Morning Sickness May Protect Mother and Child

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“Since the beginning of time, pregnant women have been [known] to suffer…nausea and vomiting [during pregnancy].” “The term ‘morning sickness’ is [actually] misleading,” since women can feel sick all day long. And sometimes, it can get so serious women have to be hospitalized.

Researchers at Harvard’s Brigham and Women’s Hospital found that saturated fat seemed to be a primary dietary risk factor for severe sickness. Five times the odds for each 15 grams’ intake of saturated fat, like a quarter-pound cheeseburger’s worth. The reason saturated fat intake may be such a strong risk factor could be through its effect on estrogen, as “saturated fat has been shown to increase circulating levels of estrogen.”

Why would we evolve to have such a negative reaction to saturated fat? Why would we evolve to get sick at all? “Pregnancy sickness is a universal phenomenon, [with nausea and vomiting] affecting 70 to 85% of all pregnant women.” If you include food aversions in the definition, then the incidence is more like 100%. “Because pregnancy sickness is such a common phenomenon, one must question why this is so. Is there a purpose for such a potentially devastating condition?” Well, in the past, pregnancy sickness was dismissed as all just in women’s heads, but “recent…studies have reconsidered pregnancy sickness as an embryo-protective mechanism, an evolutionary adaptation to protect the baby.”

Protect the baby from what? Maybe from meat. “Meat is the principal source of pathogens for humans. Meat is also the most common type of food avoided by pregnant women.” So, the development of an aversion to meat during pregnancy could be protective, as “meat may have toxins that are mutagenic, carcinogenic, and teratogenic”—meaning birth defect-causing. Tainted meat may also be contaminated by pathogens, and “pregnancy is a time of relative immunosuppression.” Normally, we can fend off most meat pathogens; however, by design, pregnant women are immunosuppressed to not reject the developing embryo, since half the baby—from the father’s side—is foreign.

So, maybe morning sickness evolved as a way to get us to stay away from meat during this vulnerable time. This would be consistent with a “profound overrepresentation” of taboos against meat eating during pregnancy in sample societies around the world.

If this theory is true, then we should be able to make five predictions. If nausea and vomiting in pregnancy is there to be protective, then women who have it should have better pregnancy outcomes. And, indeed, women who experience nausea and vomiting are significantly less likely to miscarry, or suffer a stillbirth.

Prediction #2 would be that the triggering foods contain things that can be particularly harmful to the baby. And, indeed, “of all food types, animal protein (including meat, poultry, eggs, and seafood…) is the most dangerous. Meat is the source of a wide range of pathogens that pose a grave threat to pregnant women and their developing babies.”

Nausea and vomiting in pregnancy should also coincide with when the embryo is most vulnerable. That’s between like, you know, weeks 5 and 15, when all the critical organ structures are being formed—which is right when nausea and vomiting is peaking, which is right when pregnant women find meat, fish, poultry, and eggs most aversive. 

And, finally, if this theory is true, one would expect a lower frequency of morning sickness among plant-based populations. And, yes, the few societies where you don’t see such morning sickness problems are the ones that tend to have only plants as dietary staples, rather than meat.

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Image thanks to Kai Schreiber via flickr. Image was modified.

• animal products
• animal protein
• carcinogens
• eggs
• estrogen
• fish
• foodborne illness
• meat
• miscarriage
• morning sickness
• nausea
• Plant-Based Diets
• poultry
• pregnancy
• protein
• saturated fat
• seafood
• women's health