[ckilmer]

I recently started taking two grams each of glycine and nac —three times a day.

This combination has significantly increased my feeling of health and well being

I’ve not read of any upper limits for the safe intake of glycine much below 10 grams daily

However, the literature generally limits the safe intake of NAC to only 2 grams daily. However, the only study on unsafe NAC limits I’ve seen were at about 10 grams daily and that was outlier.

Have you read about any safe upper limits to NAC daily intake.

[ConservativeMind]

I would take smaller doses more frequently. Whatever can't be immediately used to make glutathione or SOD is used elsewhere in one-off amino acid situations, which can be good, but can be bad. For instance, some cancers love cysteine. If, instead, you take equal amounts of glycine with cysteine (NAC), your body preferentially converts it to the much needed glutathione, while other processes (including cancer) get just residual, more normal, amounts, as I've read. Do note we still make a little cysteine and get some from food, but no longer enough for our total needed processes. Glutathione lasts just a few hours in our cells before it's used up.

Too much glycine, by itself, can make people pretty drowsy. Too much NAC, by itself, without a direct, known, bodily need hasn't been generally tested in people for much beyond a handful of weeks, in my readings. So acute ingestion of glycine and chronically high amounts of NAC appear to have concerns not well fleshed out, in my thinking.

Do note, however, the two GlyNAC studies were done on 70-80 year old people, and their ingestion rates were at or above 7,000 mg (7 grams) for each of glycine and NAC, but seemingly done periodically through the day, as they most noted the glutathione results causing so much good, with secondary results from excess glycine and cysteine. How do you get the most glutathione into your body's cells each day? Take a lot of smaller doses of GlyNAC, spaced a few hours apart.