What are toxic levels of Vitamin B (Vit B)?

From the Guidelines

Toxic vitamin B levels can occur at specific doses, including above 100 mg/day for Vitamin B6, causing sensory neuropathy, as indicated in the evidence-based nutrition principles 1. When considering the potential toxicity of vitamin B, it's essential to look at the different types of B vitamins and their respective upper intake levels.

• Vitamin B6 toxicity can occur at doses above 100 mg/day, leading to sensory neuropathy, as shown in Table 6 of the evidence 1.
• For other B vitamins like folate (B9), the risk of toxicity is relatively low, but excessive supplementation above 1,000 mcg/day may mask B12 deficiency symptoms.
• Vitamin B12 has an insufficient amount of data to set an upper intake level, suggesting its toxicity risk is very low 1.
• Other B vitamins such as thiamine (B1), riboflavin (B2), have insufficient data to set upper intake levels, implying minimal toxicity risk even at high doses 1. It's crucial to be aware of these levels to prevent adverse health effects, especially since some neurological effects from B6 toxicity can be permanent if not addressed promptly.
• Discontinuing supplements immediately and consulting a healthcare provider is recommended if vitamin B toxicity is suspected.
• Blood tests can confirm excessive levels and guide treatment, emphasizing the importance of monitoring and medical supervision when dealing with potential vitamin toxicity.

From the Research

Toxic Levels of Vitamin B

Toxic levels of vitamin B can occur with excessive intake, particularly with vitamins B6 and B12. The following points highlight the toxic levels of these vitamins:

• Vitamin B6 toxicity can occur at intakes of 1000 mg per day or more, which is about 800 times the daily intake from foods 2.
• The US authorities set the no-observed-adverse-effect-level at 200 mg per day and the safe upper limit at 100 mg per day for vitamin B6 2.
• Plasma pyridoxal 5'-phosphate (PLP) concentration above 100 nmol/L or 25 μg/L can lead to neurotoxicity when administered daily in supraphysiologic doses 3.
• Vitamin B12 toxicity can occur with multiple high doses, such as 12 mg of cyanocobalamin, leading to symptoms like acne, palpitations, anxiety, and headache 4.

Safe Upper Limits

The safe upper limits for vitamin B intake are:

• Vitamin B6: 100 mg per day 2.
• Vitamin B12: no specific safe upper limit is mentioned, but high doses can lead to toxicity 4.

Neurotoxicity

Neurotoxicity can occur with high doses of vitamin B6, particularly when plasma PLP levels exceed 100 nmol/L or 25 μg/L 3. Vitamin B12 toxicity can also lead to neurological symptoms, such as anxiety and headache 4.

Monitoring and Treatment

Monitoring of serum vitamin B levels is essential to prevent toxicity, particularly in patients with neurological symptoms 3, 5. Treatment with vitamin B supplements should be done under medical supervision, with careful monitoring of serum levels to avoid toxicity 3, 6.