Too much vitamin b
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Effects of Excess Vitamin B: A Comprehensive Overview
Introduction to Vitamin B Overconsumption
Vitamin B is essential for numerous bodily functions, including metabolism, brain function, and the synthesis of neurotransmitters. However, excessive intake of certain B vitamins can lead to adverse effects. This article synthesizes research findings on the impact of high doses of vitamin B, particularly focusing on vitamin B6 and B12.
Impact of Excess Vitamin B6 on Brain and Serum Amino Acids
Altered Amino Acid Concentrations
Excessive intake of vitamin B6 can significantly alter amino acid concentrations in the brain and serum. A study on rats fed with varying levels of pyridoxine HCl (vitamin B6) showed that high doses (10x and 100x the recommended level) increased concentrations of several amino acids in the caudate nucleus and serum by 130% to 200% compared to control levels1. This suggests that high vitamin B6 intake can disrupt normal amino acid metabolism.
Serotonin Receptor Binding
The same study found that high doses of vitamin B6 affected the binding properties of serotonin receptors in the brain cortex. Specifically, the antagonist binding affinity and the maximal number of binding sites were higher in groups receiving 10x and 100x the recommended dose compared to the control group1. This indicates that excessive vitamin B6 can influence neurotransmitter systems, potentially affecting mood and cognitive functions.
High-Dose Vitamin B Supplementation and Oxidative Stress
Reduction in Oxidative Stress
A randomized control trial investigated the effects of high-dose B-group vitamin supplementation on oxidative stress markers. The study found that supplementation significantly increased levels of vitamins B6 and B12 while reducing homocysteine levels, a marker of oxidative stress2. This suggests that high doses of these vitamins can help mitigate oxidative stress and inflammation, which are linked to various chronic diseases.
Brain Metabolism
The same study also noted significant relationships between vitamin B6 and neural metabolites such as N-acetylaspartate (NAA), choline, and creatine, indicating that high-dose B vitamins may promote brain health by enhancing cellular metabolism and energy storage2.
Cognitive Function and Vitamin B Intake in Older Adults
Limited Benefits on Cognition
A systematic review and meta-analysis examined the association between vitamin B6, B12, and folate intake and cognitive function in older adults. The findings suggested that higher levels of vitamin B12 and folate were associated with better cognition in cross-sectional studies, but these benefits were not significant in sensitivity analyses or prospective studies. High vitamin B6 concentrations showed no significant benefit on cognition or dementia risk3. This indicates that while B vitamins are crucial for brain health, their role in preventing cognitive decline may be limited.
Risks of Excess Vitamin B6: Peripheral Neuropathy
Tolerable Upper Intake Level
The European Food Safety Authority (EFSA) has established a tolerable upper intake level (UL) for vitamin B6 to prevent peripheral neuropathy, a well-documented adverse effect of excessive intake. The UL for adults is set at 12 mg/day, based on evidence from case reports and studies indicating that higher doses can lead to nerve damage6. This highlights the importance of adhering to recommended intake levels to avoid potential toxicity.
Conclusion
While B vitamins are essential for numerous physiological functions, excessive intake, particularly of vitamin B6, can lead to significant health issues, including altered amino acid metabolism, changes in neurotransmitter receptor binding, and peripheral neuropathy. High-dose supplementation may offer some benefits in reducing oxidative stress and supporting brain metabolism, but the risks associated with overconsumption underscore the need for careful management of vitamin B intake.
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Most relevant research papers on this topic
Dietary excess of vitamin B-6 affects the concentrations of amino acids in the caudate nucleus and serum and the binding properties of serotonin receptors in the brain cortex of rats.
Excess dietary pyridoxine affects brain and serum amino acid concentrations and serotonin receptor binding properties in a biphasic pattern in rats.
RCTThe Effect of a High-Dose Vitamin B Multivitamin Supplement on the Relationship between Brain Metabolism and Blood Biomarkers of Oxidative Stress: A Randomized Control Trial
High-dose B-group vitamin supplementation may reduce oxidative stress and inflammation by increasing oxidative metabolism, potentially promoting myelination, cellular metabolism, and energy storage.
RCT
Very Rigorous Journal
Highly CitedVitamin B12, B6, or Folate and Cognitive Function in Community-Dwelling Older Adults: A Systematic Review and Meta-Analysis.
Vitamin B12 and folate may not be modifiable risk factors for slowing cognitive decline in community-dwelling older individuals.
Meta-Analysis
Rigorous JournalVitamin B-12 supplementation during pregnancy and early lactation increases maternal, breast milk, and infant measures of vitamin B-12 status.
Oral vitamin B-12 supplementation during pregnancy and early lactation significantly increases vitamin B-12 status in mothers and infants, potentially reducing the risk of adverse pregnancy outcomes.
RCT
Large Human TrialVery Rigorous JournalHighly CitedA Randomized Pilot Trial to Evaluate the Bioavailability of Natural versus Synthetic Vitamin B Complexes in Healthy Humans and Their Effects on Homocysteine, Oxidative Stress, and Antioxidant Levels
Natural and synthetic vitamin B complexes have comparable bioavailability and both show similar effects on antioxidants, homocysteine levels, and oxidative stress.
RCTRigorous JournalScientific opinion on the tolerable upper intake level for vitamin B6
The EFSA Panel on Nutrition, Novel Foods, and Food Allergens has established a tolerable upper intake level of 12 mg/day for vitamin B6 for adults, based on a reference point of 50 mg/day and animal studies.
Literature ReviewB Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review
Adequate levels of all eight B-vitamins are essential for optimal physiological and neurological functioning, and addressing deficiencies in these vitamins, rather than just homocysteine metabolism, is crucial for brain health.
Literature ReviewVery Rigorous JournalHighly CitedHow prevalent is vitamin B(12) deficiency among vegetarians?
Vegetarians are at risk for vitamin B(12) deficiency, with higher rates observed among vegans and those adhering to a vegetarian diet since birth.
Systematic ReviewHighly CitedImbalance of Vitamin B Factors
Imbalance of vitamin B factors can cause secondary deficiencies, potentially causing symptoms in patients with multiple deficiencies.
Low-dose vitamin B-6 effectively lowers fasting plasma homocysteine in healthy elderly persons who are folate and riboflavin replete.
Low-dose vitamin B-6 supplementation effectively lowers fasting plasma homocysteine levels in healthy elderly individuals who are folate and riboflavin replete, suggesting its inclusion in treatment or prevention of hyperhomocysteinemia.
RCTHighly Cited