vitamin B6 - pyridoxine

Foods Richest in vitamin B6 - pyridoxine

About vitamin B6 - pyridoxine

Basic description

Vitamin B6 is a water-soluble vitamin that is found in a variety of forms in the foods we eat as well as in our bodies. These forms include pyridoxal 5’-phosphate (PLP), which appears to be the most active form as a human vitamin. Other forms include pyridoxal (PL), pyridoxamine (PM), pyridoxine (PN), pyridoxamine 5’-phosphate (PMP) and pyridoxine-5’-phosphate (PNP). Nearly half of all WHF provide you with measurable amounts of vitamin B6. In addition, you can find nearly 30 excellent or very good sources of this nutrient among our core 100 WHF.

There has been substantial debate about blood levels of vitamin B6 and their relationship both to dietary intake and overall health. This debate has centered around the fact that a person can consume the recommended dietary amount of vitamin B6 (our WHF recommended level is 1.7 milligrams) and yet have a blood level of vitamin B6 (in the form of plasma PLP) that may not be optimal for metabolism. While we continue to recommend the highest adult Dietary Reference Intake (DRI) level for B6 as established by the National Academy of Sciences, we recognize that this amount might eventually be revised upward based on future research in this area. We would also note that the Tolerable Upper Limit (UL) for vitamin B6 is set at a relatively high level of 100 milligrams for adults, allowing plenty of room for B6 intake substantially above the DRI level.

Role in health support

Production of red blood cells

Hemoglobin is complicated protein present in red blood cells, and one of its primary roles is to help carry oxygen around the body. Heme is a key section of the hemoglobin molecule and the initial production of heme in bodies requires the presence of vitamin B6. (Although heme production can occur in multiple places throughout the body, the primary places involve the liver and bone marrow.) The importance of vitamin B6 in red blood cell production is underscored by relatively rare types of anemia called sideroblastic anemias.

Metabolism of carbohydrates

Vitamin B6 is involved at several steps in the metabolism of carbohydrates. In particular, the enzyme that pulls carbohydrates out of storage in the cell (in the form of a molecule called glycogen) requires vitamin B6 for its activity.

While nobody would do an experiment like this in humans, researchers have been able to induce problems in carbohydrate metabolism by feeding rats diets deficient in vitamin B6. Since breakdown of carbohydrates is an ongoing process that occurs in our bodies throughout the day to help us sustain our physical energy level, daily consumption of whole foods rich in B6 also makes good sense for maintaining ongoing energy levels.

Brain and nervous system health

Vitamin B6 is one of several B vitamins required for neurotransmitter synthesis. Three neurotransmitters (GABA, dopamine, and serotonin) depend on pyridoxal phosphate, the active coenzyme form of B6, at specific steps in their biosynthetic pathways.

Just as an example of how important this nutrient can be to proper brain and nervous system, function, there is a condition called pyridoxine-dependent epilepsy where a genetic mutation interferes with normal vitamin B6 function. In people who have this mutation, the brain does not develop properly and epileptic seizures are experienced beginning in infancy. Luckily, this condition is rare.

However, we may be at risk of other more common problems that can be brain and nervous-system related if our B6 intake is poor. Depression is a good example in this area. Researchers in Japan have found that the risk of depressed mood is higher in people with lower levels of vitamin B6 in their diet (in comparision with the general population). Another research group concluded that this link between risk of depression and B6 intake becomes even stronger when dietary folic acid—a nutrient that works very closely with vitamin B6 in brain and nervous system chemistry—is deficient as well. Recent research has also begun to indicate a link between B6 deficiency and risk of development for attention deficit disorder (ADHD). So once again, we are looking at the possible widespread importance of B6 for brain and nervous system support.

Liver detoxification

Generally speaking, we remove unwanted chemicals from our blood in the liver and kidney, and this process involves two steps. The first of these two steps is to make the chemicals more water soluble to allow for the second step of binding and removal. The number of nutrients required for this first step is long, but vitamin B6 is clearly one of the most important. It is so important that researchers can induce liver dysfunction in animals by feeding them a pyridoxine-depleted diet.

Other health support roles

Preliminary research on inflammation-related chronic diseases has shown likely connections between the risk of these diseases and B6 deficiency. Interestingly, in addition to increased risk of these conditions in association with B6 deficiency, the presence of chronic inflammatory conditions also appears to be associated with depletion of vitamin B6.

In animal studies, B6 has been shown to play a role in the development of healthy immune system function. This potential health benefit from B6 appears to be associated with its role in metabolism of the amino acid tryptophan.

