Vitamin B12 is an essential vitamin for the proper functioning of the nervous system. It is involved in the synthesis of protein structures in the myelin sheath and nerve cells.

B12 is essential for the conversion of homocysteine to methionine for the production of SAMe to provide methyl groups for the biosynthesis of monoamine neurotransmitters, serotonin, epinephrine and dopamine. Without adequate SAMe, neurotransmitter levels decrease in the cerebrospinal fluid, contributing to depression.


What causes B12 deficiency?

1. Inadequate intake, which is likely to occur on a vegan or vegetarian diet.

2. Impaired gastric function with low hydrochloric acid, which impairs absorption of B12.

3. Inadequate zinc levels, as zinc is required to make hydrochloric acid.

4. Use of protein pump inhibitors (eg Nexium) for reflux as they reduce hydrochloric acid.

5. Impaired pancreatic function which decreases the pH of the intestinal tract and impairs the release of B12.

6. Pernicious anemia, which is an autoimmune condition that impairs the release of intrinsic factor. Without intrinsic factor, B12 cannot be absorbed.

7. Impaired intestinal function including Celiac Disease or Crohn’s Disease.

8. Intestinal parasites can impair B12 absorption.

9. Excessive alcohol intake. Alcohol depletes all B vitamins

Signs & Symptoms of B12 deficiency

  • Fatigue
  • Muscle weakness
  • Memory loss
  • Irritability
  • Confusion
  • Depression
  • Apathy
  • Insomnia
  • Pain or numbness or tingling
  • Sore mouth and tongue
  • Laboured breathing

Testing B12

There are 3 main tests available to assess B12 levels.

Serum B12 measures both the inactive and active form. Levels should be >400pmol/L

Serum Holotranscobalamin measures specifically the fraction of B12 which enters the cells for metabolic activities (‘active B12’). Levels should be >128pmol/L

Methylmalonic acid (MMA) is a functional measure of vitamin B12 status and raised serum methylmalonic acid is evidence of tissue B12 deficiency. This test is often only ordered once a patient has tested low serum and or active B12. It can be tested in both the blood and urine. The urine test is the most accurate for detecting tissue-cellular B12 deficiency.

Correcting a Vitamin B12 deficiency

1. If the deficiency is due to inadequate dietary intake of animal protein, dietary adjustments need to be made to include animal protein OR supplementation is essential.

2. If the deficiency is due to the overuse of proton pump inhibitors (Nexium), the underlying cause of acid reflux needs to be addressed and the patient weaned off the drug. There are many wonderful herbs that can help with this process. Supplementation with B12 during this process is also important.

3. Impaired gut function such as celiac or Crohn’s disease – here it is often important to bypass the gut with either the use of B12 injections of transdermal creams.

4. Zinc levels need to be optimal (approx. 17) to ensure adequate hydrochloric acid production. Increasing zinc intake in the diet or supplementation is very important.

5. Gut parasites – these need to be removed from the gut to ensure proper B12 absorption. There are many very effective herbs to treat gut parasites.

It is very important to supplement with B12 until you have adequate levels, whilst the underlying cause of your B12 deficiency is addressed.

Which form of B12 to use?


  • Used in most ‘retail’ supplements.
  • Cyanocobalamin is not metabolized or utilized as effectively as other forms of B12.


  • This form is very well tolerated and unlikely to cause side effects.
  • Hydroxycobalamin will covert into adenoslycobalamin and methylcobalamin.
  • The hydroxyl form is good for people with low homocysteine as it will mop up nitric oxide caused by a CBS pathway up regulation.
  • Use this form if you are not sure if you will have an adverse reaction to methylcobalamin.


  • Adenosylcobalamin is involved in the conversion of methylmalonyl-CoA to succinyl-CoA, without which the krebs cycle can’t operate properly. The Krebs cycle is the body’s energy cycle inside each cell.
  • This form is currently not available for sale in Australia.


  • Methylcobalamin is neurological B12.
  • Methylcobalamin is essential for folate metabolism and the proper functioning of the methylation cycle via the recycling of homocysteine to methionine.
  • This form CAN cause serious side effects including suicidal thoughts, so should only be taken under the prescription of a trained practitioner.

Correcting a Vitamin B12 deficiency can help significantly with mood including depression. If you suspect you have a deficiency, it is very important you get tested, as B12 deficiency can cause irreversible neurological damage.


Author: Joanne Kennedy

Joanne Kennedy is a degree qualified Naturopath practising in the Sydney CBD. Areas of speciality include: MTHFR, Women’s hormones; stress, fatigue and insomnia; anxiety & depression; gut/digestive health; and histamine intolerance. Jo has helped hundreds of patients with chronic and complicated health issues gain control of their health and finally heal.

Jo is currently seeing patients in the Sydney CBD at Sydney Health & Wellness Centre and via Skype. For appointments call Jo on 0400 658 003 or email