Vitamin D is a fat-soluble vitamin, which means the vitamin goes into our fat cells and the body does not excrete it. It is a required vitamin for our body to stay healthy as all the other vitamins and minerals are necessary. Vitamin D may decrease from certain medications such as certain anti-seizure, corticosteroids, heparin, certain antibiotics, mineral oil, and antacids; or certain disease states such as celiac disease, Crohn’s disease and Whipple’s disease. 2000 IU is the tolerable upper intake level for adults; supplementation over that may cause a risk for toxicity can cause hypercalciuria, hypercalcemia, bone and soft tissue calcification, and kidney stones. (Increase calcium, weak muscles, weak bones, excessive bleeding, and severe headaches). Vitamin D is available through our foods - Fortified milk, breakfast cereals, egg yolks, fatty fish, and fish oils. Sit at a window with the sun shining in for about 1/2 hour (few times a week) and that will help you get enough Vitamin D. Suggest you go to your MD and get blood work done to determine your Vitamin D levels before you start to take supplementation.
You can't rely on just one thing. However, as one who nearly died from severe vitamin D deficiency, I know about the validity in bringing attention to this vitamin that has pretty much been ignored for my entire life. From personal experience, I do know that when I keep my vitamin D levels up high enough, I haven't caught any viruses for a good four or five years. I didn't say I didn't have other health problems, but I have at least not had to deal with the seasonal colds and flus. I still use good sense concerning avoiding crowded areas and using good hygeine and avoiding touching my face even though my allergies make my eyes or nose itch badly at times.
It is not a cure all by any stretch of the imagination, so it is not the end all be all. If it were, a lot of deadly diseases would have already been cured. However, you should not be so quick to dismiss its value. It is still a critical part of your immune system. I nearly died because of the pervasive dismissive attitude that had been the long standing norm concerning vitamin D. My levels were so low that they scared the conventional doctor.
Really, as with anything else, good sense should be used. The Vitamin D Council suggests that for starters, one should test their vitamin D level to see where they're at. Then, the next thing to do would be to take a specific dosage daily for 3-4 months and get tested again and this would help to determine if the amount you're taking is the correct amount for you or not. This is how I know that the amount I take myself is not too much. Many conventional doctors don't want people to take more than 2,000 iu/day if their vitamin D level is where it should be. The Vitamin D Council recommends 5,000 iu/day but to monitor it by testing it again in three months. Most people are deficient and are not going to get vitamin D toxicity. There is a greater liklihood of vitamin A toxicity in our part of the world than there is in vitamin D toxicity. The Vitamin D Council does point out some important information here about how much healthy adults should take when they recommend the 5,000 iu/day. Each person does metabolize vitamin D differently. This is why they recommend monitoring the level to see which dosage is right for you. What is right for someone like me with auto-immune issues may be far too much for someone who has a healthier more normal immune system. Five to six thousand iu/day is not really too much for a great number of us, and for people who spend sufficient amount of time in the sun, those people can actually get by without taking any vitamin D supplements during the sunny season. That is the natural way of getting vitamin D without any concern of overdosing whatsoever.
When people are as severely vitamin D deficient as I was, they are prescribed a once weekly megadose of vitamin D 2. But, they are still told to take a daily dosage of vitamin D3 of 2,000 iu. The idea behind this is to not only boost with the megadose, but to maintain with the daily dose. It matters overall which form of vitamin D you supplement with. So long as you don't need to raise your vitamin D level, then you only need to supplement with natural D3. Also, depending on what your starting out vitamind D level is will help to determine how much you should take daily.
There is sufficient evidence and sufficient personal experience that says that it is not a "scam", but I wouldn't call it a "cure all" either. The truth is actually somewhere in between, but it is a very critical part of your immune system. Dr. Mercola explains how it works and so does the Vitamin D Council. I would recommend looking at both sites and not just surface scanning, but look at the research.
Also, don't forget what I said in my own case. I really did almost die from not having enough vitamin D in my system. I still have health problems, but I'm still better off than I was. I'm still going to have to deal with certain health problems, but giving my immune system this important support is what has kept me alive and what has kept me from constantly catching every virus out there like what was happening before. This may not be a 100% guarantee that I never will catch one of these viruses again, but this is still much better than catching these viruses every time I turn around.
i take 10,000 to 15000 units a day. my level went from 19 to 58 in a good few months...from february to october. although i took a week off of any vitamin d before testing..so it could have been higher. iwant to maintain at 85....from my knowledge, 5,000 units a day MAINTAINS ur current level....vigtamin d goes away if u dont keep taking in adeuate d....so taking 2k a day will prob slowly make you deficient again. be sure to take d3 not d2. also get the 25oh test not 125oh.