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Agreed.
Forget the old total B12 assays now, measure holotranscobalamin and plasma MMA. It gives completely different and much more informative results.
A substantial number of our patients are vegetarians or vegans and they turn out to be B12 deficient unless they are receiving methyl B12 injections. Remember the B12 in supplements in cyano-cobalamin (it’s more stable) and in many cases seems to result in a raised serum B12 (sometimes quite high) without correcting intracellular B12 deficiencies. It can also give you a spectacularly high urine cobalt output, but that’s another story.
Nick Miller
London
From: Clinical biochemistry discussion list [mailto:[log in to unmask]] On Behalf Of Jonathan Kay
Sent: 05 December 2012 12:03
To: [log in to unmask]
Subject: Re: Vitamin B12 testing in vegans
1 All vegans should take B12 supplements.
2 What's the clinical question here? Does the patient have anything suggesting B12 deficiency, or is she just generally worried or interested?
3 I think we'll all be doing a lot more methylmalonic acid assays in the future as the limitations and non transferability of current B12 assays and the clinical effects of B12 deficiency both become more widely known.
Jonathan
On 5 Dec 2012, at 11:46, Sally Brady wrote:
Dear collective brain,
I have had a GP write to me asking for some help as one of his vegan patients presented him with the following information from the Vegan Society. Was anyone else aware of this and how did you deal with it?
Testing B12 status
A blood B12 level measurement is a very unreliable test for vegans, particularly for vegans using any form of algae. Algae and some other plant foods contain B12-analogues (false B12) that can imitate true B12 in blood tests while actually interfering with B12 metabolism. Blood counts are also unreliable as high folate intakes suppress the anaemia symptoms of B12 deficiency that can be detected by blood counts. Blood homocysteine testing is more reliable, with levels less than 10 micromol/litre being desirable. The most specific test for B12 status is methylmalonic acid (MMA) testing. If this is in the normal range in blood (<370 nmol/L) or urine (less than 4 mcg /mg creatinine) then your body has enough B12. Many doctors still rely on blood B12 levels and blood counts. These are not adequate, especially in vegans.
Thanks,
Sally
Dr Sally Brady
Senior Clinical Scientist
Blood Sciences
The Hillingdon Hospital
01895 279924
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------ACB discussion List Information-------- This is an open discussion list for the academic and clinical community working in clinical biochemistry. Please note, archived messages are public and can be viewed via the internet. Views expressed are those of the individual and they are responsible for all message content. ACB Web Site http://www.acb.org.uk Green Laboratories Work http://www.laboratorymedicine.nhs.uk List Archives http://www.jiscmail.ac.uk/lists/ACB-CLIN-CHEM-GEN.html List Instructions (How to leave etc.) http://www.jiscmail.ac.uk/