Understanding B12

edition 3This the unedited version of my B12 article from Edition 3 of

The Australian Vegan Magazine

You can order your back copy here.


Vitamin B12 is produced by microorganisms, bacteria, algae and fungi. Humans have B12-producing microorganisms living in our intestinal tracts, but the quantity of B12 in our mouths is far too small to prevent deficiency and the B12 we produce in our intestines is too far downstream of our absorption site. Non-vegans can source B12 from eating the flesh, eggs, and milk of other animals, all of which are contaminated with the B12-producing microorganisms that live in the intestinal tracts of animals, but vegans need to supplement.

“If you could grow your vegetables in truly organic soil, without tons of pesticides, and you ate those vegetables with minimal washing, you would likely get enough B12,” says Dr Garth Davis in his book Proteinaholic. Garth decided to try sourcing his B12 solely from vegetables grown at “a very organic local farm… complete with grubs, soil and many insects.” He says his B12 levels remained stable during this time, but Garth doesn’t say how long his experiment lasted. I suspect it wasn’t long, given that he was “kind of grossed out by the number of insects.” Garth now prefers the much cleaner organic produce from supermarkets and farmers’ markets and takes a B12 supplement once a week.

Stories like this need to be treated with caution. Aside from the fact that there are no proper research studies proving that uncleaned, organic produce can correct a B12 deficiency, there are no guarantees your wee patch of organic soil will provide all the B12 you need, especially if you are squeamish about consuming bugs and soil, and you would rather not use animal manure as a fertiliser. Garth may have been able to survive for months or perhaps even years on unwashed organic produce, but that doesn’t mean he wasn’t eventually going to become deficient. Nor does his experiment prove anything about how long you or I might last without B12 supplementation. If you already had excellent B12 stores in your liver from years of meat, dairy and egg consumption before you went vegan, and your body is particularly good at recycling it’s B12 stores, you could thrive for years before the first deficiency symptoms began to appear.

In Becoming Vegan- comprehensive edition: the complete reference to plant-based nutrition, authors Brenda Davis RD and Vesanto Melina tell the story of a North American study which followed a group of 49 adults on a vegan or near-vegan diet without B12 supplementation for 2-4 years. Like Garth, these people were trying to course their B12 from plant-based sources such as raw fruits and vegetables, probiotics, fermented foods, dried greens, dulse, nori, blue-green algae, or spirulina. Others were betting on intestinal production, not knowing that the B12 absorption site is a long way downriver from our B12 production site in the gut. Not surprisingly, testing showed that three-quarters of the 49 adults were all in the early stages of deficiency, even though none of them reported any deficiency symptoms.

“You may not realize you have a deficiency until it’s too late,” says plant-based dietician Julieanna Hever in her book The Complete Idiots guide to Plant-Based Nutrition. “Symptoms include decreased sensation, dementia, difficulty walking, loss of bladder or bowel control, weakness, optic atrophy, and depression.” The longer it takes to address a B12 deficiency, the greater the risk of irreversible nerve damage and permanent paralysis, because B12 maintains the muscle sheaths that surround and protect our nerve fibres. For babies, the stakes are even higher: deficiencies in early pregnancy can lead to neural tube defects, and deficiencies in infancy can lead to coma or death.

While long term B12 deficiency damages nerve cells, short term deficiency damages blood cells. In ‘megaloblastic anaemia’ a lack of B12 hampers the ability of our bone marrow to produce red blood cells, resulting in symptoms such as fatigue, weakness, shortness of breath, palpitations and pale skin. These symptoms can serve as an early warning of nerve damage coming later, but unfortunately, they are often mistaken for iron or folic acid deficiency. To make matters worse, supplements containing folic acid can resolve the symptoms without addressing the underlying cause, and the hidden B12 deficiency goes unaddressed for longer, taking you another step closer to irreversible nerve damage. A healthy vegan diet is full to overflowing with folate, the natural food-based form of folic acid, so some vegans have megaloblastic anaemia (and hence B12 deficiency) without any obvious symptoms at all.

When the vegans in the North American study found out they were B12 deficient in spite of their lack of symptoms, 25 of them very kindly agreed to take part in a follow up study. They continued their diet for another three weeks, but with one of the following modifications: one group added sublingual vitamin B12 supplements, another group used nutritional yeast, and the third group took probiotics. The B12 supplements were highly effective in quickly reversing deficiency. The nutritional yeast had some impact but was less reliable, with the deficiency taking longer to reverse. Probiotics were ineffective.

It was once thought that we could source vitamin B12 from plant-foods such as fermented soy products (eg tempeh and miso) and spirulina, but it turns out the B12 found in these foods are “posers”, as my husband’s Irish cousins would put it. Technically referred to as “inactive analogues”, these B12 imposters look like the real deal but they can’t do all of the important jobs that real B12 does in your body. Worse, they block our B12 receptor sites, stopping our real B12 from working its magic. As Davis and Melina say in Becoming Vegan “deficiency symptoms or lab results have been shown to worsen when vegans try to use dulse, nori, and spirulina as sources of this essential nutrient.”

Algaes such as Chlorella and Aphanizomenon flos-aquae seem to contain real B12, but more research needs to be done to find out how available this is to the human body and whether it can actually reverse B12 deficiency. To date, the results of research studies have been inconsistent which means the only plant-based foods we can rely on for genuine B12 are foods that have been fortified with artificially added B12. In contrast to the United States, where foods are extensively fortified with vitamin B12, Australia permits only a limited number of foods to be fortified with vitamin B12. This includes selected soy milks, nutritional yeast, and vegetarian meat analogues such as soy-based burgers and sausages. Nutritional yeast is a favourite B12 source for many of us, its cheesy flavour a welcome topping sprinkled on many a dish, but if you are relying on nutritional yeast as your sole B12 source, add a generous serving to each and every meal and make sure you read the label to check the B12 dose: not all nutritional yeasts are created equal.