As mentioned earlier, B6 plays a well-researched role in the synthesis and metabolism of certain nervous system messaging molecules. While we emphasized the nervous system aspects of this health support role earlier in this section, we would also like to point out that the messaging molecules pathways described earlier involve specific amino acids (building blocks of protein), making B6 a potentially important vitamin for support of general amino acid and protein-related metabolism. Interestingly, many of our WHF that rank as excellent or very good sources of protein also rank as excellent or very good sources of B6. This overlap may not be a coincidence, given the role played by B6 in protein and amino acid metabolism. It is also worth mentioning that diets especially high in protein may increase risk of B6 depletion, even though many protein-rich foods are also rich in B6. The reason for this risk involves differing nutrient concentrations in which the concentration of protein in a particular food might be significantly greater than the concentration of B6. While this difference might not be important at ordinary protein intakes, unusually high intakes (for example, intakes well over 100 grams) might make the difference more of an issue.

Summary of food sources

An unusually broad range of foods qualify as good to excellent sources of vitamin B6; nearly half of WHF foods fall into this category. Both plant and animal foods are well represented. The top sources by nutrient density span leafy vegetables, root vegetables, fruits, fish, and poultry.

With the exception of tuna, all of our excellent sources of vitamin B6 are vegetables. As with so many other nutrients, our discussion of B6-rich foods starts here. We encourage having at least a serving of greens most days, if not every day, along with several other minimally cooked fresh vegetables. And we encourage you not to skimp on the amount, but to consider having 1-1/2 cups in a serving.

Among animal foods, tuna is the sole excellent source. Beef, chicken, and salmon rank as very good. Shrimp and cod fall in the good category.

Some, but not all, fruits are strong sources of vitamin B6. Bananas, pineapples, and avocados are all good to very good sources of this nutrient.

A number of legumes contain between 10-30% of the DRI for vitamin B6 per serving and can be good contributors toward your intake goal. Similarly, a number of the whole grains contain 10-20% of the DRI and can help to build up your daily vitamin B6 nutrition.

Nutrient rating chart

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WHF ranked as quality sources of
vitamin B6

Food

Serving
Size

Cals

Amount
(mg)

DRI/DV
(%)

