Shrimp, Cholesterol, and Heart Health

Years ago, shrimp was considered to be taboo for heart patients or people watching their cholesterol numbers. That’s because a small serving of 3.5 ounces supplies about 200 mg of cholesterol. For people at high risk for heart disease, that amounts to a full day’s allotment. (For everyone else, 300 mg is the limit.) However, shrimp is very low in total fat (about 1.5 grams per serving) with almost no saturated fat at all. Saturated fat is known to be particularly harmful to the heart and blood vessels, in part because our bodies can efficiently convert it to LDL (or bad) cholesterol.

Since my patients often ask me about shrimp and cholesterol, I decided to review the medical literature and discovered a fascinating study from Rockefeller University. In 1996, Dr. Elizabeth De Oliveira and colleagues put a shrimp-based diet to the test. Eighteen men and women were fed about 10 ounces of shrimp, supplying nearly 600 mg of cholesterol, every day for three weeks. On a rotating schedule, the subjects were also fed a two-eggs-per-day diet, furnishing about the same amount of cholesterol, for three weeks, as well as a baseline very low cholesterol diet for another three weeks.

Learn How Shrimp And Other Foods Affect Your Cholesterol & What You Can Do To Control It »

After the three weeks were up, the shrimp diet did raise LDL cholesterol by about 7 percent compared to the low cholesterol diet. However, it also increased HDL (good cholesterol) by 12 percent and lowered triglycerides by 13 percent. The egg diet came out looking worse, bumping up LDL by 10 percent while raising HDL by only about 8 percent.

The bottom line? Shrimp can be part of a heart-smart diet as long as it is enjoyed in moderation, eaten boiled, baked, or grilled, and not served fried or drowning in butter. Perhaps just as important, find out where your shrimp comes from. Much of the shrimp now sold in the United States comes from Asia, where farming practices, including the use of pesticides and antibiotics, have been environmentally devastating and may have detrimental effects on human health. Read more about shrimp farming on National Geographic’s website.

Description

Shrimp are crustaceans (just like lobsters and crabs) and they belong to a category of living things called arthropods. Like all arthropods, shrimp have their skeleton on the outside instead of the inside (it’s called an exoskeleton) and this outer skeleton is one of the features that gives shrimp their unusual look – almost like having a head shield that blocks out all of their features except their eyes, mouth opening, and antennae. In the U.S., consumers don’t typically eat the outer skeleton, heads, or tails of shrimp, even though these parts are often rich in nutrients and commonly consumed in other countries. Shrimp accounts for about 25% of all seafood sold in the United States.

The terms “shrimp” and “prawns” can be confusing. Even scientists often use these words inconsistently. In the popular press and many restaurants, larger shrimp—often from freshwater habitats—are referred to as “prawns,” while smaller shrimp—often from saltwater habitats—are called “shrimp.” In terms of size, “large” typically means that you get about 40 or less per cooked pound (in comparison to about 50 for “medium” and 60 for “small”). But from a scientific perspective, both shrimp and prawns can come from saltwater or freshwater, and there is no absolute standard for measuring small, medium, or large. In this article and throughout our website, we’ll be using the word “shrimp” as a general term that includes all species—even those which might be referred to as “prawns” in some research studies or some restaurants.

Many people ask about the way shrimp sizes (small, medium, large, jumbo) are determined. While there is no precise method typically used for shrimp sizing, count per pound is the most common method used. (Count per pound refers to the number of shrimp that you get when you purchase or consume one pound.) With small cooked shrimp, that number is usually around 60. With medium-cooked shrimp, it falls to about 50 (since the shrimp are bigger, and each one weighs more). For large shrimp, the count per pound is about 40. For jumbo shrimp, the count per pound is about 30.

Traditionally, shrimp have been grouped into categories based on their natural habitats. Warm-water shrimp come from tropical waters in southern parts of the world, and cold-water shrimp come from northern climates. Much warm-water shrimp belong to one specific family called Penaeidae. Tiger prawns, tiger shrimp, and Indian prawns are members of this family. Many cold-water shrimp belong to a second family called Pandalidae. Spot shrimp, striped shrimp, dock shrimp, humpback shrimp, Northern shrimp, and Northern prawns are members of this second family. You’ll find white shrimp, pink shrimp, and brown shrimp that come from both water-warm and cold-water regions.

Both warm-water and cold-water shrimp belonging to these two families are saltwater shrimp. They are found in many of the world’s oceans and seas, where they are typically caught by trawling.

Freshwater shrimp is a third category based on habitat. Just like the name implies, freshwater shrimp are not native to oceans and seas but to non-salt waters including lakes, rivers, and streams. Freshwater shrimp belong to a scientific category of living things called Caridea.

