What is vitamin B6?
Vitamin B6, also known as pyridoxine, is one of eight water-soluble B vitamins. (26) In the body, vitamin B6 plays a vital role in the function of more than 100 enzymes, which carry out various functions. (26) Vitamin B6 catalyzes reactions that are involved in the maintenance of blood sugar, amino acid metabolism, synthesis of neurotransmitters such as serotonin and dopamine, and red blood cell formation. (31) Vitamin B6 present in our foods exist in several forms including pyridoxine, pyridoxal, and pyridoxamine. Yeasts and meat mostly contain vitamin B6 as pyridoxal and pyridoxamine, while plants primarily contain vitamin B6 as pyridoxine. (31) Despite these various forms, the body converts these into the active coenzyme form, pyridoxal 5’-phosphate (PLP), which is produced by the liver. (31) Vitamin B6 supplements often contain the salt form of vitamin B6, pyridoxine hydrochloride, which is converted into PLP by the liver. (27)(31)Vitamin B6 foods
Vitamin B6 can be found in many foods, including chickpeas, bananas, and beef liver. The graphic below shows the amount of vitamin B6 in various foods.
Vitamin B6 is found in various plant-based and animal-sourced foods. (26)
Vitamin B6 benefits
Since vitamin B6 is needed for many important processes in the body, it also has various potential clinical benefits. Vitamin B6 can be toxic at high doses and supplementation should be used under the guidance of your healthcare practitioner. (8)1. Sideroblastic anemia
Oral vitamin B6 may be effective for treating a particular form of anemia, known as sideroblastic anemia. (7) Sideroblastic anemia is a disorder in which developing red blood cells are unable to produce enough hemoglobin, despite there often being an accumulation of iron. (22) Hemoglobin is an iron containing component of red blood cells, which delivers oxygen to our tissues. (4) One possible reason the body is unable to make sufficient hemoglobin is if it lacks PLP, as PLP is needed for the synthesis of the heme component of hemoglobin. (31) Studies demonstrate that B6-responsive sideroblastic anemias are improved by PLP supplementation (the active coenzyme form) but not pyridoxine. (10)(31) This suggests that there may be an enzymatic deficiency or inhibition of the enzyme that converts vitamin B6 into the active PLP form. (17) For cases of primary sideroblastic anemia, PLP may help if there is no response to pyridoxine. (31)2. Hyperhomocysteinemia
Homocysteine is an intermediate in the metabolism of the amino acid methionine. (31) One of the pathways in which homocysteine is metabolized by the body uses two enzymes that require PLP in order to function. (31) A vitamin B6 or other B vitamin deficiency such as vitamin B12 or folate (folic acid) can lead to elevated levels of homocysteine in the blood, known as hyperhomocysteinemia. Hyperhomocysteinemia is correlated with ischemic heart disease, deep vein thrombosis, and stroke. (35) Lowering homocysteine levels may decrease the risk of such cardiovascular conditions, (35) although some studies report no significant impact on cardiovascular outcomes. (2)(14) Studies investigating vitamin B6’s potential to lower homocysteine levels have produced mixed results. One study demonstrated that vitamin B6 supplementation alone can lower homocysteine concentrations when folic acid and vitamin B12 are at normal levels. (20) Other studies demonstrated that vitamin B6 supplementation in combination with folic acid and vitamin B12 also lower homocysteine. (29)(34) A large study of 5,500 adults with known cardiovascular disease found that supplementation of vitamin B6, vitamin B12, and folic acid for five years not only reduced homocysteine levels but decreased stroke risk by 28%. (29) Studies that have tried to distinguish between the potential beneficial effects of folic acid versus vitamin B6 found that folic acid is more effective at lowering homocysteine than vitamin B6 (31) and that vitamin B6 supplementation provided no added benefit. (33)
Vitamin B6 supplementation may ease nausea and vomiting during pregnancy.
