From the Guidelines
Functional B6 deficiency should be addressed by supplementing with pyridoxal-5-phosphate (P5P) directly, rather than standard pyridoxine supplements, to bypass the conversion problem and provide the body with the active form it needs. To determine the optimal dosage, it's essential to consider the most recent and highest quality study available. According to the study by 1, the optimal parenteral B6 dose for infants and children is not clear, but the ESPGHAN 2005 guidelines proposed doses of 0.15-0.2 mg/kg/d for infants and of 1.0 mg/kg/d for children. However, since the question is about functional B6 deficiency, which is not specifically addressed in this study, we need to consider other factors. Signs of functional B6 deficiency include:
- Peripheral neuropathy
- Anemia
- Depression
- Confusion
- Weakened immune function This condition often occurs in people with certain genetic variations, liver disease, alcoholism, or those taking medications like isoniazid or oral contraceptives that interfere with B6 metabolism. Blood tests may show normal B6 levels but elevated homocysteine or decreased activity of B6-dependent enzymes. When supplementing, it's crucial to start at a lower dose and increase gradually if needed, taking it with food to improve absorption. P5P supplements are generally well-tolerated, but excessive doses can cause nerve damage, so it's essential not to exceed recommended amounts without medical supervision. Addressing underlying conditions and ensuring adequate intake of other B vitamins, particularly B2 which helps activate B6, is also important for comprehensive treatment. In the context of pregnancy, vitamin B6 (pyridoxine) may be suggested as a first-line treatment for mild cases of hyperemesis gravidarum, as mentioned in the study by 1. However, this is not directly related to functional B6 deficiency. In real-life clinical practice, it's crucial to prioritize the patient's morbidity, mortality, and quality of life when making treatment decisions. Therefore, supplementing with P5P directly at 25-50mg daily is recommended, while also addressing underlying conditions and ensuring adequate intake of other B vitamins.
From the FDA Drug Label
CLINICAL PHARMACOLOGY Natural substances that have vitamin B6 activity are pyridoxine in plants and pyridoxal or pyridoxamine in animals. All 3 are converted to pyridoxal phosphate by the enzyme pyridoxal kinase. The physiologically active forms of vitamin B6 are pyridoxal phosphate (codecarboxylase) and pyridoxamine phosphate The tryptophan load test appears to uncover early vitamin B6 deficiency by detecting xanthinurea.
The functional B6 deficiency can be detected by the tryptophan load test which uncovers early vitamin B6 deficiency by detecting xanthinurea 2.
- The physiologically active forms of vitamin B6 are pyridoxal phosphate and pyridoxamine phosphate.
- Riboflavin is required for the conversion of pyridoxine phosphate to pyridoxal phosphate.
- Vitamin B6 acts as a coenzyme in the metabolism of protein, carbohydrate, and fat.
From the Research
Functional B6 Deficiency
- A functional B6 deficiency can occur when the body's vitamin B6 requirements are not met, despite adequate dietary intake 3.
- Vitamin B6 plays a crucial role in amino acid metabolism, and its deficiency can lead to various health problems, including peripheral neuropathy 4.
- The recommended daily intake of vitamin B6 is 15 micrograms/g dietary protein, and a minimum safe intake is 11 micrograms/g dietary protein 3.
- Certain groups, such as pregnant and lactating women, the elderly, and individuals with rheumatoid arthritis, may require higher intakes of vitamin B6 3, 5.
Health Consequences of Functional B6 Deficiency
- Functional B6 deficiency has been linked to various health conditions, including:
- Peripheral neuropathy: High vitamin B6 levels can lead to the development of peripheral neuropathy, while low levels may be seen in patients with the condition 4.
- Rheumatoid arthritis: Patients with rheumatoid arthritis may have subnormal vitamin B6 status, which can be corrected with pyridoxine supplementation 5.
- Idiopathic sideroblastic anemia: Vitamin B6 metabolism may be impaired in patients with idiopathic sideroblastic anemia, although supplementation may not improve erythropoiesis 6.
- Other diseases: Vitamin B6 deficiency may be associated with various diseases, including diabetes, heart disease, cancer, and COVID-19 7.
Diagnosis and Treatment of Functional B6 Deficiency
- Diagnosis of functional B6 deficiency can be made through measurements of plasma and erythrocyte pyridoxal 5'-phosphate concentrations, as well as other biochemical markers 5, 6.
- Treatment of functional B6 deficiency typically involves supplementation with pyridoxine or other forms of vitamin B6 5, 6.
- However, high doses of vitamin B6 can be toxic, and supplementation should be done under medical supervision 3, 4.