Of all the nutritional concerns that can plague vegetarians - and especially complete vegetarians or vegans - I doubt any is more daunting than the specter of vitamin B12 deficiency. This is especially so because conventional wisdom has it that this essential vitamin is virtually unavailable from plant foods.
Because I have often wondered how valid this thinking is, I've asked myself why, if the health benefits of a plant-based diet are as comprehensive as contemporary research suggests - meaning that Nature did the packaging for us during our evolution and that a plant-based diet is our natural diet - then why did she leave out this one very important piece of the puzzle? Having paid attention to the research literature and having questioned clinicians who treat vegan patients, I've reached the following somewhat unorthodox conclusions and observations:
1. Contrary to the most recent U.S. Dietary Guidelines, B12 can be found in plants.
2. Organically grown plants contain higher levels of B12 than plants grown non-organically with chemical fertilizers.
3. Plant roots are able to absorb certain vitamins produced by soil microorganisms, thus suggesting that plants grown in healthy soil, full of microflora and microfauna, are more nutritious.
4. Vegans - and anyone else - should be able to obtain B12 by consuming organically grown produce.
5. Evidence that plants obtain vitamins from the soil has been available for several decades.
To understand what has brought me to these conclusions, let's ask three essential questions: (1) Are vegans really at greater risk of B12 deficiency? (2) Does a vegan diet provide all the B12 that we need? (3) Assuming that there is at least a good chance that we evolved on this type of diet, how did we get our B12?
Are vegans really at greater risk of B12 deficiency? Some evidence says yes; some invites skepticism. Clearly, vegans do generally have lower blood concentrations of B12. A number of studies have shown this. But these low concentrations mean little unless there is a higher incidence of the accompanying blood (megaloblastic anemia) and nerve (parathesia) disorders, for which there seems to be little or no evidence. What should be acknowledged is that the concentrations of other blood factors, such as cholesterol, also are very different among vegans, and for very good health reasons at that. Why should we expect the lower B12 levels to be an exception?
A look at the B12 Biases
I must say that I feel some of the confusion surrounding this issue is due to the biases of the early B12 researchers who, over the years, made their beliefs very clear that vegetarianism and any other alternative approach to good ol' Western nutrition and medicine bordered on health fraud. Yet one of the more renowned of these investigators, Victor Herbert, reported that "inadequate absorption [in the digestive tract] accounts for more than 95% of the vitamin B12 deficiency cases seen in the United States." 1 The strong implication here is that the real problem in these cases is not due to an insufficient intake of B12 brought on by a vegan diet but that something is wrong with the so-called "intrinsic factor" which is secreted in the stomach and which is required for B12 absorption.
Acknowledging this possibility, let's move on to our second question: Does a vegan diet provide all the B12 that we need? To consider this question, we must keep in mind the prevailing view that B12 is only found in animal-based foods. It's worth noting this point has been so prominent that the latest USDA dietary guidelines, while allowing for the possibility that vegetarian diets may be reasonably healthful, nonetheless admonish vegans to "supplement their diets with a source of this vitamin." According to the Victor Herbert position, "There is no active vitamin B12 in anything that grows out of the ground; storage is found only in animal products where it is ubiquitous and where it is ultimately derived from bacteria." 2 He also states that vegans thus can get adequate B12 from their food only if it is fertilized with human waste, or if they "ingest some of their own feces" or fail to observe hygienic practices.3 What a prospect Herbert and the USDA folks have given to the poor vegans!
I find this view to be highly constrained and, indeed, illogical, especially if one assumes the strong possibility that humans survived on a plant-based diet in our evolutionary past. I do believe there is overwhelming evidence that this is so even though it has not yet been scientifically proven. Please understand that I say this approach is no better or worse than that of Herbert and the USDA, I'm simply saying it's worth serious consideration.
The B12 Breakthrough
So, on to my third question, based on the assumption that we did evolve on a plant-based diet, and then asking, how did we get our B12? To begin, let's examine an exciting new research paper from Switzerland that was recently brought to my attention by my colleague, Dr. Jeffrey Gates.4 (Please see related story). Dr. Mozafar, the investigator, wanted to know if plants fertilized with organic matter (cow dung in this case) rather than those grown in control soils might acquire higher levels of B12. He was relying on a considerable amount of older research going back to 1926. Plants grown in soil fertilized with organic matter contained more of some B vitamins than plants grown in chemically fertilized soil, thus yielding plant products better able to sustain growth in experimental animals. Mozafar hypothesized that B12 produced by soil microorganisms might be absorbed through the roots into the plant itself.
He investigated the question in a couple of ways. First, he showed for soybeans, barley and spinach - his three test plants - that those grown on soil fertilized with cow dung showed substantially higher levels of B12 than those grown without cow dung, the increases for barley and spinach being statistically significant. Then he examined the B12 content of soils that had been routinely fertilized over the previous 16 years either with inorganic or with a mixture of organic plus inorganic fertilizers, and found that those receiving organic fertilizer had significantly higher levels of B12.
Putting the Nail in the Coffin
These results not only confirm earlier results concerning other B vitamins, but they seem to put the nail in the coffin of the Herbert-USDA hypothesis, namely that plants do not contain B12. They certainly do contain B12, even more of it when they are grown organically. Having said all this, I am still left with two questions: (1) Would other chemicals capable of killing soil microflora (pesticides, herbicides) have an effect similar to chemical fertilizers? and (2) How long will it take for our society to acknowledge the overall health value of plant-based diets, thus altering the cultural bias that leads Herbert and the USDA to "discover" problems such as that of B12 deficiency? I can say with some confidence that time will tell quite a different story than the one we've been hearing.
1 Herbert, V. Recommended dietary intakes (RDI) of vitamin B12 in humans. American Journal of Clinical Nutrition, 45:671Âº678, 1987.
2 United States Department of Agriculture, and United States Department of Health and Human Services. Dietary Guidelines for Americans, Fourth Edition, p. 43. Washington, D.C.:1995.
3 Herbert, V. Vitamin B12 : plant sources, requirements, and assay. American Journal of Clinical Nutrition, 48:852Âº858, 1988.
4 Mozafar, A. Enrichment of some B-vitamins in plants with application of organic fertilizers. Plant and Soil, 167:305Âº311, 1994
This was written in 1996. Now, 12 years later, I still don't know that this view whether this view is right. However, in the meanwhile, I have been influenced by two of my clinician colleagues, Dr. Michael Greger and Dr. Alan Goldhamer, that their understanding of the literature and their experience in the clinic suggest that B12 deficiency may be seen in vegans, thus advocate B12 supplementation. I defer to their view.