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Pregnancy Sickness

Is Nausea in Pregnancy Nature's Way of Protecting The Fetus From Toxins?

by Rick Weiss


For Margie Profet, a walk through the vegetable section of the local Safeway is like a stroll through the streets of Love Canal.

Those crispy stalks of celery and vitamin-rich carrots are chock-full of chemical irritants called psoralins, she said during a recent visit. Those mushrooms over there are stuffed with hydrazines, a class of chemical familiar to NASA scientists as an ingredient in rocket fuels. And that bunch of fresh basil ready to be made into a delicious pesto is really a toxic tangle of estragol, a plant hormone known for its ability to cause genetic mutations.

Profet, a maverick scientist and recipient of a MacArthur Foundation "genius" award, has no grudge against these surprisingly noxious plants. She knows they must make these bitter chemicals to fend off insects and other predators. And she knows that we humans are endowed with detoxifying enzymes that neutralize the poisons so they won't make us sick.

But Profet is concerned about the effects such foods may have on developing embryos. She suspects that a fetus nestled in the womb lacks the metabolic wherewithal to fend off toxins that its mother has consumed. She fears that tiny organs can end up deformed if they are exposed to such compounds in the first weeks of life.

"You may think these are small quantities of toxins, but the embryo is only this big," Profet said, holding up her thumb. "It doesn't take a lot to cause a problem."

With that in mind, Profet has come up with a controversial theory that sees morning sickness that nauseous right of passage that forces most women onto bland diets during the first months of pregnancy as an evolutionary safety mechanism meant to keep women from eating foods that might be dangerous to the fetus. Pregnancy sickness (the proper term for the ailment, since symptoms are rarely restricted to the morning) is a good thing, she said. Rather than trying to overcome it, women should heed its message by avoiding vegetables and certain other foods until the second trimester, by which time fetal organs have taken their basic shape.

No one denies that birth defects represent a significant unsolved problem for modern medicine. About 2 to 3 percent of all infants born in North America have serious birth defects, such as deformed limbs, and another 4 to 10 percent have minor defects such as partial deafness or incomplete bowel or bladder control. Although many birth defects are the result of specific genetic syndromes or maternal drug expo sures, an estimated two-thirds of all defects have no known cause.

But Profet's proposal that food may be to blame summarized in her new book, Protecting Your Baby-to-Be (Addison Wesley, 1995) is stirring some commotion in scientific, medical and baby-shower circles. Some experts are concerned that Profet's advice to pass up the vegetables relies too much on scientific speculation and not enough on experimental proof. Indeed, some think her hypothesis may be completely wrong and her advice downright unwise.

"It's certainly legitimate to have a theory, and it's provocative and it may even stimulate new research," said Richard Johnston, a physician who serves as scientific director for the March of Dimes Birth Defects Foundation in White Plains, N.Y. "But when you're giving public health advice, you have to be very careful. I think the main problem is that she is giving public health advice not based on scientific data."

Profet agreed that her theory is just a theory. "A lot of this is educated guesses because that's the best we can do for now," she said. "A good study would be almost impossible because you'd have to document not only what people ate but how much, and it would take huge numbers of women."

But pregnant women are getting advice all the time, Profet said from doctors, from friends and from a growing number of popular books about pregnancy. And in her opinion, much of it is based on wrongheaded science and has a real potential to increase the risk of birth defects. "The safest strategy is to err on the side of caution," she said.

The Evolutionary View

By taking the evolutionary perspective, Profet at least has Charles Darwin on her side. Darwin's theory of evolution states that organisms have pretty much tried everything during millions of years of evolution, and any physical, chemical or behavioral novelty that took too big a toll on survival got left in the dust a long time ago. Conversely, most traits that have survived this process probably benefit the organism, even if that benefit is not immediately apparent.

Thinking along those lines, Profet wondered: What could a pregnant woman possibly gain from weeks of nausea, high lighted by repeated trips to the toilet (or its prehistoric equivalent), only to see those precious calories and nutrients meant for her baby getting flushed away?

"Pregnancy sickness is very costly and we would not have it if it were not needed for something," Profet said. "We should pay attention."

Profet considered the abundant data on women's appetites and tastes during early pregnancy, and found that bitter foods especially cabbage-family vegetables like broccoli and cauliflower were especially nauseating, while bland foods were generally acceptable. Having worked in the laboratory of Bruce Ames, the University of California biochemist who is an expert in naturally occurring toxins, she was aware that bitter foods tend to be rich in naturally occurring toxins their bitter taste providing a universal warning to insects and people against overconsumption.

Profet knew that many of these toxins can break chromosomes and cause other kinds of genetic damage in laboratory-grown cells and even in some animals. For example, pregnant goats that eat large amounts of a toxin-rich weed called lupine (which they eat when other foods are unavailable) have higher rates of birth defects in their offspring.

Profet was also intrigued by a mysterious fact: Women who do not experience pregnancy sickness are significantly more likely to miscarriage. Could it be that these women, lacking the protective aversion to toxic foods are poisoning their embryos with heaps of broccoli or slightly rancid oils or meats, thus boosting their chances of early loss? The more she thought about, the more likely it seemed.

