Low serum cobalamin levels in a population study of 70- and 75-year-old subjects. Gastrointestinal causes and hematological effects

Contemporary issues surrounding folic Acid fortification initiatives

The impact of folate on health and disease, particularly pregnancy complications and congenital malformations, has been extensively studied. Mandatory folic acid fortification therefore has been implemented in multiple countries, resulting in a reduction in the occurrence of neural tube defects. However, emerging evidence suggests increased folate intake may also be associated with unexpected adverse effects. This literature review focuses on contemporary issues of concern, and possible underlying mechanisms as well as giving consideration the future direction of mandatory folic acid fortification. Folate fortification has been associated with the presence of unmetabolized folic acid (PteGlu) in blood, masking of vitamin B12 deficiency, increased dosage for anti-cancer medication, photo-catalysis of PteGlu leading to potential genotoxicity, and a role in the pathoaetiology of colorectal cancer. Increased folate intake has also been associated with twin birth and insulin resistance in offspring, and altered epigenetic mechanisms of inheritance. Although limited data exists to elucidate potential mechanisms underlying these issues, elevated blood folate level due to the excess use of PteGlu without consideration of an individual's specific phenotypic traits (e.g. genetic background and undiagnosed disease) may be relevant. Additionally, the accumulation of unmetabolized PteGlu may lead to inhibition of dihydrofolate reductase and other enzymes. Concerns notwithstanding, folic acid fortification has achieved enormous advances in public health. It therefore seems prudent to target and carefully monitor high risk groups, and to conduct well focused further research to better understand and to minimize any risk of mandatory folic acid fortification.

Holotranscobalamin is not influenced by decreased renal function in elderly men: the MrOS Sweden study

BACKGROUND

Subclinical cobalamin deficiency is common in the elderly, but the sensitivity and specificity of serum total cobalamin for this diagnosis is poor. Serum holotranscobalamin (holoTC), a measure of biologically available cobalamin, is considered a better marker for early cobalamin depletion than total cobalamin. However, in elderly populations, health-related reference intervals for holoTC and correlations to renal function are not entirely clear.

METHODS

HoloTC was determined with an automated microparticle enzyme immunoassay (AxSYM®) in 790 elderly non-vitamin-supplemented Swedish men, median age 75.3 years. Renal function was assessed with creatinine, cystatin C and estimated glomerular filtration rate (eGFR calculated from creatinine).

RESULTS

Median holoTC was 51.8 pmol/L, the health-related reference interval 19.6-132.3 pmol/L. There was no significant difference in mean holoTC in probands with normal compared to high creatinine (P = 0.80) and cystatin C (P = 0.82). No significant differences between the quartiles of creatinine or cystatin C in mean of log holoTC were seen. HoloTC correlated strongly with total cobalamin (r = 0.69, P < 0.001), weaker with eGFRcreatinine (r = -0.09, P < 0.05) and creatinine (r = 0.09, P < 0.05), the latter correlation was only seen in subjects with creatinine <100 µmol/L. HoloTC correlated negatively with plasma total homocysteine (r = -0.24, P < 0.001), but not with cystatin C and age.

CONCLUSIONS

Serum holoTC in healthy elderly men shows the same distribution as earlier described for a younger reference population. In this group of elderly subjects, holoTC did not correlate to reduced renal function. Thus, holoTC appears to be a promising tool for evaluating cobalamin status also in elderly populations.

Hyperhomocysteinemia is not associated with reduced bone quality in humans with hip osteoarthritis

BACKGROUND

Recent clinical and animal studies suggest that increased serum homocysteine (HCY) concentrations may be a risk factor for osteoporosis. In vitro studies showed that increasing HCY concentrations stimulate the activity of human osteoclasts. However, there is no data demonstrating that circulating HCY is related to structural and biomechanical properties of human bones. This study investigated the relationship between morphological as well as biomechanical bone properties and HCY serum concentrations in humans suffering from hip osteoarthritis (OA).

METHODS

Fasting blood samples and femoral heads were obtained from 94 males and females who underwent hip arthroplasty due to OA. Bones were assessed by dual energy X-ray absorptiometry (DXA), biomechanical testing (indentation method), and histomorphometry. Blood was collected for measurement of HCY, folate, vitamin B6, and vitamin B12. Subjects were classified as hyperhomocysteinemic (>12 micromol/L, n=47) and normohomocysteinemic (<12 micromol/L, n=47) according to their serum HCY concentrations.

RESULTS

Folate and vitamin B6, but not vitamin B12, were significantly lower in hyperhomocysteinemic subjects compared with controls. However, DXA, biomechanical testing, and histomorphometry did not reveal significant differences in bone quality between hyperhomocysteinemic subjects and controls.

CONCLUSIONS

The results of the present study do not indicate a significant relationship between circulating HCY concentrations and morphological or biomechanical bone properties in humans with OA of the hip.

How common is vitamin B-12 deficiency?

In considering the vitamin B-12 fortification of flour, it is important to know who is at risk of vitamin B-12 deficiency and whether those individuals would benefit from flour fortification. This article reviews current knowledge of the prevalence and causes of vitamin B-12 deficiency and considers whether fortification would improve the status of deficient subgroups of the population. In large surveys in the United States and the United Kingdom, approximately 6% of those aged > or =60 y are vitamin B-12 deficient (plasma vitamin B-12 < 148 pmol/L), with the prevalence of deficiency increasing with age. Closer to 20% have marginal status (plasma vitamin B-12: 148-221 pmol/L) in later life. In developing countries, deficiency is much more common, starting in early life and persisting across the life span. Inadequate intake, due to low consumption of animal-source foods, is the main cause of low serum vitamin B-12 in younger adults and likely the main cause in poor populations worldwide; in most studies, serum vitamin B-12 concentration is correlated with intake of this vitamin. In older persons, food-bound cobalamin malabsorption becomes the predominant cause of deficiency, at least in part due to gastric atrophy, but it is likely that most elderly can absorb the vitamin from fortified food. Fortification of flour with vitamin B-12 is likely to improve the status of most persons with low stores of this vitamin. However, intervention studies are still needed to assess efficacy and functional benefits of increasing intake of the amounts likely to be consumed in flour, including in elderly persons with varying degrees of gastric atrophy.

Serum biomarkers for atrophic gastritis and antibodies against Helicobacter pylori in the elderly: Implications for vitamin B12, folic acid and iron status and response to oral vitamin therapy

OBJECTIVES

To investigate the prevalence of serological markers for chronic atrophic gastritis (AG) and Helicobacter pylori antibodies (HPAb) in an elderly population, and to examine the interrelationship and significance for cobalamin, folic acid and iron status and response to oral vitamin therapy.

