Pregnancy is a time when women will want to get everything right. And even if that’s not going to happen – you can’t get everything right all the time – you want to at least know what you ought to be doing!
But there’s a lot of conflicting advice about what pregnant women should eat, and what they should avoid. So, can pregnant women eat shrimp?
There’s a couple of great things about seafood. It’s quite low in fat. It’s also very high in protein, and it’s often rich in essential fatty acids, trace element nutrients, oils and vitamins that are hard to get elsewhere. In fact, as a source of lean protein, seafood is hard to beat!
But there can be dangers with eating any food from a marine source, whether that’s fish or seafood. One is the risk of infection. Many seafood sources, like mussels, live in polluted waters or are classed as ‘bottom-feeders.’ That means they draw their food from the detritus from the ocean that falls from higher up to the sea bed – the bottom. In waters off the shores of populated areas, that can often mean sewage. Raw oysters, mussels and clams can be dangerous because they contain bacteria that originate in human faeces, and these are the bacteria responsible for some serious types of food poisoning.
The bad news for shrimp lovers is that shrimp can be subject to this problem. A metastudy from the International Association for Food Protection looked into the data from FDA studies of shrimp and found that there was a link between fecal bacteria in the intake and surrounding waters of shrimp growing ponds and the liklihood that the shrimp themselves would be infected with salmonella. [1] Salmonella is a bacteria that can cause serious food poisoning, and which kills about 30 Americans a year.[2]
Most cases of food poisoning are from chicken or egg products, or from ill-cooked meat that has been contaminated during the handling process. However, there is a slight risk of contracting cholera from shrimp!
The mention of potential food poisoning shouldn’t put you off a food. If you look up the foods that can give you food poisoning, you’ll find that everything, from potato salad to rice, is potentially fatal! Instead, concentrate on getting shrimp from a reputable source and cleaning it, and cooking it well.
The other danger of shrimp is from the mercury content. Shrimp don’t naturally contain mercury, but it’s a heavy metal that was pumped into the atmosphere and the rivers and oceans before the risks were properly understood. It accumulates in the bodies of animals and some don’t have any way to excrete it. Others have a maximum speed they can excrete mercury at, that is lower than the speed they absorb it, and so it builds up in their bodies. Obviously, that means predator animals have more mercury than prey animals, because they take on all their prey’s mercury when they eat them. But fish and seafood like shrimp are exposed to mercury in the seawater and they absorb it, so they are considered to be high in mercury.
In human beings the build-up rate of mercury in our bodies is determined by the ‘half-life’ in the blood – the length of time it takes for blood mercury levels to fall by half. There’s a lot of variance, but the averages are between 30 and 70 days.
The real danger of mercury is not that it builds up in your system: that by itself wouldn’t matter. The real problem is that mercury causes mercury poisoning.
Mercury poisoning can come in different forms and can take the form of several specific diseases. But they share elements. Mercury in whatever form poisons the nervous system and it can cause organ failure. It’s the cause of Niigata Minamata disease, named for the Japanese prefecture where the disease was first noted. Niigata Ninamatadisease is a good object lesson in how mercury poisoning happens and what its effects can be.
An electrical plant used mercury sulfate in its production system and this compound was released into the surrounding waterways afterwards. Here, it bioaccumulated – increased the higher up the food chain you look, as we spoke about earlier – and contaminated the fish in the local bay, which people who lived there ate a lot of. Over 600 people suffered from very severe mercury poisoning which caused numbing of their hands and feet, ataxia (difficulty controlling movements), general muscle weakness, narrowing of the field of vision and damage to hearing and speech. In Japan, Mercury poisoning is classed as one of the four big Japanese pollution diseases. In the US, industrial pollution, often from industries that are no longer active, has caused all 50 states to issue warnings about mercury from fish caught in their waters.
It’s best to avoid mercury in the diet at all, or to minimise it. But if you’re pregnant it’s especially bad. That’s because adult nervous systems can be damaged, but the nervous systems of fetuses can be prevented from developing properly in the first place. Additionally the fetus by far the most susceptible to mercury poisoning. Studies conducted in the US showed that mothers with no mercury exposure symptoms were still having babies with mercury-induced illnesses[3] which was taken to show that the fetus is more susceptible than adults. In fetal mercury poisoning, the symptoms can include ‘impacts on cognitive thinking, memory, attention, language, and fine motor and visual spatial skills’.[4]
Because of these considerations the recommended amounts of mercury that a pregnant woman should eat are far lower than for the general population and reflect a margin of safety, and an assumption of an average mercury exposure in the foods themselves – if you live in or source your shrimp from a highly mercury-exposed area, see a professional or find some local information, perhaps by looking at the EPA Fish Consumption Website.
In general, shrimp are classified as low-mercury seafood, and the American Pregnancy Association recommends up to two six-ounce servings a week of shrimp. The amount you can eat is based partly on your weight as well.
If you’re in any doubt about how much seafood you’re eating, try talking to your doctor about it. Like so many things in life, it’s a question of balancing the risk against the reward and a couple of shrimp-based meals a week is probably the best balance for most pregnant women. Make sure it’s the best you can get and clean and cook it carefully!
[1] International Association for Food Protection (Koonse, Brett, et al), ‘Salmonella and the Sanitary Quality of Aquacultured Shrimp,’ Journal of Food Protection®, Volume 68, Number 12, December 2005 , pp. 2527-2532(6), stored at http://www.ingentaconnect.com/content/iafp/jfp/2005/00000068/00000012/art00006, retrieved July 5 2012
[2] Black, Jane, and O’Keefe, Ed, ‘Overhaul of Food Safety Rules in the Works,’ Washington Post, July 8, 2009, stored at http://www.washingtonpost.com/wp-dyn/content/article/2009/07/07/AR2009070702343.html?hpid=topnews, accessed July 5 2012
[3] U.S. Environmental Protection Agency, ‘Health Effects: Mercury,’ February 7 2012, stored at http://www.epa.gov/hg/effects.htm, retrieved July 11 2012.
