What is Vitamin B12 (Cobalamin)?

Vitamin B12, also called cobalamin, is a vital nutrient your body needs for red blood cells, nerves, DNA, and energy. It is unique because it contains cobalt (hence “cobalamin”) and is the largest, most complex vitamin. Without enough B12, cells cannot function properly, leading to fatigue, brain fog, nerve issues, anemia, and long-term health problems.

Chemical Structure and Size

B12 is a water-soluble vitamin with a central cobalt atom surrounded by a corrin ring structure. Its molecular weight is 1,355 g/mol, much larger than other vitamins (e.g., vitamin C is 176 g/mol, vitamin D is 385 g/mol). This large size makes B12 difficult to absorb from food or oral supplements. In practice, injections or sublingual forms often work better than standard pills.

Where B12 Comes From

B12 is made only by certain bacteria, not plants or animals themselves. Animals get B12 from gut bacteria or diet, then store it in muscle, liver, and other tissues. Humans obtain B12 from animal products: meat, fish, eggs, dairy, and organ meats. Plant foods contain almost no B12 unless contaminated with bacteria (e.g., unwashed produce or soil residues). Vegans and vegetarians are at high risk of deficiency without supplementation.

Does the Human Body Produce B12?

Yes, gut bacteria in the colon produce B12. No, you cannot absorb it. Absorption occurs in the ileum (end of small intestine), but B12-producing bacteria live lower down in the colon. The B12 they make stays below the absorption site and is lost in stool. Some animals (rabbits, rats, horses) eat their own stool (coprophagy) to recycle B12. Humans do not do this effectively, so dietary or supplemental sources are essential.

How B12 Is Absorbed

Absorption is complex and requires multiple steps:

1. In the mouth - Haptocorrin (R-protein) from saliva binds B12 to protect it from stomach acid.

2. In the stomach - Stomach acid (pH <2) and pepsin loosen B12 from food proteins.

3. In the duodenum (upper part of small intestine) - Intrinsic factor (produced by stomach parietal cells) binds B12 after the haptocorrin releases it.

4. In the ileum (lower part of small intestine) - The intrinsic factor-B12 complex is absorbed into the bloodstream.

5. Transport - Transcobalamin proteins carry B12 to tissues, especially liver (major storage site).

Any disruption, low stomach acid (hypochlorhydria), acid-blocking drugs (antacids like tums), lack of intrinsic factor (pernicious anemia), gut inflammation, or ileum issues blocks absorption. This explains why many people become deficient despite eating B12-rich foods.

Daily Requirements

The Dietary Reference Intake (DRI) is 2.4 mcg/day for adults (2.6 mcg pregnancy, 2.8 mcg lactation). This amount prevents severe deficiency in most healthy people but is often too low for optimal function, especially with stress, aging, gut issues, or chronic illness. Many patients need higher doses for energy, nerve health, and mood.

Functions of Vitamin B12

B12 works in two main pathways:

• Converts homocysteine to methionine (supports heart health, methylation, detoxification).

• Converts methylmalonyl-CoA to succinyl-CoA (energy production in mitochondria).

It is critical for:

• Red blood cell formation (prevents anemia).

• Myelin sheath maintenance (nerve insulation).

• DNA/RNA synthesis (cell division and repair).

• Brain health (neurotransmitter production, mood).

• Energy metabolism (mitochondrial function).

Every cell uses B12; deficiency affects the whole body.

Forms of B12

• Methylcobalamin - Natural, active form; directly used in methylation. Best for nerve health and brain support.

• Hydroxocobalamin - Natural, long-lasting; preferred for injections in deficiency states.

• Adenosylcobalamin - Mitochondrial form; supports energy production.

• Cyanocobalamin - Synthetic, common in supplements and fortified foods. Contains cyanide (detoxified by body), but less bioavailable.

We prefer methyl- and hydroxocobalamin for most patients.

Deficiency Causes

• Poor absorption (low stomach acid, antacids, pernicious anemia, gut disorders).

• Vegan/vegetarian diets without supplementation.

• Aging (reduced stomach acid and intrinsic factor).

• High stress or chronic illness (increased demand).

Symptoms of Low B12

Early signs (even with “normal” labs): fatigue, brain fog, low mood, irritability, tingling/numbness, balance issues, memory problems, sore tongue, weakness.

Severe: megaloblastic anemia, nerve damage (neuropathy), dementia-like symptoms, infertility, increased homocysteine (heart risk).

Summary

Vitamin B12 is essential for energy, nerves, blood, and brain health. It is made by bacteria, stored in animal tissues, and difficult to absorb. Many people need more than the DRI of 2.4 mcg/day especially if stressed, aging, or eating limited animal products.

At Jones Chiropractic & Functional Medicine we test B12 status (serum B12, methylmalonic acid, homocysteine), consider symptoms and absorption, and use bioavailable forms (methyl/hydroxy) when needed. If you feel tired, foggy, or “off” despite “normal” labs, B12 may be a missing piece.

Disclaimer: The content presented on this website serves educational and informational purposes and is not meant to replace professional medical advice, diagnosis, or treatment. Consult your doctor for any inquiries concerning medical conditions. Do not disregard or delay seeking professional medical advice based on information obtained from this website.