Down The Toxins Aisle

Recently, while visiting Washington, Profet walked through a Safeway supermarket in Georgetown and pointed out some of the dangers she saw lurking in its healthful-looking aisles.

"Red cabbage, brussels sprouts, cabbage, all these contain L-isothiocyanate, which can break chromosomes," she said cheerfully, as nearby shoppers raised their eyebrows and appeared to reassess their selections. "Potato [skin] has solanine, which is a poison, so I would peel them. Tomatoes are fruits, but they are related to potatoes, so don't trust them," she said.

In the meat aisle, Profet explained that hormonal changes associated with pregnancy affect the smell and taste centers in the brain, making expectant moms extremely sensitive to odors. This hypersensitivity benefits the embryo, she said, because anything that is the least bit rotten becomes instantly unpalatable. "Meat is great but it has to be very fresh. And barbecue smoke is usually repulsive, probably because it contains mutagens and teratogens," substances that cause genetic mutations and birth defects.

"Here's the smelly cheeses," she continued. "I don't think she's going to want them. Fresh ricotta, maybe."

Profet stopped at the coffee grinders. "An aversion to coffee is often the first sign of pregnancy," she said. "Coffee contains more than 1,000 different toxins. And caffeine is just one of them, so decaf coffee doesn't take care of it. Nor are teas necessarily good substitutes. "Herb teas are herbs. And herbs, like spices, are full of natural toxins. One pregnancy book I saw recommended fennel tea, which contains ergestrol. I wouldn't drink that if I were pregnant."

Indeed, Profet said, one has to wonder where some of these pregnancy books get their ideas from. "You hear a lot of things, like 'Now that you're pregnant, eat a lot of vegetables.' Well, I don't think that's sage advice no pun intended to say take this food that's repulsive to you and inflict it on your embryo. That's 180 degrees different than what's sensible."

Critics Con and Pro

Profet suspected she'd get some criticism for her theory, and she was right. "She's wastefully scared a lot of people about these vegetables," said Judith Brown, a nutritionist at the University of Minnesota's School of Public Health in Minneapolis. At the doses found in most vegetables, Brown said, "it's not even clear these are toxins at all."

Brown is involved in an ongoing study of diet and pregnancy that has tracked 714 deliveries. While she and her colleagues have not specifically looked for a link between maternal diets and birth defects, they have noted that high maternal consumption of fruits and vegetables is linked to higher birth weights in babies, generally considered a good sign.

Brown also thinks evolutionary explanations are often overstated, with their presumption that everything in life has a biological purpose. "A number of things are terrible and uncomfortable," she said, "but that doesn't mean they are good for you."

For example, Brown said, the pain of inflammation is not in itself useful but is just a side effect of the body's response to infection. Similarly, she said, morning sickness may have nothing to do with a need to avoid certain foods; it may be just a side effect of gestational hormone changes. If that's the case, then women who have the highest levels of pregnancy supporting hormones can also expect to be saddled with more nausea, perhaps accounting for the link between morning sickness and low miscarriage rates.

Brown and other critics also express concern that Profet may be causing unnecessary angst in pregnant women who innocently ate broccoli during their first trimester or guilt in women who have already given birth to children with deformities.

But other scientists and doctors think Profet may be on to something. Among them is George C. Williams, a retired professor of ecology and evolution at the State University of New York at Stony Brook, who wrote with physician Randolph M. Nesse a book on Darwinian medicine called Why We Get Sick (Times Books, 1995). "The theory makes sense," Williams said. "Margie comes down on the side of caution. I think it's unlikely her advice can do any harm, and it may help."

As for the risk of instilling ex post facto vegetable-guilt in mothers of children born with birth defects, Williams said: "When something bad happens, like a child with a birth defect, it seems to me women will inevitably look back and try to see if it's something they did or did not do. If they didn't have Margie's book to blame it on, they'd blame it on something else."

Profet has also garnered praise from Cassandra E. Henderson, associate director of perinatology at Montefiore Medical Center in New York, and Richard I. Feinbloom, former director of the family health care program at Harvard Medical School.

It could be a long time before the links between diet and birth defects get sorted out. Meanwhile, Profet is not suggesting that pregnant women spend the first trimester eating nothing but crackers. She recommends a variety of foods, including grains (especially processed grains, with their bitter husks removed), fruits, mild cheeses and even some non-bitter vegetables such as green beans and peas as can be tolerated. For women who cannot stomach a reasonable array of foods, she endorses vitamin supplements.

Is that so radical? Even Johnston of the March of Dimes said he doesn't favor forcing pregnant women to eat foods unpalatable to them. So at least for those pregnant women who do find themselves perpetually on the edge of nausea, Johnston and Profet have similar advice, though they put it quite differently.

"Eat a balanced diet," Johnston says. While Profet exhorts, "Diversify your toxins!"

Internet Source: http://darwin.clas.virginia.edu/~rjh9u/profet.html

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