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Vitamin B6 is a crucial molecule in the human body. It’s involved in more than 150 processes (or chemical reactions) that range from protecting your brain to making sure you have enough energy to get through the day (Stach, 2021).
In some cases, vitamin B6 supplements can help treat tough cases of morning sickness during pregnancy and can be used as antidotes to treat poisonings.
Researchers are also looking into ways these supplements may be able to help against a variety of diseases, such as cancer (Abosamak, 2021).
But, despite its benefits, too much vitamin B6 can be harmful. So, what are the signs to watch for if you’ve taken too much? How do you best balance this B vitamin? Let’s explore the basics of vitamin B6.
What is vitamin B6?
Vitamin B6, also called pyridoxine, is a water-soluble vitamin. That means you need to get enough vitamin B6 each day because excess B6 is excreted in the urine. Fortunately, it’s in many of the foods we eat (Abosamak, 2021).
Vitamin B6 has three natural forms: pyridoxine, pyridoxal, and pyridoxamine. Your body converts all of these to the active form of vitamin B6 called pyridoxal 5-phosphate (Abosamak, 2021).
Health benefits of vitamin B6
Here’s how vitamin B6 impacts your body:
Vitamin B6 and metabolism
B6 plays a role in metabolizing food into energy by helping enzymes break down carbohydrates, fats, and proteins. In other words: B6 helps turn the food you eat into the energy you need to get through each day (Abosamak, 2021).
Vitamin B6 also helps make hemoglobin, the molecule in red blood cells needed to deliver oxygen throughout the body. Being low on vitamin B6 could cause fatigue if this production slows down.
Vitamin B6 and the brain
Vitamin B6 is essential to the brain and nervous system. It helps create neurotransmitters, the brain’s chemical messengers, like dopamine, serotonin, and GABA.
Even mild deficiencies of these neurotransmitters can lead to changes in your day-to-day life. For instance, not enough GABA can affect your sleep. Low amounts of serotonin, dopamine, and GABA can affect your mood.
Vitamin B6 also helps regulate energy in the brain and might help protect the brain against inflammation, which is linked to dementia and cognitive decline. (Kennedy 2016; Holton, 2021).
Vitamin B6 and the heart
Vitamins B6 and other B vitamins like B12 and B9 folate (folic acid) are important for the breakdown of homocysteine, an amino acid. High homocysteine levels are thought to increase the risk of heart disease and stroke. Though B6 supplements can lower homocysteine levels, major studies have been mixed about whether supplements can reduce disease risk (NIH, 2021).
A trial of more than 5,500 adults with cardiovascular disease showed taking B6 (50 mg/day), vitamin B12 (1 mg/day), and folic acid (2.5 mg/day) lowered homocysteine levels and decreased stroke risk by about 25%. However, the study didn’t include a separate vitamin B6 group. Some other studies of B12 and B6 supplements, as well as B6 alone, showed no benefits from supplements (NIH, 2021).
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Vitamin B6 and cancer
Research has shown getting enough B6 through the diet may offer some protection against cancer. Studies have linked low vitamin B6 levels with an increased risk of colorectal cancer (Gylling, 2017).
However, this does not mean these same effects occur with supplements, and the exact role the B-complex vitamins play in cancer prevention has been mixed. In the past, high doses of vitamin B6 and B12 have been linked to an increased risk of lung cancer in men (Brasky, 2017). In order to truly determine B6’s effects on various types of cancer, additional research is needed.
Vitamin B6 as an antidote
Vitamin B6 is used as an emergency antidote for several different types of poisonings. The most common is for use in overdoses of ethylene glycol (used in antifreeze) and isoniazid (an antibiotic used to treat tuberculosis). It’s also an antidote for hydralazine (blood pressure medication) and mushroom poisoning (Brown, 2021).
How much vitamin B6 do you need?
Getting too much vitamin B6 through food is not possible, but too much in the form of supplements can lead to vitamin B6 toxicity (more on that below). The following recommended daily intake guidelines show what the body needs each day (NIH, 2021):
- Men: 14-50 years old: 1.3 mg (milligrams)
- Women: 14-18: 1.2 mg; 19-50: 1.3 mg
- Pregnant/lactating: 1.9 mg/2.0 mg
- Ages 50+: 1.5 mg for women and 1.7 mg for men.
- Check with your pediatrician about needs for children (Recommended daily intake: birth-6 mos.: 0.1mg; 7-12 mos.: 0.3mg; 1-3 years: 0.5 mg; 4-8 years: 0.6 mg; 9-13 years: 1.0 mg)
The upper intake level (UL) or maximum daily dose for adults 19 and older is 100 mg per day, with lesser amounts for children and teens. But, higher doses may be advised for those with medical conditions or deficiencies (NIH, 2021).
