His arguments are compelling. Most people are significantly deficient in vitamin D, which is something that I've heard from many sources (including my own physician.) Vitamin D is a hormone that is vital to quite a few metabolic processes, and deficiency can have some fairly nasty repercussions. I'm not a biochemist, but his arguments feel relatively sound to me. It's consistent with other material that I've read about the topic.
On the other hand, his book has more than a whiff of quackery about it. Whenever I see one thing promoted as the miracle cure for a variety of ailments, I get suspicious. When the author says that (some set of people) don't want you to know about this because (whatever reason, usually because it cuts into their profits), I raise a very skeptical eyebrow. When the author has his own line of products to sell you, complete with his smiling mug on the labels, I pretty much call bullshit on the whole thing. Dr. Zaidi scores a bullshit bingo here.
Even with all of the red flags, his book feels to me like it's probably more true than false.
Anyone have information on this?
Also, I really wish it was possible to just waltz into a lab and order your own bloodwork.