Longevity Articles

Vitamin B12: Why You Need It and How to Take It

Vitamin B12 is an essential nutrient needed for proper cell and nerve functioning

Vitamin B12 is a water-soluble nutrient that comes in several different forms. Due to containing the mineral cobalt, all types of vitamin B12 fall into the “cobalamin” family. 

Vitamin B12 plays a significant role in red blood cell and DNA synthesis, as well as proper neurological function. Therefore, vitamin B12 deficiency involves cellular and neurological symptoms, including anemia, fatigue, poor cognition, weakness, shortness of breath, bleeding gums, and tingling of the hands and feet. 

However, many subclinical problems of inadequate vitamin B12 intake can arise before neurological symptoms do, including detrimental effects on cardiovascular, bone, and eye health. 

Subclinical vitamin B12 deficiency is especially common in the elderly, as the gastrointestinal absorption of the vitamin declines after age 50. Certain medications, including metformin and proton pump inhibitors, may reduce the ability to absorb vitamin B12. Additionally, chronic stress may deplete B12 levels, making it a noteworthy vitamin for people of all ages. 

Dietary Sources of Vitamin B12

The best and most bioavailable sources of vitamin B12 are animal products, including liver, red meat, shellfish, fish, eggs, and dairy. Some foods, like breakfast cereals, are fortified with synthetic vitamin B12. 

Animals get their vitamin B12 in two ways: First, vitamin B12 is synthesized by bacteria in the gastrointestinal (GI) tracts of animals, which gets absorbed and concentrated in their tissues. Second, these same bacteria are also present in soil and manure, therefore, animals may get some vitamin B12 through accidental consumption. 

Because certain bacteria synthesize vitamin B12, some fermented foods, like tempeh, have been reported to supply the vitamin — albeit in small amounts. Other plant-based foods, including mushrooms and seaweed, contain analogs of vitamin B12 that are not bioavailable in humans. 

Thus, if you’re vegan or vegetarian and don’t consume animal products, are over age 50, or just need a mental or physical boost, supplemental vitamin B12 may be a smart choice for you. 

Animal foods are the best sources of vitamin B12.

Top Benefits of Vitamin B12

1. Cognition

As vitamin B12 plays a large role in maintaining neurological health, adequate intake of the vitamin is thought to improve cognitive function

The link between cognition and vitamin B12 involves the amino acid homocysteine. During the metabolism of another amino acid, methionine, homocysteine can accumulate unless the body has adequate vitamin B12 (along with folate and vitamin B6) to methylate it. A buildup of homocysteine can be neurotoxic and generate free radicals, causing oxidative damage to cells and DNA and impairing cognitive functions. 

In a 10-year long cohort study published in the American Journal of Clinical Nutrition, individuals with low serum levels of holotranscobalamin (a biologically active form of vitamin B12) and high levels of homocysteine experienced a significantly more rapid cognitive decline. A doubling of holotranscobalamin levels was linked to a 30% slower rate of cognitive decline, suggesting B12 may help optimize brain function.    

Furthermore, B12 may provide you with a short-term mental jumpstart when it comes to cognitive functions like alertness and concentration. However, research has yet to determine if it plays a long-term role in the prevention or treatment of cognitive disorders like dementia.  

2. Energy

Due to vitamin B12’s role in producing red blood cells, fatigue is a common symptom of inadequate intake. When the body does not have enough red blood cells, oxygen isn’t able to circulate to all of the body’s tissues, resulting in weakness, tiredness, and eventually, anemia.

In a September 2019 trial published in Frontiers in Pharmacology, patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), a complex illness marked by profound, lasting fatigue and other life-altering symptoms, supplemented with a high dose of vitamin B12 via nasal drops. After three months, approximately two-thirds of the 51 patients responded well, as evidenced by increases in serum vitamin B12 levels. These individuals also experienced significant improvements on both a physical functioning scale and a fatigue scale. 

Another study, published in PLoS One, looked at fatigue levels in people who just had a stroke. Interestingly, they found that those with vitamin B12 deficiency were significantly more likely to experience both severe fatigue and depressive symptoms following the event.  

The effects of vitamin B12 on energy appear to be most pronounced in those with inadequate or deficient levels. If you constantly feel run down, you may benefit from shoring up your B12 levels.

Vitamin B12 is linked to increased energy.

3. Liver Detoxification 

The liver is the primary site of detoxification in the body. This process can be thwarted by overexposure to toxins, including alcohol, medications, pesticides, industrial chemicals, and pollution. 

Detoxification in the liver has two stages that work to transform and eliminate harmful molecules. The first phase uses enzymes to convert fat-soluble toxins into water-soluble intermediary compounds through oxidation. The second phase uses many nutrients, including vitamin B12, to transform those intermediary compounds into a harmless compound to be excreted. 

