My friend Adrienne said if vitamin B12 was a person, she thinks I might marry it. Maybe she’s right. I’m a big fan. Oh, I like lots of the vitamins, don’t get me wrong… love me some vitamin D for example, but you can overdose vitamin D, so you need to exercise some caution, and some feel supplementation of vitamin D can cause problems if you suffer from a autoimmune disease. As far as I know, while B12 is the only B-vitamin that seems to be stored by the body (in the liver), there are no known risks of overdose.
Where does vitamin B12 come from? It’s found in meat and dairy products. Vegans should consider vitamin B12 supplementation. Of course, my interest is in cats and if they’re fed properly (recognizing they are true carnivores) they should be getting vitamin B12 in their diet, but most commercial foods and homemade recipes supplement all the B-vitamins, just in case. The B-vitamins are water-soluble and, as I noted, generally not stored by the body, so there’s no known risk of overdose.
What can cause deficiency of Vitamin B12 in cats? Anything that causes excessive drinking and/or urination (diabetes, hyperthyroidism, kidney disease, etc.) can deplete B12 and the other B vitamins as they are “washed out” of the body. Giving sub-q fluids could deplete vitamin B. Chronic diarrhea can also deplete B12 as most B-12 is lost in fecal matter. Cats with an inflamed gastro-intestinal tract (such as cats with IBD) may not absorb B12 properly as it’s absorbed in the intestines. Vitamin B12 deficiency can cause anemia, neuropathy, other neurological issues, etc.
Vitamin B12 is also known as cobalamin. There are various forms of cobalamin, including methylcobalamin, cyanocobalamin, adnosylcobalamin and hydroxocobalamin. Oral and injectable supplements most frequently use cyanocobalamin. A portion of cyanocobalamin would be broken down by the body into methylcobalamin, a coenzyme form of B12. The methyl- form most directly affects the central nervous system. Since cyano- and methyl- forms are the forms most readily available for use in supplementation, I’ll focus on those two.
I noted the possible causes for vitamin B12 deficiency. You can generally *assume* deficiency if one of those conditions exists (which is what I do, since there’s no risk of overdose), or there are a few strong indicators of a deficiency:
- neuropathy – most commonly seen in poorly-regulated diabetic cats, the cat will generally be down on its hocks, that is, rather than being up on their paws or “toes”, they’ll be flat on their legs up to the joint similar to our knee or elbow. I have a video of a diabetic foster cat that came to me with neuropathy.
- GI function tests – blood test can now test for cobalamin and folate (vitamin B9). This test is most often done when cats display gastro-intestinal symptoms, such as vomiting or diarrhea.
- anemia – a blood test may show decreased hematocrit (HCT) or packed cell volume (PCV) results
How to supplement B12, in my opinion, on WHY you are supplementing. For the vast majority of cases, I feel oral supplementation is the route to take. In fact, since there’s really little-to-no reason to think they are deficient in B12 but not deficient in other B vitamins – I prefer to supplement with oral B-complex. If you’re making your own cat food, you can follow the recipes at catinfo.org, catnutrition.org, or blakkatz.com. If not, I’d follow the directions on a vitamin for cats, or use a B-25 product designed for humans (or half of a B-50 product, or one-quarter of a B-100 product). My favorite brands (since I’ve found people often want specific recommendations) are:
- Life Extension Cat Mix (a nice multi-vitamin with taurine and digestive enzymes as well as methylcobalamin)
- Jarrow Formula’s B-Right (a B-complex product containing methylcoblamin, and it’s lower in odor which is nice if mixing in food – each capsule is about a B-25 strength
- Now Food’s B-50 capsules or powder (the powder being nice for making food, rather than opening capsules)
- Source Natural’s or Jarrow Formula’s methylcobalamin (if you do choose to supplement only B12)
Having said that, pretty much any product is fine! Many diabetic caregivers recommend Xobaline. The sublingual vitamin B12 products like Xobaline and Source Naturals and Jarrow do contain a little sugar and flavorings as they’re intended for humans to dissolve under the tongue. Obviously that is not happening with a cat. I haven’t had any issues with the small amounts of sugar in these products, but if they concern you, I’d recommend one of the other products noted above.
