I know many people who would be more likely to see a doctor for evaluation and treatment of a B12 deficiency if they could have oral supplements as opposed to injections. However, correct diagnosis and optimal treatment is critical to avoid serious health problems from B12 deficiency. The following is some background that may help in discussing B12 treatment with physicians. Remember to confirm the accuracy of this information through your own research and discussion with your medical professional.
SOME BACKGROUND FACTS TO UNDERSTAND:
Bioavailability is the fraction of the drug dose that reaches the systemic circulation in an unchanged or active form and is therefore available for distribution to the intended site of action. In general, drugs injected into a vein (intravenous or IV) have 100% bioavailability. Drugs given by other routes have less bioavailability because all of the drug may not be absorbed, or metabolism of the drug might occur before reaching the site of action.
Bioavailability of drugs given by routes other than intravenous injection:
Parenteral administration: Injection directly into the body, by-passing the skin and mucous membranes. Common routes of parenteral administration (in addition to the intravenous or IV route):
- Injected into a muscle (intramuscular or IM): greater bioavailability than drugs injected into the layer of fat (adipose tissue) under the skin.
- Injected into the layer of fat under the skin (subcutaneous or SC): greater bioavailability than drugs taken orally.
Taken under the tongue (sublingual): The sublingual mucosa offers a rich supply of blood vessels through which drugs can be absorbed. It offers rapid absorption into the systemic circulation and it ensures that the substance will risk degradation only by salivary enzymes before entering the bloodstream.
Oral route: The drug must pass through the gastrointestinal tract. Some drugs given by oral route may have 100% bioavailability but this is rare, so the dose given orally is usually higher than that given by injection.
“Solid dose forms such as tablets and capsules have a high degree of drug stability and provide accurate dosage. The oral route is nevertheless problematic because of the unpredictable nature of gastro-intestinal drug absorption. For example, the presence of food in the gastrointestinal tract may alter the gut pH, gastric motility and emptying time, as well as the rate and extent of drug absorption.” (Nursing Times.net)
During its passage through the gastrointestinal tract, stomach acid, bile, or various enzymes can degrade the drug. In addition, after absorption from the gastrointestinal tract, the drug must pass to the liver, where it may be altered (known as the first pass effect of drug metabolism), before entering the general circulation.
SO WHAT DOES THIS MEAN WHEN TAKING B12?
According to Pacholok and Stuart in Could It Be B12? (2nd Edition):
“In our opinion B12 injections are preferable to oral B12 in many cases, and they are absolutely necessary when neurological symptoms are present. This is an area of controversy, but we’ve personally seen cases in which high-dose oral B12 and lozenges simply didn’t work, and such cases are reported in the literature as well (p. 195) … We ourselves have seen cases in which injected B12 resulted in far greater benefits than oral supplementation.” (p. 227)
“Many doctors will argue that the literature indicates – although it does not prove – that oral B12 is adequate in most cases…. Our philosophy is simply this: Given that bi-monthly shots of B12 are virtually painless thanks to microfine needles, and given the multiple ways in which the B12 pathway can be disrupted between your mouth and your bloodstream, why take a chance?” (p. 196)
“Moreover, while there are many over-the-counter B12 lozenges, pills, drops, nasal gels, skin patches, gums and drinks, it’s not possible to know the efficacy of each of these products or to predict each individual’s response. What studies were done to test them, and how many people were involved? Were these studies done on healthy people or B12-deficient patients? What was the cause of the patients’ B12 deficiency? Did any of the studies include patients with severe neurologic symptoms? All of these factors – as well as the form of B12 in a product and the shelf life of the product – must be considered when selecting a B12 therapy.” (p. 196)
“Thus, we advise caution. If a patient responds to oral B12 or B12 lozenges – great! But if not, injections are always indicated as a trial.” (p. 196)
“A Final Word About Oral B12: We don’t dismiss the use of oral B12 supplements entirely. If you and your doctor agree on oral B12, we recommend a high dose (2,000 mcg per day) in lozenge or sublingual (under the tongue) form, and prefer methyl-B12. You should switch to an oral formula only after you’ve received initial shots to get your B12 stores back to normal, and you should have at least yearly B12 tests to make sure the oral formula is working for you.” (p. 197)
Rev Med Suisse. 2008 Oct 15;4(175):2212-4, 2216-7.
Vitamin B12 deficiency: a challenging diagnosis and treatment
“Oral treatment of vitamin B12 deficiency is possible whatever the etiology, but it has only been validated in small series. Parenteral treatment remains indicated for severe neurologic deficits or whenever patient adherence with treatment is doubtful.”
BMC Fam Pract. 2011 Jan 13;12:2. doi: 10.1186/1471-2296-12-2.
Oral vitamin B12 for patients suspected of subtle cobalamin deficiency: a multicentre pragmatic randomised controlled trial.
“CONCLUSIONS: Oral vitamin B12 treatment normalised the metabolic markers of vitamin B12 deficiency. However, a one-month daily treatment with 1000 μg oral vitamin B12 was not sufficient to normalise the deficiency markers for four months, and treatment had no effect on haematological signs of B12 deficiency.”
Comment from Could It Be B12?: “ … some patients, especially those with neurologic symptoms, would benefit from having their stores rapidly replenished.” [As with injections] (p. 228, 2nd Edition)
American Family Physician, March 1, 2003
Vitamin B12 Deficiency
“Contrary to prevailing medical practice, studies show that supplementation with oral vitamin B12 is a safe and effective treatment for the B12 deficiency state. Even when intrinsic factor is not present to aid in the absorption of vitamin B12 (pernicious anemia) or in other diseases that affect the usual absorption sites in the terminal ileum, oral therapy remains effective.”
http://www.aafp.org/afp/2003/0301/p979.html. Scroll down to “Oral vs. Parenteral Therapy” at the end of the article.
Life Extension Magazine August 1999
“For decades, people have been injecting themselves with vitamin B12 because they thought oral supplements were not adequately absorbed. New research indicates that oral B12 supplements may be as good or better than injections.”
THE LANCET • Vol 354 • August 28, 1999
Sublingual therapy for cobalamin deficiency as an alternative to oral and parenteral cobalamin supplementation
“Effectiveness of sublingual cobalamin-replacement therapy was studied in 18 people with cobalamin deficiency. Administration was efficacious and convenient, and compliance was high.”
BLOOD 1998 92: 1191-1198
Antoinette M. Kuzminski, Eric J. Del Giacco, Robert H. Allen, Sally P. Stabler and John Lindenbaum
Effective Treatment of Cobalamin Deficiency With Oral Cobalamin
“In cobalamin deficiency, 2 mg of cyanocobalamin administered orally on a daily basis was as effective as 1 mg administered intramuscularly on a monthly basis and may be superior.”
Comment from Could It Be B12?:
“This study strongly supports the view that oral B12 at doses of 2,000 mcg can replace injection therapy in some situations. Although this was a very small study with only thirty-three patients, it used serum MMA and Hcy markers, demonstrating a reduction in these metabolites.” (2nd Edition, p. 227)
“This study is consistent with findings from the 1950’s and 1960’s, which showed that 1 percent of the oral B12 dose consumed is absorbed by an alternate pathway, via passive diffusion throughout the small intestine, in the presence of intrinsic factor or a functioning terminal ileum. It also is consistent with clinical practice in Sweden, where oral B12 maintenance therapy has been used for more than twenty-five years.” (2nd Edition, p. 227)
“We believe, however, that additional research is needed to confirm the efficacy and safety of oral B12 for patients whose deficiencies stem from a variety of etiologies.” (2nd Edition, p. 227)