1973 study showed simple sugars slow white blood cell mobility. Drug companies have tried to counter this with studies with rats running on treadmills, which conveniently clears excess blood glucose. Also, vitamin C helps white blood cell mobility, but is chemically similar to simple sugars and competes in white blood cells, so consuming large amounts of sugar negates the benefits of vitamin C. Unless, of course, you can go for a jog every time you consume sugar while you're sick.