Does Protein Ease Morning Sickness?

By various estimates, nausea and vomiting affect 50 to 80 percent of pregnant women during the first three months of their pregnancy. Morning sickness — so called because it tends to be worst upon rising — is more than a miserable inconvenience. Many women find it difficult to keep working, at home or on the job, and the condition compromises their overall health status. Physicians are reluctant to prescribe anti-nausea medications because of possible effects on the developing fetus. Other therapies, such as acupressure and acupuncture, have not been shown to be effective. For the most part, doctors recommend modifying the diet, typically proposing all-carbohydrate meals such as soda crackers, a stalwart in the prevention of sea sickness. The reports supporting this approach are primarily anecdotal, however.

The exact cause of morning sickness nausea is uncertain, simply because most of the techniques for studying stomach action are invasive and therefore unsafe in pregnant women. The best current explanation, based on a noninvasive technique called electrogastrography, is that the nausea comes from disturbances in the normal wave patterns of the stomach's muscular walls, producing a rhythm that is either too fast or too slow.

Recently, a group of scientists at the University of Michigan reported on an investigation to see which type of meal best reduced the symptoms of morning sickness and what effect this type of meal had on the stomach's activity.1 The study population consisted of 14 women in the first three months of pregnancy who had experienced nausea continuously or intermittently during the prior two weeks. After fasting overnight, the women were given a meal, then their stomach activity was monitored via electrogastrography for 45 minutes to see what effect the meal had. Over the course of the study, each woman ate eight types of meals: liquid protein, solid protein, liquid carbohydrate, solid carbohydrate, liquid fat, solid fat, liquid noncaloric, and solid noncaloric. The protein in the first two meals was a whey protein contained in a commercially-available protein supplement powder.

While they were fasting, the pregnant women exhibited abnormal stomach rhythms to a much greater degree than did a control group of nonpregnant women, indicating that this was indeed one likely cause of their nausea and vomiting. The protein-supplemented meals caused a marked decrease in nausea, while the carbohydrate- and fat-rich meals led to no statistically significant change. The change produced by solid and liquid protein meals was similar, indicating that the physical form was less important than the predominant nutrient. The lessening of symptoms and a change in the stomach wave pattern toward normal occurred simultaneously, indicating a relationship between the reduction of nausea and the normalization of gastric rhythm.

Fats and carbohydrates also decreased the abnormalities in gastric waves, though less so than protein, and they had a much lower effect on nausea symptoms. Thus it is possible that the protein may have had beneficial effects in addition to normalizing gastric rhythm.

This study is only preliminary, as the authors themselves admit. The study sample was small, and each participant ate each kind of meal only once, limiting the available data. A longer-term study with a larger sample is needed to replicate and verify the results. If they are confirmed, physicians may now have at their disposal a simple palliative for the miseries of morning sickness.

<> Jednak, M. A., Shadigian, E. M., Kim, M. S., Woods, M. L., Hooper, F. G., Owyang, C., and Hasler, W. L. 1999. Protein meals reduce nausea and gastric slow wave dysrhythmic activity in first trimester pregnancy. Am J. Physiol. (Gastrointest. Liver Physiol. 40) 277: G855-861.