To B12 or Not to B12?
B12 is the vitamin that meat-eaters love to throw in plant-eaters faces. The funny thing is that B12 comes from bacteria and not meat. That being said, B12 is still very important. I learned this because I was so bad about taking pills I neglected to take B12. I have been following a strict oil-free, low fat, plant based diet and after a few years started developing all sorts of vague GI complaints including terrible reflux as well as stomach cramps. I kept trying to connect these symptoms to certain food allergies but nothing was making sense. Eventually, I looked into the B12 issue and learned the hard way that taking it sporadically every few weeks was not enough. So after seeing a low B12 number and elevated MMA I loaded myself with B12. Within weeks all of these vague symptoms went away. I began eating all of the foods I thought I was allergic to without problems and have not had similar symptoms since. Does this prove that my symptoms were due to B12 deficiency? No…but is interesting nevertheless. So let’s talk about B12.
What is it?
B12 is a water soluble vitamin that plays an important role in synthesizing DNA (our genetic material), forming red blood cells, and maintaining proper brain and neurological functioning.
Where can we find it?
Vitamin B12 is made exclusively by bacteria and in today’s hygiene conscious culture, it is found mostly in unfortified foods such as meat, fish, eggs, and dairy or in fortified foods like cereals, yeast extracts, and non-dairy beverages (soy milk, rice milk, etc). Interestingly enough, in developing countries where many vegetables are eaten unwashed, there is less B12 deficiency.
There are claims that you can find B12 in spirulina and some algae. Unfortunately, the studies show that these are mostly, if not entirely, B12 analogues – substances that are very similar to B12. So similar, in fact, that they are recognized and measured in medical tests evaluating B12 levels. These analogues, however, are not biologically active in the human body – meaning they do not perform the functions that vitamin B12 does. As a result, vegetarians and vegans may have a vitamin B12 deficiency even though their tests measure normal levels.
How much do we need?
Normal vitamin B12 levels are between 200-900 pg/ml. Although values less than 200 pg/ml are generally associated with symptoms, some individuals (especially the elderly) may exhibit symptoms with levels between 200-500 pg/ml. For those of you with low-normal levels of B12, it is wise to also check a methylmalonic acid (MMA) level. An elevation in MMA is highly specific for B12 deficiency no matter what the actual serum B12 level is. MMA can only be metabolized with sufficient levels of B12 so elevations in MMA are specific for B12 deficiency.
To maintain adequate levels of B12, the recommended daily allowance is 2.4 micrograms for adults (14 and older), 2.6 micrograms for pregnant females, and 2.8 micrograms for lactating females. Some sources even recommend a daily dose of 5 micrograms, especially if you are a vegetarian or a vegan. These recommendations are great provided you absorb B12 properly. If you are without symptoms and have consistently normal B12 and MMA levels then the amount of B12 you are consuming is enough and is being adequately absorbed.
Who can become deficient?
Unlike most other water-soluble vitamins, B12 can be stored in the body (about 5000 mcg in adults, mostly stored in the liver). This is especially so for people on a typical Western diet of meat and dairy. For these people, B12 is consumed in more than sufficient amounts and deficiency is more often associated with an inability to absorb B12 (ex. pernicious anemia) rather than a nutritional deficiency. Absorption of B12 requires binding with a protein secreted in the stomach called intrinsic factor. The B12-intrinsic factor complex is then absorbed in the last part of the small intestine called the ileum. Problems with intrinsic factor will cause problems with B12 absorption.
Having said that, there are some populations in which nutritional vitamin B12 deficiency could be a concern. These include vegetarians and vegans (especially those that do not supplement or eat foods fortified with B12), the elderly (who don’t absorb B12 as effectively), and newborns of vegan mothers (who have not adequately supplemented B12). This last category is particularly important because infants do not have B12 stores and if they are not getting sufficient amounts with breast-feeding, they could become deficient and exhibit symptoms very quickly.
What are some signs and symptoms of deficiency?
Unusual fatigue, anemia, digestive problems, no appetite, nausea, loss of menstruation, numbness and tingling of the hands and or feet, anxiety, diarrhea, depression, frequent respiratory infections, impotence, and infertility
What about homocysteine levels?
