Ultimo aggiornamento 2020-06-21 19:15:08
La vitamina B12 è un insieme di molecole fra cui le più note sono la cianocobalamina e la idrossicobalamina. E’ una vitamina idrosolubile del gruppo B, detta anche cobalamina, una molecola complessa con un atomo di cobalto nel centro (1).
Non è sintetizzata dall’organismo umano e quindi deve necessariamente essere introdotta con gli alimenti o con integratori. A livello gastrico si lega al “fattore intrinseco di Castle“, una sostanza secreta dalle cellule parietali gastriche che si lega alla vitamina B12 (fattore estrinseco) e ne permette l’assorbimento. La causa della mancanza del Fattore Intrinseco è rappresentata dall’atrofia della mucosa ghiandolare gastrica, causata da un processo autoimmune. Molto spesso questa vitamina viene a mancare ai vegani, che si privano anche del latte e delle uova.
I valori plasmatici normali di vitamina B12 sono di 2-9 mcg/ml.
Di norma ogni individuo necessita della seguente dose di vitamina B12 al giorno:
- Bambini: tra 1 e 3 microgrammi
- Gravidanza e allattamento: fino a 5 microgrammi
- Adulti: da 2 a 4 microgrammi
- La sua funzione principale è di favorire la sintesi degli eritrociti nel midollo osseo attraverso la regolazione della sintesi dell’emoglobina e la sintesi del DNA a cui partecipa l’ac. folico (Vit. B9)
che trasporta il carbonio essenziale per la sintesi dell’eme (14,15). L’emoglobina è formata da 4 eme ed ogni eme contiene un atomo di ferro. Quando la carenza di vitamina B12 non viene rilevata in tempo, può provocare l’anemia megaloblastica, caratterizzata dalla presenza di megaloblasti (cellule progenitrici immature dei macrociti) e macrociti (globuli rossi di dimensioni superiori alla norma ⌈9-12 µm⌉). Comunque la popolazione eritrocitaria risulta inferiore al normale per eritropoiesi inefficace a causa della
difettosa sintesi del DNA (16). Inoltre gli eritroblasti sono sottoposti a catabolizzazione precoce nel midollo osseo (20-50% circa), apoptosi, aumentato turnover eritrocitario (v. n. 1%/die), emolisi (25), iperbilirubinemia non coniugata come prodotto della degradazione emoglobinica (1). L’anemia megaloblastica può essere accompagnata da caratteristiche anomalie neurologiche (17-23).
- La Vit B12 partecipa alla sintesi del rivestimento mielinico delle fibre nervose. Conseguentemente la carenza di vitamina B12 provoca gravi disturbi psicologici e alterazioni della fisiologia neuromotoria e predispone verso la sclerosi multipla e il m. di Alzheimer.
- La vitamina B12, inoltre, stimola la conversione dei carotenoidi in vitamina A e, assieme ad altre sostanze, partecipa alla sintesi del DNA e RNA.
- Agisce sul metabolismo dell’omocisteina. In caso di deficit della cobalamina, l’iperomocisteina è causa di aterosclerosi, infarto e ictus.
- La vitamina B12 è indispensabile per la sintesi del DNA nelle cellule di tutto l’organismo.
- Livelli plasmatici ottimali di vitamina B12 sono importanti per:
- Vitalità, ottimismo, buon umore (3)
- Risposta positiva allo stress
- Freschezza mentale
- Lavoro muscolare
- Cervello e sistema nervoso
- Ossa sane
- metabolismo dei lipidi
- Energia (2)
- Metabolismo del ferro
Un alimento supplementare eccellente è lievito di birra. I lieviti sono microrganismi che sintetizzano la vitamina in natura.
Un insufficiente apporto di vitamina B12 è raro e si verifica:
- nei vegetariani che rifiutano la carne e pesce, oltre a uova e latticini, ma la carenza si manifesta solo dopo 2 o 3 anni di continua e inadeguata assunzione di vitamina B12.
- parassitosi intestinale
- Atrofia della mucosa gastrica o gastrite cronica atrofica su base autoimmune (tipo A) o da infezione da Helicobacter pylori (tipo B) (7-13).
- Gastrectomia
- Ilectomia: l’intestino ileo è il tratto intestinale deputato all’assorbimento di vitamina B12.
