Phytanic acid and the risk of non-Hodgkin lymphoma

Phytanic acid, an inconclusive phytol metabolite: A review

Phytanic acid (PA: 3,7,11,15-tetramethylhexadecanoic acid) is an important biometabolite of the chlorophyll-derived diterpenoid phytol. Its biological sources (occurrence) and ADME (absorption, distribution, metabolism, and elimination) profile are well-discussed in the literature. Cumulative literature suggests that PA has beneficial as well as harmful biological roles in humans and other animals. This study aimed to sketch a brief summary of PA's beneficial and harmful pharmacological effects in test systems on the basis of existing literature reports. Literature findings propose that PA has anti-inflammatory and immunomodulatory, antidiabetic, anti-obesity, anticancer, and oocyte maturation effects. Although a high plasma PA-level mediated SLS remains controversial, it is evident to link it with Refsum's disease and other peroxisomal enzyme deficiency diseases in humans, including RCDP and LD; ZHDA and Alzheimer's disease; progressive ataxia and dysarthria; and an increased risk of some lymphomas such as LBL, FL, and NHL. PA exerts toxic effects on different kinds of cells, including neuronal, cardiac, and renal cells, through diverse pathways such as oxidative stress, mitochondrial disturbance, apoptosis, disruption of Na+/K+-ATPase activity, Ca2+ homeostasis, alteration of AChE and MAO activities, etc. PA is considered a cardiac biomarker in humans. In conclusion, PA may be one of the most important biometabolites in humans.

Association between Meat, Fish, and Fatty Acid Intake and Non-Hodgkin Lymphoma Incidence: The Japan Public Health Center-Based Prospective Study

BACKGROUND

Meat, fish, and fatty acid intakes have been reported to be associated with non-Hodgkin lymphoma (NHL), although results have been inconclusive. We hypothesized that red meat and SFA intakes increase NHL risk, and fish and PUFA intakes decrease NHL risk.

OBJECTIVES

We investigated the association between NHL incidence and meat, fish, and various fatty acid type intakes using the Japan Public Health Center-based Prospective Study.

METHODS

The current cohort study included 93,366 participants aged 45-74 y who were eligible for analysis; they were followed up until December 2012. Participants answered an FFQ between 1995 and 1999. We analyzed the effects of meat, fish, total fatty acid, SFA, and PUFA intakes on NHL incidence using the Cox proportional hazard model.

RESULTS

The median age was 57 y (IQR: 51-63 y), and 46.5% of the participants were men. Participants were followed up for 1,345,001 person-years, and 230 patients with NHL were identified. Total fatty acid and SFA intakes were associated with an increased incidence of NHL, with an adjusted HR of 1.56 (95% CI: 1.04, 2.34 highest compared with lowest quartile; P-trend = 0.062), and 1.63 (95% CI: 1.11, 2.41; P-trend = 0.074), respectively. In subtype analysis, total fatty acid and SFA intakes were also associated with increased incidence of follicular lymphoma but were not significantly associated with diffuse large B-cell lymphoma. Conversely, total meat, processed meat, unprocessed meat, red meat, poultry, fish, MUFA, PUFA, n-3 (ω-3) PUFA, and n-6 (ω-6) PUFA intakes were not significantly associated with the incidence of NHL or its subtypes.

CONCLUSIONS

Total fatty acid and SFA intakes were associated with increased incidence of NHL in the Japanese adult population. Further large-scale studies are warranted to test whether fatty acid intakes affect the development of NHL.

Environmental risk factors for non-Hodgkin's lymphoma: umbrella review and comparison of meta-analyses of summary and individual participant data

Objectives

To summarise the range, strength, and validity of reported associations between environmental risk factors and non-Hodgkin's lymphoma, and to evaluate the concordance between associations reported in meta-analyses of summary level data and meta-analyses of individual participant data.

Design

Umbrella review and comparison of meta-analyses of summary and individual participant level data.

Data sources

Medline, Embase, Scopus, Web of Science Core Collection, Cochrane Library, and Epistemonikos, from inception to 23 July 2021.

Eligibility criteria for selecting studies

English language meta-analyses of summary level data and of individual participant data evaluating associations between environmental risk factors and incident non-Hodgkin's lymphoma (overall and subtypes).