Nutrient
Density

World’s
Healthiest
Foods Rating

Tuna

4 oz

147.4

1.18

69

8.5

excellent

Spinach

1 cup

41.4

0.44

26

11.3

excellent

Cabbage

1 cup

43.5

0.34

20

8.3

excellent

Bok Choy

1 cup

20.4

0.28

16

14.5

excellent

Bell Peppers

1 cup

28.5

0.27

16

10.0

excellent

Turnip Greens

1 cup

28.8

0.26

15

9.6

excellent

Garlic

6 cloves

26.8

0.22

13

8.7

excellent

Cauliflower

1 cup

28.5

0.21

12

7.8

excellent

Turkey

4 oz

166.7

0.92

54

5.8

very good

Beef

4 oz

175.0

0.74

44

4.5

very good

Chicken

4 oz

187.1

0.68

40

3.8

very good

Salmon

4 oz

157.6

0.64

38

4.3

very good

Sweet Potato

1 cup

180.0

0.57

34

3.4

very good

Potatoes

1 cup

160.9

0.54

32

3.6

very good

Banana

1 medium

105.0

0.43

25

4.3

very good

Winter Squash

1 cup

75.8

0.33

19

4.6

very good

Broccoli

1 cup

54.6

0.31

18

6.0

very good

Brussels Sprouts

1 cup

56.2

0.28

16

5.3

very good

Collard Greens

1 cup

62.7

0.24

14

4.1

very good

Beet Greens

1 cup

38.9

0.19

11

5.2

very good

Kale

1 cup

36.4

0.18

11

5.2

very good

Carrots

1 cup

50.0

0.17

10

3.6

very good

Swiss Chard

1 cup

35.0

0.15

9

4.5

very good

Asparagus

1 cup

39.6

0.14

8

3.7

very good

Mustard Greens

1 cup

36.4

0.14

8

4.1

very good

Tomatoes

1 cup

32.4

0.14

8

4.6

very good

Leeks

1 cup

32.2

0.12

7

3.9

very good

Summer Squash

1 cup

36.0

0.12

7

3.5

very good

Chili Peppers

2 tsp

15.2

0.11

6

7.6

very good

Sunflower Seeds

0.25 cup

204.4

0.47

28

2.4

good

Pinto Beans

1 cup

244.5

0.39

23

1.7

good

Avocado

1 cup

240.0

0.39

23

1.7

good

Lentils

1 cup

229.7

0.35

21

1.6

good

Green Peas

1 cup

115.7

0.30

18

2.7

good

Lima Beans

1 cup

216.2

0.30

18

1.5

good

Onions

1 cup

92.4

0.27

16

3.1

good

Shrimp

4 oz

134.9

0.27

16

2.1

good

Pineapple

1 cup

82.5

0.18

11

2.3

good

Cod

4 oz

96.4

0.15

9

1.6

good

Mushrooms, Shiitake

0.50 cup

40.6

0.12

7

3.1

good

Cantaloupe

1 cup

54.4

0.12

7

2.3

good

Corn

1 each

73.9

0.11

6

1.6

good

Beets

1 cup

74.8

0.11

6

1.6

good

Eggplant

1 cup

34.6

0.09

5

2.8

good

Turmeric

2 tsp

15.6

0.08

5

5.4

good

Mushrooms, Crimini

1 cup

15.8

0.08

5

5.3

good

Green Beans

1 cup

43.8

0.07

4

1.7

good

Celery

1 cup

16.2

0.07

4

4.6

good

Strawberries

1 cup

46.1

0.07

4

1.6

good

Watermelon

1 cup

45.6

0.07

4

1.6

good

Romaine Lettuce

2 cups

16.0

0.07

4

4.6

good

Figs

1 medium

37.0

0.06

4

1.7

good

Sea Vegetables

1 TBS

10.8

0.05

3

4.9

good

World’s Healthiest
Foods Rating

Rule

excellent

DRI/DV>=75% OR
Density>=7.6 AND DRI/DV>=10%

very good

DRI/DV>=50% OR
Density>=3.4 AND DRI/DV>=5%

good

DRI/DV>=25% OR
Density>=1.5 AND DRI/DV>=2.5%

Impact of cooking, storage and processing

Pyridoxine in foods is fairly stable during storage. Approximately 25% of B6 content is lost over one year, a relatively high figure but irrelevant in practice since whole foods are rarely stored that long. Most excellent and very good B6 sources are best consumed fresh.

Prolonged exposure to heat can degrade vitamin B6 in most foods. Perhaps as a result of the difference in structural forms, we see more degradation of this vitamin in animal meats than in vegetables.

Both steaming and boiling result in relatively low amounts of B6 loss. We’ve see research on Brussels sprouts, for example, showing 10-20% loss of B6 based on these two cooking methods. (As in most research on steaming and boiling, boiling in this study resulted in greater B6 loss than steaming, presumably because of submersion in water allowing more surface-to-water contact with the Brussels sprouts.)

Perhaps counterintuitively, lower pH tends to stabilize the vitamin under heat. So adding a little vinegar or tomato into a sauce, for example, may help keep the vitamin B6 more intact.

Risk of dietary deficiency

Based on NHANES data from 2009-2010, average B6 intake for adults 20 and older, as well as all U.S. residents ages 2 and older, exceeded the 1.7 mg recommended daily intake.

As mentioned earlier in this article, however, there has been significant debate in the clinical research over the relationship between blood levels of vitamin B6 and overall health, and it is possible that consumption of the DRI level for B6 may not support optimal blood levels of the PLP form of this vitamin. Exactly how this specific area of clinical research relates to overall B6 deficiency risk is an area of research that will be important to follow in future studies.

Other circumstances that might contribute to deficiency

Women who take oral contraceptive pills (OCP) have an increased risk of vitamin B6 deficiency. According to one research group, 40% of OCP users have biochemical evidence for deficiency, a number much greater than would be predicted based on diet alone.

OCP are not unique in their ability to lead to loss of vitamin B6. A number of other medications have been reported to have this effect, including steroids, antibiotics, and drugs used to treat Parkinson’s disease.

Even at a consistent dietary intake, people over the age of 65 years show lower blood levels of vitamin B6. There are several proposed explanations for this phenomenon, including decreased absorption, more difficulty activating the vitamin to its most active form, and increased breakdown. Regardless of the cause, older people may need to pay special attention to dietary vitamin B6 intake. In fact, the highest DRI set for B6 by the National Academy of Sciences (other than the DRIs related to pregnancy and lactation) is the DRI for older men of 1.7 milligrams.

Relationship with other nutrients

The B complex of vitamins works as a team in carbohydrate metabolism, and deficiency of one can affect the whole process in a detrimental way. Because vitamin B6 deficiency is more likely than most of the other B vitamins, it should be a particular focus in making sure that this energy generation process occurs smoothly.

In particular, folic acid and vitamin B12 are intimately related to vitamin B6 in their core biochemical pathways. Each of these is a nutrient with potential for dietary deficiency, each can be prone to damage or absorption problems, and each comes from different food types. We get vitamin B12 from a relatively small number of foods (primarily animal and fermented foods), folic acid predominantly from vegetables and legumes, and vitamin B6 from many food groups. Enjoyment of food diversity is clearly an ideal way.

Every reaction in your body that uses vitamin B6 also uses magnesium as a mineral co-factor. Like vitamin B6, magnesium is a nutrient that many Americans fail to eat enough of on a regular basis. Tuna, spinach, and pumpkin seeds are all examples of foods rich in both vitamin B6 and magnesium. Our Chicken Breast With Honey-Mustard Sauce recipe contains more than the RDA for vitamin B6 and 85% of the requirement for magnesium.

