It is very rare for an atheist to make a good objection to the Creation narrative. Most are simply regurgitated from the leading atheists and have already been answered adequately dozens of times. The atheists are simply not looking for answers. However, on occasion, a sincere seeker will ask a question that deserves an answer. Such a question was recently posed to me regarding how people were able to get the required Vitamin B12 in the pre-fall world when the prescribed diet was purely plant-based. This is actually a good question as B12 usually comes from animal material in the post-flood world. Thus it may have been difficult for anyone following God’s prescribed diet in the pre-flood world to get the B12 they needed in their diet. There is, however, an answer to this question.
As noted, Vitamin B12 is usually obtained in the human diet from meats. A lack of vitamin B12 can cause a variety of issues, from anemia to various neurological problems. On occasion, this has been cited as evidence that man could not have been vegetarian at the beginning of creation, most often by theistic evolutionists and old-earth creationists. However, this is not a good argument against a Biblical view of creation for a number of reasons.
The primary reason B12 fails as an argument against the plain Biblical narrative is, there are plants today which produce B12 and are regularly consumed as parts of the diet in various areas of the world. For example, the far East consumes a seaweed called nori which is loaded with B12. Another marine alga, spirulina, while less commonly used, also contains pseudo B12 though this has not been proven effective as yet. Barley grass also contains B12. Thus, even in today’s world, it is possible, albeit somewhat difficult, to obtain the proper amount of B12 purely by eating greens. Of course in the modern world, we can fortify foods with vitamin B12 to ensure people get enough of the vitamin while eating a purely plant-based diet.
Some may argue that in the pre-flood world the ancients would not have had access to things like nori. That argument, however, falls upon inspection. Nori is a shallow-water marine alga, found in tide pools and along the coast. It has been part of Japanese culture since antiquity and may have been part of other cultures as well, albeit to a much lesser extent than in Japan where it was even used as payment for taxes. Given that we think the pre-flood world had much shallower seas than they are in the present world, nori may have been even more abundant than it is today. This may have made it even easier to get B12 in the pre-flood world.
However, there is another reason the B12 problem is not really a problem for a young earth view. That is the fossil record. If you look at the plant fossils we have, the Flood clearly wiped out whole families of plants. The horsetails, ferns, cycads and so on were hammered during the Flood, with many being wiped out completely during the Flood. Given we cannot analyze the nutritional content of fossil plants, we have no way to know what the B12 content of any of the extinct plants was. This being the case, any argument claiming B12 deficiency would have occurred prior to the Flood is specious. We simply don’t know enough about the nutritional content of fossil plants to make a determination.
This question is not one that comes up frequently. When someone asks it, it is an example of them actually doing some critical thinking, which we want to encourage. However, this question has an answer. B12 is not an issue for a creationist view. There are multiple natural plant-based ways to obtain vitamin B12 in even the most stringent vegan diets even today. This may even have been easier in the pre-flood world where there was a much greater variety of plants, some of which may have been fortified with B12. In either instance, B12 presents no problem for a creationist view. Natural sources exist, even in the modern world, and there may have been more sources in the pre-flood world.