Another fact, like many concerting vitamin D, which most people are unaware, is vitamin B12 has many different types. Which I will not go into a lot of detail, but you can find here if interested. 1 This makes testing for its deficiency more difficult. When vitamin B12 levels are inadequate. Which will be more likely once one accelerates their metabolism and healing with optimal doses of vitamin D3. Vitamin B12 deficiency is more likely. Its deficiency may be better spotted by testing for elevated levels of unmetabolized methylmalonic acid and homocysteine. 1 As these are more prevalent when vitamin B12 levels are inadequate. Here’s the kicker, even then those with vitamin B12 deficiency symptoms but normal vitamin B12, methylmalonic acid and homocysteine levels may respond to dosing with vitamin B12.2 If vitamin B12 levels are low or deficient then these substances levels will rise.

Then going back to vitamin B12’s absorption into the body is complicated. See vitamin B12 needs to be present then to combine once separated from food sources with intrinsic factor to be absorbed through the gut wall. Many conditions like pernicious anemia, gastric bypass surgery and gut infections can prevent its absorption. Though a highly respected group the Cochrane Group in 2005 found high oral doses 1,000-2,000 mcg/d of oral vitamin B12 as effective if not more than intramuscular dosing I believe you will have a hard time convincing some.3 This even in those with gut conditions just listed, conditions that would normally prevent its absorption.

As you may have experienced it is often the favorite substance of many a grandparent. Who loves getting a vitamin B12 shot from their doctor, as your grandparent states is to boost their energy. Ever wonder why then just didn’t take it in a pill? Why go to all the trouble of seeing their doctor and getting it through an injection? Your grandparents or parents swearing the injected vitamin B12 worked so much better. Why, unless you think your grandmother was crazy did, they claim injections worked so much better then pills?

Part is for many as they age, they have some degree of gastric atrophy. So, with gastric atrophy the acid released in the stomach decreases which separates vitamin B-12 from other food particles and they also produce less intrinsic factor. Yes, there may be other reasons your grandparent wanted to see the doctor but despite what you might think they are no idiot. Injection of vitamin B12 assures that all the dose is absorbed is delivered into the blood stream which is not guaranteed in pill form. If the small intestine is compromised or their intrinsic factor is decreased, then little or none of the vitamin B12 may be absorbed.

Only roughly 56% of a 1 mcg oral dose of cobalamin is absorbed. But this percentage drops off quickly once the capacity of intrinsic factor is exceeded which is 1-2 mcg of cobalamin.  Such that only 10 mcg of a 500 mcg of an oral dose of vitamin B12 is absorbed due to the limited amount of intrinsic factor present in the stomach. 4

So how does vitamin D3 effect vitamin B12 absorption? For one a healthier body will be able to produce more intrinsic factor and other substances to free up the vitamin B-12 in your food. Also, calcium is important to facilitate the absorption of vitamin B-12. But none of these are that significant. So after searching for a connection I really found none but as this is useful and important information so I opted to publish it anyway as vitamin B-12 is complex, poorly understood and many people are suffering from its deficiency.

  1. Cravens DD, Nahelsky J. (January 2007) How do we evaluate a marginally low B12 level? J Fam Pract. 56(1):62-63.
  2. Solomon LR. (2005) Cobalamin-responsive disorders in the ambulatory care setting: unreliability of cobalamin, methylmalonic acid, and homocysteine testing. Blood. 105:978-985.
  3. Carmel R. (2008) How I treat cobalamin (vitamin B12) deficiency. Blood. 112:2214-21.
  4. Vidal-Alaball J, Butler CC, Cannings-John R, et al. (rev 2005) Oral vitamin B12 versus intramuscular vitamin B12 for vitamin B12 deficiency. Cochrane Database Syst. (3):CD004655.


*The information posted above is for educational purposes only. Always check with your doctor before initiating any changes in your medical treatment. If you do not, then The Two-Minute Health Fact, Dr. Judson Somerville, nor The Optimal Dose is responsible!


Leave a Reply

Avatar placeholder

Your email address will not be published. Required fields are marked *