Trevor Marshall and his protocol - more salesmanship than science
Trevor Marshall is often mis-identified as a biochemist, while in reality he is an electrical engineer with a somewhat shady background. See:
http://sci.tech-archive.net/Archive/sci.med.diseases.lyme/2005-08/msg01695.html
As one article skeptical of Marshall noted, his views that people should avoid vitamin D and avoid sunlight run counter to the overwhelming bulk of qualified opinion. None of his theories about vitamin D have been proven in vitro, and especially not in vivo. Sometimes a lone wolf who turns out to be against the overwhelming tide of opinions and evidence to the contrary is correct, but I don't think Marshall is such a wolf.
Convincing people about Vitamin D dangers is vitally important to attract people to Marshall's highly controversial protocol, and thus vitally important to the profits he and his fellow board members with vested interests in the protocol depend on. It is Marshall and his group who have authored numerous articles and papers against Vitamin D and in support of his protocol. Proper scrutiny reveals them to be self-serving articles where they cherry-picked and misrepresented studies and facts to support their premise about vitamin D and thus their protocol.
To put is succinctly, most things you see which support the Marshall protocol originate from Marshall and his group and boil down to much more salesmanship than science.
For more on Marshall, his protocol and his cohorts:
Bacteriality.com is a Marshall Protocol shill site