Fun fact: Doritos don’t contain tartrazine in Europe (including the UK). It’s not banned, but food products containing it must be labelled with “may have an adverse effect on activity and attention in children” in the EU.
Notably, only one local chain sources M&Ms from Europe, so we buy from them. All other stores source M&Ms from the US and have these colours. You can see the difference in the candies.
0: https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2026...
The kosher rules have more to do with cultural identity: "we are the people who eat/don't eat X". We have similar rules today. We revile people who eat foods we consider dirty (insects, dogs, horse, etc), but they suffer no ill effects.
They do reconsider the kosher rules in modern lights. Insect derived dyes are banned, for example. But they don't need scripture to tell you what's healthy. They use science for that.