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

像凱澤永久醫療集團—美國最大的健康維護組織之一

diets “the new normal for [its] patients and employees”; or the president of the

他們希望蔬食能成為病人和員工的新生活常態

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

美國心臟醫學會主席—金·威廉斯醫師，一向極力推崇純素飲食

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

美國哈佛大學營養學系主任—魏勒特博士，也建議我們以植物性蛋白質取代動物性蛋白質

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

由於大眾對植物營養有越來越多認識

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

「純素飲食」與「維生素 B12 缺乏」的相關議題也隨之受到關注

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

有些人可能會問「如果純素飲食真的健康又自然，我為何還要

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

留意維生素 B12 水平，或服用維生素 B12 補充劑呢？ 」這是個很好的問題

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

現在就讓我們來看看當前一些與維生素 B12 的相關資訊，以及造成

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

「維生素 B12 缺乏」和「維生素 B12 普遍攝取不足」的原因，維生素 B12 也叫作鈷胺素—一種水溶性維生素

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

維生素 B12 是由細菌產生，並非來自動物或植物，所以動物，包含人類

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

都必須直接或間接經由細菌取得維生素 B12 養分，在過去，來自細菌的維生素 B12

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

會自然存在於植物性食物中，而且該維生素 B12 的來源更為可靠，然而今日，在現代的衛生規範下

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

我們的食物得到更徹底的清潔與消毒，加上土壤

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

接觸到抗生素與殺蟲劑，因而導至眼前的情況，這也是大部分的植物都不再是

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

維生素 B12 可靠來源的原因，但若為了讓我們的食物保有更多細菌

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

而回頭去撤除食品衛生規範，似乎也不太妥當，因此

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

我們也有遇過不食用動物性食品的人維生素 B12 水平較低的情況

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

但我們該了解到的是，在一般人口當中，維生素 B12 缺乏症並不罕見

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

無論採用哪種飲食方式，即使是食用大量動物性食品的人，也會有維生素 B12 缺乏的可能

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

這篇美國臨床營養雜誌的評論指出「由多份研究報告顯示—

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

拉丁美洲有大約 40% 的兒童和成人，都有維生素 B12 缺乏

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

或瀕臨缺乏的情況」患有維生素 B12 缺乏症的美國人口當中

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

年齡在 40-59 歲之間者占 4%，60 歲以上則佔了 6%

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

在 60 歲以上的人口當中，出現維生素 B12 瀕臨缺乏的情況者佔約 20%，在一般人口當中

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

維生素 B12 缺乏是一種很普遍的現象，另一則評論，也綜合分析了九份美國的研究報告

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

發現 40% 的病患，都有不明的維生素 B12 水平偏低的情況，研究人員將此症狀

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

稱為「食物維生素 B12 吸收不良症」即食物中所含的維生素 B12

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

無法被正常吸收，所幸這樣的人，仍能夠吸收

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

結晶型的維生素 B12 —它是一種存在於「補充劑」和「 B12 強化食品」中的 B12 形態

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

所以不管是哪一種飲食習慣，身體在利用或吸收維生素 B12 時

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

有很多環節都可能出差錯，因為吸收維生素 B12 的機制

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

相當複雜，並且需要特定的生理條件，才能順利吸收足夠的維生素 B12

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

以這個關健的生理要素為例，維生素 B12 必須先和

called “intrinsic factor,” which is produced in the parietal cells in our stomach.

胃壁細胞分泌的「內在因子」結合

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

接著，大部分的結合物會在小腸的

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

第三部分 (迴腸) 被吸收，因此，若這些部位的消化道出問題

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

即會導致維生素 B12 缺乏的情況，例如幽門桿菌感染、

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

酗酒、吸菸、萎縮性胃炎，以及一些會造成腸胃蠕動緩慢的病症

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

像是糖尿病、硬皮病、食道狹窄、大腸憩室症

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

這些都和維生素 B12 的缺乏有關，有很多情況都會影響消化道功能

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

導致維生素 B12 缺乏，大至人們熟悉的胃繞道

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

或胃切除手術，小至較常見的上腸道細菌過度滋生

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

但幸運地是，即使有細菌過度滋生的問題

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

仍可適當吸收添加於食品和補充劑中的結晶型維生素 B12

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

有些藥物也會造成我們的維生素 B12 缺乏，包括長期使用

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

制酸劑 (胃酸抑制藥)，附帶一提，制酸劑在美國

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

是最常被使用的藥物，胃酸是將

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

維生素 B12 與食物蛋白質分離的必要物質，經分離的維生素 B12 才能被人體吸收，因此

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

抑制胃酸分泌的藥物，會造成維生素 B12 吸收不良

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

而這份研究的結論是，維生素 B12 缺乏症與過去或現在使用制酸劑有關，最後要提的是

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

有些人的體內帶有維生素 B12 轉運子變異基因

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

該基因和體內的 B12 水平偏低也有關係，有 20% 的人口都帶有這種變異基因

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

由此可見，攝足維生素 B12 是人人都得多加留意的環節，而維生素 B12 的缺乏

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

對大眾來說則是相當普遍的現象，因此，不管採用哪種飲食方式

people need to be mindful of. Now moving on to other issues – where can we find vitamin B12?

