Breathing in oxygen causes oxidative stress, hence antioxidants

Note that many things called antioxidants (e.g. whats in some fruits) are actually oxidizing but trigger your body's own antioxidant production mechanisms

But notice they also said there is no evidence toast makes a measurable contribution to this, so toast all you want.

Or what I really got out of it was

• don’t burn your toast
• don’t burn your potatoes
• eat fewer chips

This is good advice in general though

We have to toast them get toasted or we'll dyyyy