I think you're being downvoted because of the "Withdrawn statements" comment. It looks like this has been posted multiple times in the same thread, but the statement was not withdrawn.
> appropriately planned vegetarian, including vegan, diets
Most people's diets are not "appropriately" planned because most people never actually consult a nutritionist. This means most of those diets miss their mark and since that diet narrows the alternatives it's far easier to lose those benefits.
And can't see anything about any disbenefits of introducing animal products in that diet in "appropriately planned" quantities. Would introducing certain amounts of animal products in your diet affect in in any direction? So would adding a moderate amount of fish in your vegad diet sabotge or improve it? Or no difference?