Adequate intake of vitamin B12 ensures that the second phase of liver detoxification can be completed, reducing the liver's toxic load and helping you feel your best.  

How to Take Supplemental Vitamin B12

Supplemental vitamin B12 typically comes in the form of methylcobalamin, the type found in food, or cyanocobalamin, a synthetic form of the vitamin. 

In addition, adenosylcobalamin and hydroxy form of B12 can be found in supplements; these forms work primarily in fatty acid metabolism and detoxification, respectively. Combining the various forms of vitamin B12 can ensure maximum benefits. 

While the Recommended Dietary Allowance is just 2.4 micrograms for most adults, you can safely take higher doses, as vitamin B12 is water-soluble and does not accumulate in the body and has not shown to cause harm. 

The type of vitamin B12 you take may impact its absorption. There are four main methods for supplementing with vitamin B12: 

  • Lozenges: Lozenges, which dissolve in the mouth, tend to have high bioavailability, as vitamin B12 will absorb through the mucus membranes and avoid the GI tract. As many older adults have low amounts of protein in the stomach that is needed to absorb vitamin B12, lozenges are a good choice for those over age 50. Because they dissolve, they are also a superior form for those wanting to maximize absorption or avoid swallowing a capsule or tablet. 
  • Sublingual: Like lozenges, sublingual preparations also dissolve through the mouth's mucous membranes and bypass the GI tract for greater absorption.   
  •  Capsules and tablets: Capsules or tablets of vitamin B12 may have lower bioavailability than lozenges, depending on the individual's age and ability to absorb it. However, some studies have shown that oral vitamin B12 is as effective as injections when taken in high doses. 
  • Injections: Injections are given intramuscularly by a doctor or healthcare practitioner and are useful for supplying large amounts of vitamin B12 at once. However, this is the least accessible and most painful way to increase vitamin B12 levels, and consequently might not be readily available to most people. 

Key Takeaway

  • Vitamin B12 is an essential nutrient for red blood cell formation, DNA synthesis, and neurological function. 
  • The top benefits of vitamin B12 include its association with improved cognition and vision, increased energy, and support to the liver and detoxification process. 
  • Low levels of vitamin B12 cause high levels of homocysteine, which is linked to cardiovascular disease and dementia. 
  • Taking vitamin B12 in lozenge form may be the most bioavailable option. 


Butler CC, Vidal-Alaball J, Cannings-John R, et al. Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency: a systematic review of randomized controlled trials. Fam Pract. 2006;23(3):279-285. doi:10.1093/fampra/cml008

Christen WG, Glynn RJ, Chew EY, Albert CM, Manson JE. Folic acid, pyridoxine, and cyanocobalamin combination treatment and age-related macular degeneration in women: the Women's Antioxidant and Folic Acid Cardiovascular Study. Arch Intern Med. 2009;169(4):335-341. doi:10.1001/archinternmed.2008.574

Clarke R, Birks J, Nexo E, et al. Low vitamin B-12 status and risk of cognitive decline in older adults. Am J Clin Nutr. 2007;86(5):1384-1391. doi:10.1093/ajcn/86.5.1384

Hodges RE, Minich DM. Modulation of Metabolic Detoxification Pathways Using Foods and Food-Derived Components: A Scientific Review with Clinical Application. J Nutr Metab. 2015;2015:760689. doi:10.1155/2015/760689

Huang P, Wang F, Sah BK, et al. Homocysteine and the risk of age-related macular degeneration: a systematic review and meta-analysis. Sci Rep. 2015;5:10585. Published 2015 Jul 21. doi:10.1038/srep10585

Huijts M, Duits A, Staals J, van Oostenbrugge RJ. Association of vitamin B12 deficiency with fatigue and depression after lacunar stroke. PLoS One. 2012;7(1):e30519. doi:10.1371/journal.pone.0030519

Mahamid M, Mahroum N, Bragazzi NL, et al. Folate and B12 Levels Correlate with Histological Severity in NASH Patients. Nutrients. 2018;10(4):440. Published 2018 Apr 2. doi:10.3390/nu10040440

O'Leary F, Samman S. Vitamin B12 in health and disease. Nutrients. 2010;2(3):299-316. doi:10.3390/nu2030299

Soni RM, Tiwari SC, Mahdi AA, Kohli N. Serum Homocysteine and Behavioral and Psychological Symptoms of Dementia: Is There Any Correlation in Alzheimer's Disease?. Ann Neurosci. 2019;25(3):152-159. doi:10.1159/000487068

van Campen CLM, Riepma K, Visser FC. Open Trial of Vitamin B12 Nasal Drops in Adults With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Comparison of Responders and Non-Responders. Front Pharmacol. 2019;10:1102. Published 2019 Sep 20. doi:10.3389/fphar.2019.01102

Older post Newer post