Whether it’s an energy drink, supplements, or shot, chances are you’ve seen vitamin B12 splayed somewhere on the label. This water-soluble vitamin is a key component of the diet that’s been proposed to boost energy, enhance concentration and focus, and improve mood, but what does science say?

Are the claims that energy supplements make real?

While it may not be time to put aside your coffee just yet, we’re diving into the research on B12 and giving you everything you need to know about vitamin B12—what it is, what it does, the link between B12 and energy, and how to know if you need a bit more B12 in your life.

Breaking Down Vitamin B12

Vitamin B12, also known as cobalamin, is a water-soluble vitamin that is a key player in several important biological functions:

  • DNA synthesis
  • Erythropoiesis (red blood cell formation)
  • Regeneration of bone marrow, GI lining, and respiratory tract lining
  • Nervous system development and maintenance
  • Prevention of anemia

While a B12 deficiency isn’t as prevalent as something like vitamin D or folate, it’s estimated that 10-15% of people over the age of 60 are low in B12, likely due to loss of intrinsic factor (we’ll talk about that more below) 1.

In addition to the functions we just mentioned, B12 is also essential to the conversion of the amino acid homocysteine to another less toxic amino acid, methionine.

Methionine is then activated into S-adenosyl-methionine that donates its methyl group to methyl acceptors like myelin (nervous system), neurotransmitters, and membrane phospholipids, all of which are required for maintaining the integrity of the nervous and hematopoietic systems 1.

Inadequate levels of B12 can disrupt this cycle and lead to the accumulation of homocysteine, which is toxic to neurons and poses a major risk factor for vascular disease and cognitive decline.

Unlike some other vitamins, the absorption of B12 isn’t as straightforward. Adequate levels of stomach acid are needed to facilitate the breakdown of B12 found in food.

Once breakdown starts, intrinsic factor—a protein released by parietal cells in the stomach—binds to vitamin B12 in the duodenum (small intestine) and forms a B12–intrinsic factor complex that allows B12 to be absorbed in the terminal portion of the small intestine 1.

As such, insufficient levels of stomach acid interfere with the absorption of B12 and can lead to a deficiency, even if dietary intake is optimal.

B12 and Fatigue

The main reason people tout B12 as an energy-boosting supplement is because of its role in blood cell formation and oxygen transport. Fatigue is one of the primary complaints of people with a B12 deficiency because cells require sufficient levels of B12 to function properly.

There is a major interplay between vitamin B12, folate, and iron in the formation of red blood cells—a process known as erythropoiesis 2. Red blood cells are constantly undergoing regeneration whereby new erythrocytes replace the old ones (roughly 1%), which are phagocytosed and destroyed daily.

However, for erythropoiesis to occur, the body requires three key nutrients: folate, vitamin B12, and iron.

Erythroblasts—immature red blood cells—require folate and vitamin B12 for proliferation during their differentiation phase 2.

A deficiency of either B12 or folate impairs purine and thymidylate syntheses, DNA synthesis, and results in erythroblast apoptosis. The result is the development of anemia from ineffective erythropoiesis.

This form of anemia is called megaloblastic anemia and leads to the formation of large, abnormal, immature red blood cells and impaired DNA synthesis 3, 4. Abnormal blood cells of any kind impair their ability to carry oxygen, which again results in fatigue.

On top of that, erythroblasts also require significant amounts of iron for hemoglobin synthesis. Large amounts of iron are recycled daily from hemoglobin breakdown during the destruction of old red blood cells, but sufficient dietary intake is also required.

Lack of iron can impair the proper formation of RBCs and result in impaired erythrocyte production with cells that are small and contain less hemoglobin 2. As such, oxygen-carrying capacity is impaired, and we experience major fatigue and weakness.

Can Supplementing B12 Give You More Energy?

Maybe—all the B vitamins are involved in energy production, but it’s not like any one vitamin can directly boost energy levels to a significant degree. With that said, fatigue can result from a dysfunction of the oxygen supply to muscles and the brain, in which B12 is involved.

Although small, the brain consumes 3.5 mL O2 per minute and per 100g of tissue, which corresponds to about 20% of the oxygen needs of the entire body 5. Compromised oxygen delivery due to nutrient deficiencies or physiological damage can harm the brain and result in intellectual impairment.

In comparison to the brain, resting muscle consumes about 1 ml O2 per minute and per 100g of tissue, but can increase up to 50-fold when contracting during exercise to enhance performance.

When anemia is present, i.e., low levels of the oxygen carrier hemoglobin, it results in impaired oxygen delivery, which affects not only cognitive function but also physical performance and perception of fatigue and tiredness 6.

Research does suggest, however, that deficiencies of vitamin B12 can decrease energy and exercise tolerance, along with causing fatigue and shortness of breath 5. These symptoms tend to disappear with B12 supplementation, but the extent will depend on the severity of the deficiency.

On top of that, we also have B12s role in the respiratory chain. Vitamin B12 serves as a cofactor for the enzymatic reaction that produces succinyl-coenzyme A, or succinyl-CoA, which can enter the Krebs cycle or the respiratory chain 7.

Without getting into too much detail, the Krebs cycle and respiratory chain are the last two stages of cellular respiration—the processes by which carbs, proteins, and fat are broken down to produce energy. Dysfunction of the respiratory chain means low ATP production and, as a result, low energy.

Simply put, without sufficient levels of B12, both energy production and red blood cell formation are impaired, leading to symptoms of B12 deficiency, such as low energy and fatigue.

So, if you want to bump up your energy levels and ensure your ATP production pathways are working optimally, getting enough B12 is essential.

8 Signs And Symptoms You May Need More B12

It’s estimated that about 20% of people over the age of 60 are deficient in B12 8. Because the ability to absorb B12 decreases with age, older people are at a higher risk of deficiency—but that doesn’t exempt younger people and children.

Watch out for these signs and symptoms of a B12 deficiency:

  1. Fatigue
  2. Weakness
  3. Anxiety or depression
  4. Brain fog
  5. Unexplained weight loss
  6. Frequent colds
  7. Pins and needles
  8. Cognitive impairment

B12 is found mainly in animal products, so vegans and vegetarians have to be cautious about intake. A B12 deficiency can also be the result of 8, 9:

  • Cobalamin malabsorption (intestinal diseases, gastric/intestinal resection, atrophic gastritis, pancreatic insufficiency)
  • Low gastric intrinsic factor (dietary intake deficits are less common)
  • Alcoholism
  • Drug interactions

If alarm bells are going off suggesting that this might be you, adding in a B12 supplement or a multi with B12 may be to your advantage.

Final Thoughts

B12 is a nutrient that plays critical roles in overall health and well-being. Whether it’s red blood cell production, DNA synthesis, or brain function, getting enough B12 in your diet is key to optimal performance.

However, while B12 plays an important role in energy production and supplementing to maintain normal serum concentrations can support your energy production pathways, researchers aren’t sold on B12 supplementation for boosting energy unless you’re deficient; that is, it’s not likely to increase energy levels in people with normal levels of B12.

Regardless, making sure you’re taking in B12 through diet or supplementation—especially for plant-based eaters—should be top of your list.


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