I eat fruit, mainly berries and kefir most mornings and I haven't had so much as a sniffle since before COVID. I've really let my diet go this Christmas and had a week long cold.
Obviously I can't say it was totally because of my diet but it certainly felt like it. Hardly drink, green tea and a couple of pieces of dark chocolate each day, lean meats, fish once a week, good breakfast of fruit and kefir and 6-10 fruit and veg a day. lots of walking, 8 hours plus sleep each night and I genuinely feel 100% better. More energy, rarely ill, no anxiety.
I do eat red meat, but high quality