There are lots of men on The Peak Testosterone Forum that are megadosing Vitamin C, and I'm one of them for the reasons I outline here: Why Take Vitamin C? That said, I cannot emphasize enough that, in general, megadosing on antioxidants is very unwise due to some rather horrifying issues uncovered in recent research: The Dangers of Megadosed Antioxidants.
But let's say, like me, you've drunk the koolaid and believe that Vitamin C is the one antioxidant that we can and should be megadosing, then here are 3 Critical Ways to Take Vitamin C To Hopefully Keep From Hurting Yourself:
1. Buffered on an Empty Stomach. I don't believe anyone takes straight ascorbic acid any more, but just in case: they now have great buffered forms such as this: Ester-C Vitamin C that are gentle on the stomach and very absorbable. And, if you want the turbocharged version, consider liposomal Vitamin C.
Why is it so important to take on an empty stomach? The reason is that Vitamin C can increase iron absorption. This is potentially dangerous and could increase ferritin and body iron stores, something that has been linked (on the high end) to various types of chronic disease. If you ask me, it's better to play it safe and take it with no food in your stomach - and Ester-C should not upset your stomach.
2. 500 mg 2-3 Times Per Day. In my opinion Vitamin C is best taken several times during the day. The reason for this is simply to make sure that plasma levels stay high as this can improve nitric oxide levels in your arteries and potentially collagen formation and artery protection. The NO increase is not huge with Vitamin C alone but every little bit helps, eh? It should also be noted that, if you combine Vitamin C and garlic, you can get a HUGE synergistic effect on nitric oxide, something I discuss in my page on Garlic and Erectile Dysfunction. In fact, this strategy boosts nitric oxide so much that I believe you have to be careful using it. (You don't want to increase inducible nitric oxide in the process.)
By the way, you will still often read that, if you take more than 200 mg/day of Vitamin C, it does not significantly raise plasma levels and so it is a waste of time and money. This was completely disproven by the research here: Liposomal Vitamin C, where the authors showed that Liposomal Vitamin C could greatly increase plasma levels beyond the 200 mg per day "saturation point" and, furthermore, that long time megadosers have plasma levels that are significantly higher due to tissue reabsorption. In the case of the latter, Vitamin C is stored in tissues and released later.
3. Never With Fat In Your Stomach. If you do consume Vitamin C at or near meal time, then realize that there is a study out there showing that, if the contents of your stomach contains over 10% fat, then Vitamin C could increase nitrosamine formation. What are nitrosamines? Basically, these are carcinogenic chemicals that exist, for example, in certain types of processed meats.