Does food play an importnt role when taking doxycycline wit regards to efficacy of the drug to treat ailments or infections? Do you have to eat often?

Affects absorption. Foods, especially ones that contain calcium like milk affect the absorption. If you eat when you take it will not be as effective.
Oral absorption. Food does not play a significant role in the absorption of the doxycycline, unlike other similar medications. Some people experience GI upset, such as nausea with this medication, so taking it with food may be advisable for this reason.