G6PD-Deficiency Disorder and/or Favism
This is a genetic condition in which the red blood cells (RBCs) are inadequately protected from certain proteins commonly found in legumes. The entire legume family of plants must be tightly restricted in the diet of someone with G6PD, which, on a vegan diet, eliminates all of the best sources for lysine, an essential amino acid. If the individual has access to one of the following foods, and does not have a food sensitivity toward it, these foods have high quantities of lysine without being in the legume family:
- quinoa (a chenopod)
- Lamb's quarters / goosefoot (a chenopod)
There may be a few more, but most lysine comes from legumes! Most of Asia does not have these chenopods.
G6PD, in the case of Favism, can be deadly. A bowl of fava or Lima beans could kill a G6PD-deficient child due to hemolysis of the red bloods cells and sudden loss of hemoglobin.
Non-vegan, but vegetarian foods (dairy products), including milk and eggs, have lysine in adequate quantities--which is why a G6PD individual may find a vegetarian diet acceptable, although not a vegan diet.
More G6PD Resources
[As the literature suggests, G6PD is not yet fully understood, and some confusion exists as to what can and cannot be eaten with it. I have close ties to multiple persons with the condition, and can attest that it is best for them not to eat beans generally, except in very small quantities so as to limit the ill effects. One bean won't kill anyone--but a full serving of Lima beans could kill a child with favism.]
Vitamin B12 Deficient
A strictly vegan diet has no reliable source of vitamin B12.
Some argue that certain cultures are vegan, living solely off the land in an agricultural area, but this is not well studied, and they may ingest some bacteria from the plants' soil (assuming the vegetables are not thoroughly washed) or even some insects along with their harvest.
Years ago, it was thought that certain species of seaweed contained vitamin B12; however, it is now known that no seaweed has B12--what they have is, instead, a B12 analogue which is not bioequivalent to actual B12 and which works against vitamin B12 in the body because it takes the place of B12 in the metabolic pathways without performing the necessary functions of B12.
It is said that people produce B12 in the gut. This is true; however, the B12 in the gut is produced well beyond the point at which it could be absorbed in the intestine--too far downstream to have benefit at all.
It is thought that some B12 may be created by the bacteria that forms plaque on the teeth, and that this may help to boost the body's B12 levels. Most people, however, brush that "ugly" plaque away, and do not ingest it. Furthermore, the amounts that this could conceivably produce and supply, even if ingested, are so minimal as to likely be unworthy of consideration.
A B12-deficient individual may have one or more of the following symptoms (listed in approximate order of increasing severity):
- numbness/tingling in hands or feet
- loss of taste or smell
- loss of short term memory
- weakness / fatigue
- inability to concentrate
- weakened nervous system
- more easily experience motion sickness
- vertigo / tinnitus
- permanent brain damage
- loss of eyesight
- partial paralysis
IMPORTANT NOTE: Vegans typically consume high amounts of folate (supplement form is called "folic acid"), a B-vitamin found in green leafy vegetables, which masks the deficiency of vitamin B12. Vegans, therefore, may not experience the early symptoms of B12 deficiency, and be unaware of their lack until permanent brain damage has already been caused.
Please see some official warnings on this grave danger here:
[Scroll down to "Health Risks from Excessive Folate".]