都須要留意維生素 B12 的水平，現在繼續下一個問題「維生素 B12 該由哪裡取得？」

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

請記得，維生素 B12 是來自細菌，我們腸道內有

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

排泄物以及製造維生素 B12 的細菌，但這些能製造維生素 B12 的細菌

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

大部分都存於大腸之中，而位於大腸下端的小腸末端 (迴腸)

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

則是大部分的 B12 被吸收的地方，所以許多腸道內所產生的 B12

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

都會隨著排泄物被排出體外，不過根據一些研究的顯示

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

位於小腸內的細菌，也能合成非常大量的維生素 B12

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

但該數量是否能達到我們營養上的需求，目前尚不明確

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

人類的排泄物含有大量的維生素 B12，接下來的部分可能會讓人感到不舒服

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

其實我們有時候會不小心吃進排泄物，這件事要帶入

another source that has B12 from bacteria – animal foods. Now, just like us, animals

另一個源自細菌的維生素 B12 來源—動物性食品，動物就和我們一樣

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

本身不會製造維生素 B12，牠們是透過直接或間接的方式，從細菌獲得維生素 B12

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

在食物中添加糞便就能使維生素 B12 的含量上升，科學家甚至發現

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

「添加糞便的土壤所長出的菠菜葉含有維生素 B12」

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

許多動物性食品中，都含有大量被細菌汙染的糞便

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

感謝 FDA (美國食品藥物管理局) 的肉品監測記畫讓我們得知，在收集超過七年的肉品樣本中

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

含有糞便細菌的樣本比例，雞胸肉佔 98%、火雞絞肉佔 94%、牛絞肉佔 93%

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

豬排肉的比例稍低，佔 86.9%，但含量仍非常高，畜牧業甚至會

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

使用某些動物的糞便來飼養其他動物，雖然這樣

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

可提高肉品的維生素 B12 含量，但同時也會造成嚴重的健康問題

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

除了由細菌汙染所造成的相關感染性疾病外

products – regardless of how clean they may be – are not the best source for vitamin

動物性食品—不管多衛生，都不是最好的維生素 B12 來源

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

因為食用動物性食品，會造成體內某些物質的增加

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

如促癌激素 IGF-1、膽固醇、氧化三甲胺、磷、血基質鐵，以及其他

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

會影響健康的物質，添加維生素 B12 的植物性食品，才是較理想的維生素 B12 來源

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

像非動物性的植物奶和營養酵母之類的食品，而某些植物

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

也富含維生素 B12，這是因為在生產的過程中

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

遭到了細菌的汙染，或是因為它們和細菌共生的關係

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

例如，這篇營養雜誌的文章，指出以下幾種含有維生素 B12 的食物：

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

天貝—一種黃豆發酵食品，其生產需藉細菌來發酵

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

以及藉細菌發酵的蔬菜產品、各式各樣的茶葉、

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

香菇的子實體，與其他類型的蕈類，當然，還有被大量食用的藻類

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

都含有或多或少的維生素 B12，在未經消菌的湖水中，也可以發現維生素 B12

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

雖然一般來說，我們不鼓勵生飲湖水

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

但我們也能藉由這件事再次了解到，維生素 B12 源自細菌，而非來自動物

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

再重複一次，若為了讓飲食中出現更多能夠製造維生素 B12 的細菌

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

而回頭撤除食品衛生規範恐怕不恰當，因為細菌也可能導致疾病

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

而透過動物性食品來取得維生素 B12 也不是一種好方法

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

因為它會造成前面所提到的那些問題，經由動物性食品而產生的健康問題

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

就健康的角度而言，以植物性食品為主的「純素飲食」才是最理想的，如同哈佛

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

「健康飲食餐盤」的建議—選擇蔬食，以植物為主的飲食方式是最佳的

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

所以我的建議是：定期檢驗維生素 B12 水平，或服用補充劑，或者兩者並行

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

還有，食用添加維生素 B12 的食品，我個人並沒有

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

服用維生素 B12 補充劑，但我每年都會做維生素 B12 水平檢驗，我採蔬食為主的純素飲食

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

不吃任何動物製品，已有五年之久，而我最近期的

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

年度健康檢查報告顯示，維生素 B12 水平為 884 pg/mL (每毫升含 884 皮克) 在正常範圍內

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

假使數值不在正常範圍內，我只要服用補充劑即可，這很容易解決

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

當然我也會持續留意我的維生素 B12 水平，也建議所有的純素者

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

與非純素者都這麼做，非常感謝大家