening was cost effective compared with no screening, methodological flaws limit the quality of these findings. Assumptions regarding clinical penetrance, effectiveness of screening, health-state utility values (HSUVs), exclusion of early symptomatology (such as fatigue, lethargy and multiple arthropathies) and quantification of costs associated with HH were identified as key limitations. Treatment studies concluded therapeutic venepuncture was the most cost-effective intervention.

CONCLUSIONS

There is a paucity of high-quality health economic studies relating to HH. The development of a comprehensive HH cost-effectiveness model utilising HSUVs is required to determine whether screening is worthwhile.

Dupuytren's Contracture in Alabama HFE Hemochromatosis Probands

BACKGROUND

Dupuytren's contracture (DC) and HFE hemochromatosis occur in some of the same at-risk populations and present with similar comorbid conditions.

METHODS

We estimated DC prevalence in two cohorts of white Alabama hemochromatosis probands (294 C282Y homozygotes, 67 C282Y/H63D compound heterozygotes) in a retrospective study. We performed logistic regressions on DC using the following independent variables: age, body mass index, heavy ethanol consumption, serum ferritin, elevated serum AST/ALT, non-alcoholic fatty liver disease, viral hepatitis, cirrhosis, and diabetes.

RESULTS

One man and two women with C282Y homozygosity had DC (prevalence 1.02%; 95% CI 0.35%-2.96%). A man with C282Y/H63D had DC (prevalence 1.49%; 95% CI 0.26%-7.98%). DC occurred as an autosomal dominant trait in his kinship. In regression analyses, no single variable predicted DC. We observed no new DC cases after the diagnosis of hemochromatosis (mean follow-up 12.9 ± 7.5 years (1 SD), and 9.0 ± 5.1 years, respectively).

CONCLUSIONS

Our prevalence estimates of DC in white Alabama hemochromatosis probands are similar to those found in the white US population cohorts. DC risk was unrelated to the variables we studied.

Oral iron prophylaxis in pregnancy: not too little and not too much!

An adequate supply of iron is essential for normal development of the fetus and newborn child. Iron deficiency and iron deficiency anemia (IDA) during pregnancy increase the risk of preterm birth and low birth weight. Iron is important for development of the fetal brain and cognitive abilities of the newborn. Children born to iron-deficient mothers will start their lives suffering from iron deficiency or even IDA. Oral iron prophylaxis to pregnant women improves iron status and prevents development of IDA. The Danish National Board of Health has since 1992 recommended prophylactic oral iron supplements to all pregnant women and the currently advocated dose is 40–50 mg ferrous iron taken between meals from 10 weeks gestation to delivery. However, 30–40 mg ferrous iron is probably an adequate dose in most affluent societies. In developed countries, individual iron prophylaxis guided by iron status (serum ferritin) has physiological advantages compared to general iron prophylaxis. In contrast, in most developing countries, general iron prophylaxis is indicated, and higher doses of oral iron, for example, 60 mg ferrous iron or even more should be recommended, according to the present iron status situation in the specific populations of women of fertile age and pregnant women.

Iron in pregnancy: How do we secure an appropriate iron status in the mother and child?

Iron deficiency and iron deficiency anemia (IDA) during pregnancy are risk factors for preterm delivery, prematurity, and small for gestational age birth weight. Iron deficiency has a negative effect on intelligence and behavioral development in the infant. It is essential to prevent iron deficiency in the fetus by preventing iron deficiency in the pregnant woman. The requirements for absorbed iron increase during pregnancy from ∼1.0 mg/day in the first trimester to 7.5 mg/day in the third trimester. More than 90% of Scandinavian women of reproductive age have a dietary iron intake below the recommended 15 mg/day. Among nonpregnant women of reproductive age, ∼40% have plasma ferritin ≤30 μg/l, i.e. an unfavorable iron status with respect to pregnancy. An adequate iron status during pregnancy implies body iron reserves ≥500 mg at conception, but only 15-20% of women have iron reserves of such a magnitude. Iron supplements during pregnancy reduce the prevalence of IDA. In Europe, IDA can be prevented by a general low-dose iron prophylaxis of 30-40 mg ferrous iron taken between meals from early pregnancy to delivery. In affluent societies, individual iron prophylaxis tailored by the ferritin concentration should be preferred to general prophylaxis. Suggested guidelines are: ferritin >70 μg/l, no iron supplements; ferritin 31-70 μg/l, 30-40 mg ferrous iron per day, and ferritin ≤30 μg/l, 60-80 mg ferrous iron per day. In women with ferritin <15 μg/l, i.e. depleted iron reserves and possible IDA, therapeutic doses of 100 mg ferrous iron per day should be advised.

