I recently had some lab tests done as a part of an annual check-up. I am considered to be in excellent health and live a healthy lifestyle (low-fat and organic diet, regular exercise, don't drink, don't smoke, have never used drugs, etc.). All of my lab results were completely normal with the exception of my ALT level. A year and a half ago, my ALT level was 56. Four days ago it was 102. Today it was 169. What could be causing this?