Before eating on Shabbos morning, there is an obligation to make kiddush. This obligation to recite kiddush only starts after davening shacharis. Until then it is not permitted to eat just as every other day of the week that it is not permitted to eat until after davening. Anything permitted to eat before davening, such as tea or coffee, can also be eaten on Shabbos before kiddush. The Mishna Berura 289:1 says that if someone needs to eat a meal before davening on Shabbos (for health purposes), he is obligated to make kiddush first.
The halacha for some women is different. A woman who is unable to daven due to her obligation to take care of her children, is required to make kiddush before eating even a small amount of food. Being that she is not going to daven, the mitzvah of kiddush starts as soon as she wants to eat. Rav Moshe Feinstein O”H 4:101:2 says that even in such a situation a married woman is not required to say kiddush until after her husband returns from shul. Rav Shlomo Zalman Aurbach disagrees. A woman should make her own kiddush if she needs to eat before the seuda.

Rabbi Tzvi Aryeh HymanMir Yeshiva, Jerusalem- [email protected]