Even though God's Word does benefit our physical bodies, the Word is spiritual and must be understood through the spirit. God's Word is spirit and it takes our spirit to bring the light of its truths to our minds.
The Word of God is not paper and ink. Jesus is the Word, and He existed in spiritual form long before any words were inspired to be written down by the Holy Ghost. The Bible is simply a physical statement of Jesus and spiritual truth. It is inspired of God and is totally accurate and reliable, but, until we receive the Spirit expressed in these words, the Bible will not profit us. This is why many people have read the Word, maybe even memorized it, and aren't reaping any benefits from it.
Just as our physical man receives life from the food we eats, so our spiritual man receives life as we partake of Jesus, the "bread of life. Jesus plainly stated that the words He spoke were spiritual, not physical.
If we want to know what spiritual truth is, we must believe the Bible, because it is spirit and life. If we want to be led by the Spirit, then we must follow God's Word. If we want to hear from the Spirit of God, then we must listen to what God says in His Word. The Spirit (Holy Spirit) and the Word (Jesus - John 1:1) are one.