3. Nausea and vomiting in pregnancy
Nausea and vomiting commonly occur in early pregnancy and can sometimes last until birth. (9) There are many ingredients that can help manage this, including vitamin B6. A 2016 systematic review demonstrated that vitamin B6 can reduce mild symptoms of nausea and vomiting to a greater degree than placebo. (21) In fact, vitamin B6 is considered a first-line treatment for nausea and vomiting in pregnancy by the American College of Obstetrics and Gynecology. (1)(9) However, if vitamin B6 alone is not sufficient, it is combined with doxylamine (an antihistamine commonly used to relieve allergy symptoms and also promotes drowsiness), which together may reduce nausea and vomiting by 70%. (5) The effectiveness of vitamin B6 for nausea and vomiting has also been compared to other natural ingredients, such as ginger. One study demonstrated that while both ginger and vitamin B6 significantly reduced nausea and vomiting in early pregnancy, ginger was more effective than vitamin B6. (12) Both groups, however, reported minor side effects such as heartburn. (12) On the other hand, other trials report that vitamin B6 and ginger are both equally effective in reducing nausea and the number of vomiting episodes during pregnancy. (30)4. Premenstrual syndrome
Systematic reviews demonstrate that vitamin B6 alone (37) or in combination with chasteberry (Vitex agnus-castus) is effective in reducing premenstrual syndrome (PMS) symptoms. (36) Vitamin B6 is associated with significant reductions in a broad range of PMS symptoms, including moodiness, irritability, forgetfulness, bloating, and especially, anxiety. (13) Vitamin B6’s potential to reduce mood-related symptoms of PMS may have to do with its role as a coenzyme in the synthesis of neurotransmitters. (3) Vitamin B6 levels have a significant impact on the production of serotonin and GABA, key neurotransmitters involved in depression, pain perception, and anxiety. (18)5. Kidney stones
Among the different types of kidney stones, calcium stones are the most common. Calcium stones are comprised of oxalate, a compound found in some foods (e.g., beans, nuts, spinach, sweet potatoes, coffee), and produced as a waste product by the body that is excreted through urine. (25) High levels of oxalate can increase the risk of calcium stone formation. Fortunately, studies have shown that vitamin B6 supplementation can reduce oxalate levels. (24)(28) For example, one study demonstrated that vitamin B6 supplementation significantly decreased oxalate in patients with high levels of urinary oxalate and who suffered from recurrent calcium oxalate kidney stones. (28) Furthermore, a large prospective study demonstrated that a high intake of vitamin B6 can reduce the risk of developing kidney stones. (6) The study followed a cohort of 85,557 women with no history of kidney stones and monitored their vitamin consumption from both foods and supplements over time. They found that women with the highest total intake of vitamin B6 were least likely to develop kidney stones. (6)6. Vitamin B6 deficiency
Severe vitamin B6 deficiencies are uncommon; however, individuals may have marginal vitamin B6 status. (16) The recommended daily intake of vitamin B6 for adults ranges from 1.3 to 1.7 mg, depending on age and sex. (32) Vitamin B6 status can most directly be assessed by measuring the amount of circulating PLP from a blood sample. (15) Inadequate vitamin B6 status is often associated with low amounts of other B vitamins, particularly vitamin B12 and folate. (26) People experiencing a vitamin B6 deficiency may not show any symptoms for months or years, but as it progresses, signs and symptoms can become more evident. Vitamin B6 deficiency symptoms include:- Anemia
- Mental health symptoms, such as depression and confusion
- Neurological problems, such as convulsions and seizures in infants
- Scaling and cracks at the corners of the mouth
- Skin conditions
- Swollen tongue (26)
The bottom line
Vitamin B6 is needed for many important processes including blood sugar maintenance, protein metabolism, red blood cell formation, and central nervous system function. Although the daily requirements of vitamin B6 are typically attainable through diet alone, certain groups are at a greater risk of vitamin B6 deficiency. If you are at all concerned about your vitamin B6 status or thinking about supplementation, talk to your healthcare provider.References
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