Vitamins: Vitamin B12 - Cobalamin

Question 1

Vitamin B12 – Cobalamin

Answer 1

Vitamin B12 refers to a family of cobalamin compounds containing the essential mineral cobalt in the centre.
* The most active B12 analogues include:
o Methylcobalamin
o Hydroxocobalamin
o Adenosyl cobalamin
o Cyanocobalamin
* These are the only analogues recognised by the body. There are others found in nature but they are not bioavailable to humans.
* Vitamin B 12 is synthesized by bacteria. Vitamin B12 found in animal-based foods originates from their ingestion of bacterial-contaminated feed, or from B12 that has been given to the animal.
* The human microbiota produces B12, but it is not absorbed
Cobalamin = from cobalt + vitamin

Question 2

Storage

Answer 2

B12 storage in the liver lasts between 3-5 years

Question 3

Vegan B12 vegan sources

Answer 3

• Chlorella pyrenoidosa (e.g. 9 g per day)
• A substantial amount (133.8 ug / 100g) of vitamin B12 has also been found in dried Korean purple laver (Porphyra sp).
• Nutritional yeast
• Nori and Kombu sea vegetables (nori, kombu, kelp and dulse)
• Shitake and Lion’s mane mushrooms

Question 4

Animal B12 food sources

Answer 4

• Meat
• Liver
• Milk
• Cottage and feta cheese
• Organic eggs
• Fish (esp. sardines, mackeral and wild salmon)

Question 5

Nervous System: functions and therapeutic uses

Answer 5

• Function:
  o Myelin Production
  o Neurotransmitter production (Dopamine, serotonin)
  o Choline – Key for brain function
• Therapeutic uses:
  o MS
  o Tingling/pins and needles
  o Sciatica

Question 6

Erythropoiesis

Answer 6

• Function:
  o B12 is required for erythropoiesis
• Therapeutic use:
  o Megaloblastic anaemia

Question 7

Methylation

Answer 7

• Function:
  o Homocysteine cycle (conversion of amino acid homocysteine to methionine)
• Therapeutic uses:
  o Cardiovascular disease
  o Alzheimer’s

Question 8

Energy production: functions and therapeutic uses

Answer 8

• Function:
  o Energy production from fats and proteins
• Therapeutic uses:
  o Fatigue

Question 9

Causes of B12 deficiency

Answer 9

• Poor nutrition (Malnutrition):
  o Lack of dietary B12 intake, and a diet rich in highly-processed, nutrient-depleted foods
• GIT causes (malabsorption):
  o Stomach problems (e.g. lack of intrinsic factor, low hydrochloric acid production)
  o Low pancreatic enzymes, small intestine issues (e.g. Crohn’s disease, coeliac), high alcohol
• Note: if a client has a good dietary intake of B12, yet is deficient, it highlights a possible absorption issue or problem with methylation

Question 10

Deficiency states and increased requirements

Answer 10

• The most common cause of deficiency is malabsorption due to inadequate intrinsic factor (IF) production. It is called pernicious anaemia. Helicobacter pylori infection is also implicated.
• Pernicious anaemia is associated with an autoimmune attack with parietal cells in the stomach (the cells that synthesise intrinsic factor)
• Increased vitamin B12 requirements are associated with:
  o Pregnancy
  o Thyrotoxicosis
  o Malignancy
  o Liver disease
  o Kidney disease

Question 11

Deficiency signs and symptoms

Answer 11

• Megaloblastic anaemia: Presenting as fatigue, breathlessness, pallor, etc. Supplementation with B9 will alleviate the anaemia, however, other symptoms of vitamin B12 deficiency progress
• Neurological abnormalities: tingling, numbness, loss of balance, burning sensations, weakness, confusion and decreased reflexes
• Anaemia typically develops first, but not always if the person is consuming lots of folate
• Changes occur slowly, and once the patient experiences neurological symptoms, they may be irreversible

Question 12

B12 testing

Answer 12

• Serum B12 testing reference ranges are typically anything between from 110 ng / L up to 900 ng / L. this is the most common means of assessing B12 conventionally
• However, many people experience signs of B12 deficiency with normal B12 serum
• A more accurate reflection of B12 levels would involve testing methylmalonic acid (available in serum or urine testing) – gives an indication of how B12 is used in cell metabolism and is the gold standard test

Question 13

Toxicity

Answer 13

• Vitamin B12 is one of the safest vitamins. No adverse effects have been associated with large intakes (2mg) of vitamin B12 from food or supplements in healthy people

Question 14

Drug interactions

Answer 14

• The OCP, metformin, excessive alcohol, protein pump inhibitors and H2-receptor antagonists lower B12 levels
• Calcium may enhance B12 absorption, including with metformin use
• People with autoimmune disease are considered more at risk of pernicious anaemia

Question 15

B12 cobalamin functions

Answer 15

Nervous system
Erythropoiesis
Methylation
Energy production