Prevalence of C282Y, H63D, and S65C mutations in hereditary HFE-hemochromatosis gene in Lithuanian population

HFE-hemochromatosis is a common autosomal recessive disease caused by HFE gene mutations and characterized as iron overload and failure of different organs. The aim of this study was to determine the prevalence of C282Y (c.845 G>A), H63D (c.187 C>G), and S65C (c.193A>T) alleles of HFE gene in the Lithuanian population. One thousand and eleven healthy blood donors of Lithuanian nationality were examined in four different ethnic Lithuanian regions to determine HFE gene alleles and genotype frequencies. The samples of DNA were analyzed for the presence of restriction fragment length polymorphism and validated by DNA sequencing. Among 1,011 blood donors tested, the frequency of C282Y, H63D, and S65C alleles were 2.6%, 15.9%, and 1.9%, respectively. One third of the tested subjects (n = 336) had at least one of the C282Y or H63D HFE gene mutations. The screening of Lithuanian blood donors has detected 13 (1.3%) subjects with a genotype C282Y/C282Y or C282Y/H63D responsible for the development of HFE-hemochromatosis. The prevalence of C282Y mutation was significantly higher among the inhabitants of Zemaitija (Somogitia) at the Baltic Sea area (5.9%) in comparison to the regions of continental part of Lithuania (2.4% in Dzukija, 2.3% in Aukstaitija, and 2% in Suvalkija, p < 0.05). These data support the hypothesis that the p.C282Y mutation originated from Scandinavia and spread with the Vikings along the Baltic Sea coast. The first epidemiological investigation of HFE gene mutations in ethnic Lithuanians showed that the frequencies of H63D, C282Y, and S65C of HFE gene alleles are similar to the other North-Eastern Europeans, especially in the Baltic region (Estonia, Latvia), Poland, and part of Russia (Moscow region).

Hemochromatosis gene mutations in the general population of Slovakia

This is an epidemiologic study of the Slovak population with the aim of determining the frequencies of three hemochromatosis gene (HFE) variants C282Y, H63D and S65C known to be associated with manifestation of hereditary hemochromatosis and to assess deviations of these frequencies from those reported elsewhere. Mutations were detected in 359 ethnic Slovaks by real-time PCR assay based on TaqMan technology. The allelic frequencies were 4.03% for C282Y, 12.67% for H63D and 1.25% for S65C mutation. We observed 0.28% of C282Y/C282Y homozygotes, 3.34% H63D/H63D homozygotes, 0.84% of C282Y/H63D compound heterozygotes and 0.56% of H63D/S65C compound heterozygotes. This is the first time the frequencies of H63D and S65C mutations have been reported in the general population in Slovakia. The observed allelic frequencies are consistent with the previous studies of Slavic and Central European populations.

Low prevalence of hereditary hemochromatosis in multiethnic populations in Northern Norway

OBJECTIVE

Hereditary hemochromatosis has an autosomal recessive inheritance. The C282Y homozygosity is the most common genetic mutation in persons of Northern European descent. A screen of two multiethnic populations in Northern Norway was performed to investigate whether the prevalence of hereditary hemochromatosis was consistent with previous results in Northern Europe.

MATERIAL AND METHODS

Participants in two population-based studies in Northern Norway were analyzed for serum ferritin (s-ferritin) and transferrin saturation. Participants with s-ferritin or transferrin saturation above the reference limits in two separate blood samples were tested for three different HFE mutations, namely C282Y, H63D and S65.

RESULTS

The estimated prevalence of the C282Y/C282Y mutation in the two municipalities studied was lower than in comparable studies in Norway. The prevalence was the lowest in the Sør-Varanger population (men 0.19% and women 0.22%), which also had the highest proportion of individuals with Sami and Kven affiliation. In Tromsø, the prevalence was consistent with previous results in Norway.

CONCLUSIONS

The prevalence of hereditary hemochromatosis is lower in multiethnic populations in Northern Norway than in previous studies from other parts of Norway.

Prevalence of H63D, S65C, and C282Y hereditary hemochromatosis gene variants in Madeira Island (Portugal)

Hereditary HFE Hemochromatosis is an inherited disorder of iron metabolism that results from mutations in the HFE gene. Almost all patients with hereditary hemochromatosis show a C282Y mutation in homozygosity or in compound heterozygosity with H63D. Also, the mutation S65C has been shown to be associated to a milder iron overload. Since allele and genotype frequencies of these three variants of the HFE gene vary between populations, the determination of their prevalence in Madeira Island will clarify the population susceptibility to hereditary hemochromatosis. One hundred and fifty-four samples from Madeira Island were genotyped for the three most common HFE gene mutations, H63D, C282Y, and S65C, by polymerase chain reaction followed by restriction fragment length polymorphism analysis. Results have shown a prevalence of 20.5%, 0.33%, and 1% for H63D, C282Y, and S65C, respectively. Accordingly to our estimates, both genotypes associated to hereditary hemochromatosis, C282Y homozygotes and C282/H63D compound heterozygotes, could be present in Madeira Island population in 1,648 individuals, which represents 0.65% of the total population.

