I keep reading having an unhealthy diet gives you toenail fungus!

I keep reading having an unhealthy diet gives you toenail fungus! As a former professional footballer for 22 years I have had the best dietician, personal trainers fitness programmes I've maintained very good fitness all my life and a healthy balanced diet. I have never had any toenail issues until 15 years ago after my career. I shared changing rooms with many other team mates including showers etc.