Diets very high in protein are known to increase risk of vitamin B6 depletion. . For this reason, some researchers have suggested increased B6 when protein intake is especially high. For example, we have seen one research study in which researchers recommended nearly double the DRI for B6 with intake of 150 grams of protein per day by young women. Our conclusions from this research are two-fold: first, it does not make sense to consume excessive amounts of protein, unless specifically following a medical food regimen or under other specific health-related circumstances. Second, if you are consuming especially high levels of protein, it makes sense to take a closer look at your B6 intake and make sure that you are focusing on whole foods equally right in protein and B6.

Risk of dietary toxicity

At amounts above the Tolerable Upper Intake Level (UL) of 100 mg per day, vitamin B6 has been reported to cause changes in sensation in the hands and feet. Given that even the 95th percentile of vitamin B6 intake in the U.S. is less than 10 mg per day, reaching 100 mg on a regular basis from foods alone is very unlikely. In fact, every report of vitamin B6 toxicity that we can find involved the use of mega-dose supplementation. We find no reason to be concerned about the health effects of diets rich in vitamin B6, even when this dietary richness involves 200%-500% of the recommended DRI level.

Disease checklist

• Premenstrual syndrome
• Fibrocystic breast disease
• Anemia
• Carpal tunnel syndrome
• Morning sickness
• Asthma
• High homocysteine
• Epilepsy
• Depression
• Seborrheic dermatitis
• ADHD

Public health recommendations

In 1998, the National Academy of Sciences established a set of Dietary Reference Intakes (DRI) that contained Recommended Dietary Allowances (RDA) for vitamin B6 by age and gender. These are summarized in the chart below. Note that the recommendations for infants under one year are Adequate Intake (AI) standards. The RDAs and AIs are as follows:

• 0-6 months: 0.1 mg
• 6-12 months: 0.3 mg
• 1-3 years: 0.5 mg
• 4-8 years: 0.6 mg
• 9-13 years: 1.0 mg
• 14-18 years, female: 1.2 mg
• 14-18 years, male: 1.3. mg
• 19-50 years, female: 1.3 mg
• 19-50 years, male: 1.3 mg
• 50+ years, female: 1.5 mg
• 50+ years, male: 1.7 mg
• Pregnant women: 1.9 mg
• Lactating women: 2.0 mg

The Tolerable Upper Intake Limit (UL) for vitamin B6 is set at 100 mg. Given that most foods contain less than a milligram of vitamin B6 per serving, reaching this level of intake without the use of supplements appears impossible. Intakes of vitamin B6 as high as 200-500% of the DRI still fall far below this UL guideline and have no research basis for any concern.

The Daily Value (DV) for vitamin B6 intake is 2 mg per day per 2000 calories. This is the value found on food labels.

As our WHF recommended daily intake level for B6, we chose the highest adult DRI level of 1.7 milligrams.

What events can indicate a need for more high-vitamin B6 foods ?

• Fatigue or malaise
• Anemia
• Skin disorders including eczema and seborrheic dermatitis
• Convulsions or seizures

Excellent sources of vitamin B6 include bell peppers, summer squash, turnip greens, shiitake mushrooms, and spinach.

WHF rich in
vitamin B6

FoodCals%Daily Value

Tuna15859%

Chicken18734%

Turkey15332%

Venison21727.5%

Potatoes16127%

Cod11926%

Sunflower Seeds20423.5%

Halibut15922.5%

Spinach4122%

Banana10521.5%

For serving size for specific foods, see Nutrient Rating Chart below at the bottom of this page.

• Description

• Function

• Deficiency Symptoms

• Toxicity Symptoms

• Cooking, storage and processing

• Factors that affect function

• Nutrient interaction

• Health conditions

• Food Sources

• Public Health Recommendations

• References

Description

What is vitamin b6?

First researched in the mid-1930’s, vitamin B6 is one of the best-studied of all B vitamins and has one of the greatest varieties of chemical forms. The forms of this vitamin all begin with the letters “pyr,” and include pyridoxine, pyridoxal, pyridoxamine, pyridoxine phosphate, pyridoxal phosphate, and pyridoxamine phosphate.

The vitamin was not originally given this name, however, but was referred to as “antidermatitis factor.” This term pointed to the skin (dermis) because skin inflammation (dermatitis) seemed to increase when foods with B6 were eliminated from the diet. Topical B6 creams are used to this day in treatment of skin inflammation, particularly in relationship to symptoms of seborrheic dermatitis.

How it functions

What is the function of vitamin b6?

Much of the body’s chemistry depends upon enzymes. Enzymes are proteins that help chemical reactions take place. Because vitamin B6 is involved with more than 100 enzymatic reactions, its function in the body is diverse and far-reaching.

Synthesis of essential molecules

It is difficult to find a chemical category of molecules in the body that do not depend in some way on vitamin B6 for their production. Many of the building blocks of protein, called amino acids, require adequate supplies of B6 for synthesis. Nucleic acids used in the creation of DNA in our genes also require this vitamin.