Data extraction and synthesis

Summary effect estimates from meta-analyses of summary level data comparing ever versus never exposure that were adjusted for the largest number of potential confounders were re-estimated using a random effects model and classified as presenting evidence that was non-significant, weak (P<0.05), suggestive (P<0.001 and >1000 cases), highly suggestive (P<0.000001, >1000 cases, largest study reporting a significant association), or convincing (P<0.000001, >1000 cases, largest study reporting a significant association, I2 <50%, 95% prediction interval excluding the null value, and no evidence of small study effects and excess significance bias) evidence. When the same exposures, exposure contrast levels, and outcomes were evaluated in meta-analyses of summary level data and meta-analyses of individual participant data from the International Lymphoma Epidemiology (InterLymph) Consortium, concordance in terms of direction, level of significance, and overlap of 95% confidence intervals was examined. Methodological quality of the meta-analyses of summary level data was assessed by the AMSTAR 2 tool.

Results

We identified 85 meta-analyses of summary level data reporting 257 associations for 134 unique environmental risk factors and 10 subtypes of non-Hodgkin's lymphoma nearly all (79, 93%) were classified as having critically low quality. Most associations (225, 88%) presented either non-significant or weak evidence. The 11 (4%) associations presenting highly suggestive evidence were primarily for autoimmune or infectious disease related risk factors. Only one association, between history of coeliac disease and risk of non-Hodgkin's lymphoma, presented convincing evidence. Of 40 associations reported in meta-analyses of summary level data that were also evaluated in InterLymph meta-analyses of individual participant data, 22 (55%) pairs were in the same direction, had the same level of statistical significance, and had overlapping 95% confidence intervals; 28 (70%) pairs had summary effect sizes from the meta-analyses of individual participant data that were more conservative.

Conclusion

This umbrella review suggests evidence of many meta-analyses of summary level data reporting weak associations between environmental risk factors and non-Hodgkin's lymphoma. Improvements to primary studies as well as evidence synthesis in evaluations of evironmental risk factors and non-Hodgkin's lymphoma are needed.

Review registration number

PROSPERO CRD42020178010.

Red and processed meat consumption and cancer outcomes: Umbrella review

The purpose of this umbrella review was to evaluate the quality of evidence, validity and biases of the associations between red and processed meat consumption and multiple cancer outcomes according to existing systematic reviews and meta-analyses. The umbrella review identified 72 meta-analyses with 20 unique outcomes for red meat and 19 unique outcomes for processed meat. Red meat consumption was associated with increased risk of overall cancer mortality, non-Hodgkin lymphoma (NHL), bladder, breast, colorectal, endometrial, esophageal, gastric, lung and nasopharyngeal cancer. Processed meat consumption might increase the risk of overall cancer mortality, NHL, bladder, breast, colorectal, esophageal, gastric, nasopharyngeal, oral cavity and oropharynx and prostate cancer. Dose-response analyses revealed that 100 g/d increment of red meat and 50 g/d increment of processed meat consumption were associated with 11%-51% and 8%-72% higher risk of multiple cancer outcomes, respectively, and seemed to be not correlated with any benefit.

Fish consumption and risk of non-Hodgkin lymphoma: A meta-analysis of observational studies

Objectives: Whether a relationship between fish consumption and non-Hodgkin lymphoma (NHL) risk exists is an open issue. We carried out a meta-analysis to explore this association according to the published observational studies.Methods: We performed a search of databases in MEDLINE and EMBASE to identify relevant studies. We derived meta-analytic estimates using random-effects models, and assessed between-study heterogeneity using the Cochran's Q and I² statistics.Results: We identified a total of seven case-control and two prospective cohort studies, including 7696 subjects with NHL. The summary relative risks (SRRs) estimated for NHL were 0.80 (95% confidence intervals (CIs): 0.68-0.94) for those in the highest fish consumption category compared with those in the lowest consumption category. There was evidence of significant heterogeneity across studies (Q = 26.72, P_{heterogeneity} = 0.002, I² = 66.3%). Stratified analysis by study design indicated that a significant risk association between fish consumption and NHL was observed in case-control studies, but not in cohort studies. Based on the dose-response meta-analysis, the SRRs of NHL were 0.85 (95% CIs: 0.71-1.01) for three servings increased per week of fish consumed with evidence of significant heterogeneity (P_{heterogeneity} = 0.007, I² = 63.9%).Conclusions: Findings from our meta-analysis indicate that consumption of fish may be not related to NHL risk.

