The B6 Paradox

Vitamin B6 has been widely used in the treatment of morning sickness, and other types of nausea. B6 has been known to have antiemetic effects since the 1940s. There are multiple forms in blood circulation and knowing which form had the most significant effect on nausea and vomiting had been a bit of a mystery until newer research pointed to the pyridoxal-5-phosphate (P5P) form of B6 as being associated with the decrease in nausea and vomiting symptoms. But, it's not just this simple (of course)

B6 for Nausea Support

A study done in 2014 and published in the Journal of Clinical Pharmacology found a correlation between levels of P5P and a decrease in nausea and vomiting symptoms. The results came after an analysis of 283 pregnant women experiencing pregnancy nausea symptoms. The participants were randomized to receive a vitamin B6 medication in the form of pyridoxine hydrochloride or a placebo for 14 days. The effectiveness of the treatment was assessed by the Pregnancy-Unique Quantification of Emesis (PUQE) scoring system. Blood samples were taken at days 0, 4, 8, and 14 to measure the values of the different vitamin B6 forms; pyridoxal, pyridoxine, and P5P.

Among the women in the group receiving the supplemental pyridoxine hydrochloride, PUQE scores consistently improved over the 14 days. When they broke down the blood samples, the values of pyridoxal and pyridoxine remained constant and low, while the blood values of P5P increased in association with the antiemetic effects. 

How cool is that? 

From this study we can deduct that pyridoxine and pyridoxal were preforms of the P5P and that the P5P form was the form with the therapeutic effects. Based on these findings, treatment with the P5P form directly may be more beneficial in treatment that using the pyridoxine HCL form typically found in supplementation. Especially for those women who may have genetic conditions that limit their ability to convert pyridoxine to P5P, or who are insufficient in nutrients needed for conversion to happen. 

The B6 Paradox

There is a little something I want to touch on here, since we’re talking about B6 conversion, called the B6 paradox. We see this in supplements, typically high dose B complexes or isolated B6 supplements. One of the known side effects of B6 overdose is neurotoxicity with tingling in the extremities and neuropathy type presentations. Until 2017, the exact mechanism behind this was unknown. 

In this study they compared the neurological effects of different vitamin B6 forms, pyridoxine, pyridoxamine, pyridoxal, and P5P on different types of cells. What they found was that high doses of pyridoxine cause cell death, while none of the other vitamers affected the viability of the cells. Moreover, the P5P dependent enzymes were inhibited by the high dosed pyridoxine. This explains why symptoms of vitamin B6 toxicity mimic vitamin B6 deficiency since the supplemental pyridoxine causes a deficiency in P5P function. 

This is just one example of why vitamin form in supplementation is important. 

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About Sarah

Sarah is the author of Functional Maternity, the first and only book to highlight the role functional medicine and nutrition play into maternal health, pregnancy and childbirth outcomes. 

Sarah is the leading expert in the field of functional medicine in maternity and pregnancy care.

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The content in this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding your medical condition. 

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