It is impossible to have a healthy body without a healthy mind. The only thing the human immune system cannot defend itself against is mental stress (anger, fear, grief, worry, etc.). It shuts down the entire immune system (think twice before reading and/or listening to the news reports).
In addition, avoid sugar, 'cause it drastically decreases the capability of one's mind and immune system. It is as addictive as cocaine and causes more diseases than all known narcotics combined.
This audio track is a part of Reverend Ike's lesson on mind power, which was recorded in New York City, 1974.