The Five Element Philosohpy is based upon the various elements that are found in the natureal world: Fire, Earth, Metal Water, and Wood.
The predominate atmospheric energies are Wind in the spring (Wood - Liver & Gall Bladder are the most vulnerable), Heat in the early summer (Fire - Heart, Small Intestine, Pericardium, Triple Heater), Dampness in late summer (Earth, Stomach and Spleen), Dryness in the fall (Metal, Lungs and Large Intestine), and Cold in the winter (Water, kidneys & Bladder).
Five Element Acupucture, like Western medicine, recognizes that checks and balances exist in the body. One of the checks and balances recognized in TCM is the Victor-Vanquished relationship. What this says it that each Element controls another. These are:
Wood (Liv, GB) controls Earth (Sp, St) Fire (Ht, SI) controls Metal (Lu, LI) Earth (Sp, St) controls Water (Kd, Bl) Metal (Lu, LI) controls Wood (Lv, GB) Water (Kd, Bl) controls Fire (Ht, SI)
If Wood is too "strong", Earth will be over controlled. If Wood is too "weak", Earth will be out of control.
Some people have imbalances in the Spleen because of problems in the Spleen. Simply supplementing with Spleen-strengthen foods and herbs will help these people. End of problem. BUT, sometimes the reason the Spleen is "weak" is not because of something in the Spleen but because the Liver is too "strong". In these cases just giving Spleen-strengthening herbs and foods to the person is going to be like continuously bailing a leaky rowboat. You have to keep bailing until the leak is plugged. In this case the "leak" is that the Liver is too "strong". It's suppressing the Spleen, not allowing it to perform in tiptop shape. It's not enough in these cases just to tonify the Spleen, you also have to sedate the Liver. Calm that Liver down some so it's not a control freak overcontrolling and suppressing the Spleen.
Wood overacting on Earth (the terminology for it in the Elemental approach to diagnosis) is the same thing as Liver Invading the Spleen (the term for it in the Organ Analysis approach).
Each of the 5 main tastes have an affinity for different Elements and Organs. The sour taste has an affinity for Wood (Lv, GB), bitter for Fire (Ht, SI), sweet for Earth (Sp, St), acrid or pungent or spicy for Metal (Lu, LI), and salty for Water (Kd, Bl). If an Organ gets too much or too little of what it needs, it can run into problems. For example, cut too far back on salt, and a person can run into some major problems like the loss of too much fluid through the urinary system. But load up on too much salt, and it can be damaging to the heart. Water (Kd) controls Fire (Ht). When a person consumes too much salt, water literally is in excess and the heart can be stressed as a result.
In addition, each taste has certain properties. The sour taste tends to generate fluids and Yin, and it also "plugs leaks" (can be good for excessive sweating, diarrhea, etc.). Wood (Lv) controls Earth (Sp). The Spleen plays a major role in the transformation and transportation of food and drink. Translation: When the Spleen is weak, one possible symptom is Dampness accumulates. The last thing a person with Dampness problems needs is something that generates fluids.
The bitter taste tends to clear Heat, to sedate, and to harden. It also tends to clear Damp Heat and to subdue rebellious Qi. Fire (Ht, SI) controls Metal (Lu, LI). Too many bitter herbs can trigger problems in the Lungs. The bitter taste tends to be drying. Even though the Lungs don't like to be Damp, they also don't like to be too dry.