Hello, Thank you for asking your question at health care magic There are several dietary restrictions while taking Isoniazid. The key is to avoid food rich in histamine(like tuna,mackeral,shell fish,anchovies,mushroom,tropical fish) as this can result in low blood pressure and also avoid food rich in tyramine . When tyramine is taken with isoniazid it causes blood pressure to shoot up.The tyramine content increases as food ages.Avoid overripe and dried fruits as well as fermented vegetables like kimchee and sauerkraut. Fermented soy bean , tofu ,fermented and aged cheese ,fermented and dry sausages,pepperoni,salami , chocolate are also considered high in tyramine. Regarding bread products avoid home made yeast breads, sourdough bread as yeast extracts contain high levels of tyramine. Instead, choose commercially prepared breads: white, wheat, rye, French bread and bagels. Even when purchasing commercially prepared breads,look if it contains yeast extract,marmite(also made from yeast extract) or brewer s yeast . You can have sweets as long as it do not contain any histamine/tyramine rich ingredients.Avoid desserts containing chocolate,cocoa powder Avoid alchohol while taking Isoniazid and Prifitin. When in doubt always consult/call your health provider before taking the food. Hope I was able to answer your question Please feel free to address any more questions or concerns Regards, Dr.Lekshmi