Vitamin B12 Daily Requirement: RDA
Vitamin B12 is an essential vitamin. This means that our body cannot produce it alone in a useable form and we therefore must ensure that we consume it regularly through our diet in order to maintain a healthy, functioning body.
But how much vitamin B12 do we need? And how much are we able to consume from our diet? Is this amount different for vegetarians or vegans? When is it really important to take vitamin B12 supplements? This article aims to answer this and other questions regarding the consumption of vitamin B12.
RDA and Recommended Daily Intake – the Daily Requirements for Vitamin B12
The daily requirement of vitamin B12 is difficult to specify scientifically and depends on a number of different factors. This explains the slight variations in the international recommended figures for the daily requirement of vitamin B12. Benchmarks for this daily intake amount are given as the ‘recommended daily allowance’ (RDA) in the EU1 and the USA2, or the ‘DGE’ in Germany3. The WHO/FAO has also issued recommended values which match those given in the USA.4
Table: daily requirement of vitamin B12 according to DGE, WHO and EU
Adults (over 14)
Vitamin B12 Daily Requirement During Pregnancy and Breastfeeding
The body’s need for vitamin B12 is greater during pregnancy and breastfeeding. According to WHO and DGE, pregnant women require around an extra 0.2 – 0.5 µg of vitamin B12 in order to cover the requirement of the foetus – totaling 3.5 µg. The vitamin B12 concentration in the placenta and the blood of newborns is around double that of the concentration in the serum of the mother, and this vitamin B12 has to be delivered through the body and nutrition of the mother. Vitamin B12 plays an important role in the development of the foetus, which is why it is pivotal to take an adequate amount during the pregnancy. If the mother doesn’t proceed to take the necessary additional B12, the requirement can be covered in some cases by the built up supply in the mother’s B12 body store, but this represents an unnecessary risk for the child.
During breastfeeding, women lose a large amount of vitamin B12 through breast milk, so the requirement for B12 is even higher at this point than it is during pregnancy. The DGE recommends a minimum dose of 4 µg – so an extra 1 µg on top of the daily need for adults. Breast milk contains as much vitamin B12 as a mother’s blood – so it is especially important for vegetarians and vegans to take supplements during this time, as they are at a much higher risk of deficiency whilst breastfeeding; which poses a serious risk for the mother as well as the child.5
WHO & DGE Recommendations and Daily Requirement – what is the ‘RDA’?
The WHO & DGE recommendations, or RDA, are in fact not the body’s daily requirement exactly, but rather the amount of vitamin B12 which, according to recommendations of the corresponding organisations, should suffice, in order to cover the minimum daily requirement of 97.5% of healthy people. The recommendations do already include a certain safety buffer, to account for different metabolisms.6
It is therefore important to be aware that this recommended daily dose is only intended to cover the requirement of healthy people. It does not take fully into account the heightened need for vitamin B12 during times of stress, illness or malnutrition, as well as for smokers, drinkers, those taking medicine and those with stomach or intestinal absorption problems. There are further issues with the current recommendations, which will be discussed below.
The RDA should thus not be treated as the exact daily dose required, but as a benchmark of the minimum requirement, which in ideal situations can be enough to prevent a deficiency. In many individual cases, the actual daily requirement of vitamin B12 can be considerably higher.
How Exactly is the Vitamin B12 Daily Requirement Determined?
How is the value for the daily need of vitamin B12 actually calculated? They are essentially just a derivative of various scientific observations. For vitamin B12, these include:
- The amount of B12 excreted daily
- The size of the body’s B12 storage
- Analysis of nutritional studies
- Analysis of studies with the anaemic, vegetarians and vegans
The argument of the current recommendations is roughly as follows: humans excrete around 1 – 2 µg of vitamin B12 per day, which is consequentially lost from the body store, which comprises of roughly 2,500 µg of vitamin B12 in total.
According to various studies, the body seems to only require around 0.5 – 1 µg of vitamin B12 per day, but these results were most likely derived from studies carried out using injections, which bypass the critical phase of absorption from food in the intestine.7 An intake of just this 0.5 – 1 µg would, however, slowly empty the body storage over many years as a results of the slightly higher loss per day. For this reason, a daily requirement of between 1 and 3 µg was installed, to ensure that people were consuming not only the quantity necessary for regular health maintenance, but also a surplus, enough to refill the body store. Through this, the storage can balance out the body’s requirement in times of lower absorption, which is particularly important in old age.
