Your body needs vitamin B12 to carry out several different functions, from the creation of new red blood cells to keeping your nervous system healthy. You can get vitamin B12 from certain foods, like beef, fish, chicken, eggs and dairy products, but some people need to take more in supplemental form.
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Vitamin B12 supplements come in several different forms, but there's one type, methylcobalamin, or methyl B12, that's more easily absorbed by the body, especially if you have trouble with a body process called methylation.
Methyl B12 is a form of the vitamin that's already in its active state, which makes it's more biologically available to your body. It's important for anyone with a methylation defect to take methyl B12 over any of the other forms of the vitamin.
Vitamin B12 Functions
Vitamin B12 acts as a coenzyme, a substance that plays a role in virtually every chemical reaction in your body. Although the functions of vitamin B12 are widespread, it has notable roles in keeping both your brain and nervous system healthy.
Vitamin B12 also helps your body create new red blood cells. According to Medical News Today, your body creates millions of new red blood cells every minute; and without adequate amounts of vitamin B12, these cells aren't produced properly.
Your metabolism also relies on vitamin B12. The vitamin helps break down fatty acids so that you can use them for energy and is vital for the proper absorption of another B vitamin, folate.
Types of B12
There are four types of B12 available for purchase in supplements:
Methylcobalamin, adenosylcobalamin and hydroxycobalamin are biologically identical to the forms of vitamin B12 that are found in food and the human body. Cyanocobalamin is a synthetic version of the vitamin that's made in a lab and added to supplements and fortified foods.
Although cyanocobalamin is generally the least expensive form of the vitamin, your body can absorb and use methylcobalamin, or methyl B12, more quickly and easily.
What Is Methyl B12?
Methylcobalamin, or methyl B12, is a form of the vitamin that's already in its active state. When you eat foods that contain B12 or take a vitamin B12 supplement that's not methyl B12, your body takes it from an inactive state and turns it into a version of the vitamin that's biologically available.
If you're healthy, this conversion isn't a problem. However, it's not so easy for those with severe vitamin B12 deficiency or methylation defects. If you have a methylation defect, it's also important that you take methyl B12 instead of other, inactive forms of the vitamin.
The Process of Methylation
Methylation is a physiological process involving the transfer of carbon and hydrogen atoms between substances. It occurs countless times throughout your day and plays a role in several different biochemical processes that affect almost every structure in your body.
Methylation plays a role in:
- Glutathione production
- The stress response
- Energy production
- Gene and DNA expression
- Neurotransmitter production
- Immune response
What Is a Methylation Defect?
Unfortunately, according to Dr. Alan Miller, a naturopathic doctor and staff member at the supplement company Thorne, approximately 60 percent of Americans have at least one genetic mutation that disrupts the proper functioning of the methylation system.
Among a host of other problems, when you have a methylation defect, and your methylation system isn't working properly, you're generally not able to convert synthetic forms of vitamin B12 into forms that your body can use. You don't have a problem absorbing vitamin B12. You just have a problem converting inactive forms of vitamin B12, like cyanocobalamin, to active forms that your body can actually use.
Because of this, people with a methylation defect may have normal levels of vitamin B12 in their blood, but their bodies can't effectively use it. This also makes it difficult to correctly diagnose deficiencies.
The Power of Methyl B12
One remarkable study was published in the Journal of the American Geriatrics Society in 2014. For this study, researchers followed the vitamin B12 status of an 83-year-old woman who was experiencing several symptoms of severe vitamin B12 deficiency, such as cognitive impairment, fatigue, psychosis, paranoia and insomnia, even though the levels of B12 in her blood were normal.
Researchers put the study participant on 3,000 micrograms of methyl B12 and 1,200 micrograms of folic acid. Within two weeks, her paranoia went away, her cognition improved, and she was back to her normal behaviors.
After the improvements, researchers changed the B12 supplement she was receiving to hydroxocobalamin, an inactive form of B12. All symptoms returned within two months. After switching back to methyl B12, normal functioning was restored again.
Symptoms of B12 Deficiency
- Swollen tongue
- Memory loss
- Numbness and/or tingling in the hands and feet
- Difficulty walking (problems with balance)
- Pale skin
- Shortness of breath
- Decreased appetite
- Weight loss
In severe cases, vitamin B12 deficiency can cause:
The Recommended Dosage
The current recommended dietary allowance of vitamin B12 for adults is 2.4 micrograms per day. However, the Linus Pauling Institute notes that some people with severe deficiency or pernicious anemia may need to take as much as 2,000 micrograms per day.
Vitamin B12 is water soluble, so any excess amounts of the vitamin are excreted in your urine, rather than stored in the body. Because of this, there is a low potential for developing a toxicity or side effects from taking even high doses of the vitamin.
Vitamin B12 Side Effects
If side effects do occur, the most common include:
These side effects are typically only seen in very high doses of supplemental B12. Always talk to your health care provider before taking supplements, especially at dosages that are higher than typically recommended.
- Journal of the American Geriatrics Society: Unexpected Recovery of Moderate Cognitive Impairment on Treatment With Oral Methylcobalamin
- University Health News: Vitamin B12 Deficiency Symptoms Can Range Far Beyond Fatigue
- Oregon State University: Linus Pauling Institute: Vitamin B12
- Harvard Health Publishing: Vitamin B12 Deficiency Can Be Sneaky, Harmful
- Mayo Clinic: Vitamin B-12
- BMJ: Vitamin B12 Deficiency
- Thorne: What Is Methylation and Why Should You Care About It
- National Institutes of Health: Office of Dietary Supplements: Vitamin B12
- Medical News Today: Everything You Need to Know About Vitamin B-12
- Integrative Medicine: A Clinician's Journal: Comparative Bioavailability and Utilization of Particular Forms of B12 Supplements With Potential to Mitigate B12-Related Genetic Polymorphisms
- MTHFR Gene Health: MTHFR and Vitamin B12