- Deficit ereditario di fattore intrinseco
- Sindrome da malassorbimento
- Morbo di Crohn
- farmaci antiulcera
- Metformina: le pazienti che ricevono metformina hanno una diminuzione dell’assorbimento della vitamina B12 a causa di un meccanismo di competizione recettoriale calcio-dipendente a livello ileale. Meccanismo reversibile con supplementazione di calcio (4-6).
- Facile affaticabilità
- Infiammazione alla bocca
- Ansia costante
- Cattivo odore del corpo
- Intorpidimento delle braccia e delle gambe
- Difficoltà a camminare
- Balbuzie
- Mucose pallide
- Facile stancabilità
- Neuropatia cronica (3)
- Ipersensibilità al freddo
- Cefalea
- Vertigini
- Tachicardia
- tachipnea
Esami di laboratorio:
- Livelli plasmatici di vitamina B12 ridotti: spesso non si osserva correlazione fra valori sierici di vitamina B12 e sintomatologia da carenza della vitamina. Si deve ipotizzare che, almeno nelle fasi iniziali, grandi quantità della vitamina vengano richiamate dagli organi di deposito, fegato soprattutto, ed immessi in circolo ad opera dei folati come reazione al diminuito apporto alimentare di vitamina B12 (24).
- Eritrociti, leucociti e piastrine diminuiti
- LDH diminuito
- iperbilirubinemia
- iperomocisteinemia (25)
- HbA1c aumentata
- MTHFR polimorfismo: il metilentetraidrofolato permette la trasformazione di omocisteina in metionina; a questa reazione partecipa inmaniera determinante anche la vitamina B12 (26)
- Puntura del midollo osseo, mielobiopsia, in grado di rilevare megaloblasti.
- Usando il test di Schilling, un disturbo di ricezione di vitamina B12 può essere rilevato nel piccolo intestino.
- Esame delle feci per la ricerca di parassiti
- Una gastroscopia allo stomaco mostra, nel caso di anemia, una mucosa gastrica con i segni tipici della lesione cronica.
Terapia:
Trattare la causa della carenza di vitamina B12 è la cura fondamentale, ma questo è possibile solo in caso di infestazione da parassiti o nella malnutrizione. La terapia sintomatica prevede la somministrazione di preparati contenenti la cobalamina:
- Epargriseovit fl im/ev (cianocobalamina 1250 mcg; acido folico 0,35 mg; nicotinamide 6 mg; acido ascorbico 75 mg).
- Eparmefolin fl im/ev (Cianocobalamina 2 mg; Calcio folinato 0,9 mg).
- Benexol B12 5.000 fl im: Tiamina (vitamina B1) 38 mg, piridossina cloridrato (Vit. B6) 300 mg, idroxocobalamina (Vit. B12) 5000 µg
- Benexol B12 fl im vitamina B1 38 mg, piridossina cloridrato (Vit. B6) 200 mg, idroxocobalamina (Vit. B12) 1000 µg
- Benexol B12 cpr: tiamina cloridrato (Vit. B1) 250 mg, piridossina cloridrato (Vit. B6) 250 mg, cianocobalamina (Vit. B12) 500 µg.
- Mionevrasi fl im: cianocobalamina mg 1, piridossina cloridrato mg 100, tiamin-difosfato cloruro (cocarbossilasi) mg 38,20.
- Adenoplex forte: Cocarbossilasi mg 38,3; Piridossina cloridrato mg 300; Cianocobalamina mg 0,5
Bibliografia:
- Mark J. Koury: “New insights into erythropoiesis: The Roles of Folate, Vitamin B12, and Iron*1 Annual Review of Nutrition Vol. 24: 105-131 (Volume publication date July 2004)
-
Hartmann F: HARTMANN F.[The mechanism of action of vitamin B12 in fat metabolism]. “Naunyn Schmiedebergs Arch Exp Pathol Pharmakol. 1959;237:375-80.
- Destito D, Canonico N, Tentori-Montalto T. Analgesic activity of Benexol-B12 in the painful vertebral syndrome. Acta Vitaminol Enzymol. 1985;7(1-2):9-18.
-
Laird RD, Drill VA: “Lipotropic activity of vitamins B12 and B13 concentrates”. Toxicol Appl Pharmacol. 1962 Jan;4:1-13.
-
Cosin J.: “[Lipotropic action of vitamin B 12]”. Medicina (Madr). 1961 Jul;29:311-5.