MATERIAL AND METHODS

The study included community-dwelling subjects (n=209), mean age 76 years, randomized to 4 month of oral daily treatment with 0.5 mg cyanocobalamin, 0.8 mg folic acid and 3 mg vitamin B(6) or placebo (double-blind). Biochemical tests were carried out before and after treatment.

RESULTS

AG, as indicated by a pepsinogen I/II ratio <2.9, occurred in 14% (26/190) and HPAb in 54% (102/190) of the subjects. AG subjects had higher levels of serum methylmalonic acid (MMA) (p<0.001), plasma homocysteine (tHcy) (p<0.05), lower haemoglobin (Hb) (p<0.01) and a higher prevalence of vitamin B(12) deficiency (p<0.01). HPAb was associated with AG, whereas AG subjects without HPAb had higher tHcy and MMA levels. There was no correlation between AG and iron status. Oral vitamin treatment led to greater (albeit non-significant) improvements in MMA, tHcy and total cobalamins in AG subjects compared to non-AG subjects.

CONCLUSIONS

AG is a common condition and is a significant determinant of vitamin B(12) status. AG is correlated to HPAB and lower Hb. Elderly AG subjects respond at least as well as non-AG subjects to oral treatment with B-vitamins in the doses employed.

Gastric status and vitamin B12 levels in cardiovascular patients

Proper absorption of vitamin B12 requires gastric corpus mucosa that functions appropriately and secretes intrinsic factor needed as an essential cofactor for the absorption of dietary vitamin B12 in the small bowel. Here we describe the prevalence of vitamin B12 deficiency and atrophic corpus gastritis (ACG) in patients with coronary heart disease. Fasting serum was obtained from patients who were admitted for cardiovascular diseases at the Coronary Care Unit in Nijmegen, the Netherlands. The status of gastric mucosa was assessed by using the serum levels of pepsinogens I and II, gastrin-17, and Helicobacter pylori IgG antibodies and analyzed over vitamin B12 level subgroups. The study population consisted of 376 patients (mean age, 65 years [SD, 13 years], 227 [60%] males). Low vitamin B12 levels (<150 pM) were detected in 28 patients (7%). Of these 28 patients, 5 (18%) had ACG according to the biomarker assays. Altogether, another 140 patients (37%) had vitamin B12 levels between 150 and 250 pM, of whom 10 (7%) had ACG. Of the remaining patients, five (2%) had ACG. Deficiency of vitamin B12 is common among subjects with coronary heart disease. Up to 20% of these deficiencies are related to ACG.

Hyperplastic gastric polyposis, hypergastrinaemia and colorectal neoplasia: a description of four cases

BACKGROUND AND AIMS

Previous reports have suggested a possible association between hyperplastic polyposis and colorectal neoplasms. Increased gastrin may be the link between these two conditions insofar as gastrin has been reported to be a growth-promoting tumoural agent. This report describes gastric polyposis, hypergastrinaemia and colorectal neoplasms in four elderly patients.

METHODS

Four male patients with no family history of cancer, who were found to have multiple gastric hyperplastic polyps, hypergastrinaemia and colorectal cancers or an adenomatous polyp, were evaluated. Assessment included clinical evaluation, biochemical and haematological profiles, fasting gastrin levels, Helicobacter pylori serology, cobalamin, parietal cell antibodies, gastroscopy with biopsies of polyps and gastric mucosa, urease tests, and colonoscopy with biopsies of colorectal neoplasms. Immunohistochemistry of specimens from gastric polyps and colonic carcinomas was performed for chromogranin A, synaptophysin, Leu 7, neuron-specific enolase and gastrin.

RESULTS

The mean age at diagnosis of gastric polyps was 71.2 years and at removal of colorectal neoplasm was 70.0 years. In two patients, the gastric lesion was diagnosed before the colonic lesion and conversely in the two remaining patients. Gastrin was very high (1604 pg/ml; normal level, < 115 pg/ml) in one patient with pernicious anaemia, and the mean level for the other three was 324 pg/ml. H. pylori were found in two patients. Immunohistochemistry failed to identify neuroendocrine cells in the hyperplastic gastric polyps and three of the colonic carcinomas.

CONCLUSIONS

Occurrence of sporadic colorectal neoplastic lesion in patients with diffuse hyperplastic gastric polyposis and hypergastrinaemia may represent a new syndrome. Gastrin is not secreted by the gastric polyps or colonic carcinomas and may be related to gastric mucosal changes and H. pylori colonization. In patients with hyperplastic gastric polyposis and hypergastrinaemia, colorectal neoplasms should be ruled out.

Reduction of plasma homocysteine and serum methylmalonate concentrations in apparently healthy elderly subjects after treatment with folic acid, vitamin B12 and vitamin B6: a randomised trial

OBJECTIVES

To investigate, in an elderly population: (1) the effects of oral B-vitamin therapy on P-tHcys, S-MMA and Hb/MCV, (2) the appropriate decision limit for 'high' metabolite concentrations and (3) the estimated prevalence of vitamin B(12)/folate deficiency on the basis of different decision limits.

DESIGN

Double-blind placebo-controlled intervention study.

SETTING

Outpatient clinic.

SUBJECTS

A total of 209 community-dwelling subjects, median age 76 y (range 70-93) y.

INTERVENTION

Four months of oral daily supplementation with 0.5 mg cyanocobalamin, 0.8 mg folic acid and 3 mg vitamin B(6).

RESULTS

High P- tHcys was found in 64% of men and 45% of women, high S-MMA in 11% of both. Vitamin B(12) deficiency was observed in 7.2% and folate deficiency in 11% of all subjects. Health-related upper reference limits for the metabolites at the start were higher than the laboratory's upper reference limits. The latter were, however, similar to those of the vitamin replete group. There was a significant decrease in P-tHcys (P<0.001) and S-MMA (P=0.009) after 4 months of vitamin treatment. In a multivariate analysis, the P-Hcys change correlated positively with baseline P-tHcys and inversely with baseline P-folate and transferrin saturation (Fe/TIBC ratio). The S-MMA change correlated with baseline S-MMA and inversely with baseline vitamin B(12) and age.

CONCLUSIONS

Suboptimal vitamin status is an important cause of elevated P-tHcys and S-MMA in apparently healthy elderly subjects. Oral B-vitamin therapy is an effective and convenient way to normalise P-tHcys and S-MMA.

