Hi Mike, welcome and thanks for the info 
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This is the mice study that showed Nicotinamide Riboside normalized healthspan and lifespan of mice lacking ATM function. You can purchase Nicotinamide Riboside from Truniagen.com or amazon.com. The only legiate Nicotinamide Riboside is the Tru Niagen brand. I have been taking it for 3 years and it has great anti aging benefits.
How much of Nicotinamide Riboside do you take day?
Re Nicotinamide Riboside, it has to be said that most research has been done on animals, and much more high quality research is needed before recommending it as a treatment.
Nicotinamide Riboside is a new vitamin B3. It is very safe. It is worthwhile to give it a try. It has been shown in a clinical trial that Nicotinamide Riboside is the most effective against ALS. More effective that drugs costing over &100,000 per year.