Two Studies Undermine Fish Oil's Role as a Brain Food

By Jennifer Welsh | November 3, 2010 3:20 pm

fishoilTwo recent studies are refuting the claims of omega-3 enthusiasts that the fatty acid, which is produced mainly by algae and is found in the animals that eat them (like fish), is the ultimate “brain food.”

Anecdotal reports had suggested that these fatty acids, called omega-3 because they have a kink in their structure three bonds from the end of the carbon chain, could improve brain function for everyone from the elderly to the unborn. Vitamin supplements of fish oil have therefore been flying off the shelves.

People who eat lots of fish are less likely to develop dementia or cognitive problems late in life. Observational studies have also found that taking omega-3s during pregnancy can reduce postpartum depression and improve neurodevelopment in children. What’s more, animals with an Alzheimer’s-like condition are helped by docosahexaenoic acid (DHA), one of several omega-3 fatty acids. And DHA disappears from the brains of people with Alzheimer’s. [ScienceNOW]

In an Alzheimer’s study published in The Journal of the American Medical Association, researcher Joseph Quinn gave about 400 patients suffering from mild to moderate Alzheimer’s 2 grams of either omega-3 DHA or a placebo each day. After 18 months, none of the patients showed improvement of their Alzheimer’s symptoms.

“It’s a very solid and unfortunately negative result,” says Quinn. He thinks now that the intervention came too late, and he’s not alone. “If you’ve got big holes in your brain, no amount of DHA” is going to seal them up, says Alan Dangour, a public health expert and nutritionist at the London School of Hygiene & Tropical Medicine. [ScienceNOW]

It’s possible that omega-3 might be effective if taken over the long term before the disease develops, since studies of people who eat large amounts of fish often show they are less likely to suffer from dementia in old age. But following people for a large portion of their lives under controlled dosage conditions of DHA would be an extraordinarily expensive undertaking.

“That’s been shown loads and loads of times,” [Dangour] says, and “it looks like there’s some link.” But the connection may not be in the fish, he says. Instead, it could be in what the fish-eaters aren’t consuming—for example, meats with saturated fat that have been associated with dementia. [ScienceNOW]

In another study, published in JAMA two weeks ago, 2,300 pregnant women took either 800 milligrams of DHA or vegetable oil per day. They were tested for postpartum depression after the birth, and their children were tested for cognitive function after 18 months. The results showed no differences between the fish oil and vegetable oil groups.

“I think a lot of us have been skeptical that something as easy as taking a DHA supplement would improve neurologic development,” said Dr. William Barth Jr., chief of maternal-fetal medicine at Massachusetts General Hospital. “I wish it were so simple, that there was a pill we could take to make our children smarter.” [The New York Times]

While some may be disappointed to find that omega-3 fatty acids aren’t brain wonder drugs, there is still evidence that they play an important role in heart and immune system health. And it’s possible that DHA may improve cognitive function in patients who are part of a subset of the general population, like premature babies or people who don’t carry a particular Alzheimer’s gene, though conclusive studies have yet to be performed on those groups.

Related  content:
80beats: Did Dining on Seafood Help Early Humans Grow These Big Brains?
80beats: Gorging on Omega-3 Shrimp Gives Birds Extra Endurance
80beats: Omega-3’s in a Cow’s Diet Provide a Health Boost—to the Atmosphere
DISCOVER: Fish Oil Is No Snake Oil
DISCOVER: I’ll Have My Burger Petri-Dish Bred, With Extra Omega-3

Image: Flickr/D’Arcy Norman

CATEGORIZED UNDER: Health & Medicine, Mind & Brain
  • nick

    “In another study, published in JAMA two weeks ago, 2,300 pregnant women took either 800 milligrams of DHA or vegetable oil per day. They were tested for postpartum depression after the birth, and their children were tested for cognitive function after 18 months. The results showed no differences between the fish oil and vegetable oil groups.”