Reported symptoms and clinical findings in relation to serum cobalamin, folate, methylmalonic acid and total homocysteine among elderly Swedes: a population-based study

OBJECTIVES

The early stages of tissue B12 or folate deficiency often cause diagnostic problems. In this report, the levels of serum cobalamin, folate, methylmalonic acid (MMA) and total homocysteine (tHcy), and their relationships with clinical findings and reported symptoms in a representative random population sample are presented.

DESIGN

Cohort study.

SETTING

A general central Swedish population 70 years or older.

SUBJECTS AND METHODS

A 20% random sample of persons 70 years or older in a defined geographical area were invited to a survey. A total of 235 (85%) persons responded, of whom 161 had no interfering diseases or medication. Blood specimens for serum cobalamin, folate, MMA and tHcy analyses were drawn.

MAIN OUTCOME MEASURES

Presence of anaemic, gastrointestinal, neurological and psychiatric symptoms, obtained by questionnaire, and vibration sense measurement and findings at a physical and Mini Mental State Examination.

RESULTS

Among a large number of symptoms and clinical findings that traditionally have been linked to vitamin B12 or folate tissue deficiency, only changes in the tongue mucosa and mouth angle stomatitis turned out to be significantly associated with abnormal serum tHcy and serum folate levels. There were no relationships to serum cobalamin and serum MMA.

CONCLUSIONS

Changes in the oral mucosa were the only signs and symptoms found in this study, indicating that these may be the very early markers of metabolic defects. The traditional symptoms of vitamin deficiency may appear later in the course.

Plasma vitamin B-12 concentrations in an elderly latino population are predicted by serum gastrin concentrations and crystalline vitamin B-12 intake

The prevalence of vitamin B-12 deficiency increases with age, probably resulting from malabsorption of food-bound B-12 secondary to gastric atrophy. On the basis of this assumption, the Institute of Medicine (IOM) recommends those aged >50 y consume crystalline vitamin B-12. There is limited information on the prevalence of gastric atrophy in the elderly and whether the IOM recommendation would be effective. The objective of this study was to assess predictors of vitamin B-12 status and their interactions in free-living elderly. Individuals (n = 57) with deficient plasma vitamin B-12 (p-B12 < 148 pmol/L) were compared with 68 individuals with marginal p-B12 (148-221 pmol/L) and 52 with normal p-B12 (>221 pmol/L) in a cross-sectional sample (n = 1546) of elderly (>60 y) Latinos in California. Associations were examined among p-B12 and serum gastrin, vitamin B-12 intake from food and crystalline sources, and medications that putatively affect vitamin B-12 absorption. Serum gastrin was elevated, indicating gastric atrophy, in 48% of participants with deficient p-B12, 23% with marginal p-B12 and 21% of normal p-B12 participants, and was a significant predictor of deficient p-B12 and high plasma homocysteine (p-tHcy). Median total vitamin B-12 intake exceeded recommendations and was similar among status groups. Crystalline vitamin B-12 intake in the normal p-B12 group was higher than in the deficient p-B12 group (P < 0.01), and tended to be higher than the marginal group (P = 0.07). When serum gastrin was elevated, p-B12 was predicted by crystalline vitamin B-12, but not by intake of vitamin B-12 from food. Elevated serum gastrin was highly prevalent and predicted vitamin B-12 depletion. Crystalline vitamin B-12 intake predicted p-B12 in individuals with elevated serum gastrin, supporting IOM recommendations to increase consumption of crystalline vitamin B-12.

Screening for cobalamin deficiency in geriatric outpatients: prevalence and influence of synthetic cobalamin intake

OBJECTIVES

To describe the prevalence of cobalamin (Cbl) deficiency in older adult outpatients and to determine whether regular intake of a synthetic source of cobalamin confers protection against Cbl deficiency.

DESIGN

Cross-sectional study.

SETTING

Two university-affiliated geriatric medicine outpatient clinics.

PARTICIPANTS

Three hundred fifteen older adults (age range 65-100) without a history of previously diagnosed or treated Cbl deficiency, severe anemia, or a life-threatening illness.

MEASUREMENTS

Detailed information on total synthetic Cbl intake (from vitamins, fortified cereal, and supplemental nutritional formula sources) and laboratory measures of serum Cbl, metabolite panel (serum methylmalonic acid, homocysteine, cystathionine, and 2-methylcitric acid), complete blood count, and serum creatinine levels.

RESULTS

Cbl deficiency (serum Cbl < or =300 pg/mL and methylmalonic acid (MMA)>271 nmol/L) was found in 13% of screened patients. Forty-six percent of screened patients reported regularly taking a source of synthetic Cbl. Serum Cbl correlated with synthetic Cbl intake, and patients regularly taking synthetic Cbl were significantly less likely to be Cbl deficient than persons not taking supplemental Cbl (8% vs 17%, P =.02).

CONCLUSION

Regular use of a multivitamin/synthetic Cbl source confers some degree of protection against Cbl deficiency in older adults. The relatively high prevalence rates and benefit of synthetic Cbl intake in this study reinforce recommendations that older adults should be screened for Cbl deficiency and should incorporate synthetic sources of Cbl as part of a balanced diet. Appropriate screening intervals and the optimal dose of supplemental Cbl to prevent Cbl deficiency remains to be determined.

Small bowel disease in the elderly: diarrhoea and malabsorption

Diarrhoea and malabsorption are common problems in elderly persons. Worldwide, diarrhoea is the second leading cause of mortality. In the developed world, 85% of its mortality affects the elderly. The diagnostic work up for diarrhoea and malabsorption is more complex for the elderly than for the young patient. If diarrhoea persists for more than 24 h, oral rehydration solutions or intravenous fluids must be administered promptly in order to prevent hypotension and organ failure in the often multi-morbid patient. Both the immunocompromised patient and the severely affected out-patient should have stool culture performed. Malabsorption usually presents with weight loss, osteoporosis, anaemia, skin and neurological symptoms. The careful diagnostic work-up must aim at the identification of treatable disorders such as coeliac disease, Crohn's disease and bacterial overgrowth. Often, a detailed drug history is of help in identifying a readily treatable cause.

Nutrient-dense foods and exercise in frail elderly: effects on B vitamins, homocysteine, methylmalonic acid, and neuropsychological functioning

BACKGROUND

Frail elders are at risk of suboptimal micronutrient status, functional decline, and neurologic disorders. The influence of oral multimicronutrients in physiologic doses and of moderately intense physical exercise on homocysteine (Hcy), methylmalonic acid (MMA), and neurologic functioning have not yet been investigated.

OBJECTIVE

Our goal was to determine the effects of enriched foods and exercise on blood vitamins, Hcy, MMA, and neuropsychological functioning in the frail.

