Deuterium levels differ in different part of your body. Where deuterium is required for biological processes it is high, like your blood (150 ppm). But in your mitochondrial nanomotor it must be low or preferably absent as they only use hydrogen to ”rotate” the engine.
Some researchers feel deuterium in tissue should not exceed 130 ppm based on levels found in green plants and grass-fed animals.
Deuterium depleted water helps reducing deuterium levels in the body.