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  • More and more mainstream health authorities are promoting plant-based vegan dietslike

  • Kaiser Permanente, one of the largest HMOs in the U.S. that wants to make plant-based

  • dietsthe new normal for [its] patients and employees”; or the president of the

  • American College of Cardiology, Dr. Kim Williams, who vigorously promotes a vegan diet; or the

  • chair of Harvard's Department of Nutrition, Dr. Walter Willett, who recommends choosing plant proteins over animal proteins.

  • As we see this awareness about plant-based nutrition increase,

  • concern is sometimes expressed about vegan diets and vitamin B12 deficiencies.

  • Some might ask, “If a vegan diet really is healthy and natural, why do I need to watch

  • my vitamin B12 levels or take vitamin B12 supplements?” And this is a great question.

  • So, let's review the current information about vitamin B12, and the causes and prevalence

  • of vitamin B12 deficiencies. Vitamin B12, also called cobalamin, is a water-soluble vitamin.

  • It is produced by bacteria, not animals or plants. So animals, including humans, must

  • obtain vitamin B12 directly or indirectly from bacteria. In the past, vitamin B12 from

  • bacteria was naturally and more reliably present in plant foods. Today, however, with modern hygienic practices

  • that more deeply clean and sanitize our produce, along with the soil

  • being exposed to more antibiotics and pesticides, most plant foods are no longer reliable sources

  • for vitamin B12. And, it's probably not a good idea to go back and reverse sanitary

  • practices just to get more of this bacterial product in our diet. For this reason, we have

  • seen that people who abstain from eating animal foods can have lower levels of vitamin B12.

  • But it's important to also know that vitamin B12 deficiencies are not uncommon in the general

  • population regardless of diet, even among many those eating large amounts of animal foods.

  • As this review in the American Journal of Clinical Nutrition notes, "across studies

  • in Latin America, ≈40% of children and adults [were found to have a] deficient or marginal

  • status" of vitamin B12. In the U.S., full-blown vitamin B12 deficiencies are estimated to

  • occur in about "≈4% of those aged 40-59", and "≈6% of those aged ≥60", with approximately

  • 20% of those over the age of 60 having a marginal status. That's a really high prevalence

  • for a vitamin deficiency in the general population. Another review that combined nine studies

  • in the U.S. found that 40% of patients had unexplained low B12 levels, which the researchers

  • attributed to what's called "food cobalamin malapsorption", where the B12 that is naturally

  • present in foods is simply not absorbed. Luckily, these people are still able to absorb the

  • crystalline form of vitamin B12, which is the form that is used in supplements and B12-fortified foods.

  • So, it happens to be the case that there are many things that can go wrong with

  • our bodies using or absorbing vitamin B12, regardless of our diet, because the absorption

  • process is fairly complex and requires specific physiologic elements to take place for it to occur adequately.

  • One crucial factor, for example, is a step where vitamin B12 has to be coupled with a substance

  • calledintrinsic factor,” which is produced in the parietal cells in our stomach.

  • Then, most of the absorption for this coupled pair occurs in the third

  • segment of the small intestine (or ileum). As such, any problem in those portions of

  • our gastrointestinal tract can lead to B12 deficiencies. For example, H. pylori infection,

  • alcohol abuse, smoking, atrophic gastritis, and conditions that slow the movement of food in our gastrointestinal tract

  • (such as diabetes, scleroderma, strictures, diverticula) are

  • all associated with vitamin B12 deficiencies. So many conditions that affect the gastrointestinal

  • tract can lead to B12 deficiencies, from something big and notorious like a gastric bypass or

  • resection, to something much more common like bacterial overgrowth in the upper intestine.

  • But, fortunately, here too, with bacterial overgrowth, the crystalline form of vitamin

  • B12, which is the form that is added to fortified foods and used in supplements, can still be absorbed okay.

  • Some medications can also cause vitamin B12 deficiencies, including long-term

  • use of antacids (or acid-suppressing drugs) – which, by the way, have been classified

  • as the most commonly used pharmaceuticals in the U.S. Gastric acid in our stomach is

  • required to separate vitamin B12 from dietary proteins for it to be absorbed. Thus,

  • medications that suppress the production of gastric acid can lead to B12 malabsorption.

  • This study concluded, both previous and current antacid use was associated with B12 deficiency. Lastly,

  • there is also a genetic variant of a B12 transporter in our body that some people have that is

  • associated with low B12 levels, and this genetic variant is present in 20% of the population.

