Question

have to do .many of the ideas which scientists tell us have

Answer 1

many of the ideas (which /scientists tell us/have no foundation ) have to do with mixtures of foods.

用括号括起来的句子是定语从句,没有括的地方是主句./../之间的是插入语

have to do with也可以是处理什么事情,和什么有关的意思.

这句话的意思是：

科学家告诉我们的,许多和食物混合料有关的想法是毫无根据的.