Food cravings can be distracting for pregnancy nutrition. They may feature foods you’ve never wanted before or a spike in the consumption of your servings. Cravings are said to be the body’s way of demanding nutrients for pregnancy. The rule of thumb is to indulge these cravings with moderation as guide.

Janet Pope, PhD, an associate professor of nutrition and dietetics at Louisiana Tech University in Ruston believes that just as women have cravings during menstruation which are powered by hormones, the same thing can happen during pregnancy.

While these are all theories as of now, it is a common observation that the taste preferences of pregnant women change during this phase. Here are some scientific offerings from Valerie Duffy, PhD, an associate professor in the School of Allied Health at the University of Connecticut in Storrs, showing that women:

- Liked sour tastes more in the second and third trimesters than in the first trimester or before pregnancy. Like a preference for sweet tastes, a sour preference helps women get a more varied diet later in pregnancy so they can get enough calories, says Dr. Duffy. A yen for sour foods also seems to explain the classic pickle craving. And since fruit is typically a combination of sweet and sour tastes, it also explains why fruit is the most common pregnancy craving.

- Showed an increased preference for salty tastes — which would include foods like potato chips and pickles (again!) — as their pregnancy went along. During pregnancy, a woman’s blood volume increases, so this taste change may be tied to her greater need for sodium.

- Had an intensified perception of bitterness during the first trimester. Scientists suspect that being able to isolate bitter tastes during pregnancy is an evolutionary protection, because many toxic plants and fruits taste bitter. This taste change helps warn pregnant women against consuming poisons, such as alcohol, during critical phases of fetal development, agrees Dr. Duffy. Interestingly, the aversion to bitter tastes typically lessens by the third trimester, when the crucial phases of fetal development have ended.