Scientific opinion on the tolerable upper intake level for vitamin B6

Vitamin B6, B12, and Folate's Influence on Neural Networks in the UK Biobank Cohort

BACKGROUND

One-carbon metabolism coenzymes may influence brain aging in cognitively unimpaired adults.

METHODS

Baseline data were used from the UK Biobank cohort. Estimated intake of vitamin B6, B12, and folate was regressed onto neural network functional connectivity in five resting-state neural networks. Linear mixed models tested coenzyme main effects and interactions with Alzheimer's disease (AD) risk factors.

RESULTS

Increased B6 and B12 estimated intake were linked with less functional connectivity in most networks, including the posterior portion of the Default Mode Network. Conversely, higher folate was related to more connectivity in similar networks. AD family history modulated these associations: Increased estimated intake was positively associated with stronger connectivity in the Primary Visual Network and Posterior Default Mode Network in participants with an AD family history. In contrast, increased vitamin B12 estimated intake was associated with less connectivity in the Primary Visual Network and the Cerebello-Thalamo-Cortical Network in those without an AD family history.

CONCLUSIONS

The differential patterns of association between B vitamins and resting-state brain activity may be important in understanding AD-related changes in the brain. Notably, AD family history appears to play a key role in modulating these relationships.

Does Dietary Supplement Use Increase Micronutrient Intake Adequacy in Healthy Adults with Habitual Omnivorous, Vegetarian, Vegan, and Low-Carbohydrate High-Fat Diets?

Diets omitting whole food groups pose a risk for micronutrient insufficiencies, but there are no data as to whether those are suitably attenuated with dietary supplements (DS). Micronutrient intakes with food and DSs were analyzed in 130 healthy adults: 32 vegans, 37 vegetarians, 24 following low-carbohydrate high-fat diet (LCHF), and 37 omnivores. A total of 63% used DS (84% of vegans, 75% of LCHF, 54% of vegetarians, and 46% of omnivores); however, a DS did not always tackle dietary insufficiencies. Vitamin B12 was often supplemented in vegans in doses substantially higher than recommended, but it was supplemented less often in vegetarians, despite the low prevalence of sufficient intake. Only 43% of participants supplemented vitamin D in wintertime, 23% of them with an insufficient dose. Supplementation of potassium, calcium, and iodine was rare, despite low intake adequacy with food alone in all groups. Some micronutrients were supplemented unnecessarily, such as vitamin K, riboflavin, biotin, and iron. Multimicronutrient DSs were used often; they increased intake adequacy of group B vitamins but failed to sufficiently supplement vitamin D, potassium, calcium, and iodine. Although DS use increased micronutrient intake sufficiency when used properly, the knowledge on micronutrient inadequacy in all dietary patterns should be increased and the public should be educated on the proper use of DSs. Multimicronutrient DSs should be reformulated to tackle the insufficiencies.

Vitamin B6: a scoping review for Nordic Nutrition Recommendations 2023

Pyridoxal 5´-phosphate (PLP) is the main form of vitamin B6 in animal tissue and functions as a coenzyme for more than 160 different enzymatic reactions in the metabolism of amino acids, carbohydrates, lipids, and neurotransmitters. Estimated dietary intake of vitamin B6 and plasma PLP values differ a lot between studies, something which may be due to variable use of supplements, variations in dietary assessment and analytical methods. These factors make it difficult to achieve precise data for setting a correct recommended intake of vitamin B6. In addition, a plasma PLP concentration of 30 nmol/L is considered to be sufficient and the current recommendations for vitamin B6 intake is based on this concept. However, the metabolic marker for vitamin B6 status, HK ratio (HKr), starts to increase already when plasma PLP falls below 100 nmol/L and increases more steeply below 50 nmol/L, indicating biochemical deficiency. Consequently, a plasma PLP concentration of 30 nmol/L, may be too low as a marker for an adequate vitamin B6 status.

Vitamin B6 Toxicity Secondary to Daily Multivitamin Use: A Case Report

Vitamin B6 is a water-soluble vitamin that is an important cofactor in various metabolic processes. Although rare, its consumption can sometimes result in toxicity, which typically presents with peripheral neuropathy in the early stage. While vitamin B6 toxicity is most often associated with supplemental mega-doses of more than 50 mg/day, more recent studies have shown that toxicity can occur in cases of much smaller doses as well. We present a case of a 73-year-old male with a three-year history of progressive peripheral neuropathy who was found to have a serum vitamin B6 level of 259.9 nmol/L (reference range: 20-125 nmol/L) but only reported taking a daily multivitamin containing 6 mg of vitamin B6. This case of toxicity in the setting of a daily intake lower than the European Food Safety Administration's (EFSA) newly established Tolerable Upper Intake Level (UL) of 12 mg/day highlights the need for further research into the effects of relatively low-dose vitamin B6 supplementation.