Why do you get ridges in your fingernail as you get older?

My mom and grandma both have deep ridges in their fingernails now that they are older. I am 32 and have noticed tiny ridges starting in mine to. Anyone know why this is and if there is anything I can do to prevent it further?Why do you get ridges in your fingernail as you get older?
Lack of proteins. Try increasing your uptake on protein: drink gelatin (ones that is used for making aspic); or eat lots of organic nut butters (peanut, cashew or almond) from a health food store. You'll notice the difference in a few days.Why do you get ridges in your fingernail as you get older?
I thought it was only me. I'm almost 16 and I sometimes have little ridges in my nails. I didn't know it has anything to do with age, and I'm not sure it does.