Can you take too much Vitamin B6?
Taking multiple nutritional supplements each day can increase the risk of Vitamin B6 toxicity.
By Dr Nicole Kellow AdvAPD
Recent news reports have highlighted the potentially harmful side effects of consuming large doses of Vitamin B6 in nutritional supplements. Let’s have a look at this vitamin in more detail.
Vitamin B6, also known as pyridoxine, is a water-soluble vitamin important for healthy immune function, growth of red blood cells, production of neurotransmitters (chemical messengers in the brain) and the breakdown of dietary fats, carbohydrates and proteins. Vitamin B6 is an essential nutrient and must be obtained from our diet. The average daily requirement for Vitamin B6 is 1.1-1.4 mg per day for adults, with a slightly higher average requirement during pregnancy of 1.6 mg per day. A healthy diet will easily provide enough Vitamin B6 to meet daily needs, from foods such as lean red, fish, chicken & turkey, bananas, potatoes, fortified breakfast cereals, chickpeas. For example, one cup or 40 grams of Special K cereal contains 0.4mg of Vitamin B6. This is equivalent to approximately 20% of an average adult daily intake.
Vitamin B6 is also found in multivitamin and mineral supplements, Vitamin B complex supplements, combined Vitamin B and magnesium supplements, some sports drinks, and weight loss shakes. A typical vitamin B6 supplement recommends a daily intake of one tablet, which contains 100mg of vitamin B6. It is used for a short period of time to relieve pre-menstual tension symptoms. Consuming more than 50 mg per day of Vitamin B6 for long periods of time has been associated with a condition called peripheral neuropathy – a condition which initially involves symptoms such as burning, tingling or numbness of the hands and feet, but can progress to difficulty with balance or walking, and ultimately lead to painful and irreversible neurological problems. All known cases of peripheral neuropathy from Vitamin B6 toxicity have been the result of taking high doses of nutritional supplements, there have never been any cases of Vitamin B6 toxicity from eating foods alone.
The Australian Therapeutic Goods Administration (TGA) requires all nutritional supplements containing more than 50 mg of Vitamin B6 to display a warning on the label, which advises consumers to stop taking the product and see a healthcare professional if they experience tingling, burning or numbness. However, many people take supplements containing less than 50 mg of Vitamin B6 without realising that taking multiple capsules or taking several different Vitamin B6-containing products each day can easily raise their B6 intake above safe levels.
Some Vitamin B6 supplements promoted to women for the management of morning sickness (nausea and/or vomiting) during pregnancy or for the management of premenstrual syndrome (PMS) contain up to 100mg of Vitamin B6 per capsule. This is too much Vitamin B6, especially when taken in combination with other supplements that also contain Vitamin B6. There is also limited evidence to support the effectiveness of high doses of Vitamin B6 for these conditions (1, 2). A pregnancy or general multivitamin (which already meets average daily Vitamin B6 requirements) along with dietary food sources of Vitamin B6 is recommended.
Do stick to the recommended dose of any supplements that are used as overdosing can cause problems.
References:
1. Matthews A, Dowswell T, Haas DM, Doyle M, O’Mathuna DP. Interventions for nausea and vomiting in early pregnancy. Cochrane Database Syst Rev. 2014;(3):CD007575. doi: 10.1002/14651858.CD007575.pub3.
2. Chocano-Bedoya PO, Manson JE, Hankinson SE, Willett WC, Johnson SR, Chasan-Taber L, Ronnenberg AG, Bigelow C, Bertone-Johnson ER. Dietary B vitamin intake and incident premenstrual syndrome. Am J Clin Nutr. 2011; 93(5):1080-6. doi: 10.3945/ajcn.110.009530. Epub 2011 Feb 23. PMID: 21346091; PMCID: PMC3076657.
Dr Nicole Kellow is a Senior Lecturer and NHMRC Early Career Research Fellow in the Department of Nutrition and Dietetics at Monash University. Nicole is an Advanced Accredited Practising Dietitian (AdvAPD) and a Credentialled Diabetes Educator (CDE) with over 18 years of clinical experience. She currently investigates the role of dietary Advanced Glycation End-products (AGEs) in endocrine and fertility disorders, and the relationship between diet and the gut microbiota.
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