The presence of other substances (soluble fiber for example) that slow metabolism of carbohydrates. (sugar-and-sweetener-guide.com)
In addition, mercury impairs many enzymes needed to metabolize food into energy, including pyruvate dehydrogenase, which is required for metabolism of carbohydrates but not fats or proteins. (westonaprice.org)
VITAMIN B12 SOURCE: Bioavailable vitamin B12 is essential for normal metabolism of carbohydrates, fat and protein. (healthy4lifeonline.com)