I have elsewhere remarked on the apparent lack of benefit to taking multivitamins and the possible harm; so one might well wonder about a specific vitamin like vitamin D. However, a multivitamin is not vitamin D, so it’s no surprise that they might do different things. If a multivitamin had no vitamin D in it, or if it had vitamin D in different doses, or if it had substances which interacted with vitamin D (such as calcium), or if it had substances which had negative effects which outweigh the positive (such as vitamin A?), we could well expect differing results. In this case, all of those are true to varying extents. Some multivitamins I’ve had contained no vitamin D. The last multivitamin I was taking both contains vitamins used in the negative trials and also some calcium; the listed vitamin D dosage was a trivial ~400IU, while I take >10x as much now (5000IU).
Directions — as a dietary supplement take 2 veggie capsules once a day . For best results take 20-30 min before a meal with an 8oz. Glass of water or as directed by your healthcare professional. As a dietary supplement take two (2) veggie capsules once a day. For best results take 20-30 minutes before a meal with an 8oz. glass of water or as directed by your healthcare professional. — Suggested Use: As a dietary supplement, adults take one (1) capsule per day. Do not exceed 2 capsules per day. —
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Jump up ^ Weyandt LL, Oster DR, Marraccini ME, Gudmundsdottir BG, Munro BA, Zavras BM, Kuhar B (September 2014). "Pharmacological interventions for adolescents and adults with ADHD: stimulant and nonstimulant medications and misuse of prescription stimulants". Psychol. Res. Behav. Manag. 7: 223–249. doi:10.2147/PRBM.S47013. PMC 4164338. PMID 25228824.
On the other hand, Phillips said, Provigil's effects "have attenuated over time. The body is an amazing adjusting machine, and there's no upside that I've been able to see to just taking more." A few years ago Phillips tired of poker and started playing competitive Scrabble. He was good, but not that good. He was older than many of his rivals and he needed to undertake a lot of rote memorisation, which didn't come as easily as it once had. "I stopped short of memorising the entire dictionary, and to be really good you have to get up to eight- and nine-letter words," he told me. "But I did learn every word up to five letters, plus maybe 10,000 seven- and eight-letter words." Provigil, he said, helped with the memorisation process but, "it's not going to make you smarter. It's going to make you better able to use the tools you have for a sustained period."
The main concern with pharmaceutical drugs is adverse effects, which also apply to nootropics with undefined effects. Long-term safety evidence is typically unavailable for nootropics. Racetams — piracetam and other compounds that are structurally related to piracetam — have few serious adverse effects and low toxicity, but there is little evidence that they enhance cognition in people having no cognitive impairments.