DESIGN

A 17-wk randomized controlled intervention trial was used to study 1) enriched foods plus a social program, 2) regular foods plus exercise, 3) enriched foods plus exercise, and 4) regular foods plus a social program. Enriched foods contained multiple micronutrients (25-100% of the Dutch recommended dietary allowances); exercises focused on strength, coordination, flexibility, and endurance. Vitamin (cobalamin, red blood cell folate, and pyridoxal 5'-phosphate), Hcy, and MMA concentrations were measured and 2 neuropsychological tests were conducted.

RESULTS

Vitamin concentrations were higher in the supplemented groups than in the unsupplemented groups (P < 0.001; total n = 130). Compared with baseline, cobalamin in the supplemented groups was increased by 22%, plasma folate by 101%, red blood cell folate by 87%, and pyridoxal 5'-phosphate by 68%. Concentrations in the unsupplemented groups changed by -2%, -6%, 1%, and -13%, respectively. Hcy decreased by 25% and MMA by 30% in the supplemented groups, compared with a small increase in Hcy (2%) and decrease in MMA (9%) in the unsupplemented groups. Exercise did not significantly affect vitamin, Hcy, or MMA concentrations. No significant effect of either intervention was observed on the neuropsychological tests.

CONCLUSIONS

The decrease in Hcy and MMA in frail elders confirms a subclinical metabolic deficiency state. Enriched foods containing physiologic amounts of micronutrients have a beneficial effect on these metabolites. No effects of B vitamins on mental health were identified.

Role of homocysteine, cystathionine and methylmalonic acid measurement for diagnosis of vitamin deficiency in high-aged subjects

BACKGROUND

Intracellular B-vitamin and folate deficiency indicated by hyperhomocysteinemia is very frequent in the elderly population. Hyperhomocysteinemia increases the risk of atherothrombotic diseases and neuropsychiatric complications. Our aim was to evaluate the prevalence of increased serum metabolite concentrations in subjects of a higher age, and whether the measurement of metabolite concentrations is more effective in diagnosing B-vitamin deficiency than mere homocysteine.

MATERIALS AND METHODS

Homocysteine (HCY), cystathionine (CYS) and methylmalonic acid (MMA) were investigated in serum together with vitamin B-12, B-6 and folate in 90 high-aged subjects (85-102 years), 92 seniors (65-75 years), and in 50 younger subjects (19-50 years).

RESULTS

Elderly subjects (high-aged and senior) had elevated serum concentrations of metabolites. High-aged subjects had a higher frequency of pathological increases than seniors: HCY 62% vs. 24%; MMA 62% vs. 23%; CYS 81% vs. 36%. Folate and vitamin B-6 concentrations were significantly decreased in both elderly groups; vitamin B-12 was only decreased in high-aged subjects. Utilising vitamin B-6, B-12 and folate for diagnosis of intracellular vitamin deficiency, the rate was 30% in seniors and 55% in high aged subjects. However, utilising the metabolites (HCY, MMA and CYS) for the diagnosis of intracellular vitamin deficiency, there was a distinctly increased rate of 55% in seniors respective to 90% in high-aged subjects. Backward multiple regression analysis revealed that only folate, MMA, creatinine and age were independent variables influencing the HCY concentration. Furthermore, the MMA concentration was significantly and independently influenced by folate, vitamin B-12, HCY and creatinine, and the serum concentration of CYS by vitamin B-12, creatinine and age.

CONCLUSION

The metabolites HCY, MMA and CYS are sensitive indicators diagnosing impaired remethylation of homocysteine to methionine with parallel activation of catabolic pathway. Compared to mere HCY or B-vitamins in serum, the efficiency of diagnosing a disturbed HCY metabolism increases very much in utilising the metabolites HCY, MMA and CYS. For differential diagnosis, parallel measurement of folate and creatinine is recommended. The early and correct diagnosis of B-vitamin deficiency in elderly subjects is of high clinical relevance.

The marker of cobalamin deficiency, plasma methylmalonic acid, correlates to plasma creatinine

OBJECTIVE

To examine the relationship between the two diagnostic tests, plasma methylmalonic acid and plasma cobalamins, and their association with plasma creatinine, age and sex.

DESIGN

Cross-sectional study of simultaneous laboratory measurements.

SETTING

County of Aarhus, Denmark.

SUBJECTS

Records on 1689 patients who had their first plasma methylmalonic acid measurement during 1995 and 1996, and who had a simultaneous measurement of plasma cobalamins. Plasma creatinine values measured within a week of measurements of plasma methylmalonic acid and plasma cobalamins were available for 1255 of the patients.

MAIN OUTCOME MEASURES

Predictors of variation in plasma methylmalonic acid; plasma cobalamins, plasma creatinine, age and sex.

RESULTS

Plasma methylmalonic acid was positively correlated with plasma creatinine, even for plasma creatinine within the normal range. These associations remained in a multiple regression analysis. For plasma cobalamins below 200 pmol L-1, there was a strong negative correlation between plasma methylmalonic acid and plasma cobalamins, whilst the association was weak for higher plasma cobalamin levels. Plasma methylmalonic acid increased and plasma cobalamins decreased with age.

CONCLUSIONS

The strong correlation between plasma methylmalonic acid and plasma creatinine suggests that plasma creatinine - also within the normal range - must be taken into consideration when interpreting plasma methylmalonic acid.

Vitamin B12 deficiency in the elderly

Vitamin B12 deficiency is estimated to affect 10%-15% of people over the age of 60, and the laboratory diagnosis is usually based on low serum vitamin B12 levels or elevated serum methylmalonic acid and homocysteine levels. Although elderly people with low vitamin B12 status frequently lack the classical signs and symptoms of vitamin B12 deficiency, e.g. megaloblastic anemia, precise evaluation and treatment in this population is important. Absorption of crystalline vitamin B12 does not decline with advancing age. However, compared with the younger population, absorption of protein-bound vitamin B12 is decreased in the elderly, owing to a high prevalence of atrophic gastritis in this age group. Atrophic gastritis results in a low acid-pepsin secretion by the gastric mucosa, which in turn results in a reduced release of free vitamin B12 from food proteins. Furthermore, hypochlorhydria in atrophic gastritis results in bacterial overgrowth of the stomach and small intestine, and these bacteria may bind vitamin B12 for their own use. The ability to absorb crystalline vitamin B12 remains intact in older people with atrophic gastritis. The 1998 recommended daily allowance for vitamin B12 is 2.4 micrograms, but elderly people should try to obtain their vitamin B12 from either supplements or fortified foods (e.g. fortified ready-to-eat breakfast cereals) to ensure adequate absorption from the gastrointestinal tract. Because the American food supply is now being fortified with folic acid, concern is increasing about neurologic exacerbation in individuals with marginal vitamin B12 status and high-dose folate intake.

