What Causes Severe Calf Muscle Spasms At Night?

I get severe calf muscle spasms at night, I notice when I drink beer I am sometimes awaken with the cramping. It is not always in my calves but also in my feet, it seems to get worse when I drink beer. 6 years ago I had gastric bypass surgery, I have been taking a chewable vitamin daily. It is very uncomforatble and painful I have to walk around and put pressure on my feet or legs to get the cramping and pain to stop. I am 46 years old 5 foot six and approx 215lbs