Phytol and its metabolites phytanic and pristanic acids for risk of cancer: current evidence and future directions

This review summarizes the current evidence on the potential role of phytol, a microbial metabolite of chlorophyl A, and its metabolites, phytanic and pristanic acids, in carcinogenesis. Primary food sources in Western diets are the nut skin for phytol and lipids in dairy, beef and fish for its metabolites. Phytol and its metabolites gained interest as dietary compounds for cancer prevention because, as natural ligands of peroxisome proliferator-activated receptor-α and -γ and retinoid X receptor, phytol and its metabolites have provided some evidence in cell culture studies and limited evidence in animal models of anti-carcinogenic, anti-inflammatory and anti-metabolic-syndrome properties at physiological concentrations. However, there may be a narrow range of efficacy, because phytol and its metabolites at supra-physiological concentrations can cause in vitro cytotoxicity in non-cancer cells and can cause morbidity and mortality in animal models. In human studies, evidence for a role of phytol and its metabolites in cancer prevention is currently limited and inconclusive. In short, phytol and its metabolites are potential dietary compounds for cancer prevention, assuming the challenges in preventing cytotoxicity in non-cancer cells and animal models and understanding phytol metabolism can be mitigated.

Metabolomics-A Promising Approach to Pituitary Adenomas

Background: Metabolomics-the novel science that evaluates the multitude of low-molecular-weight metabolites in a biological system, provides new data on pathogenic mechanisms of diseases, including endocrine tumors. Although development of metabolomic profiling in pituitary disorders is at an early stage, it seems to be a promising approach in the near future in identifying specific disease biomarkers and understanding cellular signaling networks. Objectives: To review the metabolomic profile and the contributions of metabolomics in pituitary adenomas (PA). Methods: A systematic review was conducted via PubMed, Web of Science Core Collection and Scopus databases, summarizing studies that have described metabolomic aspects of PA. Results: Liquid chromatography tandem mass spectrometry (LC-MS/MS) and nuclear magnetic resonance (NMR) spectrometry, which are traditional techniques employed in metabolomics, suggest amino acids metabolism appears to be primarily altered in PA. N-acetyl aspartate, choline-containing compounds and creatine appear as highly effective in differentiating PA from healthy tissue. Deoxycholic and 4-pyridoxic acids, 3-methyladipate, short chain fatty acids and glucose-6-phosphate unveil metabolite biomarkers in patients with Cushing's disease. Phosphoethanolamine, N-acetyl aspartate and myo-inositol are down regulated in prolactinoma, whereas aspartate, glutamate and glutamine are up regulated. Phosphoethanolamine, taurine, alanine, choline-containing compounds, homocysteine, and methionine were up regulated in unclassified PA across studies. Intraoperative use of ultra high mass resolution matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI), which allows localization and delineation between functional PA and healthy pituitary tissue, may contribute to achievement of complete tumor resection in addition to preservation of pituitary cell lines and vasopressin secretory cells, thus avoiding postoperative diabetes insipidus. Conclusion: Implementation of ultra high performance metabolomics analysis techniques in the study of PA will significantly improve diagnosis and, potentially, the therapeutic approach, by identifying highly specific disease biomarkers in addition to novel molecular pathogenic mechanisms. Ultra high mass resolution MALDI-MSI emerges as a helpful clinical tool in the neurosurgical treatment of pituitary tumors. Therefore, metabolomics appears to be a science with a promising prospect in the sphere of PA, and a starting point in pituitary care.

Dietary fat intake and risk of non-Hodgkin lymphoma in 2 large prospective cohorts

