The answer to this type of question from a client is unlikely to help them much, but may lead to a useful conversation on making those handful of changes which will bring the biggest benefits.
Daily movement – You make time in your day for movement, eg 3 x 10 minute brisk walks.
Steady state cardio – Spend some time each week performing your favourite cardio for 20-40 mins where your heart rate is at (180 – Age)beats per minute
Load bearing exerise – A couple of times per week work on your strength using body-weight, gym weights, bands etc.
Relaxation – take time out to relax and contemplate your day, mix in some mobility work at the same time should you wish.
Adequate sleep – as an adult make it a priority to get between 7-9 hrs of restful sleep?
Nourishment – Eat a balanced diet full of a rich variety of seasonal vegetables, fruit and some good quality fish and meat if yuou desire. Reduce the amount of processed food you consume. Try to be strict with yourself 5 days out of 7, that’ll give you the chance you enjoy a few of your treats be that food or drink on a couple of days/week.
Obviously for a performance athlete things would be different, if all the basics are in place then nuances of sweet potatoes versus white potatoes, kale versus spinach, ice baths after training, cycling intensity and peaking for events come into play. At that point getting many small things right can add up to a competitive advantage. For most, who are looking for the health and longevity benefits, getting the basics right and being consistent will get you to where you need to be.
Back to the original question “Should I swap my fresh spinach for kale in my weekly shop?”. I’d probably suggest buying what’s in season or alternating week to week for variety because it doesn’t really matter.