Unfortunately, the traditional ways of classifying shrimp listed above are no longer adequate for understanding shrimp in the marketplace due to the quick rise of shrimp farming and globalization of the food supply. It’s become common for shrimp to be removed from their native habitat and raised in farm settings that don’t always resemble their native conditions. Today, the vast majority of shrimp available in U.S. groceries are farmed shrimp, and the quick rise in shrimp farming has raised concerns among many consumers about the health safety and environmental safety of shrimp. For more information about these concerns, please see our Individual Concerns section.

As described above, it’s possible to find white shrimp, pink shrimp, and brown shrimp that are native to warmer southern waters as well as older northern ones. However, the flesh of virtually all shrimp—when cooked—turns a vibrant shade of pink.

History

Shrimp and other shellfish were enjoyed in the world’s Mediterranean region during the early centuries AD. Classical Greek and Roman texts include shrimp recipes and descriptions of fishing practices. During most of the shrimp’s culinary history, farming was not used as a method of shrimp production. Shrimp were caught in pots or traps—not only by hand but also in relatively small amounts. During certain periods of history, the labor-intensive nature of shrimp fishing turned shrimp into a delicacy that was both rare and costly.

Beginning in the 1400-the 1500s, trawling became a more widespread method for catching shrimp. Trawling refers to the attachment of a large net behind a fishing boat (trawler) that gets dragged through the water as a means of trapping the fish. Shrimp trawlers became a way of catching more shrimp more quickly, and with less manpower. However, large nets ended up trapping other sea creatures, not just shrimp. This problem—which became known as “by-catch”—continues to this day. For example, in 1989, the U.S. Congress passed a law banning the import of wild-caught shrimp from Thailand because Thai shrimp trawlers had failed to install turtle excluder devices (TEDs) that could help prevent sea turtles from getting caught up in the fishing nets.

Beginning in the 1970s, a new trend began to emerge in the shrimp industry. This new trend was shrimp farming. Many factors led to the development of shrimp farming, including depletion of wild shrimp stock, technological developments in aquaculture (the raising of fish in containment facilities), globalization of the food supply, and economic opportunities associated with large-scale shrimp production. In what has been called the “Blue Revolution,” world production of shrimp went from 25,000 metric tons in the 1970s to more than 750,000 metric tons in less than two decades. Today there are more than 25,000 shrimp farms in Thailand alone, and shrimp farms line the coastal areas of many Asian countries, including Vietnam, Indonesia, and China. India, Myanmar (Burma), Bangladesh, Australia, and the Philippines are also important shrimp farming countries, as are the Central American countries of Ecuador, Guatemala, and Honduras as well as the South American countries of Colombia, Venezuela, and Peru. In North America, Canada, Mexico, and the United States also produce important amounts of farmed shrimp. Many individuals have concerns about the consequences of shrimp farming for the environment as well as for human health. For more information about these concerns, please see our Concerns section.

The smell is a good indicator of freshness; good quality shrimp have a slightly saltwater smell. Since a slightly “off” smell cannot be detected through plastic if you have the option, purchase displayed shrimp as opposed to those that are prepackaged. Once the fishmonger wraps and hands you the shrimp that you have selected, smell them through the paper wrapping and return them if they do not smell right. When fresh shrimp have been left out for too long, some people describe them as having an “ammonia” smell.

Color can also be an indicator of poor fresh shrimp quality. Unless you are purchasing spotted or striped shrimp, you should not see dark spots or rings of any kind. These markings are usually a sign of deterioration.

When storing any type of seafood, including shrimp, it is important to keep it cold since seafood is very sensitive to temperature. Therefore, after purchasing shrimp or other seafood, make sure to return it to a refrigerator as soon as possible. If the shrimp is going to accompany you during a day full of errands, keep a cooler in the car where you can place the shrimp to make sure it stays cold and does not spoil.

The temperature of most refrigerators is slightly warmer than ideal for storing seafood. Therefore, to ensure maximum freshness and quality, it is important to use special storage methods to create the optimal temperature for holding the shrimp.

One of the easiest ways to do this is to place the shrimp in a zip-lock bag in a baking dish layered with ice or ice packs. Place ice or ice packs over the shrimp as well. The baking dish and shrimp should then be placed on the bottom shelf of the refrigerator, which is its coolest area. Replenish ice one or two times per day. Shrimp can be refrigerated for up to two days although it should be purchased as close to being served as possible.

You can extend the shelf life of shrimp by freezing it. To do so, wrap it well in plastic and place it in the coldest part of the freezer where it will keep for about one month.

To defrost shrimp, place it in a bowl of cold water or the refrigerator. Do not thaw the shrimp at room temperature or in a microwave since this can lead to a loss of moisture and nutrients, and can increase the risk of contamination.