Hereditary hemochromatosis (HFE) genotypes in heart failure: relation to etiology and prognosis

Background

It is believed that hereditary hemochromatosis (HH) might play a role in cardiac disease (heart failure (HF) and ischemia). Mutations within several genes are HH-associated, the most common being the HFE gene. In a large cohort of HF patients, we sought to determine the etiological role and the prognostic significance of HFE genotypes.

Methods

We studied 667 HF patients (72.7% men) with depressed systolic function, enrolled in a multicentre trial with a follow-up period of up to 5 years. All were genotyped for the known HFE variants C282Y, H63D and S65C.

Results

The genotype and allele frequencies in the HF group were similar to the frequencies determined in the general Danish population. In multivariable analysis mortality was not predicted by C282Y-carrier status (HR 1.2, 95% CI: 0.8-1.7); H63D-carrier status (HR 1.0, 95% CI: 0.7-1.3); nor S65C-carrier status (HR 1.2, 95% CI: 0.7-2.0). We identified 27 (4.1%) homozygous or compound heterozygous carriers of HFE variants. None of these carriers had a clinical presentation suggesting hemochromatosis, but hemoglobin and ferritin levels were higher than in the rest of the cohort. Furthermore, a trend towards reduced mortality was seen in this group in univariate analyses (HR 0.4, 95% CI: 0.2-0.9, p = 0.03), but not in multivariate (HR 0.5, 95% CI: 0.2-1.2).

Conclusion

HFE genotypes do not seem to be a significant contributor to the etiology of heart failure in Denmark. HFE variants do not affect mortality in HF.

The global burden of iron overload

There have been major developments in the field of iron metabolism in the past decade following the identification of the HFE gene and the mutation responsible for the C282Y substitution in the HFE protein. While HFE-associated hemochromatosis occurs predominantly in people of northern European extraction, other less-common mutations can lead to the same clinical syndrome and these may occur in other populations in the Asian-Pacific region. The most common of these is the mutation that leads to changes in the ferroportin molecule, the protein responsible for the transport of iron across the basolateral membrane of the enterocyte and from macrophages. Recent research has unraveled the molecular processes of iron transport and regulation of how these are disturbed in hemochromatosis and other iron-loading disorders. At the same time, at least one new oral iron chelating agent has been developed that shows promise in the therapy of hemochromatosis as well as thalassemia and other secondary causes of iron overload. It is pertinent therefore to examine the developments in the global field of iron overload that have provided insights into the pathogenesis, disease penetrance, comorbid factors, and management.

Extrinsic factors modifying expressivity of the HFE variant C282Y, H63D, S65C phenotypes in 1,294 Danish men

This study analysed the influence of extrinsic factors on the phenotypic expression of HFE gene variants in ethnic Danish men. A cohort of 6,020 men aged 30-53 years was screened for HFE C282Y, H63D and S65C variants. Serum iron, serum transferrin, transferrin saturation, and serum ferritin were analysed in 1,452 men and 1,294 men completed a questionnaire on factors, which could influence iron balance. The C282Y allele was present in 5.6%, H63D in 12.8% and S65C in 1.8% of the men. In the entire series, 3% had elevated iron status markers (transferrin saturation > or =50%, ferritin > or =300 microg/L). Self-reported liver disease had an elevating effect and peptic ulcer a lowering effect on iron status markers. Age increased the fraction of men with elevated ferritin from 8.3% at 32-38 years to 16.2% at 46-53 years of age (p = 0.002). Blood donation had a lowering effect on iron status markers (p = 0.0001). Alcohol consumption elevated serum iron and serum ferritin (p = 0.001). Meat consumption had an elevating effect (p = 0.02) and milk consumption a lowering effect (p = 0.03) on serum ferritin. There was no influence of vitamin-mineral tablets on iron status markers. In adjusted logistic regression analysis, the HFE genotype had the highest impact on iron status markers; high alcohol consumption was significantly associated with elevated transferrin saturation. High age and high alcohol consumption were significantly associated with elevated ferritin and high egg consumption and blood donation was significantly associated with normal ferritin levels. In conclusion, the expressivity of HFE variant phenotypes in Danish men was enhanced by alcohol and meat consumption and decreased by milk and egg consumption and blood donation.