Tuesday, May 8, 2012

Morning sickness: Animal vs. Plant Foods

Some investigators have reported that morning sickness is less common or even unknown among people who eat plant-based diets, but common among people who eat animal-rich diets.  These authors report that women typically have greater aversions to animal products than to any other foods, and propose that morning sickness functions to reduce exposure to food-borne pathogens.

Morning sickness: a mechanism for protecting moth... [Q Rev Biol. 2000] - PubMed - NCBI


Approximately two-thirds of women experience nausea or vomiting during the first trimester of pregnancy. These symptoms are commonly known as morning sickness. Hook (1976) and Profet (1988) hypothesized that morning sickness protects the embryo by causing pregnant women to physically expel and subsequently avoid foods that contain teratogenic and abortifacient chemicals, especially toxic chemicals in strong-tasting vegetables, caffeinated beverages and alcohol. We examined this hypothesis by comprehensively reviewing the relevant medical, psychological and anthropological literature. In its support, (i) symptoms peak when embryonic organogenesis is most susceptible to chemical disruption (weeks 6-18), (ii) women who experience morning sickness are significantly less likely to miscarry than women who do not (9 of 9 studies), (iii) women who vomit suffer fewer miscarriages than those who experience nausea alone, and (iv) many pregnant women have aversions to alcoholic and nonalcoholic (mostly caffeinated) beverages and strong-tasting vegetables, especially during the first trimester. Surprisingly, however, the greatest aversions are to meats, fish, poultry, and eggs. A cross-cultural analysis using the Human Relations Area Files revealed 20 traditional societies in which morning sickness has been observed and seven in which it has never been observed. The latter were significantly less likely to have animal products as dietary staples and significantly more likely to have only plants (primarily corn) as staples than the 20 societies in which morning sickness occurred. Animal products may be dangerous to pregnant women and their embryos because they often contain parasites and pathogens, especially when stored at room temperatures in warm climates. Avoiding foodborne microorganisms is particularly important to pregnant women because they are immunosuppressed, presumably to reduce the chances of rejecting tissues of their own offspring (Haig 1993). As a result, pregnant women are more vulnerable to serious, often deadly infections. We hypothesize that morning sickness causes women to avoid foods that might be dangerous to themselves or their embryos, especially foods that, prior to widespread refrigeration, were likely to be heavily laden with microorganisms and their toxins. The alternative hypotheses that morning sickness is (i) an epiphenomenon of mother-offspring genetic conflict or hormones associated with viable pregnancies, or (ii) an indicator to potential sexual partners and kin that the woman is pregnant, resulting in reduced sexual behavior and increased nepotistic aid, were not well supported. Available data are most consistent with the hypothesis that morning sickness serves an adaptive, prophylactic function.

According to the CDC:

What foods are most associated with foodborne illness?

  • Raw foods of animal origin are the most likely to be contaminated; that is, raw meat and poultry, raw eggs, unpasteurized milk, and raw shellfish.
  • Because filter-feeding shellfish strain microbes from the sea over many months, they are particularly likely to be contaminated if there are any pathogens in the seawater.
  • Foods that mingle the products of many individual animals, such as bulk raw milk, pooled raw eggs, or ground beef, are particularly hazardous because a pathogen present in any one of the animals may contaminate the whole batch.
    • A single hamburger may contain meat from hundreds of animals.
    • A single restaurant omelet may contain eggs from hundreds of chickens.
    • A glass of raw milk may contain milk from hundreds of cows.
    • A broiler chicken carcass can be exposed to the drippings and juices of many thousands of other birds that went through the same cold water tank after slaughter.
  • Fruits and vegetables consumed raw are a particular concern. Washing can decrease but not eliminate contamination, so the consumers can do little to protect themselves.
    • Recently, a number of outbreaks have been traced to fresh fruits and vegetables that were processed under less than sanitary conditions. These outbreaks show that the quality of the water used for washing and chilling the produce after it is harvested is critical. Using water that is not clean can contaminate many boxes of produce.
    • Fresh manure used to fertilize vegetables can also contaminate them. Alfalfa sprouts and other raw sprouts pose a particular challenge, as the conditions under which they are sprouted are ideal for growing microbes as well as sprouts, and because they are eaten without further cooking. That means that a few bacteria present on the seeds can grow to high numbers of pathogens on the sprouts.
    • Unpasteurized fruit juice can also be contaminated if there are pathogens in or on the fruit that is used to make it.
 Notice that fruits and vegetables carry pathogens only if processed under less than sanitary conditions or contaminated with manure (an animal product).  Otherwise, the types of microbes that infect plants typically do not infect animals like ourselves.

This seems to provide evidence against the idea that modern humans evolved in dependence on uncooked (or cooked) meat as a source of energy to support our large brain.  

If humans spent millions of years adapting to a meat-based diet, eaten raw, as proposed by some authors, then it seems strange that pregnant women would be unable to stomach such a diet during the critical phases of pregnancy. 

Since it is certainly better for a woman to be able to ingest foods during the early critical stages of pregnancy that to be unable to do so, if an increasingly meat-based diet dominated human evolutionary time, natural selection would have favored the reproduction of women who did not get sick at the sight, smell, or ingestion of animal foods (perhaps because of much higher production of stomach acid, different odor tolerances, etc.), and eventually, it would have produced a human species that had no problems eating a diet rich in raw or cooked meat during the critical phase of pregnancy.

But instead we have a human species in which the pregnant females have the strongest aversions to animal products, and women eating plant-based diets have the lowest incidence (as low as zero) of morning sickness. 


WhereInTheWorldIsKirch said...


