I had gotten off my vitamin regimen of many years (because my wife found the box of pills that I always had on the kitchen counter to be ugly ;). My mental clarity, as measured by how many hours a day I could productively write computer programs, my job, had declined dramatically.
I divorced the wife, got back the vitamins, and am feeling younger, healthier and more alert than I have in years. Numerous minor ailments have gone away. Though still doing not a lick of exercise or enforcing any "diet" to reduce caloric intake, my weight has dropped thirty pounds and my blood pressure has normalized.
Take good care of your mom.
I had a similar experience. I had been sick for about six months of and on.
So... I started taking the vitamins again and have not had a sick day in ten years. Yes.. there have been instances in which I have been sick, but they are relatively rare.
400 IUs at least every day. I also take care to get some sunlight as I work in a windowless office. Exercise and red wine when possible.
Oh, and I recently divorced my screwball wife! lol