Vitamin B12 is extremely essential and a crucial water-soluble vitamin which plays a key role in the normal functioning of the brain and nervous system. It is involved in the metabolism of every cell of the human body, especially DNA synthesis and regulation, fatty acid metabolism, and amino acid metabolism. It is naturally attached to the protein in food and is separated from the protein in your stomach. It’s one of the 8 B-complex vitamins and also known as ‘cobrynamide, cobinamide and cobamide’. You might notice that all the names start with Co, the chemical symbol for Cobalt. Vitamin B12 is needed in smaller amounts than any other known vitamin. For instance, 10 micrograms of the vitamin spread over the period of a day, seems to supply as much as the body can utilize.
[pullquote]Vitamin B12 is the only vitamin that is not recognized as being reliably supplied from a varied wholefood, plant-based diet with plenty of fruit and vegetables, along with exposure to sun. [/pullquote]
How Can Vegans obtain Vitamin B12?
Vitamin B12 is abundant in meat sources but can also be found in some grains. Vegetables are not a good source of vitamin B12, as plants cannot produce this nutrient on their own. Vitamin B12 is the only vitamin that is not recognized as being reliably supplied from a varied wholefood, plant-based diet with plenty of fruit and vegetables, along with exposure to sun. Many herbivorous mammals, including cattle and sheep, absorb B12 produced by bacteria in their own digestive system. B12 is also found to some extent in soil and plants. Some foods like Spirulina, Tempeh, and Barley grass, are suggested as suitable non-animal alternatives, but these claims have not been substantiated.
Most vegans consume enough B12 to avoid anaemia and nervous system damage, but many do not get enough to minimize potential risk of heart disease or pregnancy complications. The only reliable vegan sources of B12 are foods fortified with B12 that include plant milks, some soy products and some breakfast cereals and B12 supplements. Some sea vegetables, like kelp, seaweed, and blue-green algae are also reported to be a good source of vitamin B12 (Sacramento Natural Foods Co-Op).
1. Eat fortified foods two or three times a day to get at least three micrograms (mcg or µg) of B12 a day.
2. Take one B12 supplement daily providing at least 10 micrograms.
3. Take a weekly B12 supplement providing at least 2000 micrograms.
If relying on fortified foods, check labels carefully to make sure you are getting enough B12. For example, if a fortified plant milk contains 1 microgram of Vitamin B12 per serving then consuming three servings a day will provide adequate vitamin B12. Few others may find the use of B12 supplements more convenient and economical.
Any B12 supplement tablet should be chewed or allowed to dissolve in the mouth to enhance absorption. Tablets should be kept in an opaque container. As with any supplement it is prudent not to take more than is required for maximum benefit, so intakes above 5000 mcg per week should be avoided despite lack of evidence for toxicity from higher amounts.
You can find more information on foods that contain highest and lowest levels of Vitamin B12 here.
What is the RDA for Vitamin B12?
National recommendations for Vitamin B12 vary significantly from country to country. The US RDA is 2.4 mcgs a day for ordinary adults and 2.8 mcgs for nursing mothers. The German recommendation is 3 mcgs a day. Recommended intakes are usually based on 50% absorption rate, as this is typical for small amounts from foods. To meet the US and German recommendations you need to obtain sufficient B12 to absorb 1.5 mcgs per day on average.
Why are Vegans at risk for not consuming Vitamin B12?
Most vegans show adequate B12 levels to make clinical deficiency unlikely but they still show restricted activity of B12 related enzymes, leading to elevated homocysteine levels. Strong evidence gathered over the past decade suggests that even slightly elevated homocysteine levels increase the risk of heart disease, stroke and pregnancy complications. Homocysteine levels are also affected by other nutrients, most notably folate. General recommendations for increased intakes of folate are aimed at reducing levels of homocysteine and avoiding these risks. Vegan intakes of folate are generally good, particularly if plenty of green vegetables are eaten. However, repeated observations of elevated homocysteine in vegans, and to a lesser extent in other vegetarians, show conclusively that B12 intake needs to be adequate as well to avoid unnecessary risk.
Vitamin B12 Deficiency
.Many people over age 50 lose the ability to absorb vitamin B12 from foods.
.People who follow a vegetarian or vegan diet should try to eat vitamin B12-fortified foods. Two subgroups of vegans are at particular risk of B12 deficiency: long-term vegans who avoid common fortified foods (such as raw food vegans or macrobiotic vegans) and breastfed infants of vegan mothers whose own intake of B12 is low.
.Those who have had gastrointestinal surgery, such as weight loss surgery, lose the ability to absorb vitamin B12.
.People who have digestive disorders, such as celiac disease or crohn’s disease, may not be able to absorb enough vitamin B12
[pullquote]Algae and some other plant foods contain B12-analogues (false B12) that can imitate true B12 in blood tests while actually interfering with B12 metabolism[/pullquote]
In the absence of an apparent dietary supply, deficiency symptoms will usually take 5 years or more to develop in adults; some may experience problems within a year. Although, a very small number of individuals appear to avoid clinical deficiency symptoms for 20 years or more. In adults, typical deficiency symptoms include:
.Loss of energy
.Reduced sensitivity to pain or pressure
Often these symptoms develop gradually over several months to a year before being recognized as being due to B12 deficiency and they are usually reversible on administration of B12. There is however no entirely consistent and reliable set of symptoms and there are cases of permanent damage in adults from B12 deficiency. Infants typically show more rapid onset of symptoms than adults. B12 deficiency may lead to loss of energy and appetite and failure to thrive. If not promptly corrected this can progress to coma or death.
Why Blood Tests Can’t Measure A B12 Deficiency?
Usually a doctor might suggest a blood test. But, a blood B12 level measurement is a very unreliable test for vegans, particularly for vegans using any form of algae. Algae and some other plant foods contain B12-analogues (false B12) that can imitate true B12 in blood tests while actually interfering with B12 metabolism. Blood counts are also unreliable as high folate intakes suppress the anemia symptoms of B12 deficiency that can be detected by blood counts.
Blood homocysteine testing is more reliable, with levels less than 10 µmol/litre being desirable. The most specific test for B12 status is Methylmalonic acid (MMA) testing. If this is in the normal range in blood (<370 nmol/L) or urine (less than 4 mg /mg creatinine) then your body has enough B12.
It’s essential for everyone, especially those particularly inclined to a plant-based diet to include sources or supplements that provide Vitamin B12. This, of course must be taken with a healthy and balanced diet, as Vitamin B12 is best absorbed in conjunction with other vitamins like Niancin, Biotin and Folic acid among other B-complex vitamins.