1) Quantity required

"The requirements for vitamin B12 are minimal, particularly as the body conserves most of the vitamin. Requirements are in the region of 1 mcg per day [1 micro-gram is a millionth of a gram], rising to 3-4 mcg per day for pregnant and breast-feeding women."

2) Time frame to develop deficiency

"In the absence of any apparent dietary supply, deficiency symptoms usually take five years or more to develop in adults, although some people experience problems within a year. A very small number of individuals with no obvious reliable source appear to avoid clinical deficiency symptoms for twenty years or more."

3) Effects of B12 deficiency

"Very low Vitamin B12 intakes can cause anaemia and nervous system damage."

"Low B12 intake is the dominant dietary cause of high homocysteine."

"Slightly elevated homocysteine is associated with increased risk of many health problems including heart disease in adults, preeclampsia during pregnancy and neural tube defects in babies."

"Those short of vitamin B12 often have anaemia, with symptoms such as exhaustion, shortness of breath on exertion, pale skin and mucous membranes. There are also characteristic changes in the nervous system, including numbeness and tingling in the hands and feet, clumsiness and difficulty with walking."

4) Sources of B12

"The best sources of vitamin B12 are liver, organ-meats, meat and, to a lesser extent, fish, dairy produce, eggs and brewers' yeast. Strict vegetarians - vegans - who eat only vegetables may be risking vitamin B12 deficiency in the long term."

5) B12 not contained in plants

"Vitamin B12 is unique among the vitamins being made exclusively by micro-organisms. Cereals, fruit, nuts, pulses, vegetables and other plant foods are apparently free from the vitamin unless contaminated by micro-organisms that produce the vitamin and by insects."

6) Herbivorous animals

"Many herbivorous mammals, including cattle and sheep, absorb B12 produced by bacteria in their own digestive system."

7) "Natural" diets

"It seeems likely that in our original 'natural' state, eating rain-washed fruits, roots and berries in the primeval forest, human beings would have developed or absorbed the necessary intestinal flora to synthesize the tiny amounts needed and have had the capacity to absorb them directly from the gut without needing to take them in through the mouth."

"All primates consume insects and dirt, either deliberately or accidentally, and this provides an important source of B12 missing in hygienic plant-based diets."

8) Sources of B12: plant sources

"Some plant foods, considered as possible B12 sources such as sea vegetables (eg. nori, wakame and kombu), fermented soy foods such as miso and tempeh, spirulina (a blue-green algae), and mushrooms, either do not contain enough of the vitamin or contain B12 analogues, which are like B12 but without the nutritional benefits."

"Claimed sources of B12 that have been shown through direct studies of vegans to be oinadequate include human gut bacteria, spirulina, dried nori, barley grass and most other seaweeds. Several studies of raw food vegans have shown that raw food offers no special protection."

"In over 60 years of vegan experimentation, only B12 fortified foods and B12 supplements have proven themselves as reliable sources of B12, capable of supporting optimal health."

9) Sources of B12: Fortified foods

"If relying on fortified foods check the labels carefully to make sure you are getting enough B12. For example, if a fortified plant milk contains 1 microgram of B12 per serving then consuming three serving a day will provide adequate vitamin B12."

10) Sources of B12: B12 naturally occurring in foods

"Reports that B12 has been measured in a food are not enough to qualify that food as reliable B12 source. It is difficult to distinguish true B12 from analogues that can disrupt B12 metabolism. Even if true B12 is present in a food, it may be rendered ineffective if analogues are present in comparable amounts to the true B12."

11) Sources of B12: Supplements

"Frequent use of foods fortified with B12 so that about one microgram of B12 is consumed three times a day, with a few hours in between, will provide an adequate amount."
"Taking a B12 supplement containing 10 mcg or more daily provides a similar absorbed amount to consuming one microgram on three occasions through the day.

"The less frequently you obtain B12 the more B12 you need to take, as B12 is best absorbed in small amounts."

"Absorption of B12 varies from about 50%, if about 1 mcg or less is consumed, to about 0.5% for doses of 1,000 mcg (1 mg) or above. So the less frequently you consume B12, the higher the total amount needs to give the desired absorbed amount."

"Take one B12 supplement daily providing at least 10 micrograms, or take a weekly B12 supplement providing at least 2000 micrograms."

"Most B12 tablets contain much more than 10 micrograms and can be broken up to provide the required daily amount at lower cost. Taking a single high potency tablet once per week will have much less effect as less B12 will be absorbed. Intakes up to 1000 micrograms a day are not harmful but are unnecessary."

Back to contents page for References