- W A Bauman, S Shaw, E Jayatilleke, A M Spungen and V Herbert: “Increased intake of calcium reverses vitamin B12 malabsorption induced by metformin”. Diabetes Care September 2000vol. 23 no. 9 1227-1231
- Robbins e Cotran, Le basi patologiche delle malattie, 7ª ed., Torino-Milano, Elsevier Masson, 2008, Pag. 813-814, ISBN 978-88-85675-53-7.
- Moss, Steven F.; Sood, Shivani, Helicobacter pylori in Current Opinion in Infectious Diseases, vol. 16, nº 5, Ottobre 2003, pp. 445-451.
- ^ De Block CE, De Leeuw IH, Van Gaal LF., Autoimmune gastritis in type 1 diabetes: a clinically oriented review. in J Clin Endocrinol Metab, vol. 93, nº 2, febbraio 2008, pp. 363-71, PMID 18029461.
- ^ Weck M N; Stegmaier C; Rothenbacher D; Brenner H, Epidemiology of chronic atrophic gastritis: population-based study among 9444 older adults from Germany. in Alimentary pharmacology & therapeutics, vol. 26, nº 6, 2007, pp. 879-87.
- ^ a b Harrison, Principi di Medicina Interna, 16ª ed., New York-Milano, McGraw-Hill, 2006, Pag. 1985-86, ISBN 978-88-386-3929-6.
- ^ Ban-Hock Toh, M.B., B.S., D.Sc., Ian R. van Driel, Ph.D., and Paul A. Gleeson, Ph.D.,Pernicious Anemia in The New England Journal of Medicine, vol. 338, nº 14, 1998, p. 995.
- ^ Wickramasinghe SN, Morphology, biology and biochemistry of cobalamin- and folate-deficient bone marrow cells in Baillieres Clin Haematol, vol. 8, 1995, pp. 441–459,DOI:10.1016/S0950-3536(05)80215-X, PMID 8534956.
-
Koury MJ1, Ponka P. New insights into erythropoiesis: the roles of folate, vitamin B12, and iron. Annu Rev Nutr. 2004;24:105-31.
- Haiden N1, Klebermass K, Cardona F, Schwindt J, Berger A, Kohlhauser-Vollmuth C, Jilma B, Pollak A. A randomized, controlled trial of the effects of adding vitamin B12 and folate to erythropoietin for the treatment of anemia of prematurity. Pediatrics. 2006 Jul;118(1):180-8.
- U. Sjögren and L. Brandt ERYTHROBLASTIC ISLANDS AND INEFFECTIVE ERYTHROPOIESIS IN VITAMIN B12 DEFICIENCY Acta Medica Scandinavica Volume 196, Issue 1-6, pages 369–372, January/December 1974
-
Anthony CA. Megaloblastic anemias. In: Hematology: Basic Principles and Practice, 2nd ed, Hoffman R, Benz EJ, Shattil SJ, et al. (Eds), Churchill Livingston, New York 1995. p.552.
- J. F. Adams, K. Boddy and A. S. Douglas: Interrelation of Serum Vitamin B12, Total Body Vitamin B12, Peripheral Blood Morphology and the Nature of Erythropoiesis British Journal of Haematology Volume 23, Issue 3, pages 297–305, September 1972
- Utkarsh Achary et al: Hemolysis and hyperhomocysteinemia caused by cobalamin deficiency: three case reports and review of the literature. Journal of Hematology & Oncology 2008, 1:26
- Giammarco, S., Chiusolo, P., Laurenti, L., D’alo’, F., Leone, G., Sica, S., VITAMIN B12 DEFICIENCY: CORRELATION BETWEEN MTHFR POLYMORPHISMS AND CLINICAL AND LABORATORY FINDINGS, Abstract de <<19th Congress of the European-Hematology-Association>>, (Milan, ITALY, 12-15 giugno 2014), <<HAEMATOLOGICA>>, 2014; 99 (Supplement no.1): 762-763
32 commenti
Hello there! I could have sworn I’ve been to this blog before but after reading through some of
the post I realized it’s new to me. Nonetheless, I’m definitely delighted
I found it and I’ll be bookmarking and checking back frequently!
I’m extremely pleased to uncover this great site. I want to to thank you for your time for
this particularly wonderful read!! I definitely really liked
every bit of it and i also have you saved as a favorite to look at new things on your website.
This website really has all of the information and
facts I needed concerning this subject and didn’t know who
to ask.
