I am PRO vitamin D supplement if your levels are low and for maintenance if you are not getting enough sun to raise your serum levels. Back in 2007, my levels were so low (12ng/ml) that I was getting sick every month or two and a simple cold would turn into sinus infections and would take 2 weeks to get over. I would have at least 2 bouts of bronchitis a year. Every virus that was going around, I would get. I had been this way for at least 2-3 years prior to getting my levels tested. BTW, optimal levels of D3 (25-hydroxy) is 65-80ng/ml, so 12 was extremely deficient. I had been taking 1,000iu D3 capsules sporadically because I'd been brainwashed into thinking that it was too high of a dose to take daily. I live in Virginia so the only time the sun was optimal for raising D3 levels was in the late spring to summer. Virginia has HOT summers, often getting into the upper 90s to over 102F by late June. Couple that with my being brainwashed about the dangers of sunlight and skin cancer, I used sunscreen if I was out in the sun for any length of time and I no longer sunbathed. It is no wonder why my levels had dropped to dangerous levels. After I found out that I was deficient, I began taking 20,000iu D3 daily and after 3 months, my levels had been boosted to 54ng/ml. After supplementing at 20,000iu for three more months, I'd gotten my levels to 70ng/ml. I now take 5,000iu daily. I no longer use sunscreen until I've been out in the sun for at least 20 minutes, but I don't get out in the sun everyday in the summer unfortunately. But I do try to get out more often than I used to.
The Bacteriality site is run by a man who has absolutely no clinical or scientific research background in genes or biochemistry. He is an electrical engineer. His information (which is just his theory) has absolutely no scientific basis and has been disproved scientifically, time and time again by the vitamin d researchers. For correct information about vitamin d and why getting your levels optimal is important, you should read the information on the vitamindcouncil.org site.