Low serum vitamin B12 levels in patients receiving ascorbic acid in megadoses: studies concerning the effect of ascorbate on radioisotope vitamin B12 assay

Herbert,; Jacob, Elizabeth; Wong, K-T J; Scott, John M.; Pfeffer, Rhonda

doi:10.1093/ajcn/31.2.253

Cited by 41 publications

(8 citation statements)

References 13 publications

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“…68 Serum B 12 levels are also usually normal in TC deficiency, and inborn errors of cobalamin metabolism. 69 Conversely, serum B 12 levels may be low in the presence of normal tissue B 12 in vegetarians, 70 in subjects taking megadoses of ascorbic acid, 71 in inherited "benign" HC deficiency, 72,73 and in a substantial proportion of patients with megaloblastic anemia resulting from folate deficiency (30%). 4 …”

Section: Serum B 12 Levelsmentioning

confidence: 99%

Vitamin B12 deficiency from the perspective of a practicing hematologist

Green

2017

Blood

283

197

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B12 deficiency is the leading cause of megaloblastic anemia, and although more common in the elderly, can occur at any age. Clinical disease caused by B12 deficiency usually connotes severe deficiency, resulting from a failure of the gastric or ileal phase of physiological B12 absorption, best exemplified by the autoimmune disease pernicious anemia. There are many other causes of B12 deficiency, which range from severe to mild. Mild deficiency usually results from failure to render food B12 bioavailable or from dietary inadequacy. Although rarely resulting in megaloblastic anemia, mild deficiency may be associated with neurocognitive and other consequences. B12 deficiency is best diagnosed using a combination of tests because none alone is completely reliable. The features of B12 deficiency are variable and may be atypical. Timely diagnosis is important, and treatment is gratifying. Failure to diagnose B12 deficiency can have dire consequences, usually neurological. This review is written from the perspective of a practicing hematologist.

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Section: Serum B 12 Levelsmentioning

confidence: 99%

Vitamin B12 deficiency from the perspective of a practicing hematologist

Green

2017

Blood

283

197

View full text Add to dashboard Cite

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“…For example, Herbert and Jacob [64] reported that large doses of ascorbic acid destroy vitamin B 1 2 in an in vitro system and proposed that large intakes of vitamin C could lead to vitamin B 1 2 deficiency [64,65]. However, the reported destruction was later shown to be an artifact of the experimental method [66].…”

Section: Health Effects Of Vitamin C Supplementationmentioning

confidence: 99%

“…A few case reports have suggested that discontinuation of high-dose vitamin C supplementation can cause "rebound scurvy" [65][66][67][68]; however, there is no experimental evidence demonstrating an effect of this type in humans [60,78].…”

Section: Health Effects Of Vitamin C Supplementationmentioning

confidence: 99%

The health effects of vitamin C supplementation: a review.

Bendich¹,

Langseth²

1995

Journal of the American College of Nutrition

127

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A comprehensive review of the literature indicates that populations with long-term consumption of higher than RDA levels of vitamin C (> or = 60 mg/day) from foods and/or supplements have reduced risks of cancer at several sites, cardiovascular disease, and cataracts. The safety of higher than RDA intakes of vitamin C is confirmed in eight placebo-controlled, double-blind studies and six non-placebo clinical trials in which up to 10,000 mg of vitamin C was consumed daily for up to 3 years. There are no clinical data which suggest that vitamin C's enhancement of non-heme iron absorption in individuals with low iron status could be a critical factor in the possible increased risk of heterozygous hemochromatosis-related cardiovascular disease. In fact, the cumulative data do not confirm that iron status is related to risk of cardiovascular disease. Moreover, higher than RDA intakes of vitamin C have been associated with several indices of lowered cardiovascular disease risk including increases in HDL, and decreases in LDL oxidation, blood pressure and cardiovascular mortality.

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“…Cobalamin is stable at cooking process temperatures; the likelihood of its transformation into inactive compounds by ascorbic acid [4] has not been later confirmed. Since the total-body cobalamin content is two to 5 mg in adults, a complete discontinuation in the absorption will take 3–5 years to deplete cobalamin stores.…”

Section: Introductionmentioning

confidence: 99%

Cobalamin Deficiency: Clinical Picture and Radiological Findings

et al. 2013

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Vitamin B12 deficiency causes a wide range of hematological, gastrointestinal, psychiatric and neurological disorders. Hematological presentation of cobalamin deficiency ranges from the incidental increase of mean corpuscular volume and neutrophil hypersegmentation to symptoms due to severe anemia, such as angor, dyspnea on exertion, fatigue or symptoms related to congestive heart failure, such as ankle edema, orthopnea and nocturia. Neuropsychiatric symptoms may precede hematologic signs and are represented by myelopathy, neuropathy, dementia and, less often, optic nerve atrophy. The spinal cord manifestation, subacute combined degeneration (SCD), is characterized by symmetric dysesthesia, disturbance of position sense and spastic paraparesis or tetraparesis. The most consistent MRI finding is a symmetrical abnormally increased T2 signal intensity confined to posterior or posterior and lateral columns in the cervical and thoracic spinal cord. Isolated peripheral neuropathy is less frequent, but likely overlooked. Vitamin B12 deficiency has been correlated negatively with cognitive functioning in healthy elderly subjects. Symptoms include slow mentation, memory impairment, attention deficits and dementia. Optic neuropathy occurs occasionally in adult patient. It is characterized by symmetric, painless and progressive visual loss. Parenteral replacement therapy should be started soon after the vitamin deficiency has been established.

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Low serum vitamin B12 levels in patients receiving ascorbic acid in megadoses: studies concerning the effect of ascorbate on radioisotope vitamin B12 assay

Cited by 41 publications

References 13 publications

Vitamin B12 deficiency from the perspective of a practicing hematologist

Vitamin B12 deficiency from the perspective of a practicing hematologist

The health effects of vitamin C supplementation: a review.

Cobalamin Deficiency: Clinical Picture and Radiological Findings

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