NutriSearch Comparative Guide to Nutritional Supplements for the Americas, Abridged Sixth Edition

When the NutriSearch Comparative Guide to Nutritional Supplements was first published in 2007, prevailing scientific wisdom held that dietary antioxidants, such as vitamin C, vitamin A, vitamin E, and other antioxidant compounds found in our foods, functioned as scavengers of dangerous oxidative compounds known as free radicals, found in the foods we eat and throughout our environment.

We now know this is only partially correct. Dietary antioxidants do function as free-radical traps in those regions of the body where they are at high concentrations, such as in the gut, the blood, and the extra-cellular spaces. Within the cells of the body, however, their concentration is not high enough to act effectively in this manner.

In 2015, as we researched the sixth edition of the Guide, strong scientific evidence had emerged showing that—with exception of vitamin E and glutathione (a principal antioxidant in the liver), which are true cellular free-radical scavengers—most dietary antioxidants do not work the way we thought they did. Instead, dietary antioxidants act as signaling messengers that engage the cell’s own evolutionarily conserved internal antioxidant defences, honed by over two billion years of evolution.

This emergent scientific understanding in how antioxidant defence at the cellular level works is a real game-changer. The findings present a quantum leap in our understanding of cellular health. First introduced with 2017 launch of the sixth edition, this information continues to be updated and explained in this 2025 abridged addition of the Guide.

With exhaustive market research on over 1,400 dietary supplements in the United States, Canada, Mexico, and Colombia, find out how our completely revised analytical criteria, based on the science of cell signaling, rate your favourite multiple vitamin and mineral products.