Homocysteine is an amino acid normally found in our blood. Elevated levels have been associated with an increased risk of heart disease and stroke. One proposed mechanism for this is that high homocysteine levels contribute to atherosclerosis (plaque build up in the arteries) by promoting clumping and clotting of certain blood cells (platelets). But high homocysteine levels could just be a by product high methionine consumption which is an amino acid found in high amounts in animal products. So there is question of whether homocysteine actually causes the damage or is just a marker of high animal product consumption (which actually causes the damage).
What does this have to do with B12? Well, vitamin B12 (along with vitamin B6 and folate) is involved in homocysteine metabolism. A deficiency of vitamin B12 would therefore cause homocysteine levels to rise (potentially increasing the risk of heart disease and stroke). However, we cannot say with certainty that elevated homocysteine levels due to B12 deficiency correlate with vascular disease the same way that elevated homocysteine levels due to high animal protein consumption correlates with vascular disease. Conversely, if you have elevated homocysteine levels because of a vitamin B12 deficiency, correcting it should bring your levels down (potentially decreasing your risk of heart disease and stroke). It is important to make this distinction here as several factors can lead to elevated homocysteine levels, including a poor diet (high in animal protein) as well as an inability to properly absorb B12 (pernicious anemia). Elevated levels due to either of these conditions will not be corrected by vitamin B12 supplementation.
What can we do?
For those of you on a typical Western diet, you most likely do not need to worry about a B12 deficiency. The exceptions to this are those of you that are unable to properly absorb B12 (those with pernicious anemia or other digestive disorders and the elderly).
For vegetarians and vegans not consuming foods fortified with B12, checking your levels may be a good idea. If you turn out to be deficient, you may want to consider supplementation. Strict vegans will likely need to supplement so it is important to consider.
If you decide to supplement, use methylcobalamin and not cyanocobalamin. The former is a natural derivative used by the body while the latter is a synthetic version that when broken down to methylcobalamin and adenosylcobalamin, leaves a minimal amount of cyanide behind.
Recommendations on supplementation vary. For those of you who are very deficient (<200) some sources recommend doing a two week loading period (taking 2000micrograms under your tongue) then taking 1000micrograms every day for maintenance and rechecking your level after a month or two. Other sources recommend a daily maintenance dose of 5micrograms. The goal with supplementation is to take the lowest amount required to maintain adequate B12 levels. Your best bet is to check your levels, try one of these methods and then re-check after a month or two. At that point you can assess whether you need to decrease, increase, or maintain your current dose.
NOTE: for those people with allergies, please be sure to read the ingredients (active and inactive) of all supplements before use.
REFERENCES:
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Herbert V. Vitamin B-12: plant sources, requirements, and assay. Am J Clin Nutr 1988;48:852-8.
Robert C. Oh, et al. “Vitamin B12 Deficiency” American Family Physician March 1, 2003
Robert A.J.M. van Dijk, Jan A. Rauwerda, Mieke Steyn, Jos W.R. Twisk, and Coen D.A. Stehouwer. Long-Term Homocysteine-Lowering Treatment With Folic Acid Plus Pyridoxine Is Associated With Decreased Blood Pressure but Not With Improved Brachial Artery Endothelium-Dependent Vasodilation or Carotid Artery Stiffness: A 2-Year, Randomized, Placebo-Controlled Trial. Arterioscler Thromb Vasc Biol. 2001 21: 2072-2079.
Selhub J, Bagley LC, Miller J, Rosenberg IH. B vitamins, homocysteine, and neurocognitive function in the elderly. Am J Clin Nutr. 2000 Feb;71(2):614S-620S.
van Dusseldorp M, Schneede J, Refsum H, Ueland PM, Thomas CM, de Boer E, van Staveren WA. Risk of persistent cobalamin deficiency in adolescents fed a macrobiotic diet in early life. J Clin Nutr. 1999 Apr;69(4):664-71.
Watanabe F, Katsura H, Takenaka S, Fujita T, Abe K, Tamura Y, Nakatsuka T, Nakano Y. “Pseudovitamin B(12) is the predominant cobamide of an algal health food, spirulina tablets.” J Agric Food Chem. 1999 Nov;47(11):4736-41.
www.nlm.nih.gov/MEDLINEPLUS/ency/article/003705.htm
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