Normal blood and tissue levels of CoQ10 have been well established by numerous investigators around the world. Significantly decreased levels of CoQ10 have been noted in a wide variety of diseases in both animal and human studies. CoQ10 deficiency may be caused by insufficient dietary CoQ10, impairment in CoQ10 biosynthesis, excessive utilization of CoQ10 by the body, or any combination of the three. Decreased dietary intake is presumed in chronic malnutrition and cachexia(12). The relative contribution of CoQ10 biosynthesis versus dietary CoQ10 is under investigation. Karl Folkers takes the position that the dominant source of CoQ10 in man is biosynthesis. This complex, 17 step process, requiring at least seven vitamins (vitamin B2 - riboflavin, vitamin B3 - niacinamide, vitamin B6, folic acid, vitamin B12, vitamin C, and pantothenic acid) and several trace elements, is, by its nature, highly vulnerable. Karl Folkers argues that suboptimal nutrient intake in man is almost universal and that there is subsequent secondary impairment in CoQ10 biosynthesis. This would mean that average or "normal" levels of CoQ10 are really suboptimal and the very low levels observed in advanced disease states represent only the tip of a deficiency "ice berg". HMG-CoA reductase inhibitors used to treat elevated blood cholesterol levels by blocking cholesterol biosynthesis also block CoQ10 biosynthesis(13). The resulting lowering of blood CoQ10 level is due to the partially shared biosynthetic pathway of CoQ10 and cholesterol. In patients with heart failure this is more than a laboratory observation. It has a significant harmful effect which can be negated by oral CoQ10 supplementation(14). Increased body consumption of CoQ10 is the presumed cause of low blood CoQ10 levels seen in excessive exertion, hypermetabolism, and acute shock states. It is likely that all three mechanisms (insufficient dietary CoQ10, impaired CoQ10 biosynthesis, and excessive utilization of CoQ10) are operable to varying degrees in most cases of observed CoQ10 deficiency.
