@Fragglemuppet -like millions of other men.....
Many foods have at least a few their nutrients lessened/destroyed by cooking btw (like vitamins B, C & potassium), even as the cooking process makes some nutrients (like beta carotene) more bioavailable, so that generality on cooking is particularly awful... because it's really "which nutrients do you most need now" as that's a part of why "a balanced diet" in concept makes sense.