Recently, as half our office seemed to be pregnant, we were faced yet again with the well-intentioned advice from medical professionals, family and friends on what to eat during pregnancy. There are certain prohibitions or norms that have always baffled us. The most obvious of these is the advice not to eat sushi while pregnant. Common sense would dictate that the entire island nation of Japan does not recommend a wholesale dietary upheaval for its pregnant citizens.

It doesn’t (more on that later), which made us wonder —  are these prescriptions, prohibitions, and recommendations more a reflection of the social and cultural milieus in which they’re dispensed, rather than the most recent science? As we poked around, it became clearer that medical standards and aversion to risk seem to vary from culture to culture.

But what has science really shown us about what’s safe to eat during pregnancy?

Eating sushi while pregnant

Fish has developed a horrible reputation among obstetricians and expectant women, either for fear of high mercury content or contracting parasites. But … it turns out there’s no scientific evidence showing that raw fish has a higher chance of containing a parasite than any other food. (In fact, you’re more likely to get a parasite from eating contaminated chicken.)

The concern about parasites would apply for any food that is not properly handled and stored. In fact, most sushi-grade fish has been flash frozen for transport and storage, which kills the parasites. And as long as you avoid fish that are high in mercury content – raw or cooked – you shouldn’t worry too much about this other common concern, either.

So, basically, it’s totally fine to eat sushi while pregnant.  And yes, in Japan, it’s not only normal for pregnant women to continue eating sushi, it’s actually considered an important part of a healthy prenatal diet.

Drinking caffeinated beverages while pregnant

Pregnant women are frequently told to avoid caffeine entirely, without reason. Studies have shown that very high quantities of caffeine consumption correlate with higher miscarriage rates, but anything under 300mg a day – that is, one large Starbucks coffee – is considered perfectly safe. Furthermore, the most recent study showing this correlation actually showed that steady use of prenatal vitamins eliminated the risk associated with increased caffeine consumption.

So, yes, if you’re looking for it, you can find two studies that have shown an elevated risk with very high levels of caffeine consumption; but virtually anything consumed in very large quantities is not good for a developing fetus. The age-old adage applies here: espresso in moderation.

Eating sprouts while pregnant

Interestingly, this is the only prohibition for which there’s compelling evidence across the board. When it comes to raw sprouts, be careful. Because they are raised in moist conditions – breeding grounds for bacteria – sprouts are more likely to have E.coli and salmonella than other raw foods. These bacteria are incredibly difficult to remove with water washing alone. The evidence seems clear on this front: pregnant women should avoid these. (Not to worry; they were the least tempting item on the list, anyway!)

Drinking alcohol while pregnant

Research is conclusive that heavy or prolonged alcohol consumption during pregnancy can cause developmental problems in fetuses, and in the worst cases, Fetal Alcohol Syndrome.

However — studies have also shown there is no harm to fetuses when mothers drank up to 8 to 10 units of alcohol (roughly, five glasses of wine) per week. The evidence varies on how much alcohol is safe to consume, especially because everyone metabolizes alcohol differently. On this point, interestingly, we weren’t able to find any consensus between various countries’ guidelines; the American perspective seems to be among the most extreme: If we don’t know what is a safe amount, it’s best to avoid alcohol altogether.

However, other countries’ guidelines are more permissive. This one seems best left to individual judgment and choice.

Eating soft cheeses while pregnant

Women are told not to consume soft cheeses during pregnancy because those cheeses are less acidic and contain more moisture than hard cheeses, making them better breeding grounds for bacteria, specifically listeria. But the real problem here is not whether the cheese is hard or soft, but rather whether it’s been made with pasteurized or raw milk. (The pasteurization process kills the listeria bacterium.)

It’s important to keep in mind that listeria is a very rare infection in any case; however, pregnant women’s immune systems are suppressed, making them more susceptible. So enjoy the soft cheese, just check the label!  (And in case you were wondering, of course French women continue to eat soft, unpasteurized cheese during pregnancy.)

Keep an eye out for the second part in this series, where we examine common pregnancy prohibitions outside the food realm. The hair dye thing? Turns out it’s total nonsense!