problems with food....

Three problems that arise through food are identifiable. The first East are natural problem of food. Foodstuffs like onion, meat, and liquor create some problems owing to the inherent nature.
If you consume these things, the mind will not get set on God. The purity of the mind will be spoilt. Lust and anger take precedence. Foodstuffs that grow under the ground like tubers, increase the dullness of the mind. (tamasic)
We have already seen that Mind is very powerful. If we go with people who have a pure mind our mind also falls in line. Does the person's mental vibrations affect the environment? Yes, it does! This is something that cannot be physically measured or seen. This can also pervade material things, therefore it becomes important, from whom we get the food.
Now for the second problem. The food items created by a loving mother will certainly always do good. If a cook comes from outside and cooks at home much depends on the mental status of the person. The worries and tensions of the person pervade the food. This is called asreya dhosha. That is why it is recommended that while cooking one must keep chanting slokas or do nama japa in praise of god.
The third problem connected to food is that of the environment in which the food is kept. Unhygienic conditions, something like insects falling in the food, mixing of dust, hair - all these will influence our mind. That is why people who were particular about the spiritual advancement do not partake food that is cooked by others.
Shri Ramanuja must have been speaking from personal experience. There is a story that relates his sufferings from food.