I have trouble buying food products as most products have many ingredients and it is really difficult (sometimes even impossible) to verify all of the ingredients as halal? How do I pick food items if I am unsure whether all materials are halal or haram? Also, is it possible for muslims to eat products that are kosher or are made for vegetarians?
The easiest way to confirm whether a particular food is Halal for a Muslim or is to look for any sign that will verify that "this product is suitable for vegetarian". Any product that is suitable for a vegetarian will contain no meat or by meat products. Therefore it will be Halal to consume.
Also vegan product are also Halal.
Kosher meat is made Halal by Allah because it is slaughtered by Jews but one should first confirm the authenticity of the Kosher certification.
And Allah knows best.
Mufti Ikram ul Haq
Fatwa Center of America