  • So, as you can see, vitamin B12 adequacy is a delicate matter, and deficiencies are fairly

  • common in the general population. So, regardless of one's diet, it's something that

  • people need to be mindful of. Now moving on to other issueswhere can we find vitamin B12?

  • Well, let's remember it's made from bacteria. Our own intestinal tract contains

  • feces and B12-producing bacteria. However, we think that the majority of the B12 produced

  • by bacteria in our gut occurs in the large intestine, which is further down from the

  • small intestine where most of the B12 absorption takes place. So, a lot of the B12 produced

  • in our intestine is excreted in our feces. Some studies have shown though that bacteria

  • in our small intestines may also synthesize significant amounts of vitamin B12, but it's

  • not clear whether sufficient amounts are made and absorbed to meet our nutritional needs.

  • So our own human feces contain large quantities of vitamin B12. As unpleasant as this may

  • sound, we actually do end up inadvertently eating feces sometimes. Which brings me to

  • another source that has B12 from bacteriaanimal foods. Now, just like us, animals

  • don't make vitamin B12. They obtain it either directly or indirectly from the bacteria that makes it.

  • Also adding manure usually results in higher vitamin B12 levels. Scientists even found

  • that adding manure to the soil where spinach was growing added B12 to the spinach leaves.

  • And, many animal foods have significant amounts of manure and thus bacterial contamination.

  • Thanks to the FDA retail meat monitoring program, we know that 98% of chicken breasts sampled

  • over seven years were contaminated with fecal bacteria; ground turkey 94%; ground beef 93%;

  • and pork chops, a little bit lower at 86.9%, but still very high. Manure from some animals

  • is even used to feed other animals in the livestock industry. And while this can raise

  • B12 levels in the animal fed the manure, it also raises some serious health concerns.

  • But apart from infectious disease related concerns with bacterial contamination, animal

  • productsregardless of how clean they may beare not the best source for vitamin

  • B12, because consuming them results in us having increased levels of cancer promoting

  • hormone IGF-1, as well as cholesterol, TMAO, phosphorus, heme-iron, and other substances

  • that are problematic for our health. Better sources of B12 are fortified plant foods,

  • like non-dairy milks, nutritional yeast and the like. And apparently some plant foods

  • can have considerable amounts of vitamin B12 due to bacterial contamination during the

  • production process, or because they live a symbiotic relationship with bacteria. For

  • example, this article in the journal Nutrients found the following plant foods to contain vitamin B12:

  • tempe, which is a fermented soybean-based food, due to bacterial process in its production;

  • vegetable products that are fermented with bacteria; various types of tea leaves; fruiting

  • bodies of shitake and another types of mushrooms; and, apparently, the most widely-consumed algae

  • also contains levels of vitamin B12. B12 can also be found in lakes if the water has not been sanitized.

  • And although it's not a good idea to drink un-sanitized water in general,

  • we really get the picture of how this is a bacterial and not an animal product.

  • Again, it's not a good idea to go back and reverse sanitary practices in order to get

  • more of this bacterial product in our diet, since bacteria can also cause disease.

  • It's also not a good idea to get vitamin B12 from animal foods, given the problematic

  • health issues associated with consuming animal foods that I mentioned earlier.

  • From a health standpoint, it's best to go with a plant-based vegan diet. Just like Harvard's Healthy

  • Eating Plate recommends, “Go with plants. Eating a plant-based diet is [best].” So,

  • what I recommend is to monitor vitamin B12 levels or take a B12 supplement, or both,

  • and include plant-based B12-fortified foods in your diet. I personally don't take a

  • B12 supplement, but I have my B12 levels checked every year. I've been eating a plant-based

  • vegan diet with no animal products for about 5 years now. And, at my most recent insurance-required

  • annual checkup, my B12 level was 884 pg/mL, which is within the normal range.

  • If it wasn't within normal range, then I would just take a supplement, which is an easy fix.

  • But, I definitely keep an eye on my levels, and I recommend both vegans

  • and non-vegans alike to do the same. Thank you very much.

More and more mainstream health authorities are promoting plant-based vegan dietslike

Subtitles and keywords

B2 H-INT b12 vitamin b12 vitamin bacteria plant bacterial

Vitamin B12: Questions Answered

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    羊奶   posted on 2018/04/06
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