Because amino acids and nucleic acids are such critical parts of new cell formation, vitamin B6 can be regarded as an essential part of the formation of virtually all new cells in the body. Heme (the protein center of our red blood cells) and phospholipids (our cell membrane components that allow messaging between cells) also depend on vitamin B6 for their creation.

Processing of carbohydrate

The processing of carbohydrate (sugar and starch) in our body depends on availability of vitamin B6. This vitamin is particularly important in facilitating the breakdown of glycogen (a special form of starch) stored in our muscle cells and to a lesser extent in our liver. Because carbohydrate processing plays such a key role in certain types of athletic events, researchers have looked closely at the role vitamin B6 plays in carbohydrate processing during physical performance.

Support of nervous system activity

The role of vitamin B6 in our nervous system is very broad, and involves many aspects of neurological activity. One aspect focuses on the creation of an important group of messaging molecules called amines. The nervous system relies on formation of these molecules for transmission of messages from one nerve to the next. (The molecules can be classified as “neurotransmitters” for this reason.) Amines are one type of neurotransmitter in the nervous system. They are often made from parts of protein called amino acids, and the key nutrient for making this process happen is vitamin B6. Some of the amine-derived neurotransmitters that require vitamin B6 for their production include serotonin, melatonin, epinephrine, norepinephrine, and GABA.

Support of sulfur and methyl metabolism

The movement of sulfur-containing molecules around the body is especially important for hormonal balance and elimination of toxic substances through the liver. Because vitamin B6 is able to remove sulfur groups from other molecules, it helps the body maintain flexibility in handling sufur-containing compounds.

Vitamin B6 plays a similar role with respect to methyl-containing molecules. The term “methyl group” refers to a chemical structure that has only one carbon atom and three hydrogen atoms. Many important chemical events in the body are made possible by the transfer of methyl groups from one place to another. For example, genes in the body can be switched on and turned off in this way, and cells can use the process to send messages back and forth.

The attachment of methyl groups to toxic substances is one way of making them less toxic and encouraging their elimination from the body. It is also a way of ensuring that substances like homocysteine, which can build up excessively in the blood and lead to risk of cardiovascular disease, are kept within a healthy range.

Prevention of unwanted inflammation

Researchers are not yet clear on the mechanisms involved yet, but repeated studies show that vitamin B6 is required to minimize risk of unwanted inflammation in the body. It’s not only the case that ample intake of vitamin B6 is associated with decreased risk of excessive inflammation; it’s also the fact that individuals with chronic, excessive inflammation need increased amounts of vitamin B6 in their diet. Unless our dietary intake is sufficient to keep our blood levels of active B6 (pyridoxal-5-phosphate) optimal, we leave ourselves at risk for chronic health problems like type 2 diabetes, cardiovascular disease, and obesity, all of which share a component of chronic, unwanted inflammation.

Deficiency symptoms

What are deficiency symptoms for vitamin b6?

Because of its key role in the formation of new cells, vitamin B6 is especially important for healthy function of body tissue that regenerates itself quickly. The skin is exactly this type of tissue, and it is one of the first to show problems when B6 is deficient. Many skin disorders have been associated with B6 deficiency, and they include eczema and seborrheic dermatitis.

The key role of vitamin B6 in the nervous system also results in many nerve-related symptoms when B6 is deficient. These symptoms can include convulsions and seizures in the case of severe deficiency. The critical role of vitamin B6 in the formation of red blood cells means that B6 deficiency can also result in symptoms of anemia, malaise, and fatigue. When anemia is exclusively related to B6 deficiency, it is usually classified as hypochromic, microcytic (pernicious) anemia.

Toxicity symptoms

What are toxicity symptoms for vitamin b6?

Imbalances in nervous system activity have been shown to result from high levels of supplemental vitamin B6 intake. These imbalances do not seem to occur until supplementation exceeds 2 grams per day. The National Academy of Sciences has set a Tolerable Upper Intake Level (UL) for vitamin B6 of 100 milligrams for adults 19 years and older, largely based on the issue of imbalanced nervous system activity described above.

Factors that affect function

What factors might contribute to a deficiency of vitamin b6?

In addition to dietary insufficiency, smoking and the use of many prescription medications can contribute to vitamin B6 deficiency. Medications that deplete the body’s supply of B6 are listed in the medications section of this nutrient profile.

Nutrient interactions

How do other nutrients interact with vitamin b6?

As a member of the B vitamin family, B6 has key interactions with many of its family members. B6 is essential for making vitamin B3 (niacin) from the amino acid tryptophan. In Down’s syndrome, for example, some of the problems related to vitamin B3 deficiency appear to be lessened by intake of vitamin B6. Vitamins B2 and B3 are both needed to convert vitamin B6 into its various chemical forms, and imbalances in vitamin B1 metabolism create imbalances in vitamin B6 metabolism. B6 deficiency can also reduce the body’s absorption of vitamin B12.

Health conditions

What health conditions require special emphasis on vitamin b6?

