I researched about polycythemia (Elevated Red Blood Cell Count), anyone has experience of how to take care of their diet?

Here's some good info on the condition and treatment, including diet.

http://www.cancercare.org/publications/191-treatment_update_polycythemia_vera#coping-with-symptoms

"Exercise and eat a healthy diet to maintain your weight. In general, the guidelines for people with PV are the same as for everyone else: eat a lower fat diet in sensible portions and plenty of fruits, vegetables, grains and legumes.

Drink plenty of fluids. Especially in warm weather, it’s important to stay well hydrated to keep your blood from thickening. Plain water, non-alcoholic drinks and sugar-free beverages are among the best choices. Try to drink six to eight eight-ounce glasses of fluids each day. It’s fine to sip them slowly throughout the day. Part of your daily water intake can come from foods. Fruits and vegetables that have a high percentage of water include cucumber, celery, iceberg lettuce, broccoli, spinach, watermelon, strawberries and cantaloupe.

Stay active. Find an activity such as walking or biking that you like to do. Talk to your doctor about the kinds of activities that would be best for you. Yoga or dancing may be enjoyable as well as beneficial for you."

Iron is not the culprit, but genetics or kidney disease may be.
His bone marrow for some reason is overproducing blood cells. I would worry more about his condition progressing to Leukemia if it is not properly treated.

Thank you for the infors, Pam you are correct that I'm afraid of.. it might turn to Leukema some point in the future.... he is trying to active but he have to take Knapp every afternoon after lunch( that he said), I'm gone for 4 days a week ....
He understand when he couldn't take care of himself, he wants move in to his only one son's house... with LTCI!!