Vitamin B-6

Vitamin B6 is a water-soluble vitamin, most commonly found in food as pyridoxine, that the body uses as a coenzyme for over 100 enzymatic reactions, including breaking down protein and making neurotransmitters and hemoglobin. Fish, poultry, organ meats, legumes, and fortified cereals are its richest everyday sources.

What is vitamin B6

Vitamin B6 is a coenzyme that Harvard T.H. Chan School of Public Health, The Nutrition Source describes as assisting more than 100 enzymes involved in breaking down protein, carbohydrate, and fat; it also helps keep homocysteine levels in a normal range and supports immune and brain function. MedlinePlus adds that vitamin B6 is needed to make antibodies and hemoglobin, maintain normal nerve function, and help regulate blood glucose. Harvard's Nutrition Source lists beef liver, tuna, salmon, fortified cereals, chickpeas, poultry, dark leafy greens, bananas, papayas, oranges, and cantaloupe as rich sources. In this project's data, spices such as sage, paprika, and cayenne-type peppers rank highest by measured amount, while chickpeas, raw yellowfin tuna, peanuts, and cantaloupe are more typical everyday sources.

Health benefits of vitamin B6

• Protein and neurotransmitter metabolism. Vitamin B6's foundational role is enabling the enzymatic reactions that break down protein and build neurotransmitters and hemoglobin, per MedlinePlus and Harvard's Nutrition Source.
• Nausea in pregnancy — strong evidence. Harvard's Nutrition Source states that over-the-counter vitamin B6, alone or combined with doxylamine, is recommended as a safe and effective first-line treatment for pregnancy-related nausea — one of the more clearly supported, specific uses of B6 supplementation.
• Heart disease — limited benefit despite a plausible mechanism. Vitamin B6 supplements lower homocysteine, a compound associated with cardiovascular risk in observational studies, but Harvard's Nutrition Source reports that supplementation has not consistently reduced actual heart attack or stroke risk in trials.
• Cognitive decline — no benefit shown. Harvard's Nutrition Source cites a Cochrane review that found no effect of B-vitamin supplementation, including B6, on cognition in adults 60 and older without dementia.

How much you need

The NIH Office of Dietary Supplements RDA for vitamin B6, corroborated via WebSearch and confirmed directly by Harvard's Nutrition Source and MedlinePlus, is 1.3 mg/day for men and women ages 19–50, rising to 1.7 mg/day for men 51+ and 1.5 mg/day for women 51+; teens ages 14–18 need 1.3 mg/day (boys) or 1.2 mg/day (girls). The Tolerable Upper Intake Level (UL) for adults is 100 mg/day from supplements. Harvard's Nutrition Source notes that documented toxicity has occurred at much higher, long-term doses — generally above 1,000 mg/day — meaning the UL is set well below the level where harm has actually been observed, as a margin of safety rather than a reflection of the exact toxicity threshold. These figures are not yet populated in this project's nutrient_rda table.

Signs of deficiency and excess

MedlinePlus lists confusion, depression, irritability, mouth and tongue sores, and peripheral neuropathy (nerve damage causing numbness or tingling) as signs of vitamin B6 deficiency, while noting deficiency is uncommon in the United States today. Harvard's Nutrition Source identifies several groups at higher risk: people with kidney disease, celiac disease, ulcerative colitis, Crohn's disease, rheumatoid arthritis, or alcoholism. At the high end, MedlinePlus describes difficulty coordinating movement, numbness, and other sensory changes from excessive intake; Harvard's Nutrition Source specifies this sensory neuropathy and ataxia (loss of coordination) have occurred with long-term, very-high-dose supplementation above 1,000 mg/day, alongside nausea — a pattern seen with supplements, not with food-based intake.

Warnings & interactions

Vitamin B6 is one of the nutrients where the gap between the UL (100 mg/day) and documented toxicity (above 1,000 mg/day, sustained) is unusually wide, which is why very-high-dose, long-term supplementation specifically — not ordinary multivitamin use or dietary intake — is the practical concern. The NIH Office of Dietary Supplements documents that vitamin B6 can interact with certain medications, most notably the Parkinson's disease drug levodopa: supplemental vitamin B6 taken without carbidopa can reduce levodopa's effectiveness by increasing how much of the drug is broken down before it reaches the brain (this specific NIH ODS fact sheet blocks automated fetching; the interaction is corroborated via WebSearch and cross-referenced academic literature — see Sourcing notes). Anyone on levodopa therapy should have their vitamin B6 intake, including from fortified foods and supplements, reviewed by their care team rather than adjusting it independently. People with kidney disease or the autoimmune/digestive conditions named above are also more likely to need individualized monitoring of B6 status.

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