Vitamin B6 may play a role in the prevention and/or treatment of the following health conditions:

• Cardiovascular system conditions, including atherosclerosis, hyperhomocysteinemia, and hypertension
• Nervous system conditions, including carpal tunnel syndrome, depression, diabetic neuropathy, autism and epilepsy
• Skin conditions, including acne, eczema, and seborrheic dermatitis
• Also linked to B6 status are alcoholism, adrenal function, asthma, HIV/AIDS, kidney stones, PMS, and vaginitis.

Food sources

What foods provide vitamin b6?

Excellent sources of vitamin B6 include summer squash, bell peppers, turnip greens, shiitake mushrooms, and spinach.

Very good food sources of vitamin B6 include garlic, tuna, cauliflower, mustard greens, cabbage, crimini mushrooms, asparagus, broccoli, kale, collard greens, Brussels sprouts, cod, chard, calf’s liver, green beans, winter squash, tomatoes, turkey, salmon, and leeks.

References

1. Cellini B, Montioli R, Oppici E, et al. The chaperone role of the pyridoxal 5'-phosphate and its implications for rare diseases involving B6-dependent enzymes. Clin Biochem. 2014 Feb;47(3):158-65. doi: 10.1016/j.clinbiochem.2013.11.021. https://doi.org/10.1016/j.clinbiochem.2013.11.021
2. Combs GF. Vitamin B6. In: The Vitamins. Academic Press, Waltham, MA, 2007. https://doi.org/10.1016/j.mam.2016.08.001
3. Food and Nutrition Board, Institute of Medicine. Dietary reference intakes for thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, biotin, and choline. Washington, DC: National Academy Press; 1998;58-86.
4. Dolina S, Margalit D, Malitsky S, et al. Attention-deficit hyperactivity disorder (ADHD) as a pyridoxine-dependent condition: Urinary diagnostic biomarkers. https://doi.org/10.1016/j.mehy.2013.11.018
5. Medical Hypotheses, Volume 82, Issue 1, January 2014, Pages 11—116.
6. Gregory JF, Park Y, Lamers Y, et al. Metabolomic analysis reveals extended metabolic consequences of marginal vitamin B6 deficiency in healthy human subjects. PloS One 2013;8:e63544. https://doi.org/10.1371/journal.pone.0063544
7. Hochberg M, Melnick D, Oser BL. On the stability of pyridoxine. J Biol Chem 1944;155:129-36. https://doi.org/10.1016/s0021-9258(18)43179-1
8. Inubushi T, Okada M, Matsui A, et al. Effect of dietary vitamin B6 contents on antibody production. Biofactors. 2000;11(1-2):93-6. https://doi.org/10.1155/2017/2197975
9. Kretsch MJ, Sauberlich HE, Skala JH, et al. Vitamin B6 requirement and status assessment: young women fed a depletion diet followed by a plant- or animal-protein diet with graded amounts of vitamin B6. Am J Clin Nutr 1995;61:1091-101. https://doi.org/10.1016/j.redox.2016.12.001
10. Leskova E, Kubikova J, Kovacikova E, et al. Vitamin losses: Retention during heat treatment and continual changes expressed by mathematical models. J Food Comp Anal 2006;19:252-76. https://doi.org/10.1016/j.jfca.2005.04.014
11. Lussana F, Zighetti ML, Bucciarelli P, et al. Blood levels of homocysteine, folate, vitamin B6 and B12 in women using oral contraceptives compared to non-users. Thromb Res 2003;112:37-41. https://doi.org/10.1016/j.thromres.2003.11.007
12. Matte JJ, LeFloc'h N, Primot Y, et al. Interaction between dietary tryptophan and pyridoxine on tryptophan metabolism, immune responses and growth performance in post-weaning pigs. Animal Feed Science and Technology, Volume 170, Issues 3—4, 22 December 2011, Pages 256-264. https://doi.org/10.1016/j.anifeedsci.2011.09.013
13. Morris MS, Sakakeeny L, Jacques PF, et al. Vitamin B-6 Intake Is Inversely Related to, and the Requirement Is Affected by, Inflammation Status. The Journal of Nutrition; Jan 2010; 140, 1; 103-110. https://doi.org/10.3945/jn.109.114397
14. Morris MS, Picciano MF, Jacques PF, et al. Plasma pyridoxal 5'-phosphate in the US population: the National Health and Nutrition Examination Survey, 2003-4. Am J Clin Nutr 2008;87:1446-54. https://doi.org/10.1373/clinchem.2003.021634
15. Nanri A, Pham NM, Kurotani K, et al. Serum pyridoxal concentrations and depressive symptoms among Japanese adults: results from a prospective study. Eur J Clin Nutr 2013;67:epub ahead of print. https://doi.org/10.1038/ejcn.2013.115
