Daily reference value of vitamin B6 is 2 mg according to the 2013 FDA food-labeling guidelines.
What Are the Recommended Dietary Allowances for Vitamin B6?
| 1–3 years | 0.5 mg |
| 4–8 years | 0.6 mg |
| 9–13 years | 1.0 mg |
| 14–18 years | 1.3 mg (boys); 1.2 mg (girls) |
| 19 years and older | 1.7 mg (men); 1.5 mg (women) |
The upper daily intake limit of vitamin B6 is 100 mg.
Vitamin B6 Supplements
• Dosage. The most common dosages of vitamin B6 supplements are 50–100 mg.
• Pregnancy. Vitamin B6 may alleviate vomiting during pregnancy. The suggested daily dose is 30 mg.
• Tardive dyskinesia. Vitamin B6 is effective in treating tardive dyskinesia. Tardive dyskinesias are involuntary movements of the face, tongue, lips, trunk, and extremities caused by long-term medication with an antipsychotic drug, such as aripiprazole. The suggested daily dose of vitamin B6, in this case, is 250 mg.
• Congenital homocystinuria. Vitamin B6 may improve the symptoms of congenital homocystinuria patients who have an excess of homocysteine in the urine. The suggested daily dose is 250 mg.
Safety Issues
• Side effects. Taking doses of vitamin B6 higher than 2 g daily may be harmful to the nervous system. Symptoms include numbness of extremities, stabbing pain, and, in severe cases, difficulty walking.
• Diseases. High doses of vitamin B6 exacerbate the risk of heart disease, stroke, and death in patients with diabetes with kidney disease.
What Types of Drugs May Interact with Vitamin B6?
• Oral contraceptives. These can reduce the blood level of vitamin B6. Women who use oral contraceptives should consider taking vitamin B6 supplements.
• Antihypertensive drugs. Vitamin B6 enhances the effect of some antihypertensive drugs, such as diltiazem and amlodipine, and interferes with medications for treating Parkinson’s disease.
• Other medications. Drugs like hydralazine to treat high blood pressure and heart failure, penicillamine to treat rheumatoid arthritis, and theophylline to treat respiratory diseases can cause vitamin B6 deficiency.
Vitamin B7 is biotin. The story of biotin is associated with raw egg whites. In 1927, Margarete Boas fed rats only raw egg whites and found that rats suffered from severe dermatitis, hair loss, and neuromuscular malfunctions. She called the disease “egg-white injury.” In subsequent years, a water-soluble nutrient was isolated from beef liver. Rats fed this water-soluble nutrient recovered from the disease. In 1942, Vincent du Vigneaud confirmed that the chemical structure of the water-soluble nutrient was biotin, called “vitamin B7.” Later, they discovered that raw egg whites contained avidin, a protein that binds tightly to biotin. Almost all biotin in raw egg whites is bound to avidin. Rats cannot absorb biotin that binds to avidin in raw egg whites, so when fed only raw egg whites, they suffered from biotin deficiency. Boiled egg whites would not present such a problem because once boiled, biotin in egg whites is released from avidin.
From an evolutionary point of view, avidin in eggs protects them against bacterial infections. Bacteria need biotin for growth and proliferation. However, biotin bound to avidin makes biotin unavailable to bacteria, guarding eggs against bacterial infections. Avidin in egg whites may allow oviparous animals to survive on Earth.
Vitamin B7 is an essential cofactor for five different carboxylases—enzymes that participate in the fixation of carbon dioxide from the air, activation of histone proteins, and gene expression. Carboxylase enzymes play an important role in transporting glucose into the cell and lowering blood glucose levels to avoid diabetes. Additionally, carboxylase is involved in fat deposition in the dermal layer of the skin, maintaining skin’s moisture, elasticity, and smoothness.
What Are the Symptoms of Vitamin B7 Deficiency?
• Vitamin B7 deficiency can lead to a wide range of physiological abnormalities, including growth retardation, nervous system malfunction, skin disorders, depression, fatigue, delusions, numbness, and/or stabbing pain in the hands and feet. Other symptoms related to vitamin B7 deficiency include hair loss and a scaly rash in the eyes, nose, and mouth.
What Are the Causes of Vitamin B7 Deficiency?
• Various foods are rich in vitamin B7; thus, vitamin B7 deficiency is rare.
