★★★★★
I've been taking a higher dose of niacin for quite a while now, wouldn't be without it.
I've found that niacin, when taken at the higher dose, is perhaps the most relaxing vitamin or mineral that I have ever experienced (Magnesium Chloride comes pretty close though). I always sleep like a baby whenever I take 500 mgs in the evening.
If you haven't got high blood pressure or heart problems then niacinamide (no flush form) is fine to use for all its immune boosting and other health benefits.