For good health, waste products of digestion such as neutral fats and cholesterol should not remain in our bodies. The circulatory system and its blood vessels compose the passage way for blood that is said a resource of life. When blood vessels are clean, blood circulates well and it leads us to absorb nutrition properly. In much the same manner you have 'spiritual waste' such as hatred, jealousy, anger, and the adulterous mind in your heart so your souls cannot maintain 'spiritual health. To the extent that you cast off such 'untruthful waste', the Word of God can be absorbed in you and you can have a good heart and healthy spirit.