While most vegans get enough vitamin B6 (pyridoxine), numerous members of one vegan family showed symptoms of vitamin B6 deficiency (1).
Symptoms of B6 deficiency include sleepiness, fatigue, sores in the sides of the mouth, and a swollen tongue (2). Bananas, navy beans, and walnuts are all good sources of vitamin B6 (2).
References
1. Crane MG, Register UD, Lukens RH, Gregory R. “Cobalamin (CBL) studies on two total vegetarian (vegan) families” Vegetarian Nutrition 1998; 2(3):87-92.
2. Groff J, Gropper S. Advanced Nutrition and Human Metabolism, 3rd ed. Wadsworth: 2000.