Combination of food stuffs?

Question

There is a traditional belief in certain countries that certain combination of food stuff is to be avoided as it is considered not good for health..
For example-Eating
Fish, onion. garlic or
citrous fruits
With any of the following
Milk[not boiled]
curd, buttermilk or a combination of that.
Since this is only a belief it may or may not be scientifically proved.However these ideas are coming from ages from the experience of people.The question is do you have in your country such bliefs regarding food combinations that are to be avoided for better health.. A knowledge of such beliefs can help those interested in taking up research on the subject .

Please give the answer in detail so that it will help people wishing to do research on the subject

Answer 1

supposedly Andrew Jackson died from eating cranberries with milk.

Answer 2

It's to do with the reaction citric acid has with milk and if the reaction was to happen inside the body then the lining of the internal organs may get corroded.