Too much vitamin b6 symptoms
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Symptoms of Excessive Vitamin B6 Intake
Introduction to Vitamin B6 and Its Importance
Vitamin B6, also known as pyridoxine, is a water-soluble vitamin essential for numerous biochemical reactions, including amino acid, carbohydrate, and lipid metabolism. It plays a crucial role in neurotransmitter production and gene expression modulation 9. However, while vitamin B6 is vital for health, excessive intake can lead to adverse effects.
Peripheral Neuropathy: A Common Symptom
One of the most well-documented symptoms of excessive vitamin B6 intake is peripheral neuropathy. This condition is characterized by damage to the peripheral nerves, leading to symptoms such as numbness, tingling, and pain, primarily in the hands and feet. High levels of vitamin B6, often resulting from supplementation, can cause a predominantly sensory neuropathy of the axonal type 24. Studies have shown that discontinuation of pyridoxine can lead to subjective improvement in symptoms, although the exact mechanism of toxicity remains unclear 3.
Neurotoxicity and Cellular Effects
Research indicates that pyridoxine, one of the forms of vitamin B6, can induce neurotoxicity. In vitro studies have demonstrated that pyridoxine can cause cell death in a concentration-dependent manner and inhibit enzymes dependent on pyridoxal-5-phosphate, the active form of vitamin B6. This inhibition can lead to symptoms similar to those of vitamin B6 deficiency, despite high levels of the vitamin 3.
Dosage and Risk Factors
The European Food Safety Authority (EFSA) has established a tolerable upper intake level (UL) for vitamin B6 at 12 mg/day for adults, including pregnant and lactating women. This recommendation is based on the relationship between excessive vitamin B6 intake and the development of peripheral neuropathy. The EFSA's findings suggest that even lower doses, such as 50 mg/day, can pose risks if taken over extended periods 5.
Case Reports and Observational Studies
Case reports and observational studies have further highlighted the risks associated with high vitamin B6 intake. For instance, a series of cases reported to the Netherlands Pharmacovigilance Centre Lareb showed that neuropathic complaints could arise even with dosages below 50 mg/day, although higher dosages and prolonged use were more commonly associated with these symptoms 4. Additionally, a study on chronic idiopathic axonal polyneuropathy (CIAP) found no significant correlation between moderately elevated plasma B6 levels and the severity of neuropathy, suggesting that standard supplementation may not have a major negative effect on CIAP 6.
Other Potential Symptoms
While peripheral neuropathy is the most common symptom, other potential adverse effects of excessive vitamin B6 intake have been reported. For example, a case report documented excessive bleeding in a pediatric patient due to pyridoxal-5-phosphate supplementation, expanding the spectrum of known vitamin B6 toxicity 7. Additionally, maternal over-supplementation of vitamin B6 in animal studies did not show adverse effects, but deficiency did lead to DNA damage and oxidative stress in offspring 8.
Conclusion
Excessive intake of vitamin B6, particularly through supplementation, can lead to significant health issues, primarily peripheral neuropathy. While the exact mechanisms of toxicity are not fully understood, the evidence suggests that caution is warranted when using vitamin B6 supplements, especially at high doses or over prolonged periods. Monitoring and adhering to recommended intake levels can help mitigate these risks.
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Most relevant research papers on this topic
The Effects of Vitamin B6 Supplementation on premenstrual Symptoms
Vitamin B6 supplementation may improve premenstrual symptoms related to autonomic reactions and behavioral changes, but caution is advised due to potential toxic effects of low doses.
RCTThe Role of Vitamin B6 in Peripheral Neuropathy: A Systematic Review
High vitamin B6 levels may cause neurotoxic peripheral neuropathy, while low B6 levels may be a potential risk factor for peripheral neuropathy, but further studies are needed.
Systematic ReviewThe vitamin B6 paradox: Supplementation with high concentrations of pyridoxine leads to decreased vitamin B6 function.
High doses of vitamin B6 supplements can cause neuropathy due to pyridoxine, which inhibits the active form of pyridoxal-5'-phosphate, leading to symptoms similar to vitamin B6 deficiency.
In Vitro Study
Highly CitedVitamin B6 in Health Supplements and Neuropathy: Case Series Assessment of Spontaneously Reported Cases
Vitamin B6 supplements may cause neuropathies, especially with higher dosages and prolonged use, but dosages 50 mg/day also cannot be excluded.
Rigorous 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 ReviewVitamin B6 levels do not correlate with severity of neuropathy in chronic idiopathic axonal polyneuropathy
Moderately elevated vitamin B6 levels, even in the 100 to 200 g/L range, are not associated with significantly worse neuropathy signs or symptoms in chronic idiopathic axonal polyneuropathy patients.
Observational StudyB6 and Bleeding: A Case Report of a Novel Vitamin Toxicity
Vitamin B6 therapy can exacerbate bleeding symptoms in patients with pyridox(am)ine-5-phosphate oxidase deficiency and mild hemophilia A, highlighting the need for vigilance in monitoring bleeding symptoms.
Case ReportEffects of maternal vitamin B6 deficiency and over-supplementation on DNA damage and oxidative stress in rat dams and their offspring.
Maternal vitamin B6 deficiency may cause chromosomal damage and hepatic lipid peroxidation in offspring, while over-supplementation has no adverse effects.
RCT
Animal StudyVitamin B6 status, deficiency and its consequences--an overview.
Suboptimal vitamin B6 status is associated with certain chronic diseases, particularly in the elderly, such as impaired cognitive function, Alzheimer's disease, cardiovascular disease, and various types of cancer.
Systematic ReviewHighly CitedVitamin B6 Supplementation Reduces Symptoms of Depression in College Women Taking Oral Contraceptives: A Randomized, Double-Blind Crossover Trial
Vitamin B6 supplementation can reduce symptoms of depression in college women using oral contraceptives.
RCT