Advantages of serum pepsinogen A combined with gastrin or pepsinogen C as first-line analytes in the evaluation of suspected cobalamin deficiency: a study in patients previously not subjected to gastrointestinal surgery

OBJECTIVES

Since there is a significant overlap in serum cobalamin concentrations between healthy and cobalamin-deficient individuals, we wanted to compare two different principles for use as supplementary tests to serum cobalamin concentration in patients with suspected cobalamin malabsorption and deficiency.

DESIGN

Clinical study of consecutive patients.

SETTING

The catchment area of Sahlgrenska University Hospital, Göteborg.

SUBJECTS

A total of 112 patients with suspected cobalamin deficiency who had not previously undergone gastrointestinal surgery.

INTERVENTIONS

Gastroduodenoscopy with biopsies taken from the gastric body and the duodenum, Schilling test, and measurement of serum methylmalonic acid (MMA), total homocysteine (Hcy), pepsinogens A and C, and gastrin.

MAIN OUTCOME MEASURES

Number of patients with gastric body atrophy identified with the combination of MMA and Hcy, and pepsinogen A combined with pepsinogen C or gastrin.

RESULTS

About 95% of the patients with severe gastric body atrophy had abnormal concentrations of serum pepsinogen A and/or gastrin or pepsinogen A/C ratio, whereas 65% had abnormal metabolite concentrations. Serum pepsinogen A combined with pepsinogen C identified 100%, and combined with gastrin 88%, of the patients with gastric body atrophy and elevated metabolite tests, and 67 and 75%, respectively, of those who had not yet developed elevated metabolite tests.

CONCLUSIONS

Pepsinogen A, combined with pepsinogen C or gastrin, should be the first option in evaluating patients with suspected cobalamin deficiency who have not previously undergone gastrointestinal surgery.

Age-related changes in cobalamin (vitamin B12) handling. Implications for therapy

Cobalamin (vitamin B12) deficiency is more common in the elderly than in younger patients. This is because of the increased prevalence of cobalamin malabsorption in this age group, which is mainly caused by (autoimmune) atrophic body gastritis. Cobalamin supplementation is affordable and nontoxic, and it may prevent irreversible neurological damage if started early. Elderly individuals with cobalamin deficiency may present with neuropsychiatric or metabolic deficiencies, without frank macrocytic anaemia. An investigation of symptoms and/or signs includes the diagnosis of deficiency as well as any underlying cause. Deficiency states can still exist even when serum cobalamin levels are higher than the traditional lower reference limit. Cobalamin-responsive elevations of serum methylmalonic acid (MMA) and homocysteine are helpful laboratory tools for the diagnosis. The health-related reference ranges for homocysteine and MMA appear to vary with age and gender. Atrophic body gastritis is indirectly diagnosed by measuring serum levels of gastrin and pepsinogens, and it may cause dietary cobalamin malabsorption despite a normal traditional Schilling's test. The use of gastroscopy may also be considered to diagnose dysplasia, bacterial overgrowth and intestinal villous atrophy in healthy patients with atrophic body gastritis or concomitant iron or folic acid deficiency. Elderly patients respond to cobalamin treatment as fully as younger patients, with complete haematological recovery and complete or good partial resolution of neurological deficits. Chronic dementia responds poorly but should, nevertheless, be treated if there is a metabolic deficiency (as indicated by elevated homocysteine and/or MMA levels). Patients who are at risk from cobalamin deficiency include those with a gastrointestinal predisposition (e.g. atrophic body gastritis or previous partial gastrectomy), autoimmune disorders [type 1 (insulin-dependent) diabetes mellitus and thyroid disorders], those receiving long term therapy with gastric acid inhibitors or biguanides, and those undergoing nitrous oxide anaesthesia. To date, inadequate cobalamin intake has not proven to be a major risk factor. Intervention trials of cobalamin, folic acid and pyridoxine (vitamin B6) in unselected elderly populations are currently under way.

Serum methylmalonic acid and total homocysteine in patients with suspected cobalamin deficiency: a clinical study based on gastrointestinal histopathological findings

We compared the sensitivity and specificity of the two metabolite tests, methylmalonic acid (MMA) and total homocysteine (Hcy) in serum, and serum cobalamin (Cbl) in patients referred to our hospital because of suspected cobalamin deficiency and a serum cobalamin value at the referring unit <200 pmol/L. All 111 patients included were investigated using upper gastrointestinal endoscopy with biopsy specimens taken from the gastric and duodenal mucosa to find a morphological basis for cobalamin malabsorption as well as the Schilling test for the validation of the serum tests. All patients were treated with cobalamin and new blood samples were taken after 4 weeks. We found no difference in sensitivity and specificity between serum MMA, Hcy, and Cbl in identifying patients with and without conditions compatible with cobalamin malabsorption. Elevated serum MMA and Hcy were also found in about 15% of the group of patients with normal Schilling tests and without a morphological basis for cobalamin malabsorption. Moreover, most patients in this group responded with decreased values of the metabolite tests following cobalamin treatment, suggesting that neither elevated metabolites nor a decrease in these values following cobalamin treatment are specific for cobalamin deficiency.

Factors related to plasma folate and vitamin B12. The SENECA study

The effects of body weight, body mass index, waist-to-hip ratio, living situation, smoking status, alcohol consumption, energy intake and animal protein intake, chronic diseases, health judgement, and ability to perform activities of daily living on plasma folate and vitamin B12 concentrations in elderly people were studied. Cross-sectional data were collected in 570 males and 554 females, aged 70-75 years and living in 17 towns in 11 European countries. The data collection was part of the SENECA study on nutrition and health in the elderly. Most of the associations with plasma vitamin B12 and plasma folate were either non significant or very small, with the exception of the relation between subjective health judgement and plasma folate levels in women. The anthropometric, life-style, and dietary factors do not seem to be major risk factors for low plasma vitamin B12 and folate concentrations in this relatively healthy elderly population.

Free and protein-bound cobalamin absorption in healthy middle-aged and older subjects

OBJECTIVE

To study free- and protein-bound cobalamin absorption and the correlation with atrophic gastritis in healthy middle-aged and older subjects.

DESIGN

A cross-sectional study.

