I was asked to write a short article comparing two brands of a food item, both brands are Jewish companies. Is it loshon hara to promote one brand over the other- specifically because one item is healthier than the other.
I wouldn’t say “don’t buy ‘x’,” I would say “‘y’ is better because…”
It is permissible to write a review and point out the various advantages each one has over the other. There is no negative intent and this is important information which is accessible to everyone on the label. Both brands will probably be happy with their product being discussed in a public forum.