    It’s possibly it’s not the fish, just the healthy oil, that has a beneficial effect. A better study would be to give people fish oil, vegetable oil, butter and no oil supplements and see what the effects are. Of course, no one would want to do that because butter is still seen as an awful, bad thing in our culture that would harm our kids.

    And you have to control for the other foods they eat, right? Just because they’re taking fish oil supplements doesn’t mean they’re not vacuuming up twinkies (or whatever) like a Dyson the rest of the time.

    I’d like to point out that the brain is mostly cholesterol. Eating foods with cholesterol doesn’t increase levels of serum cholesterol in our blood, our body just makes less natural cholesterol when we eat some. When we eat fats (at least a couple types), our levels of serum cholesterol go up. Not sure how that may all relate to brain improvement, but if the brain is mostly cholesterol, having an adequate supply must be important.

  • Bigby

    Nick, regarding your last point regarding serum cholesterol… it has been posited that serum cholesterol elevates when saturated fat is elevated — but only in the presence of elevated insulin. I can state, annecdotally, that when I was on a low carb diet — despite eating pounds of red meat and dozens of eggs a week — my serum cholesterol levels plummeted. On a low-fat diet overall serum cholesterol was 190, after 8 weeks on a low-carb diet it dropped to 142.
    Also not sure how that relates to cognitive functions, but I thought it was interesting.

  • Gretchen Vannice, MS, RD

    Good discussion.

    DHA alone is not the the answer to all that ails us. It is part of the picture. Calcium is an integral part of our bones yet calcium alone does not do the job. DHA is an integral part of our eyes and brain cells and DHA alone doesn’t do the job.

    Nutrition is a science and a supplement does not substitute for diet or lifestyle. A supplement, is, in fact, a supplement.

    As the journalist rightly states above, research clearly documents the benefit of consuming omega-3 over the lifespan.

    The harm of this recent reporting is the impact it has on the public. When taken out of context – as much of the reporting on this has been – it does damage. Timing is important with nutrition, and if developing infants don’t get DHA when they need it, we all pay the price.

    On the cholesterol comment – it is important in brain health, and we need to eat some. What we eat does not directly influence brain levels, and let’s be thankful for that. We don’t want our brain cholesterol levels to be dependent on what we’ve eaten last week. The type of fat we eat is likely more important than the amount of fat we eat.

  • scott

    I think this study is flawed…but I agree, that no oil, or any pill is a magic bullet for anything. It’s a combo of what one eats, outlook on life, lifestyle, etc.

    Does one pop a fish oil while chowing down a bag of fries or a burger thinking its making the fries ok? I know people who will eat a giant chili dog and who take fish oil thinking its going to protect them. Or does one pop a fish oil while eating an avocado over fresh crab in salad greens with olive oil and lemon juice dressing? Then add in – does this person exercise, are they happy individuals?

    And actually, I don’t need a study. I can see it in daily life. I eat a very strict grain free, high fat (coconut, olive oil, nuts, avocado and butter) and low sugar diet and hang around with some people who eat as I do for the most part but also have many friends, family and acquaintances who follow a typical american diet (burgers, fries, chicken fingers, lots of breads and grains and sugars and processed foods) and it becomes very clear which is better for the human body. The grain-processed food group are always struggling with weight, fatigue, bloating, indigestion, etc. Look at someone who is eating at IHop, McDonanlds and watches too much TV….you dont need a study to figure out their state of health. My favorite…people will tease me about my diet, the ones who are overweight, taking lipitor and feel terrible much of time.

  • Bee

    This study’s result is a great relief to me since I didn’t manage to swallow the (huge!) fish oil capsules that come with my pregnancy supplements.

  • Chris SD

    Early diagnosis and intervention will be key to managing the increase in Alzheimer’s and other forms of dementia. There are several paper-based tests that can provide a “first pass” screening for memory impairment:


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