There is no naturally occurring form of vitamin B12 that works in humans except for that made by bacteria. Animals eat the bacteria and then store the vitamin in their meat, milk, and eggs. Plants make their own vitamin B12, but its a form we cant use.
Any kind of seaweed, chlorella, fermented soybean, or other plant-based source of vitamin B12 is NOT reliable.
Only bacteria produce the form of B12 usable by the human body. Plant-based vitamin B12 contains analogues that interfere with the absorption and function of the correct form of B12.
These analogues can also interfere with the blood test for B12 giving a false reassurance of adequate levels. If youve been relying on plant/algae/chlorella derived vitamin B12 and are resistant to taking a supplement, ask your doctor to test blood levels of MMA and/or homocysteine to get a better idea of your actual B12 status. MMA and homocysteine levels in the blood are markers of vitamin B12 activity, and they rise when B12 function is inadequate.
The only other option is supplementation with fortified foods or pills.
Yeast and soy products that are fortified with B12 from bacterial or synthetic sources can provide adequate levels if ingested in sufficient quantities. Be careful though, because many of these foods contain plant-based vitamin B12 that is actually an analogue and therefore detrimental. Read the label carefully.
Commercial breakfast cereals, at least those manufactured in the United States, are usually fortified with an appropriate form of vitamin B12. If you are eating at least a full serving every day of Kelloggs All-Bran with Extra Fiber or some similarly fortified (preferably low-sugar and high fiber) commercial product, then vitamin B12 intake may be adequate.
Yeast, breakfast cereals, and soy products fortified with B12 are not natural sources. They are fortifications and thus supplements and therefore exactly what you are getting from a pill except perhaps less reliable if you dont eat adequate amounts every single day.
What to do:
Repletion. If you have not had an abundant, reliable source of vitamin B12 for two months or more, go directly to the pharmacy and buy 1000 microgram tablets. Both cyancobalamine and methylcobalamine are fine. The first is more traditionally used and therefore better studied. It doesnt matter whether you take a sublingual preparation placed under the tongue or take a pill. Take one a day for a month. After this important repletion of vitamin stores, follow the minimum daily maintenance recommendations.
Minimum daily maintenance. To get enough vitamin B12 from naturally occurring vegetarian food sources, eat at least a full cup of naturally produced yogurt (preferably sugar-free with live cultures) or low fat cottage cheese every single day. A cup of yogurt provides the bare minimum amount of vitamin B12 (or probably not if you listen to the US RDA and other recent data suggesting higher levels are much better for health). Its also a good source of calcium and of probiotic bacteria to keep the gut healthy.
An alternative for those who dont like yogurt is to drink at least two cups of milk every day. Note though that some evidence suggests that two or more glasses of milk may increase the risk of developing prostate cancer and three or more may increase the risk of developing ovarian cancer.
Eggs cannot be your primary source of vitamin B12. The amount of eggs that would need to be eaten to maintain adequate vitamin B12 levels is unrealistic and dangerous from the perspective of saturated fat and cholesterol.
Cheese might be a good source of vitamin B12, but its also loaded with saturated fat and calories, especially the best tasting variety thats made from whole milk. Getting much of your vitamin B12 from cheese isn’t a good idea.
Consider eating fortified foods like commercial breakfast cereals or yeast preparations. Make sure you check the labels to ascertain you are getting at least the bare minimum of 1 or 2 micrograms daily without unnecessary additives, preservatives, high fructose corn syrup, or sugar. For the yeast preparations, check to see that a bacterial or synthetic source of vitamin B12 has been added and not a plant derived analogue.
Ultimately, the best alternative for vegetarians (and especially vegans) may simply be to take a vitamin B12 supplement containing 25 to 100 micrograms daily. Theres concern that when mixed within a multivitamin, some chemical reactions take place that decrease B12 availability. As long as the vitamin manufacturer is reliable and the dose is 25 to 100 micrograms, the supplement should remain adequate.
You can also take the prescription strength 250 microgram tablet containing only vitamin B12 every day. There is a maximum amount that can be absorbed through a specialized mechanism in the intestines with the rest expelled through feces. Taking the higher dose may counteract a rising incidence of problems with vitamin B12 absorption such as is seen with small bowel bacterial overgrowth and low stomach acid resulting from pills taken for GERD or as a consequence of aging.
The bottom line…
Vegetarian, particularly vegan, yogis need to consider taking a commercial B12 supplement. A daily low dose tablet taken with food is more reliable than sporadic intake from various supplemented foods like breakfast cereals, soy products, and yeast.
Anyone resistant to supplementation from food products or pills should ensure they are eating abundant amounts of dairy products, preferably low fat and low calorie varieties.
Eggs cannot be relied upon as a sufficient source of adequate amounts of vitamin B12.
Anyone eating the bare minimum of one cup of yogurt or cottage cheese per day without other supplementation should have their blood levels of vitamin B12 (and/or its function with MMA and homocysteine) checked at least yearly and with any subtle manifestation of deficiency. Dont forget that if youve been ingesting plant based B12 analogues, they can interfere with the accuracy of the test.