PARTICIPANTS

Fifty-two healthy subjects, aged 26 to 87 years, apparently free from conditions known to influence the cobalamin status. Middle-aged subjects were defined as those younger than 65 years of age (median age 57 years) and older subjects as those 65 years and older (median age 75 years).

MEASUREMENTS

Protein-bound cobalamin absorption was assessed by 48-hour urinary excretion method following oral administration of scrambled egg yolk, labeled in vivo with 57 Co-cobalamin by injecting a hen with 57 Co-cyanocobalamin. The percentage of 57 Co-cobalamin bound to protein was 65%. Free cobalamin absorption was assessed by 48-hour urinary excretion method following oral administration of crystalline 57 Co-cyanocobalamin. Plasma cobalamin, folate and fasting plasma gastrin, and pepsinogen A and C concentrations were determined.

RESULTS

The median urinary excretion of egg yolk 57 Co-cobalamin in middle-aged subjects was 12.3% (25th and 75th percentiles 10.5%-14.5%) compared with 11.7% (25th and 75th percentiles 9.8%-13.6%) in older subjects (P = .283). The median urinary excretion after administration of free 57 Co-cobalamin in middle-aged subjects was 25.7% (25th and 75th percentiles 20.6%-30.7%) compared with 27.9% (25th and 75th percentiles 21.4%-34.5%) in older subjects (P = .694). Neither egg yolk nor free 57 Co-cobalamin excretion correlated with age. A ratio of pepsinogen A to pepsinogen C less than 1.6, indicating atrophic gastritis, was found in 13 subjects. Within the atrophic gastritis group, 11 subjects had a pepsinogen A concentration greater than or equal to 17 micrograms/L, indicating mild to moderate atrophic gastritis, and two subjects had a pepsinogen A concentration less than 17 micrograms/L, indicating severe atrophic gastritis or gastric atrophy. All subjects had normal fasting plasma gastrin concentrations. Free and egg yolk 57 Co-cobalamin excretions were not reduced in the atrophic gastritis group when compared with the non-atrophic gastritis group. Median plasma cobalamin concentration was not significantly lower in older subjects (P = .205). Nonetheless, plasma cobalamin concentration correlated negatively with age (r = -.36; P = .008).

CONCLUSIONS

We demonstrated no significant difference in either free or protein-bound cobalamin absorption between healthy middle-aged and older adults. In addition, no alteration in cobalamin absorption was found in subjects identified as having mild to moderate atrophic gastritis. Therefore, based on our results, the high prevalence of low cobalamin levels in older people cannot be explained by either the aging process or mild to moderate atrophic gastritis.

Spouses of demented patients with low cobalamin levels: a new risk group for cobalamin deficiency

Low serum cobalamin levels are common in conditions such as dementia and often represent mild deficiency. We surveyed serum cobalamin levels prospectively in spouses and blood relatives of demented patients to determine if any familial predisposition exists for the low levels. Cobalamin status in most of the relatives found to have low levels was assessed further by means of blood counts, metabolic tests, neurologic evaluation, absorption studies and response to cobalamin therapy. Serum cobalamin levels in 36 spouses correlated with those of the 36 demented patients related to them (r = 0.46, p = 0.004). A significant association was not seen in 34 blood relatives of 34 demented patients (r = 0.27). Most importantly, 67% of the spouses of demented patients with low serum cobalamin had low values themselves, compared with only 3% of the spouses of patients with normal levels (p = 0.001). Detailed study of 4 of the 5 spouses (and 3 blood relatives) with low cobalamin levels showed no anemia in any case. Nevertheless, 4 of the subjects had metabolic evidence of deficiency and one had electrophysiological abnormalities; all these defects improved with cobalamin therapy. These observations identify a hitherto unsuspected group of people at high risk for cobalamin deficiency and suggest that spouses of demented patients with low cobalamin levels should also have their cobalamin levels measured. The increased frequency of low serum cobalamin levels in spouses of demented patients with low levels represents in most cases a true, mild cobalamin deficiency that responds to treatment.

Cobalamin

Cobalamin (vitamin B12) is an essential nutrient derived exclusively from bacterial sources. It is an essential cofactor for three known enzymatic reactions. Untreated deficiency, caused by either the autoimmune disease pernicious anemia or nutritional lack, results in a macrocytic anemia and/or subacute combined degeneration of the spinal cord and is eventually fatal. Cobalamin in serum is bound to two proteins, transcobalamin and haptocorrin. The former is responsible for the essential delivery of cobalamin to most tissues. Inadequate tissue availability of cobalamin results in increased concentration of methylmalonic acid and homocyst(e)ine due to inhibition of methylmalonyl-CoA mutase and methionine synthase, respectively. Strict vegetarians have long been known to be at risk of cobalamin deficiency, which develops insidiously over many years. It is now clear that a significant number of the elderly and HIV-positive individuals are also at increased risk of deficiency. Any individual with reduced ability to split cobalamin from food-protein may also become deficient even though intrinsic factor is present. Diagnosis of cobalamin deficiency has frequently relied on total serum cobalamin and the Schilling test. Newer approaches such as analysis of methylmalonic acid, homocyst(e)ine, holotranscobalamin, anti-intrinsic factor antibodies, and serum gastrin may provide more cost-effective testing, as well as identify those with a covert deficiency.

Metabolite assays in cobalamin and folate deficiency

Cbl and folate are both necessary for the metabolism of HCYS, whereas only Cbl is required for MMA metabolism. During the past decade, analytical methods have been developed that are sensitive enough to detect low levels of MMA and HCYS normally present in the plasma. These methods are sufficiently precise to be used in the clinical laboratory and measurements of the serum levels of the metabolites provide sensitive and specific techniques for the identification of Cbl and folate deficiencies. These techniques constitute an important addition to the battery of diagnostic tests that are available for detecting the vitamin deficiencies and for distinguishing each from the other. By virtue of the role of Cbl and folate in the metabolic pathways that involve MMA and HCYS, levels of both metabolites rise in Cbl deficiency, but only HCYS rises in folate deficiency. During the development of Cbl or folate deficiencies, accumulation of these metabolites in the plasma signals the existence of a condition of biochemical vitamin deficiency of sufficient degree to cause impairment in the metabolic pathways which are dependent on these vitamins. Circulating metabolite levels appear to accurately reflect the nutritional status of the vitamins and a rise in serum metabolite levels is therefore one of the earliest and most reliable indicators of developing Cbl and folate deficiencies. Elevations of serum metabolites above the reference range not only precede a fall in the serum vitamin levels but also show a more consistent correlation with objective evidence of vitamin deficiency than do low blood vitamin levels. The advent of serum metabolite measurements has also made it possible to identify subtle or atypical forms of vitamin deficiency that may be associated with unusual or previously undiscovered disease manifestations. Thus, in patients who display only neurological manifestations of disease, underlying Cbl deficiency may be revealed by the finding of raised serum or urine levels of MMA. Similarly, unsuspected folate deficiency may be disclosed by the finding of a raised serum HCYS. This may have important implications with respect to disease risk, since there is mounting evidence that sub-optimal folate nutritional status may be associated with increased risks of vascular disease, neoplasia and birth defects. Finally, the measurement of serum levels of MMA, HCYS and other metabolites that accumulate in Cbl and folate deficiencies may provide important new insights into the mechanism whereby these vitamin deficiencies lead to different patterns and manifestations of disease.