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Food sources of vitamin B6 and vitamin B6 supplements
There are many good sources of vitamin B6. The following are vitamin B6 foods that offer some of the highest amounts of the nutrient (NIH, 2021):
- Chickpeas (canned, 1 cup) contains 1.1 mg
- Beef liver (3 oz) contains 0.9 mg
- Yellowfin tuna (3 oz) has 0.9 mg
- Sockeye salmon (3 oz) has 0.6 mg
- Chicken breast (3 oz) contains 0.5 mg
- Breakfast cereals (fortified with B6) 0.4 mg
- Potatoes (1 cup) contains 0.4 mg
- Banana (medium) contains 0.4 mg
- Tofu (half a cup) contains 0.1 mg
- Nuts (1 oz) contains 0.1 mg
There are plenty of other vitamin B6-rich foods, including ground beef, squash, rice, raisins, spinach, and watermelon.
While most people get enough vitamin B6 from their diets, those with medical conditions that limit nutrient absorption, as well as vegans and vegetarians, may want to check with their healthcare providers about the best ways to get enough B6 daily. Oral supplements are commonly used to prevent anemia in those who can’t absorb vitamin B6 easily or have limited dietary sources (NIH, 2021).
Vitamin B6 and pregnancy
Vitamin B6 intake recommendations are slightly higher for pregnant women to ensure a healthy pregnancy. Research shows vitamin B6 deficiency is common in pregnant women, especially during the third trimester (Hisano, 2010).
Why the slightly higher recommendations? Fetal brain development requires adequate B6. However, too much vitamin B6 is not advised. If you’re pregnant, it’s best to work with your healthcare provider and ask about supplement use. Most prescribe specific prenatal multivitamin formulas (Simpson, 2010).
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Vitamin B6 and morning sickness
If you have morning sickness, it may be worth asking your healthcare provider about B6. Research has shown vitamin B6 may help prevent feelings of nausea during periods of morning sickness. It’s often prescribed in doses of 10 mg supplements, four times a day. It’s best to work with your healthcare provider before taking supplements while pregnant or breastfeeding (Festin, 2014; NIH, 2021).
Risks and side effects of vitamin B6 imbalances
Taking too much vitamin B6 can lead to nerve damage. Not getting enough can cause medical problems as well. In either case, it’s important to contact a healthcare provider who can check vitamin B6 levels with a simple blood test. Here’s a look at what happens when levels are too low or too high:
Vitamin B6 deficiency
If you’re mildly vitamin B6 deficient, you may not notice any symptoms.
Symptoms of a B6 deficiency can include a skin rash, feeling tired because you’re low on red blood cells to carry oxygen, and feelings of fogginess or confusion. Muscle weakness, depression, a weakened immune system, and tingling in your hands and feet (neuropathy) may be other signs. A severe deficiency can lead to seizures or the inability to walk (Brown, 2021; NIH, 2021).
Low vitamin B6 levels are more likely in those with chronic alcohol dependence, kidney disease, malnutrition, a limited ability to absorb nutrients (e.g., celiac disease, bariatric surgery, inflammatory bowel disease), or in women who are pregnant (Brown, 2021).
If you’re low on vitamin B6, there’s a good chance you may be low in other B vitamins. It’s important that B vitamins are balanced, so it’s a good idea to check. A healthcare provider can typically correct the deficiency with a vitamin B6 injection or oral supplements. Treatment doses depend on the level of deficiency (NIH, 2021; Brown, 2021).
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Vitamin B6 overdose
Though it’s water-soluble and not stored in the body, you can take too much vitamin B6 in the form of supplements. Consuming vitamin B-6 through food appears to be safe, even in high amounts.
Extremely high doses (1,000 mg and above) for a year or more have led to peripheral neuropathy (tingling and pain in fingers and toes), a loss of control of body movement, and neurological problems (NIH, 2021). The neuropathy usually goes away gradually after stopping supplement use (Abosamak, 2021).
Now, you may be wondering why the symptoms of deficiency and overdose both include neuropathy. Well, a study showed that taking a high dose of B6 may compete with the active form that’s already in your body, therefore canceling it out and causing symptoms of a deficiency—even if someone took too much of the vitamin (Vrolijk, 2017).
Overall, it’s best to keep vitamin B6 in balance and talk to your healthcare provider about dietary supplements if you have a medical condition, a low meat diet, or are pregnant.
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Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.