Background: Dietary fat intake may contribute to non-Hodgkin lymphoma (NHL) pathogenesis by influencing carcinogen exposure or through immune modulation.Objective: We aimed to evaluate NHL risk associated with total and specific dietary fat intake.Design: We evaluated associations within the Nurses' Health Study (NHS) (n = 88,598) and the Health Professionals Follow-Up Study (HPFS) (n = 47,531) using repeated validated dietary assessments. We confirmed 1802 incident NHL diagnoses through 2010. Using multivariable Cox proportional hazards models, we estimated hazard ratios (HRs) for all NHL and common subtypes associated with a 1-SD increase in cumulative mean intakes of total, animal, saturated, trans, and vegetable fats and marine fatty acids. We pooled sex-specific HRs using random-effects meta-analysis.Results: Over 24-30 y of follow-up, neither total nor specific dietary fats were significantly associated with NHL risk overall. Higher total, animal, and saturated fat intakes were positively associated with the risk of the chronic lymphocytic leukemia/small lymphocytic lymphoma subtype among women only (253 cases; P-trend ≤ 0.05), driven by strong associations during 1980-1994. From baseline through 1994, among women and men combined, total fat intake was borderline-significantly positively associated with NHL overall (pooled HR per SD: 1.13; 95% CI: 0.99, 1.29) and was significantly associated with diffuse large B cell lymphoma (pooled HR per SD: 1.47; 95% CI: 1.06, 2.05), with similar trends for animal and saturated fat intake. For women only, trans fat was significantly positively associated with all NHL. In contrast, during 1994-2010, there was little evidence for associations of dietary fat intake with NHL overall or by subtype.Conclusion: Previous observations of an increased risk of NHL associated with intakes of total, animal, saturated, and trans fat with 14 y of follow-up did not persist with longer follow-up.

Non-Hodgkin lymphoma in the developing world: review of 4539 cases from the International Non-Hodgkin Lymphoma Classification Project

The distribution of non-Hodgkin lymphoma subtypes varies around the world, but a large systematic comparative study has never been done. In this study, we evaluated the clinical features and relative frequencies of non-Hodgkin lymphoma subtypes in five developing regions of the world and compared the findings to the developed world. Five expert hematopathologists classified 4848 consecutive cases of lymphoma from 26 centers in 24 countries using the World Health Organization classification, and 4539 (93.6%) were confirmed to be non-Hodgkin lymphoma, with a significantly greater number of males than females in the developing regions compared to the developed world (P<0.05). The median age at diagnosis was significantly lower for both low- and high-grade B-cell lymphoma in the developing regions. The developing regions had a significantly lower frequency of B-cell lymphoma (86.6%) and a higher frequency of T- and natural killer-cell lymphoma (13.4%) compared to the developed world (90.7% and 9.3%, respectively). Also, the developing regions had significantly more cases of high-grade B-cell lymphoma (59.6%) and fewer cases of low-grade B-cell lymphoma (22.7%) compared to the developed world (39.2% and 32.7%, respectively). Among the B-cell lymphomas, diffuse large B-cell lymphoma was the most common subtype (42.5%) in the developing regions. Burkitt lymphoma (2.2%), precursor B- and T-lymphoblastic leukemia/lymphoma (1.1% and 2.9%, respectively) and extranodal natural killer/T-cell lymphoma (2.2%) were also significantly increased in the developing regions. These findings suggest that differences in etiologic and host risk factors are likely responsible, and more detailed epidemiological studies are needed to better understand these differences.

Meat intake and non-Hodgkin lymphoma: a meta-analysis of observational studies

PURPOSE

High intake of meat has been inconsistently associated with increased risk of non-Hodgkin lymphoma (NHL). We carried out a meta-analysis to summarize the evidence of published observational studies reporting association between red meat and processed meat intake and NHL risk.

METHODS

Analytical studies reporting relative risks with 95 % confidence intervals (95 % CI) for the association between intake of red and/or processed meat and NHL or major histological subtypes were eligible. We conducted random-effects meta-analysis comparing lowest and highest intake categories and dose-response meta-analysis when risk estimates and intake levels were available for more than three exposure classes.

RESULTS

Fourteen studies (four cohort and ten case-control) were included in the meta-analysis, involving a total of 10,121 NHL cases. The overall relative risks of NHL for the highest versus the lowest category of consumption were 1.14 (95 % CI 1.03, 1.26) for red meat and 1.06 (95 % CI 0.98, 1.15) for processed meat. Significant associations were present when the analysis was restricted to case-control studies but not when restricted to cohort studies. No significant associations were found for major NHL etiological subtypes. Dose-response meta-analysis could be based only on eight studies that provided sufficient data, and compared to no meat consumption, the overall NHL relative risk increased nonlinearly with increased daily intake of red meat.

CONCLUSION

The observed positive association between red meat consumption and NHL is mainly supported by the effect estimates coming from case-control studies and is affected by multiple sources of heterogeneity. This meta-analysis provided mixed and inconclusive evidences on the supposed relationship between red and processed meat consumption and NHL.

