Dr. Ray Sahelian seems like a health-conscious, ethically-centered physician who does a pretty good job of assessing the true effects of supplements.  I like his site because his language is thoughtfully circumspect.  If he doesn't know the benefits of a particular supplement, he'll state as much.  And his recommendations seem cautious or at least contingent upon specifics.  That is rare for the internet.  Below is a sample question and answer on the supplement Benfotiamine.

QUESTION

Vitamin Supplement Little More Than 'Snake Oil,' Researcher Claims. Science Daily (2008)  — A popular vitamin supplement is being advertised with claims that are demonstrably untrue, as revealed by research published in the open access journal BMC Pharmacology. Benfotiamine is a synthetic derivative of thiamine (vitamin B1). It is marketed heavily as a dietary supplement using a selection of unsubstantiated, 'not-quite-medical' claims that tend to characterize this field. A large part of this campaign has been built around the belief that benfotiamine is lipid-soluble and, therefore, more physiologically active. Scientific research led by Dr Lucien Bettendorff of the Center for Cellular and Molecular Neurobiology at the University of Liège, Belgium, has entirely disproved these claims. According to Lucien Bettendorff, "We suspect that those companies selling benfotiamine have poisoned much of the recent literature in an attempt to bestow it with properties that it does not have". Benfotiamine has been previously shown to prevent several diabetic complications in experimental animal models. The researchers carried out experiments in mice in which it was administered using several different techniques and the resulting levels of thiamine were measured in various parts of the body. Contrary to other claims about its solubility, the results show that it is only sparingly soluble in water under physiological conditions and cannot be dissolved in octanol or oils. As Lucien Bettendorff explains, "Benfotiamine is very often considered a 'lipid-soluble' thiamine precursor from the disulfide derivative family though it is neither lipid-soluble, nor a disulfide. Sometimes, it is considered to have more biological activity than thiamine disulfides, but our study shows that it does not even penetrate cell membranes, except in those cells containing an ecto-alkaline phosphatase. There is no evidence that benfotiamine would be more effective than other precursors as a therapeutic agent for complications of diabetes." Journal reference: Marie-Laure Volvert, Sandrine Seyen, Marie Piette, Brigitte Evrard, Marjorie Gangolf, Jean-Christophe Plumier and Lucien Bettendorff. Benfotiamine, a synthetic S-acyl thiamine derivative, has different mechanisms of action and a different pharmacological profile than lipid-soluble thiamine disulfide derivatives. BMC Pharmacology, 2008.     

ANSWER

As with many supplements or medications, it often takes many years of research from various centers to finally have a good understanding of whether the supplement or medication works or whether is is ineffective. We happen to be in the early stages in terms of benfotiamine research and it is not easy for me to predict the outcome.