It depletes some of the B vitamins, the ones the body can store, from your system, and stops you absorbing others from food, which you need regularly as they cannot be stored by the body. Here are the B vitamins
thiamin (vitamin B1)
riboflavin (vitamin B2)
niacin (vitamin B3)
pantothenic acid
vitamin B6
biotin (vitamin B7)
folic acid
vitamin B12
I'm not giving medical advice, just saying that vitamin B12 is linked to memory (Allegedly)