I noted that oral B-complex was appropriate for the vast majority of cases. When is it not? Two cases, in my opinion – when you’re giving sub-q fluids and when there’s a case of IBD. There’s no reason you can’t give B-complex orally when giving sub-q fluids, but since we’re already giving the fluids I simply think it’s much easier to inject B-complex into the bag of fluids (Lactated Ringers or whatever is appropriate). Personally, I inject 2.5 cc’s of injectable B-complex (based on the strength of my vial) into a 1000 mL bag of fluids. I can get a very large vial of B-complex from my veterinarian for around $20.
More information at Feline Outreach
As for IBD, if vitamin B12 is not being absorbed correctly by the intestines, supplementing orally is going to be a struggle. Therefore, the easiest option in my opinion is cyanocobalamin injections. Texas A&M has a protocol specifically for IBD patients. Injectable cyanocobalamin is available by prescription in the U.S.
More information at Feline Outreach
You might have noticed I did not include diabetic neuropathy among my reasons I would choose to supplement in a route other than oral B-complex. I personally feel oral B-complex is fine for these cases. Many caregivers feel supplementing diabetic cats with methylcobalamin (rather than B-complex or cyanocobalamin) is the most effective route to alleviating neuropathy. (See Jasper’s page and Mr. Kitts’ Injectable Methylcobalamin Info.) Personally, I feel the KEY to alleviating neuropathy is first and foremost to get the cat’s blood sugar levels regulated. I prefer tight regulation, keeping the blood glucose as close as possible to normal. I also supplement with either B-complex and/or methylcobalamin. You can get methylcobalamin in injectable form, but it’s less readily available.
For neuropathy in diabetic cats, caregivers have traditionally given 3 to 5 mg (3,000 to 5,000 mcg) daily orally. However, that’s most likely because those are the most commonly sized oral tablets NOT because the cat needs that much.
… and now, for some quotes and links!
Effectiveness of vitamin B12 on diabetic neuropathy: systematic review of clinical controlled trials.
Three studies involved the use of vitamin B complex (including B12) as the active drug, and four used methylcobalamin.
Both the vitamin B12 combination and pure methylcobalamin had beneficial effects on somatic symptoms, such as pain and paresthesia.
With both the vitamin B12 combination and pure methylcobalamin, symptomatic relief was greater than changes in electrophysiological results.
Absorption of vitamin B12 is a complex process, subject to problems at several points.
B12 from animal food enters the stomach as part of animal proteins and must first be liberated by pepsin and hydrochloric acid. Free B12 then attaches to R-protein, which is released from the salivary cells and parietal cells (the same cells that release hydrochloric acid). To be absorbed efficiently, B12 must attach to a protein called intrinsic factor (IF) which is also secreted in the stomach. This cannot happen until the R-protein complexes are broken down by pancreatic enzymes in the small intestine. B12 then binds with the intrinsic factor and proceeds through the gut to the lower portion of the small intestine, where the intrinsic factor-B12 complex attaches to cell receptors, a process that involves calcium.
Thus, deficiencies in pepsin, hydrochloric acid, R-protein, pancreatic enzymes, intrinsic factor, calcium and cell receptors can all lead to B12 deficiency through blocked absorption.
Once in the bloodstream, transport proteins bind to B12 and deliver it to the cells. Within the cells, enzymes liberate B12 from the protein complex and convert it to its two coenzyme forms, methylcobalamin and adenosylcobalamin. Deficiency in the required enzymes can block this conversion.
Because the absorption process is so complicated, and therefore subject to various blocks, many people–particularly the elderly–may develop deficiencies even though they are taking in plentiful B12 in their food. Fortunately, the body absorbs about 1-5 percent of free B12 by a process of passive diffusion. Thus supplementation with large doses of crystalline B12 or with foods extremely rich in B12 can successfully treat deficiencies caused by compromised protein digestion or lack of R-protein, intrinsic factor or pancreatic enzymes. Supplementation with the coenzyme forms methylcobalamin and adenosylcobalamin (the forms found in the cells) can overcome B12 deficiency in the cells caused by lack of, or malfunction of, conversion enzymes.
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