The Spleen is responsible for the formation of blood coming from the Qi of food. If the Spleen is weak for whatever reason (dietary, climactic, mental strain or otherwise) then the blood formed from food intake will be weak and not nourishing to the body. One important thing here is to avoid eating too many high fat or chemically-laden foods which burden or "stagnate" the Liver system causing the Liver to "attack" the Spleen making the Spleen weak. Green juices can help relieve the Liver Qi stagnation allowing more harmony between the Liver and Spleen. Spleen Qi can be boosted by increasing energetically warming foods and relaxing the busy mind.