Bad Study On Fish Oils Wrong, Misleading

“Fish Oil May Not Prevent Depression, Says Study”, says the headline on a leading news website, even though the study isn’t about taking fish oil. Lies and misrepresentations tend to make me froth at the mouth in furious anger, so I just can’t let this go unanswered.

The latest in a long tradition of crappy science mixed with crappy journalism, this MSNBC article summarizes the results of a poorly-designed study which leaps to incorrect conclusions, and in the process, misleads the reader even more by interchanging the words “fish” and “fish oil”. Well, let’s see if Healthy Andy can’t untangle this mess for you.

First off, the study is question was published in the American Journal of Clinical Nutrition, and was based off of a large nutritional survey that followed over 50,000 nurses over ten years. To sum up, the researchers checked to see who was eating fish, compared that to who ended up getting depressed, and found no correlation. Then, they declared that EPA and DHA, the main active ingredients in fish oil, have no effect on preventing depression.

Hang on, buster. Not so fast.

Let’s start by correcting the journalist who wrote that misleading headline. This study did NOT study the effect of taking fish oils. It studied the effect of eating fish. It’s not the same thing.

Does it sound like I’m splitting hairs? Here’s why there’s a difference: dosage. Eating fish obviously will provide EPA and DHA from the oils naturally present in the fish. However, it’s nowhere near as much as you get by taking a fish oil supplement.

In fact, dosage is the big reason why this entire study and subsequent news article should be kicked in the head and shown the door. If you eat some high Omega-3 fish every day, you MIGHT end up with a gram or two of EPA and DHA. And while that’s the dosage range I recommend for people without any problems to use as a basic health maintenance dose, if you look at the dosage used to actually treat depression, that’s a whole other story.

If you want to actually treat depression or similar mood disorders, you need to think bigger than a gram or two a day.  Try more like nine or ten grams a day of EPA and DHA.

So, not surprisingly, if you only give someone about one tenth the required dose to make a certain change in the body, YOU’RE NOT GOING TO SEE ANY CHANGE.

Plus, how much fish were these women eating?  What counts as “eating fish”?  Do shellfish count?  Farm-raised fish (which has very little Omega-3)? Did they calculate out the EPA and DHA content of the fish?  That would be pretty hard to do in this case, seeing as how they are relying on a recall survey (“what did you eat yesterday?”), and people really suck at estimating portion size.  Did these women eat fish every day?  Every other day?  How much and what kind (since different varieties of fish have differing Omega-3 contents)?

The bottom line is, the researchers really can’t tell how much EPA and DHA these people were ingesting on a regular basis.  Which means, they really can’t reach any conclusions about anything.

At best… at BEST… if you ignore the  fact that the researchers couldn’t accurately estimate Omega-3 intake, this study suggests that it’s hard to eat enough fish to improve mental health.  Which, I could’ve told you before, simply by looking at the dosage used to treat depression (nine to ten grams daily… you’re talking several pounds of high-quality fish here).  But to use a headline stating that fish OIL doesn’t have any effect on depression, is just plain wrong and misleading.

In fact, fish oil does seem to have a positive effect on depression.  You just have to take a sufficient dosage.  So shut your face, MSNBC, and do your homework before you go writing headlines.