Dairy Product Consumption and Risk of Non-Hodgkin Lymphoma: A Meta-Analysis

Many epidemiologic studies have explored the association between dairy product consumption and the risk of non-Hodgkin lymphoma (NHL), but the results remain controversial. A literature search was performed in PubMed, Web of Science and Embase for relevant articles published up to October 2015. Pooled relative risks (RRs) with 95% confidence intervals (CIs) were calculated with a random-effects model. The dose-response relationship was assessed by restricted cubic spline. A total of 16 articles were eligible for this meta-analysis. The pooled RRs (95% CIs) of NHL for the highest vs. lowest category of the consumption of total dairy product, milk, butter, cheese, ice cream and yogurt were 1.20 (1.02, 1.42), 1.41 (1.08, 1.84), 1.31 (1.04, 1.65), 1.14 (0.96, 1.34), 1.57 (1.11, 2.20) and 0.78 (0.54, 1.12), respectively. In subgroup analyses, the positive association between total dairy product consumption and the risk of NHL was found among case-control studies (RR = 1.41, 95% CI: 1.17-1.70) but not among cohort studies (RR = 1.02, 95% CI: 0.88-1.17). The pooled RRs (95% CIs) of NHL were 1.21 (1.01, 1.46) for milk consumption in studies conducted in North America, and 1.24 (1.09, 1.40) for cheese consumption in studies that adopted validated food frequency questionnaires. In further analysis of NHL subtypes, we found statistically significant associations between the consumption of total dairy product (RR = 1.73, 95% CI: 1.22-2.45) and milk (RR = 1.49, 95% CI: 1.08-2.06) and the risk of diffuse large B-cell lymphoma. The dose-response analysis suggested that the risk of NHL increased by 5% (1.05 (1.00-1.10)) and 6% (1.06 (0.99-1.13)) for each 200 g/day increment of total dairy product and milk consumption, respectively. This meta-analysis suggested that dairy product consumption, but not yogurt, may increase the risk of NHL. More prospective cohort studies that investigate specific types of dairy product consumption are needed to confirm this conclusion.

Relative frequency of non-Hodgkin lymphoma subtypes in selected centres in North Africa, the middle east and India: a review of 971 cases

Comparative data regarding the distribution of non-Hodgkin lymphoma (NHL) subtypes in North Africa, the Middle East and India (NAF/ME/IN) is scarce in the literature. In this study, we evaluated the relative frequencies of NHL subtypes in this region. Five expert haematopathologists classified 971 consecutive cases of newly-diagnosed NHL from five countries in NAF/ME/IN. After review, 890 cases (91·7%) were confirmed to be NHL and compared to 399 cases from North America (NA). The male-to-female ratio was significantly higher in NAF/ME/IN (1·8) compared to NA (1·1; P< 0·05). The median ages of patients with low-grade (LG) and high-grade (HG) B-NHL in NAF/ME/IN (56 and 52 years, respectively) were significantly lower than in NA (64 and 68 years, respectively). In NAF/ME/IN, a significantly lower proportion of LG B-NHL (28·4%) and a higher proportion of HG B-NHL (58·4%) were found compared to NA (56·1% and 34·3%, respectively). Diffuse large B-cell lymphoma was more common in NAF/ME/IN (49·4%) compared to NA (29·3%), whereas follicular lymphoma was less common in NAF/ME/IN (12·4%) than in NA (33·6%). In conclusion, we found significant differences in NHL subtypes and clinical features between NAF/ME/IN and NA. Epidemiological studies are needed to better understand the pathobiology of these differences.

Non-Hodgkin lymphoma in the Far East: review of 730 cases from the international non-Hodgkin lymphoma classification project

Large and systematic studies of non-Hodgkin lymphoma (NHL) in the Far East (FE) with good comparative data are scarce in the literature. In this study, five expert hematopathologists classified 730 consecutive cases of newly-diagnosed NHL from four sites in the FE (excluding Japan) using the World Health Organization classification. The results were compared to 399 cases from North America (NA). We found a significantly higher male to female ratio in the FE compared to NA (1.7 versus 1.1; p < 0.05). The median ages of patients with low-grade (LG) and high-grade (HG) B-NHL in the FE (58 and 51 years, respectively) were significantly lower than in NA (64 and 68 years, respectively). The FE had a significantly lower relative frequency of B-NHL and a higher frequency of T-NHL (82 vs. 18 %) compared to NA (90.5 vs. 9.5 %). Among mature B cell lymphomas, the FE had a significantly higher relative frequency of HG B-NHL (54.8 %) and a lower frequency of LG B-NHL (27.2 %) than NA (34.3 and 56.1 %, respectively). Diffuse large B cell lymphoma was more common in the FE (49.4 %) compared to NA (29.3 %), whereas the relative frequency of follicular lymphoma was lower in the FE (9.4 %) compared to NA (33.6 %). Among T-NHL, nasal NK/T cell NHL was more frequent in the FE (5.2 %) compared to NA (0 %). Peripheral T cell lymphoma was also more common in the FE (9.1 %) than in NA (5.3 %). Further epidemiologic studies are needed to better understand the pathobiology of these differences.

