There are studies showing that when purity increases by 0.1%, absorption rate can be increased by 2 to 5 times. There are also studies showing that NMN with a purity of 99.3% is not absorbable at all.
Let’s take iHealth’s 99.8% purity that allows 95% absorption as a base.
Under a very conservative calculation:
99.8% purity = 95% absorption (iHealth)
99.7% purity = 47.5 % absorption (after 50% reduction)
99.6% purity = 23.8 % absorption (after 50% reduction)
99.5% purity = 11.9 % absorption (after 50% reduction)
99.4% purity = 6.0 % absorption (after 50% reduction)
99.3% purity = 3.0 % absorption (after 50% reduction)
You can see that absorption rate is close to zero at a purity of 99.3%. 99.3% sounds to be a very high number, but as far as absorption rate is concerned, it’s not.
If you are paying a similar price for a bottle that contains say, only 99.5% purity, your body is absorbing only 12% of it. That means you are paying almost 10 times comparing to those with 99.8% of purity. Another issue is that even with a low % of impurities, long term consumption of an unknown impurities from that 0.5% each day will add up to be a big concern.
iHealth’s NMN actually has close to 100% purity (even higher than 99.8%) but due to the hefty penalty imposed by the cGMP certification (prior cases of fines not less than US$500M for breaching the standard), the company selects to state only 99.8% to play safe.