It is interesting to note that the intrinsic factor – the transport molecule which enables absorption of vitamin B12 in the intestine – is only capable of absorbing around 1.5 µg of vitamin B12 per meal or dose. When studying the B12 concentration in foods, it is easy to see that the body can absorb between 4 and 7 µg of vitamin B12 per day through this method – which corresponds, not entirely coincidentally, to the necessary daily requirement for people.
Vitamin B12 Daily Requirement: Absorption vs Intake
The current definition of the daily requirement points to a number of problems. Firstly, the studies which support the current definition are very old and come from a time when new methods for determining a vitamin B12 deficiency didn’t exist whatsoever.
The other part of the discussion regarding the daily requirement of vitamin B12 is that the supply of vitamin B12 through intake of food or supplements doesn’t necessarily correspond to the actual amount of vitamin B12 absorbed. The intake via consumption and the absorption of this by the body are two very different things. Unfortunately, intake and absorption are often confused in this situation.
The current recommendations of the DGE and WHO are that it is sufficient to ensure a supply of exactly the amount of vitamin B12 which has been identified and calculated as the daily requirement. This works on the assumption, however, that the quantity of vitamin B12 supplied is absorbed in its entirety. Unfortunately, this is theoretically almost certainly not the case. Current studies in practice have proven that the supply must be considerably higher – the relevant biomarkers begin to recover from an intake of between 4 and 10 µg of vitamin B12 per day.
Here is an overview of current studies:
Bor et al, 20108
Vogiatzoglou et al, 20099
Bor et al, 200610
Kwan et al, 200211
Tucker et al, 200012
Hordaland Homocysteine Study (Norwegian)
Framingham offspring (UK)
RDA (μg Vitamin B-12/day)
It is clear to see that these current studies all agree that the actual necessary amount of vitamin B12 is considerably higher than current recommendations through the RDA, namely around 7 µg rather than 3 µg. The assumption is that this new information will be taken into account when determining the next edition of the RDA.
Covering Your Daily Requirement of Vitamin B12
The reason for the discrepancy between the body’s requirement an the supply necessary to provide this can be explained by the way in which vitamin B12 is absorbed by the body. Vitamin B12 is absorbed in two different ways:
- Via the intrinsic factor (a maximum of 1.5 µg per meal or dose, regardless of the quantity)
- Via passive diffusion (1 percent of the overall quantity)
The mechanism of absorption through the intrinsic factor (IF) recovers after several hours, meaning that more than 1.5 µg can be absorbed daily. A maximum of around 4.5 µg can be absorbed through the intrinsic factor per day.
If the absorption method via the IF fails, which is particularly common amongst older people, the body can only obtain very small amounts of B12 through passive infusion. In order to meet the RDA here, a supply of around 300 µg would be necessary. And that is also assuming a healthy intestinal flora.
This explains why many oral vitamin B12 supplements have a very high dosage level. They are designed to try to cover the daily requirement through passive diffusion alone.
How High is my Daily Requirement of Vitamin B12?
How can you determine your own specific, exact daily requirement? The RDA values are certainly a good orientation and should at least be considered as the minimum you should be consuming. The value given by current studies of around 7 µg is however certainly more reliable. The body’s requirement can increase in the following cases:
- Stress (physical, mental or emotional)
- Severe phyiscal strain on the body (also sport)
- Consumption of tobacco, alcohol or coffee
- Consumption of junk food and soft drinks
- Impairments of the stomach or intestinal mucosa
- After a long period of deficiency
It is difficult to say exactly how much more vitamin B12 is necessary in these cases. A rough guideline can be to calculate your RDA using the values of the studies above, then add between 2-3 µg or up to double the value.
How can I meet the Vitamin B12 RDA Through Food?
Am I getting enough vitamin B12 through my diet? When are supplements necessary?
Vitamin B12 is only found in animal produce such as meat, fish, eggs, milk and dairy products. Vitamin B12 is best absorbed through dairy products and fish, less so through meat. An overview of the amounts of B12 in various foods, with a useful table for comparisons, can be found in our article vitamin B12 food sources.
With an intact and functioning IF, no increased need and good health, a balanced omnivore diet should guarantee a good supply of vitamin B12. Vegetarians who eat lots of cheese and other dairy products should also successfully meet this need. However, following a vegan diet makes it almost impossible to cover the body’s daily requirement of vitamin B12 without supplements.
However, it is no guarantee that an omnivore diet will supply a sufficient amount of vitamin B12. Impairments to the intestine, consumption of alcohol, coffee or cigarettes, interactions with medication and many other factors have a very negative effect on the absorption rate of vitamin B12. Unfortunately, many of these factors are very commonplace in industrialized countries. The most obvious recommendation is the follow a healthy lifestyle in order to avoid these consequences. If you’re in any doubt about your lifestyle impacting on your vitamin B12 absorption, it can be recommended to take supplements, even on a temporary basis, in order to guard against larger health risks.