16. Pan WH, Chang YP, Yeh WT, et al. Co-occurrence of anemia, marginal vitamin B6, and folate status and depressive symptoms in older adults. J Geriatr Psychiatry Neurol. 2012;25:170-8. https://doi.org/10.1590/s0034-8910.2014048005039
17. Skodda S, Muller T. Refractory epileptic seizures due to vitamin B6 deficiency in a patient with Parkinson's disease under duodopa therapy. J Neural Transm 2013;120:315-8. https://doi.org/10.1212/wnl.0000000000009647
18. Zhao M, Lamers Y, Ralat MA, et al. Marginal vitamin B6 deficiency decreases plasma (n-3) and (n-6) PUFA concentrations in healthy men and women. J Nutr 2012;142:1791-7. https://doi.org/10.1016/s0020-7292(15)30034-5
19. Medical Hypotheses, Volume 82, Issue 1, January 2014, Pages 11–116.
20. Matte JJ, LeFloc'h N, Primot Y, et al. Interaction between dietary tryptophan and pyridoxine on tryptophan metabolism, immune responses and growth performance in post-weaning pigs. Animal Feed Science and Technology, Volume 170, Issues 3–4, 22 December 2011, Pages 256-264. https://doi.org/10.1016/j.anifeedsci.2011.09.013
21. Morris MS, Picciano MF, Jacques PF, et al. Plasma pyridoxal 5’-phosphate in the US population: the National Health and Nutrition Examination Survey, 2003-4. Am J Clin Nutr 2008;87:1446-54. https://doi.org/10.1373/clinchem.2003.021634
22. Skodda S, Muller T. Refractory epileptic seizures due to vitamin B6 deficiency in a patient with Parkinson’s disease under duodopa therapy. J Neural Transm 2013;120:315-8. https://doi.org/10.1212/wnl.0000000000009647
23. Bodwell CE, Erdman JW (Eds). Nutrient interactions. Marcel Dekker, Inc., New York, 1998;165,301-304. 1998.
24. Bryan J, Calvaresi E, Hughes D et al. Short-term folate, vitamin B-12 or vitamin B-6 supplementation slightly affects memory performance but not mood in women of various ages. J Nutr 2002 Jun;132(6):1345-56. 2002. https://doi.org/10.1093/jn/132.6.1345
25. Coleman M, Sobel S, Bhagavan HN, et al. A double-blind study of vitamin B6 in Down's syndrome infants. Part 1 - clinical and biochemical results. J Ment Def Res 1985;29:233. 1985.
26. Effersoe H. The effect of topical application of pyridoxine ointment on the rate of sebaceous secretion in patients with seborrheic dermatitis. Acta Dermatol 1954;3:272-277. 1954.
27. Fennema OR (Ed.). Food chemistry. Second edition. Marcel Dekker, New York, 1985. 1985.
28. Groff JL, Gropper SS, Hunt SM. Advanced Nutrition and Human Metabolism. West Publishing Company, New York, 1995. 1995.
29. Gvozdova LG, Paramanova EG, Goriachenkova EV, et al. The content of Pyridoxal coenzymes in the blood plasma of patients with coronary atherosclerosis on a background of therapeutic diet and after supplemental intake of vitamin B6. Vop Pitan 1966;25:40-44. 1966.
30. Gyorgy P. Developments leading to the metabolic role of vitamin B6. Am J Clin Nutr 1971;24:1250-1256. 1971.
31. Korpela TK, Christen P (Eds). Biochemistry of vitamin B6. Proceedings of the 7th International Congress on Chemical and Biological Aspects of Vitamin B6 Catalysis. Birkhauser Congress Reports, Life Sciences, Vol. 2, Birkhauser Verlag, Basel, 1987. 1987.
32. Leklem JE. Vitamin B6. In: Machlin LJ (Ed). Handbook of vitamins. Second edition. Dekker, New York, 1991;341-392. 1991. https://doi.org/10.1016/j.mam.2016.08.001
33. Merrill AH, Burnham FS. Vitamin B-6. Chapter 18 in: Brown ML (Ed). Present knowledge in nutrition. Sixth Edition. International Life Sciences Institute Nutrition Foundation, Washington, DC, 1990;157-159. 1990. https://doi.org/10.1093/jn/120.suppl_11.1503
34. Morris MS, Sakakeeny L, Jacques PF et al. Vitamin B-6 intake is inversely related to, and the requirement is affected by, inflammation status. J Nutr. 2010 Jan;140(1):103-10. 2010. https://doi.org/10.3945/jn.109.114397
35. National Academy of Sciences. Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B-6, Vitamin B-12, Pantothenic Acid, Biotin, and Choline. Institute of Medicine, Food and Nutrition Board, National Academy of Sciences. Washington, DC, National Academy Press, 1998;390-422. 1998.