To absorb vitamin B12 from food, hydrochloric acid in your stomach must first separate vitamin B12 from any protein it’s attached to. Once it’s freed up, B12 can bind then with a protein made by the stomach called intrinsic factor, which enables B12 to be absorbed from the small intestine. There is only enough intrinsic factor excreted per meal to absorb 2-4 mcg of B12, and your B12 receptors become quickly saturated with only small amounts of B12, so if a large dose is consumed in one go, a lot of it goes to waste. With a 250mcg dose for example, your receptors can only absorb about 1.5mcg and can’t absorb any more for the next 4 to 6 hours.

The take home message here is that the less frequently B12 is ingested, the higher the dose needed. If you want to play it safe with B12, follow one or a combination of the following approaches:

1) 3 servings per day or B12 fortified foods with each serve containing at least 2mcg.

2) Take a daily B12 supplement containing at least 25mcg (more if you are over the age of 50). It’s fine to take up to 100 or 250mcg daily.

3) Twice a week, take 1000-2500mcg of vitamin B12 in supplement form.

Keep in mind that the advice regarding B12 varies from one country to another; there is no international consensus. The recommended doses listed above are for cyanocobalamin, which is the most stable form of B12, and the most well researched in terms of effectiveness and safety. Most vegan doctors, dieticians and naturopaths like myself use and recommend cyanocobalamin, but you will hear a lot of noise on the internet about cyanocobalamin being unsafe because it contains cyanide. This might sound scary, but a 2,500mcg B12 tablet contains 0.2% of the lowest amount of cyanide that could be toxic for a 50kg person. To put this into context, 1 level tablespoon of flaxseeds contains 30 times as much cyanide. Small amounts of cyanide are found throughout nature and are perfectly harmless. It’s only large doses that are dangerous.

Once inside the body, cyanocobalamin is converted into methlycobalamin, one of the active forms of B12. This conversion isn’t as efficient in people who smoke cigarettes or have kidney problems, so these people are better served using supplemental methylcobalamin, which only became legally available in tablet form in Australia a few years ago. Very little research has been done on this less-stable form of B12, which might be why our TGA (Therapeutic Goods Administration) was initially wary. We still don’t know the ideal dosage but it’s thought that as much as 1000mcg daily might be required. Methylcobalamin is currently the most popular B12 form promoted via the internet, and while it isn’t as stable (or as affordable) as cyanocobalamin, TGA approval is a good vote of confidence.

Based on research so far, it doesn’t appear as though B12 has an upper limit resulting in toxicity (excess is excreted in urine), but the long-term effects of daily intake of 1000mcg doses of cyanocobalamin doses is unknown, and high doses definitely don’t agree with everyone. In my facebook group Ask the Vegan Naturopath, the occasional member agonises over whether to abandon their veganism because their B12 supplements seem to be causing outbreaks of acne or unbearable jittery feelings which make them feel anxious and unsettled. Experimenting with different forms and brands of B12 supplements, changing the time of day supplements are consumed, and initially lowering the dose then gradually increasing over the space of a few weeks until recommended levels are reached, are strategies that have proved effective in keeping these vegans vegan. Vitamin B supplements are quite stimulating so it’s a good rule of thumb to treat them like coffee and take them earlier in the day rather than in the evening, and some people do better on multi-B’s rather than B12-only (and visa versa).

B12 deficiencies are often spotted during routine blood tests. With both B12 and folate deficiencies, the amount of hemoglobin and the red blood cell count may be low and the cells themselves are abnormally large. White blood cells and platelets also may be decreased in number. A test can be done to check our blood levels of B12, but these don’t measure our B12 reserves, and it’s possible our government has set the lower limit for diagnosing B12 deficiency too high. On the 9th December 2015, SA Pathology wrote an article on their website updating doctors about changed Medicare rules regarding the provision of B12 deficiency tests, and noted that “up to 30% of patients with B12 deficiency may show serum B12 levels in the lower normal range.”

Thankfully, there are other tests used that help doctors properly diagnose B12 deficiencies and assess underlying causes. Elevated levels of a chemical called homocysteine are a useful indicator for vitamin B12 deficiency, because serum homocysteine levels increase as vitamin B12 stores fall. This isn’t a definitive test however, because homocysteine levels also increase with folate or vitamin B6 deficiency. Knowing your homocysteine levels are in a safe range is important, because even slightly elevated levels can injure the inner lining of artery walls, leading to heart disease and strokes.

The best test available for helping us diagnose B12 deficiency is a methylmalonic acid (MMA) test because it tells us when stores are depleted and deficiency has been reached, long before total serum vitamin B12 levels drop. There are also tests that can be done to check for antibodies to intrinsic factor and our stomach cells. Autoimmune-induced chronic stomach inflammation can damage the stomach cells that produce intrinsic factor, and without intrinsic factor, we can’t properly absorb B12. This is called pernicious anaemia and is usually managed with ongoing, medical doses of injected B12. Autoimmune disease is the most common cause, but for some, it can be a genetic condition, or caused by stomach surgery.

Other causes of B12 absorption problems include the prolonged use of medications for heartburn and diabetes, conditions such as celiac or Crohn’s disease, pancreas dysfunction, or surgery to the bowel. By far, the most common cause of vitamin B12 deficiency is aging, a condition which affects vegans and non-vegans alike. As we age, our stomach tends not to produce as much hydrochloric acid, which is vital for the digestion of nutrients such as vitamin B12. This is why all adults over the age of 50 are advised to supplement with B12, regardless of diet.