Red and Processed Meat Consumption Increases Risk for Non-Hodgkin Lymphoma: A PRISMA-Compliant Meta-Analysis of Observational Studies

The association between consumption of red and processed meat and non-Hodgkin lymphoma (NHL) remains unclear. We performed a meta-analysis of the published observational studies to explore this relationship.We searched databases in MEDLINE and EMBASE to identify observational studies which evaluated the association between consumption of red and processed meat and risk of NHL. Quality of included studies was evaluated using Newcastle-Ottawa Quality Assessment Scale (NOS). Random-effects models were used to calculate summary relative risk (SRR) and the corresponding 95% confidence interval (CI).We identified a total of 16 case-control and 4 prospective cohort studies, including 15,189 subjects with NHL. The SRR of NHL comparing the highest and lowest categories were 1.32 (95% CI: 1.12-1.55) for red meat and 1.17 (95% CI: 1.07-1.29) for processed meat intake. Stratified analysis indicated that a statistically significant risk association between consumption of red and processed meat and NHL risk was observed in case-control studies, but not in cohort studies. The SRR was 1.11 (95% CI: 1.04-1.18) for per 100 g/day increment in red meat intake and 1.28 (95% CI: 1.08-1.53) for per 50 g/day increment in processed meat intake. There was evidence of a nonlinear association for intake of processed meat, but not for intake of red meat.Findings from our meta-analysis indicate that consumption of red and processed meat may be related to NHL risk. More prospective epidemiological studies that control for important confounders and focus on the NHL risk related with different levels of meat consumption are required to clarify this association.

Risk of lymphoma subtypes and dietary habits in a Mediterranean area

BACKGROUND

Previous studies have suggested that diet might affect risk of lymphoma subtypes. We investigated risk of lymphoma and its major subtypes associated with diet in the Mediterranean island of Sardinia, Italy.

METHODS

In 1998-2004, 322 incident lymphoma cases and 446 randomly selected population controls participated in a case-control study on lymphoma etiology in central-southern Sardinia. Questionnaire interviews included frequency of intake of 112 food items. Risk associated with individual dietary items and groups thereof was explored by unconditional and polytomous logistic regression analysis, adjusting by age, gender and education.

RESULTS

We observed an upward trend in risk of lymphoma (all subtypes combined) and B-cell lymphoma with frequency of intake of well done grilled/roasted chicken (p for trend=0.01), and pizza (p for trend=0.047), Neither adherence to Mediterranean diet nor a frequent intake of its individual components conveyed protection. We detected heterogeneity in risk associated with several food items and groups thereof by lymphoma subtypes although we could not rule out chance as responsible for the observed direct or inverse associations.

CONCLUSIONS

Adherence to a Mediterranean diet does not seem to convey protection against the development of lymphoma. The association with specific food items might vary by lymphoma subtype.

Epidemiology and etiology of non-hodgkin lymphoma

Non-Hodgkin lymphoma (NHL) consists of many histologically and biologically distinct lymphoid malignancies with poorly understood, but possibly distinct, etiologies. The patterns of incidence and time trend vary not only by age, sex, and race/ethnicity in the USA, but also show significant geographic differences, suggesting the potential role of infectious agents, environmental factors, and lifestyle factors in addition to host genetic status in the development of NHL. Important pathogenetic mechanisms include immune modulation and chronic antigen stimulation. Epidemiologic studies in the past two decades have provided intriguing new insights on the possible causes of lymphoma and support the idea that there is some mechanistic commonality of lymphomagenesis, but significant etiologic heterogeneity clearly exists. This review presents a summary of the current understanding of the descriptive epidemiology and etiology of NHL and suggests areas of focus for future epidemiologic research.