36. Ooylan LM, Hart S, Porter KB, Driskell JA et al. Vitamin B-6 content of breast milk and neonatal behavioral functioning. J Am Diet Assoc 2002 Oct; 102(10):1433-8. 2002. https://doi.org/10.1016/s0002-8223(02)90317-2
37. Sauberlich HE. Vitamins - how much is for keeps?. Nutr Tod 1980;22:20. 1980. https://doi.org/10.1097/00017285-198701000-00004
38. Schaumberg H, Kaplan J, Windebank A, et al. Sensory neuropathy from pyridoxine abuse. A new megavitamin syndrome. N Engl J Med 1983;309:445-448. 1983. https://doi.org/10.1056/nejm198308253090801
39. Williams MH. Vitamin and mineral supplements to athletes: do they help?. Clin Sports Med 1984;3:623-637. 1984. https://doi.org/10.1016/s0278-5919(20)31308-9
40. Yates AA, Schlicker SA, Suitor CW. Dietary reference intakes: the new basis for recommendations for calcium and related nutrients, B vitamins, and choline. J Am Diet Assoc 1998;98:699-706. 1998. https://doi.org/10.1073/pnas.1407743111
41. Bodwell CE, Erdman JW (Eds). Nutrient interactions. Marcel Dekker, Inc., New York, 1998;165,301-304 1998.
42. Bryan J, Calvaresi E, Hughes D et al. Short-term folate, vitamin B-12 or vitamin B-6 supplementation slightly affects memory performance but not mood in women of various ages. J Nutr 2002 Jun;132(6):1345-56 2002. https://doi.org/10.1093/jn/132.6.1345
43. Coleman M, Sobel S, Bhagavan HN, et al. A double-blind study of vitamin B6 in Down's syndrome infants. Part 1 - clinical and biochemical results. J Ment Def Res 1985;29:233 1985.
44. Effersoe H. The effect of topical application of pyridoxine ointment on the rate of sebaceous secretion in patients with seborrheic dermatitis. Acta Dermatol 1954;3:272-277 1954.
45. Fennema OR (Ed.). Food chemistry. Second edition. Marcel Dekker, New York, 1985 1985.
46. Groff JL, Gropper SS, Hunt SM. Advanced Nutrition and Human Metabolism. West Publishing Company, New York, 1995 1995.
47. Gvozdova LG, Paramanova EG, Goriachenkova EV, et al. The content of Pyridoxal coenzymes in the blood plasma of patients with coronary atherosclerosis on a background of therapeutic diet and after supplemental intake of vitamin B6. Vop Pitan 1966;25:40-44 1966.
48. Gyorgy P. Developments leading to the metabolic role of vitamin B6. Am J Clin Nutr 1971;24:1250-1256 1971.
49. Korpela TK, Christen P (Eds). Biochemistry of vitamin B6. Proceedings of the 7th International Congress on Chemical and Biological Aspects of Vitamin B6 Catalysis. Birkhauser Congress Reports, Life Sciences, Vol. 2, Birkhauser Verlag, Basel, 1987 1987.
50. Leklem JE. Vitamin B6. In: Machlin LJ (Ed). Handbook of vitamins. Second edition. Dekker, New York, 1991;341-392 1991. https://doi.org/10.1016/j.mam.2016.08.001
51. Merrill AH, Burnham FS. Vitamin B-6. Chapter 18 in: Brown ML (Ed). Present knowledge in nutrition. Sixth Edition. International Life Sciences Institute Nutrition Foundation, Washington, DC, 1990;157-159 1990. https://doi.org/10.1093/jn/120.suppl_11.1503
52. National Academy of Sciences. Dietary Reference Intakes: Thiamin, Riboflavin, Niacin, Vitamin B-6, Vitamin B-12, Pantothenic Acid, Biotin, and Choline. Institute of Medicine, Food and Nutrition Board, National Academy of Sciences. Washington, DC, National Academy Press, 1998;390-422 1998.
53. Ooylan LM, Hart S, Porter KB, Driskell JA et al. Vitamin B-6 content of breast milk and neonatal behavioral functioning. J Am Diet Assoc 2002 Oct; 102(10):1433-8 2002. https://doi.org/10.1016/s0002-8223(02)90317-2
54. Sauberlich HE. Vitamins - how much is for keeps. Nutr Tod 1980;22:20 1980. https://doi.org/10.1097/00017285-198701000-00004
55. Schaumberg H, Kaplan J, Windebank A, et al. Sensory neuropathy from pyridoxine abuse. A new megavitamin syndrome. N Engl J Med 1983;309:445-448 1983. https://doi.org/10.1056/nejm198308253090801
56. Williams MH. Vitamin and mineral supplements to athletes: do they help. Clin Sports Med 1984;3:623-637 1984. https://doi.org/10.1016/s0278-5919(20)31308-9
57. Yates AA, Schlicker SA, Suitor CW. Dietary reference intakes: the new basis for recommendations for calcium and related nutrients, B vitamins, and choline. J Am Diet Assoc 1998;98:699-706 1998. https://doi.org/10.1073/pnas.1407743111