In severe cases, motor neuropathy may occur with "slowing of motor conduction velocities, prolonged F wave latencies, and prolonged sensory latencies in both lower extremities", causing difficulty in walking. Sensory neuropathy typically develops at doses of pyridoxine in excess of 1,000 mg per day, but adverse effects can occur with much less, so intakes over 200 mg/day are not considered safe. Trials with amounts equal to or less than 200 mg/day established that as a "No-observed-adverse-effect level", meaning the highest amount at which no adverse effects were observed. This was divided by two to allow for people who might be extra sensitive to the vitamin, referred to as an "uncertainty factor", resulting in the aforementioned adult UL of 100 mg/day. Labeling
For US food and dietary supplement labeling purposes the amount in a serving is expressed as a percent of Daily Value. For vitamin B6 labeling purposes 100% of the Daily Value was 2.0 mg, but as of May 27, 2016 it was revised to 1.7 mg to bring it into agreement with the adult RDA. A table of the old and new adult daily values is provided at Reference Daily Intake. Sources
Bacteria residing in the large intestine are known to synthesize B-vitamins, including B6, but the amounts are not sufficient to meet host requirements, in part because the vitamins are competitively taken up by non-synthesizing bacteria.Vitamin B6 is found in a wide variety of foods. In general, meat, fish and fowl are good sources, but dairy foods and eggs are not (table).
In 2001, MHLW enacted a new regulatory system, Foods with Health Claims (保健機能食品; FHC), which consists of the existing FOSHU system and the newly established Foods with Nutrient Function Claims (栄養機能表示食品; FNFC), under which claims were approved for any product containing a specified amount per serving of 12 vitamins, including vitamin B6, and two minerals. To make a health claim based on a foods vitamin B6 content, the amount per serving must be in the range of 0.3–25 mg. The allowed claim is: "Vitamin B6 is a nutrient that helps produce energy from protein and helps maintain healthy skin and mucous membranes. "In 2010, the European Food Safety Authority (EFSA) published a review of proposed health claims for vitamin B6, disallowing claims for bone, teeth, hair skin and nails, and allowing claims that the vitamin provided for normal homocysteine metabolism, normal energy-yielding metabolism, normal psychological function, reduced tiredness and fatigue, and provided for normal cysteine synthesis.The US Food and Drug Administration (FDA) has several processes for permitting health claims on food and dietary supplement labels. There are no FDA-approved Health Claims or Qualified Health Claims for vitamin B6. Structure/Function Claims can be made without FDA review or approval as long as there is some credible supporting science. Examples for this vitamin are "Helps support nervous system function" and "Supports healthy homocysteine metabolism." Absorption, metabolism and excretion
Vitamin B6 is absorbed in the jejunum of the small intestine by passive diffusion. Even extremely large amounts are well absorbed.