Field of Science

Read this if you like shrimp

Shrimp are tasty little morsels, but for years I’ve limited my shrimp intake because they’re high in cholesterol, or so I heard. Recently, though, I heard that they might good for you, so I decided to investigate. The results are a bit surprising.

First, shrimp is high in cholesterol, very high in fact. The American Heart Association recommends no more than 300 mg per day for a normal adult, but a 5-ounce serving of steamed shrimp contains 590 mg. For comparison, 2 large eggs contain about 580 mg of cholesterol.

On the other hand, shrimp is quite low in fat. That same 5-ounce (150g) serving of shrimp has just 1.7 grams of fat, while the same amount of beef has 14 grams of fat. So it’s low in fat, but high in cholesterol. What’s a shrimp-lover to do? Luckily, there’s a bona fide scientific study that attempted to answer this question – but with a catch, as we’ll see.

Searching the Web for shrimp and cholesterol, it’s easy to find lots of pages offering health and nutrition advice telling you that shrimp are good for you. But most of these webpages are from dietary advice “experts” who want to sell their books and diet plans, or from shrimp producers. Uh oh.

Many of these websites referred to the same scientific study. So I found the study and read it (you can get it here) rather than just trusting these websites. This was a legitimate, carefully done study by de Oliveira et al. at Rockefeller University, back in 1996, and here’s what it found.

The study had 3 different diets: a baseline diet with just 107 mg per day of cholesterol, a shrimp diet with 590 mg/day (5 ounces of shrimp), and an egg diet. with 580 mg/day (2 large eggs). The subjects followed each of the diets for 3 weeks each – they all tried all the diets – and the scientists measured their cholesterol levels at the beginning and end of each 3-week period.
Overall, cholesterol levels went up on both the shrimp and the egg diets, but here’s the interesting part: on the shrimp diet, HDL cholesterol (“good” cholesterol”) went up more than LDL (“bad”) cholesterol. This means that the HDL/LDL ratio actually improved on the shrimp diet. On the egg diet, the reverse happened – LDL increased more than HDL. The worst cholesterol, VLDL, was unchanged on the shrimp diet, while on the egg diet it increased. Another good outcome on the shrimp diet was the triglycerides – another bad component of total cholesterol – decreased.

To summarize: the shrimp diet had (1) slightly higher overall cholesterol (bad), (2) higher HDL cholesterol (good), (3) higher HDL/LDL ratio (good), lower triglycerides (good).

The study came up with several hypotheses for the apparent benefits (or at least for the lack of harm) of the shrimp diet. One was the overall low fat in shrimp. Another was the relatively high amount of omega-3 fatty acids in shrimp – these are found in other fish too, but were not in the egg diet used in this study.

So this seems like a big win for shrimp eaters. Volunteers ate shrimp every day for 3 weeks (yum!), and the overall effects were not at all bad. There’s one catch, though: the study involved only 18 people! And it’s never been replicated. So for the past 13 years, hundreds of health experts, websites, even the American Heart Association, have based their advice on this one study. That’s a lot of weight to give to a study of just 18 people. I’d love to see this replicated it in a larger population.

If you’ve skipped down to the bottom to find out what I learned, then the message is this: based on a single small (but well done) study, eating shrimp on a regular basis is probably not bad for you. It might even be beneficial, depending on what you would have been eating otherwise – shrimp is better for you than eggs or beef, but probably not better than fish.

As for me, shrimp is back on the table!

3 comments:

  1. Interesting post! I don't really like shrimp, but your post and the really good shrimp pops I had recently makes me rethink that :-).

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  2. I love shrimp, but I've been avoiding eating them because of environmental concerns with imported shrimp :\

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  3. I'm with Anonymous on this one. I'm more worried about the "chemicals" on imported shrimp. Of course this is mostly rumors and heresy, so maybe you could do a shrimp Part II :). I also eat 1 egg every morning for breakfast so maybe I should rethink that routine.

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