In old age, absorption through the IF becomes increasingly severely impaired, meaning taking supplements is very common, highly recommended and often even urgently necessary.
Vitamin B12 and Vegetarian and Vegan Diet
Since vitamin B12 only occurs naturally in animal products, it can be difficult for vegetarians and extremely unlikely for vegans to cover the vitamin B12 daily requirement through food alone. Taking vitamin B12 supplements is particularly essential for vegans, and this recommendation is backed up by all large vegan organizations such as the international Vegan Society.
More information on this can be found in our article about vitamin B12 in vegetarian and vegan diets.
RDA, Dosage and Overdose
Vitamin B12 is water-soluble and the quantities which are not needed by the body are simply excreted in the urine. Vitamin B12 is considered harmless and there is no defined upper limit for intake. A vitamin B12 overdose has also never been seen.
The long term consequences of a very high intake of 2000 µg of vitamin B12 per day have proven to be unproblematic for many years through studies on anemia patients. It is worth remembering, however, that the human metabolism is a very sensitive, balanced system, and an unnecessary overdose of vitamins certainly strains the body, and in particular the organs which are responsible for excreting vitamin B12.
Individual information regarding the correct dosages of vitamin B12 supplements can be found in the corresponding articles.
1 Richtlinie 2008/100/EG der Kommission vom 28. Oktober 2008 zur Änderung der Richtlinie 90/496/EWG des Rates über die Nährwertkennzeichnung von Lebensmitteln hinsichtlich der empfohlenen Tagesdosen, der Umrechungsfaktoren für den Energiewert und der Definitionen http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2008:285:0009:01:DE:HTML
2 Subcommittee on the Tenth Edition of the RDAs, Food and Nutrition Board, Commission on Life Sciences, National Research Council: Recommended Dietary Allowances: 10th Edition. National Academy Press, Washington, D.C., 1989 http://www.nap.edu/catalog.php?record_id=1349
3 Deutsche Gesellschaft für Ernährung, Österreichische Gesellschaft für Ernährung, Schweizerische Gesellschaft für Ernährungsforschung, Schweizerische Vereinigung für Ernährung (Hrsg.) „Referenzwerte für die Nährstoffzufuhr“ 1. Auflage, 5., korrigierter Nachdruck, DGE, Bonn 2013 http://www.dge.de/modules.php?name=Content&pa=showpage&pid=3&page=7
4 World Health Organization, Food and Agricultural Organization of the United Nations „Vitamin and mineral requirements in human nutrition“, Second edition, WHO, 2005.
5 Specker, B.L., D. Miller, E.J. Norman, H. Greene, and K.C. Hayes. 1988. Increased urinary methylmalonic acid excretion in breast-fed infants of vegetarian mothers and identification of an acceptable dietary source of vitamin B12. Am. J. Clin. Nutr. 47:89-92.
7 Herbert, V. „Nutritional requirements for vitamin B12 and folic acid“ Am. J. Clin. Nutr. 21:743-752, 1968.
8 Mustafa Vakur Bor, Kristina M von Castel-Roberts, Gail PA Kauwell, Sally P Stabler, Robert H Allen, David R Maneval, Lynn B Bailey Ebba Nexo „Daily intake of 4 to 7 µg dietary vitamin B-12 is associated with steady concentrations of vitamin B-12–related biomarkers in a healthy young population“ Am J Clin Nutr 2010 91: 3 571-577; First published online January 13, 2010. doi:10.3945/ajcn.2009.28082.
9 Vogiatzoglou A, Smith AD, Nurk E et al. Dietary sources of vitamin B-12 and their association with plasma vitamin B-12 concentrations in the general population: the Hordaland Homocysteine Study. Am J Clin Nutr 2009;89:1078–87.
10 Bor MV, Lydeking-Olsen E, Møller J, Nexø E . A daily intake of approximately 6 micrograms vitamin B-12 appears to saturate all the vitamin B-12-related variables in Danish postmenopausal women. Am J Clin Nutr 2006;83:52–8.
11 Kwan LL, Bermudez OI, Tucker KL. Low vitamin B-12 intake and status are more prevalent in Hispanic older adults of Caribbean origin than in neighborhood-matched non-Hispanic whites. J Nutr 2002;132:2059–64.
12 Tucker KL, Rich S, Rosenberg I, et al . Plasma vitamin B-12 concentrations relate to intake source in the Framingham Offspring study. Am J Clin Nutr 2000;71:514–22.