How many people suffer from itchy feet or athlete's foot or toenail fungus?

the fungi feeds off the keratin in skin and nails as well as the glucose in the blood, so yes a diet high in sugar would create a better environment. This is why diabetic patients are more susceptible to developing athletes foot however it has to be noted that with diabetes the immune system is compromised. Diet is important and and can also affect the immune system, but there are other factors to consider such as foot hygiene.