I think that it is wonderful that you are open to the possibility that your digestive system is clean due to the good care you have taken of your body. There is a saying "there are no absolutes" which might apply. Just because the makers of these cleansing products say that everybody needs them, does not make this so. Magnesium is very safe. As far as my understanding goes, the worst thing that could happen from taking too much magnesium is an excessive number of trips to the bathroom, and perhaps dehydration if a lot of water was lost and not replaced. Every body is different. I think it is entirely possible that the effective dose for cleansing for you, given that you are a big man, is significantly higher than the suggested dose.