Your father is probably already taking Prilosec OTC or a doctor prescribed equivalent. If not, he should really look into it to help get the acids that cause the gastric reflux under control. As far as diet, here are a few good rules of thumb: Avoid coffee, instead try clear tea such as green tea. Avoid tomato sauces, citrus, soda, alcohol and fatty foods. Last but not least, eat meat with less feet. White meat from poultry as well as fish are his best options.