Cobalamin and folate deficiency in the elderly

Elderly persons are more likely to have low values for serum and erythrocyte folate, and for serum cobalamin. Many of those with low vitamin levels have biochemical abnormalities consistent with true deficiency, including increased formiminoglutamic acid excretion, abnormal marrow deoxyuridine suppression, and raised serum levels of methylmalonic acid and homocysteine. Therapy with the appropriate vitamin reverses the biochemical defect. Despite this, the clinical consequences for most elderly persons are remarkably few. True megaloblastic anaemia is rare, and the small number of therapeutic trials to date have not improved the levels of haemoglobin in the treated subjects, although the mean corpuscular volume has decreased significantly. There has been recent concern that these low blood vitamin levels might be important causes of nervous system damage, but studies specifically of the elderly have not demonstrated overall improvements in neurological function following therapy. Vascular damage from high blood homocysteine levels secondary to cobalamin or folate deficiency remains a potential hazard. Dietary insufficiency, malabsorption of protein-bound vitamin B12 secondary to atrophic gastritis, and defective absorption of folyl polyglutamates seem the likeliest possible causes. Pernicious anaemia, although a common cause of severe megaloblastic anaemia in the elderly, is an infrequent cause for the low cobalamin levels in population studies. Although the benefits are uncertain, the balance of the evidence suggests that one should treat elderly persons with low values of cobalamin or folate. Crystalline vitamin B12 and folic acid are absorbed normally and are therefore suitable for replacement therapy, provided that pernicious anaemia is excluded.

Serum vitamin B12 levels and incidence of dementia in a healthy elderly population: a report from the Bronx Longitudinal Aging Study

OBJECTIVE

To determine whether low serum B12 levels are associated with an increased incidence of dementing illness.

DESIGN

Longitudinal cohort study, 5-year follow-up.

PARTICIPANTS

Volunteer cohort of 410 nondemented ambulatory subjects aged 75 to 85 years.

MEASUREMENTS

Annual serum B12 determinations and neuropsychological assessments including the Blessed Test of Information, Memory and Concentration (BIMC) and the Fuld Object Memory Evaluation (FOME). If subject met criteria for a major cognitive change (as defined by an increase of 4 or more points on the BIMC), a work-up that included CT, EEG, and neurologic assessment was performed. Clinical diagnoses were made according to established criteria.

RESULTS

Mean serum B12 level of entire sample was 558 pg/mL. Twenty-two subjects had low B12 levels defined as values < 150 pg/mL. Three of these 22 subjects (13.6%) became demented, compared with 57 of 388 subjects (14.7%) with higher levels. The incidence of Alzheimer disease among the low B12 group was 4.5% compared with 7.5% in the higher B12 group. The mean B12 level at time of diagnosis in subjects who did develop Alzheimer disease was 551 pg/mL. There was no evidence of hematologic disorder among the 22 subjects with low B12. Of the 3 low B12 subjects who did become demented, none responded to monthly B12 injections.

CONCLUSION

A low B12 level may not be a risk factor for dementia in general or Alzheimer disease in particular.

Cobalamin levels are not reduced in Alzheimer's disease: results from a population-based study

OBJECTIVE

To determine whether there is a relationship between serum cobalamin levels, normal aging, and Alzheimer's Disease (AD).

DESIGN

Cross-sectional survey.

SETTING

A district (Kungsholmen) in Stockholm, Sweden.

PARTICIPANTS

Population-based cohort of 545 subjects aged more than 74 years. The sample was selected on the basis of evidence of cognitive impairment from all inhabitants in an area of Stockholm (2368 individuals), both living at home or in institutions.

MEASUREMENTS

Serum cobalamin levels and diagnostic evaluation for a diagnosis of dementia and type of dementia.

RESULTS

The serum cobalamin levels in non-demented individuals decreased 5.5 pmol/L with an increase of 1 year of age (regression coefficient = -5.53; P < 0.0001). However, the regression coefficient was 0.21 (P = 0.91) in demented people and 2.57 (P = 0.32) in AD subjects. There was no difference between serum cobalamin levels in demented, AD, and non-demented subjects, except for the oldest ages where demented people and AD sufferers showed higher values. AD patients still living in their own homes had significantly lower cobalamin concentrations compared with institutionalized AD sufferers. The prevalence rate of cobalamin deficiency was 15.5% (95% CI = 11.5-19.5) in normal aging and 18.1% (95% CI = 10.3-25.9) in AD.

CONCLUSIONS

These data suggest that serum cobalamin levels decrease in normal aging, but not in dementia or AD. A lower cobalamin concentration observed in AD sufferers still living in their own homes compared with institutionalized persons with AD seemed to be related to but not fully explained by eating habits. Patients with AD living in their own homes are at risk of developing cobalamin deficiency, and monitoring of serum cobalamin concentrations might be useful in this group.

How to diagnose cobalamin deficiency

Cobalamin deficiency must be suspected in all patients with unexplained neuropsychiatric symptoms or unexplained anemia. Special attention should be paid to patients at risk of developing cobalamin deficiency such as elderly people, vegetarians, HIV-infected patients, patients with gastrointestinal diseases and patients with autoimmunity or a family history of pernicious anemia. The assays aimed to answer the question: does this patient suffer from cobalamin deficiency, include analysis of P--cobalamins and analyses of the metabolites that accumulate upon cellular cobalamin deficiency, P--methylmalonate and P--homocysteine. P--cobalamins or especially a fraction of P--cobalamins, P--TC cobalamins are markers for latent cobalamin deficiency. An increased concentration of P--methylmalonate that decreases upon injection of cobalamin indicates overt metabolic cobalamin deficiency. The same holds for P--homocysteine but this analysis is less specific than P--methylmalonate. We suggest that either assay of P--cobalamins or P--methylmalonate is employed as screening test for cobalamin deficiency, and that further tests are performed only if the initial test in combination with the clinical picture gives an unclear answer. Once cobalamin deficiency has been diagnosed, the cause for the deficiency should be sought and the patient should be treated for life. Cobalamin absorption tests such as the Schilling test are considered of limited use. Gastric atrophy is likely to be present in patients with increased P--gastrin or decreased P--pepsinogen A. However, this condition can be diagnosed also by upper gastrointestinal endoscopy.