Howdy! This is my first comment here so I just wanted to give a quick
shout out and tell you I really enjoy reading your blog posts.
Can you recommend any other blogs/websites/forums that cover the same subjects?
Thank you!
Very descriptive blog, I loved that bit. Will there be a part 2?
I’d like to find out more? I’d love to find out some additional information.
I always emailed this webpage post page to all my associates, for the reason that
if like to read it next my contacts will too.
I’m not that much of a online reader to be honest but your
sites really nice, keep it up! I’ll go ahead and bookmark your website
to come back in the future. All the best
Wow! This blog looks exactly like my old one!
It’s on a completely different topic but it has pretty much
the same page layout and design. Outstanding choice of colors!
Good day! I know this is kinda off topic but I was wondering which
blog platform are you using for this site?
I’m getting tired of Wordpress because I’ve had
issues with hackers and I’m looking at alternatives for another platform.
I would be awesome if you could point me in the direction of a good platform.
It is perfect time to make some plans for the future and it’s time to be happy.
I’ve read this post and if I could I wish to suggest you some interesting things
or suggestions. Maybe you could write next articles referring to this article.
I desire to read even more things about it!
I used to be suggested this blog via my cousin. I am no longer sure whether this post
is written by means of him as no one else recognise such
particular about my trouble. You’re incredible!
Thank you!
Excellent blog here! Also your site loads up fast! What host are
you using? Can I get your affiliate link to your host?
I wish my web site loaded up as quickly as yours lol
Great post. I used to be checking constantly this weblog and I am
impressed! Very helpful info specially the final part 🙂 I maintain such information a lot.
I used to be seeking this certain information for a long time.
Thank you and best of luck.
Instead, you should be focusing on your next course of action, and learning
when you should take action – and how you can accomplish your goals
of reestablishing that relationship. When leaving the house, have the child
use the potty even if he says he does not have to go. Potty training can be a frustrating stage in your child’s development for both you
and your child.
This is my first time pay a quick visit at here and i am truly happy to read everthing at single place.
When I originally commented I clicked the “Notify me when new comments are added”
checkbox and now each time a comment is added I get several
emails with the same comment. Is there any way you can remove people from that service?
Thanks a lot!
Useful information. Lucky me I found your web site by accident, and I
am surprised why this coincidence didn’t took place in advance!
I bookmarked it.
After looking at a few of the blog posts on your web site, I honestly appreciate
your technique of writing a blog. I saved as a favorite it
to my bookmark website list and will be checking back soon. Please check out my web site too and
let me know your opinion.
It’s amazing to pay a visit this web page and reading the
views of all friends about this piece of writing, while I am also eager of
getting knowledge.
We are a group of volunteers and opening
a new scheme in our community. Your website offered
us with valuable information to work on. You have done an impressive
job and our entire community will be grateful to you.
Excellent goods from you, man. I’ve take into accout
your stuff prior to and you’re simply extremely excellent.
I actually like what you’ve got right here, certainly like what you are saying
and the best way wherein you assert it. You’re
making it entertaining and you continue to care for to stay it sensible.
I can’t wait to learn far more from you. This is actually a wonderful website.
Quality posts is the secret to invite the users to pay a quick visit the web page, that’s what this site is
providing.
It’s hard to come by knowledgeable people for this subject, but you sound like you know what you’re talking about!
Thanks
Howdy! I know this is kinda off topic but I was wondering if you knew where I could get a captcha
plugin for my comment form? I’m using the same blog platform as yours and I’m having trouble finding one?
Thanks a lot!
I think the admin of this web page is genuinely working hard in favor of his website, because here every data is quality based material.
It’s appropriate time to make some plans for the future and
it’s time to be happy. I have read this post and if I could I wish to suggest you some
interesting things or tips. Maybe you can write
next articles referring to this article. I wish to read even more things about it!
See you soon! Sincerely. dottvolpicelli
I am genuinely pleased to read this webpage posts which consists
of lots of useful data, thanks for providing such statistics.
I am not sure where you are getting your information, but good topic.
I needs to spend some time learning more or understanding more.
Thanks for excellent information I was looking for this information for my mission.
Fastidious response in return of this query with real arguments and telling the whole thing concerning that.
When someone writes an piece of writing he/she keeps the plan of
a user in his/her brain that how a user can be aware of it.
Thus that’s why this piece of writing is perfect. Thanks!