Thiamine and magnesium deficiencies: keys to disease

Thiamine deficiency (TD) is accepted as the cause of beriberi because of its action in the metabolism of simple carbohydrates, mainly as the rate limiting cofactor for the dehydrogenases of pyruvate and alpha-ketoglutarate, both being critical to the action of the citric acid cycle. Transketolase, dependent on thiamine and magnesium, occurs twice in the oxidative pentose pathway, important in production of reducing equivalents. Thiamine is also a cofactor in the dehydrogenase complex in the degradation of the branched chain amino acids, leucine, isoleucine and valine. In spite of these well accepted facts, the overall clinical effects of TD are still poorly understood. Because of the discovery of 2-hydroxyacyl-CoA lyase (HACL1) as the first peroxisomal enzyme in mammals found to be dependent on thiamine pyrophosphate (TPP) and the ability of thiamine to bind with prion protein, these factors should improve our clinical approach to TD. HACL1 has two important roles in alpha oxidation, the degradation of phytanic acid and shortening of 2-hydroxy long-chain fatty acids so that they can be degraded further by beta oxidation. The downstream effects of a lack of efficiency in this enzyme would be expected to be critical in normal brain metabolism. Although TD has been shown experimentally to produce reversible damage to mitochondria and there are many other causes of mitochondrial dysfunction, finding TD as the potential biochemical lesion would help in differential diagnosis. Stresses imposed by infection, head injury or inoculation can initiate intermittent cerebellar ataxia in thiamine deficiency/dependency. Medication or vaccine reactions appear to be more easily initiated in the more intelligent individuals when asymptomatic marginal malnutrition exists. Erythrocyte transketolase testing has shown that thiamine deficiency is widespread. It is hypothesized that the massive consumption of empty calories, particularly those derived from carbohydrate and fat, results in a high calorie/thiamine ratio as a major cause of disease. Because mild to moderate TD results in pseudo hypoxia in the limbic system and brainstem, emotional and stress reflexes of the autonomic nervous system are stimulated and exaggerated, producing symptoms often diagnosed as psychosomatic disease. If the biochemical lesion is recognized at this stage, the symptoms are easily reversible. If not, and the malnutrition continues, neurodegeneration follows and results in a variety of chronic brain diseases. Results from acceptance of the hypothesis could be tested by performing erythrocyte transketolase tests to pick out those with TD and supplementing the affected individuals with the appropriate dietary supplements.

Cancer in British vegetarians: updated analyses of 4998 incident cancers in a cohort of 32,491 meat eaters, 8612 fish eaters, 18,298 vegetarians, and 2246 vegans

BACKGROUND

Vegetarian diets might affect the risk of cancer.

OBJECTIVE

The objective was to describe cancer incidence in vegetarians and nonvegetarians in a large sample in the United Kingdom.

DESIGN

This was a pooled analysis of 2 prospective studies including 61,647 British men and women comprising 32,491 meat eaters, 8612 fish eaters, and 20,544 vegetarians (including 2246 vegans). Cancer incidence was followed through nationwide cancer registries. Cancer risk by vegetarian status was estimated by using multivariate Cox proportional hazards models.

RESULTS

After an average follow-up of 14.9 y, there were 4998 incident cancers: 3275 in meat eaters (10.1%), 520 in fish eaters (6.0%), and 1203 in vegetarians (5.9%). There was significant heterogeneity between dietary groups in risks of the following cancers: stomach cancer [RRs (95% CIs) compared with meat eaters: 0.62 (0.27, 1.43) in fish eaters and 0.37 (0.19, 0.69) in vegetarians; P-heterogeneity = 0.006], colorectal cancer [RRs (95% CIs): 0.66 (0.48, 0.92) in fish eaters and 1.03 (0.84, 1.26) in vegetarians; P-heterogeneity = 0.033], cancers of the lymphatic and hematopoietic tissue [RRs (95% CIs): 0.96 (0.70, 1.32) in fish eaters and 0.64 (0.49, 0.84) in vegetarians; P-heterogeneity = 0.005], multiple myeloma [RRs (95% CIs): 0.77 (0.34, 1.76) in fish eaters and 0.23 (0.09, 0.59) in vegetarians; P-heterogeneity = 0.010], and all sites combined [RRs (95% CIs): 0.88 (0.80, 0.97) in fish eaters and 0.88 (0.82, 0.95) in vegetarians; P-heterogeneity = 0.0007].

CONCLUSION

In this British population, the risk of some cancers is lower in fish eaters and vegetarians than in meat eaters.