I like that you are attempting to create an alternate perspective to the "paleo" lifestyle and philosophy.

This specific post is interesting as I've ready studies and reports on this superficially in the past and have been thinking about this from time to time.

One basic point that you should consider with your argument is this phrase...

" The latter were significantly less likely to have animal products as dietary staples"

"significantly less"

Not zero.

Rather a reduced rate. This suggests to me a few possibilities...

1) It's not the meat but some other factor and you run into the causation v.s. correlation discussion

2) It is the meat but certain groups have adapted to this and it creates no harm for these genetically adapted individuals

3) The study is not detailed enough and the tribe eats meat but the women are specifically prohibited from eating meat during pregnancy

4) The studies saying that meat is more common in meat eating cultures is not detailed enough either and the type of meat or processing method is not understood. ( for example pork http://goo.gl/Uj4aI )

I think this is tenuous at best, but a valid subject to research further.

I'm personally of the opinion that the paleo v.s vegan, etc debate suffers from the same obscene bias on both sides and caloric density, stress and lack of mobility is the culprit and there are red herrings flying around every corner of the internet.

Jason Brunson said...

My wife is a strict vegetarian and had horrible morning sickness. Horrible as in she had to go to the ER because she couldn't hold down water. One experience doesn't invalidate anything but there is more to morning sickness than just meat.

Rex said...

Fascinating article. Interesting hypotheses, but does not prove anything as of yet. Thanks for posting!

Razwell said...

Hi, Don

Good article. I think this whole "Paleolithic Diet" nonsense is nothing more than a money maker for these promoters. It is all conjecture. Nobody today was around then. Add to the fact what these Internet gurus promote is not even the real thing most likely. Paleolithic Man was most likely insectivorious. It's deluded to think he was regularly hunting a large and dangerous animal like an adult Mammoth ( probably baby mammoths)Anybody who studies modern day elephants is fully aware of their speed, agility and power.

Paleolithic Man would probably take advantage of eggs, insects rodents- easy stuff.

Add to this that our ancestors did not always eat healthfully. They ONLY wanted to fill their belly.Situations did not allow it.

I would give more credibility to Chinese medicine which I have seen produce some very effective results- and has been delivbering verified results for thousands of years- observable. We westerners can learn A LOT from the Eastern cultures.

I encourage you to read Albert Einstein's views on what science is. Einstein's description of science is NOT at all congruent with what these fraudulent, self - serving , Internet scammers promote.

Einstein ( one of the greatest genuises in all of human history) saids imagination and intuition are of super value in science. He also said the mysterious is the most beautiful thing we can experience- the true source of all science.

Einstein said our intellect (he included himself ) is of extremely limited capacity to understand the natural world. We are children walking into a large library full of books writte in different languages.

What we know about biology is but a DROP in a huge ocean full of unknowns which lies before us.

The Internet scammers will never admit this- including your biggest Australian critic- who himself is the antithesis to genuine inquiry. What's worse, thousands of gullible people are being conned by him and others.

If they only understood the process of genuine inquiry better. Einstein's writings on the topic are a great way to start.

Frank said...


''Good article. I think this whole "Paleolithic Diet" nonsense is nothing more than a money maker for these promoters. It is all conjecture. Nobody today was around then. Add to the fact what these Internet gurus promote is not even the real thing most likely. Paleolithic Man was most likely insectivorious. It's deluded to think he was regularly hunting a large and dangerous animal like an adult Mammoth ( probably baby mammoths)Anybody who studies modern day elephants is fully aware of their speed, agility and power.''

No offense there, but I think it's the first time in year that I read a comment from you that I agree with :P

Indeed, indeed, when will paleo start eating the insects that primal man certainly was eating?

Have you watched the primitive nutrition series, Razwell? I'm sure you will enjoy the material presented in there.

Lauren said...

In counterpoint to Jason, yet also in full agreement with him, I'll add that I've never had food aversions to proteins during my pregnancy-induced nausea. In fact it is hunger that makes the nausea worse, so protein/fat foods keep this away best, and a good dose of magnesium in my evening tea prevents it from starting in the morning before I can get my three runny eggs in. Those with complete and healthy diets and replete nutrition stores before pregnancy seem to fare the best; perhaps the corn-eaters studied still adhere to such a traditional diet that this is assured.

majkinetor said...

Maybe that is the reason vitamin B6 is effective in reducing it - its well known important cofactor in protein metabolism and its need is sometimes expressed per gram of protein in the diet. Hypermesis Gravidarum patients usually have reduced vitamin B6 levels and that is one great model for morning sickness.

Interestingly, one very effective (and looks pretty safe) method to reduce MS is by using cannabis. Jamaican women are drinking cannabis for that reason. I know few HG patients that lived in the hospital before using small amounts of weed. I wonder how that relates to meat induced MS....

Anyway, that morning sickness is protective mechanism is nothing but speculation. There are far better alternative explanations. For instance, high protein diets provide enough building materials for hormones. HCG level is directly correlated to MS level (its diagnostic marker for HG). So, women who eat more protein can produce more HCG which makes them more sick, but ultimately, baby turns better (this is also known - kids of HG patients are developed better then the rest ). Cannabis also fits nice into this theory as cannabinoids do modulate HCG levels (and levels of other reproduction related hormones).

Bobby Fernandez said...

Razwell, funny how you just finished dismissing all the anthropological and archeological data as mere conjecture and proceede to offer your own interpretation of what early man did and didn't do. Your statement that "our ancestors did not always eat healthfully" displays your ignorance on the issue. 10,000 years ago, the only unhealthful foods around were those that were acutely toxic.

Bobby Fernandez said...
This comment has been removed by the author.