[itronitron]

If your drowsiness sets in after lunch then I'd recommend having a vegetarian sandwich (whole grain bread, shredded carrot and sliced cucumber, sprouts, etc. ) and see if you feel less drowsy afterwards. The sandwich is the epitome of unsatisfying but I've seen a real benefit in not being drowsy later.

Be physically active during the day, and breathe outside air (open a window, go outside, or have a powerful exhaust fan). Physically active means walking around and occasional standing or sitting on a tall stool. Exercise as an 'activity' has never worked for me because it just wipes me out. But walking or biking to places in 10 to 15 minute stretches gets my metabolism up enough that I'm good.

Finally, if none of this works then I recommend seeing a cardiologist.