Taking stock. The account presented above shows that vegan diets can fulfil all the nutritional requirements that are needed to support good health. Nutrients that present particular concerns are vitamin B12 and omega-3 fatty acids as few vegan foods that are currently used for human consumption contain these.

One of the earliest followers of what we now consider a vegan diet was Arab philosopher and poet Al-Maʿarri who abstained from animal products for his health and beliefs on the transmigration of souls and animal welfare.

As you read along, you'll find out that most health conditions developed by vegans are related to vitamin B12 deficiency. Without the familiar sources of vitamin B12, certain bodily functions can be disrupted, leading to anemia, gastritis, stroke, Crohn's disease, and Celiac disease.