Berkeley, California nutrition writer Clara Felix was one of the early trailblazers in using nutrition to fight disease. In the late 1990s, when vitamin D researchers discovered we needed much more vitamin D than had previously been thought, Clara upped her intake to 4,000 IU per day. After three months, an arthritic knee that had failed to improve with exemplary lifestyle, good supplements and avoidance of allergens alone became completely normal again! She was delighted to report being able to squat and do deep knee bends for the first time in eight years. It's not surprising.  Vitamin D is anti-inflammatory and also plays a role in the synthesis of synovial fluid, which lubricates the joints and prevents their wear and tear.   Studies have shown that having higher levels retards the deterioration of arthritic knee and hip joints. Clara also related this story about two chimps suffering from a "mysterious illness" who were…