Serum cobalamin and methylmalonic acid in Alzheimer dementia

The cobalamin status was evaluated in Alzheimer dementia (n = 26), other dementias (n = 24), various gerontopsychiatric disorders (n = 25), and in neuro-psychiatrically healthy controls (n = 20). Supplementing serum cobalamin we measured methylmalonic acid (MMA), a metabolite accumulating early in cobalamin deficiency. Subnormal cobalamin and/or clearly elevated MMA concentrations were found in 11 cases: 7 Alzheimer patients (27%), 2 with other dementias (8%), one psychiatric patient (4%), and one control (5%). None presented the typical neurologic features of cobalamin deficiency and macrocytosis was found in only one. The mean cobalamin concentration was significantly lower in Alzheimer patients (179 +/- 18 pmol/l) than in the age-matched controls (256 +/- 23 pmol/l) (p = 0.013) and the other patient groups. Correspondingly, the mean MMA level was higher in the Alzheimer group (0.480 +/- 0.062 mumol/l) than in any other diagnostic group (controls: 0.347 +/- 0.040 mumol/l). Comparing the Alzheimer group to the other groups as a whole, the elevation was significant (p = 0.0097). Our findings indicate that Alzheimer patients are particularly prone to cobalamin deficiency, and even subtle biochemical signs of deficiency seem to justify treatment.

Vitamin B12 in CSF: reduced CSF/serum B12 ratio in demented men

Vitamin B12 concentrations were determined in serum and cerebrospinal fluid (CSF) of 32 controls and 102 patients with dementia. The dementias were classified as Alzheimer's disease (AD), senile dementia of Alzheimer type (SDAT) and multi-infarct dementia (MID). A substantial number of patients (n = 42) could not be assigned to any of these diagnostic groups, as their dementias were of non-AD/SDAT and non-MID types. They were instead assigned to a group called non ultra descriptum (NUD). CSF B12 correlated significantly with serum B12. There were no statistically significant differences in serum B12 levels between the groups. Although with considerable overlap, CSF B12 concentrations and CSF/serum B12 ratios were significantly lower in the NUD group than in the control group. The NUD group had significantly lower CSF/serum B12 ratios than the group of patients with AD/SDAT. There was significant male predominance in the group of demented patients that had low CSF/serum B12 ratios outside the bivariate reference region. CSF and serum B12 levels appear insufficient as measures of the true brain vitamin B12 status. It may be a more dynamic approach to use the CSF/serum B12 ratio as an indication of transport function across the blood brain barrier, and possibly also across the CSF brain cell barrier.

Serum cobalamins in the elderly: a longitudinal study of a representative population sample from age 70 to 81

In a representative population sample (n = 973) born 1901-1902 and examined at the ages of 70, 75, 79, and 81, the change in serum cobalamins with increasing age was studied by trend analysis using values obtained in single individuals at all four examinations. In subsamples without definable disorders, the mean annual decline was: among men 3.4 pmol/l (p less than 0.05), among women 3.2 pmol/l (n.s.). The decline was possibly more pronounced among individuals with low and intermediate concentrations. The health-related lower reference limits (the 2.5 percentile values of subsamples without definable disorders) did not differ significantly between sexes and age groups, but low concentrations or ongoing cobalamin medication became more common with advancing age. The results indicate a slight fall in serum cobalamins between age 70 and 81 but do not call for age-related lower reference limits.

Vitamin B12-induced reduction of platelet monoamine oxidase activity in patients with dementia and pernicious anaemia

Platelet monoamine oxidase (MAO) activity has previously been shown to be increased in patients with senile dementia of Alzheimer type (SDAT) and in patients with megaloblastic anaemia. Moreover, low serum B12 levels were found to be 4-5 times more frequent in SDAT compared with an unselected population of similar age. In the present investigation, platelet MAO activity was estimated in 14 SDAT patients with relatively low serum B12 levels and in 4 patients with pernicious anaemia. Before B12 therapy, platelet MAO activity was significantly increased in both patient groups compared with a control group. After B12 therapy, platelet MAO activity was significantly reduced in both patient groups to apparently normal levels. The present results show that B12 status is a controlling factor of platelet MAO activity and confirm that a significant connection exists between vitamin B12 deficiency and primary degenerative dementia disorders, such as SDAT.

Intrinsic factor secretion and cobalamin absorption. Physiology and pathophysiology in the gastrointestinal tract

Intrinsic factor is produced by the gastric parietal cell. Its secretion is stimulated via all pathways known to stimulate gastric acid secretion: histamine, gastrin, and acetylcholine. There is, however, a different mode of secretion for both substances: atropine, vagotomy, and H2 receptor antagonists inhibit both intrinsic factor and acid secretion, but secretin and the hydrogen-potassium ATPase antagonist omeprazole have no effect on intrinsic factor while substantially reducing acid secretion. Cobalamin in food is bound to animal protein. Cobalamin deficiency due to inadequate dietary intake is rarely seen in extreme vegetarians (vegans). In the stomach cobalamin is liberated from its protein binding by peptic digestion and bound to R-proteins. Hypochlorhydria or achlorhydria, whether medically induced or not, may impair cobalamin uptake. The cobalamin-R-protein complex is split by pancreatic enzymes in the duodenum, where cobalamin is bound to intrinsic factor. Pancreatic insufficiency may lead to cobalamin deficiency. Lack of intrinsic factor is the commonest cause of cobalamin deficiency; very rarely, aberrant forms of intrinsic factor are produced, but the clinical syndrome is similar. Gram-negative anaerobe bacteria bind the cobalamin-intrinsic factor complex, and bacterial overgrowth of the small intestine diminishes cobalamin resorption. Parasitic infections with fish tape-worm and Giardia lamblia are also associated with cobalamin malabsorption. The cobalamin-intrinsic factor complex binds to the ileal receptors in the terminal ileum. Cobalamin absorption may be impaired after resection or by diseases affecting more than 50 cm of the terminal ileum, such as Crohn's disease, coeliac disease, tuberculosis, lymphoma or radiation. There is clearly a wide diversity in the aetiology of cobalamin deficiency, which requires a versatile diagnostic approach.