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You Ask, I Answer: Omega-3s Increase Type 2 Diabetes Risk?

080708193249-largeWhat are your thoughts on the reported link between omega-3 intake and type 2 diabetes recently published in an article featured in the American Journal of Clinical Nutrition?

– xo2hearts
(via Twitter)

The AJCN is a well-respected, top-of-the-line journal, so it is no surprise that many of its studies resonate all over the Internet.

This one, titled “Dietary omega-3 fatty acids and fish consumption and risk of type 2 diabetes” is particularly controversial, since its main conclusion is that there appears to be “an increased risk of type-2 diabetes with the intake of long-chain omega-3 fatty acids, especially with higher intakes (more than 0.20 g omega-3, or more than 2 servings of fish a day.)”

In case you’re wondering, the long-chain omega-3 fatty acids are docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), the type of omega 3s present in fish, crustaceans, and sea vegetables.  For the record, this study only focused on animal sources of DHA and EPA.

Omega 3s — particularly the long-chain varieties — are known to impart a plethora of health benefits, from improved cardiac health to controlled blood pressure to superior eye health.  To date, some studies have shown an association between high intakes of omega 3 fatty acids and improved blood sugar values.  Others have reported inconclusive results, but never before has a large study implicated omega 3s with an increased risk of developing type 2 diabetes.

Again, this study is worth serious consideration not only because of its size (36,328 subjects), but also because of all possible confounding factors it took into consideration to prevent as much skewing of results as possible: exercise, smoking, alcohol consumption, hypertension, menopausal status, BMI, red meat intake, total caloric intake, omega-6 intake, ALA Omega 3 intake, magnesium intake, trans and saturated fat intake, fiber intake, and glycemic index of foods consumed.  Again, the AJCN doesn’t play around!

So, then, what do we make of this latest study?  Here are a few things worth considering:

1. As the researchers point out, “subjects at risk of cardiovascular disease who may also be at increased risk of type 2 diabetes may have been advised to consume more fish by their primary care physician”.  In other words, it’s very likely that some of the individuals in the “high fish intake” group may have increased their intake as a result of, say, being diagnosed as prediabetic, thereby slightly skewing the results.

2. Keep in mind this is all self-reported data.  We of course want to think study subjects are truthful in their record-keeping, but that is not always the case.

3. I would like to know more details regarding the types of seafood consumed.  The study does mention four categories — canned tuna, dark-meat fish, white-meat fish, and crustaceans/mollusks.  This is slightly problematic, though, because it means that wild and farmed salmon were counted equally, even though wild salmon’s omega-3 profile is significantly superior.

4. According to the Johns Hopkins Diabetes Guide, 26.8 million people aged 20 – 79 in the United States are living with type-2 diabetes..  In Japan?  7.1 million.  This means that 8.72% of the United States’ adult population has been diagnosed with Type 2 diabetes, whereas 5.5 percent of Japan’s population fits that criteria.

Let’s take that one step further.  According to a study published in the also-prestigious Japan Medical Association Journal, current estimates (or, at least, as of 2007) indicate that approximately 22.1 million Japanese adults are living with Type 2 diabetes (this takes into account those who have not been diagnosed as well as those who currently have pre-diabetes).  In that case, we’re talking about 17.3 percent of Japanese adults.

On this side of the Pacific Ocean, the American Diabetes Association reveals that that 26.2 percent of the US population has been diagnosed with Type 2 diabetes, is walking around unaware they have Type 2 diabetes, or have pre-diabetes.

In either case, the United States has the higher prevalence.

I point this out for one reason only — Japan’s EPA and DHA intake is 7.5 times higher than that of the United States.  If either of these long-chain fatty acids played a significant role in Type 2 diabetes risk, wouldn’t Japanese rates be significantly higher?

5. Let’s, for a second, suppose that DHA and EPA unequivocally increase Type 2 diabetes risk.  Guess what?  I wouldn’t be too concerned.  Allow me to explain.

According to the American Diabetes Association, two out of every three diabetics die from cardiovascular disease — the very thing DHA and EPA have been proven time and time again to help protect everyone from!  The fact that diabetics are three to eight times more likely to die of a heart attack than non-diabetics makes a very strong case for why DHA and EPA intakes should be high among that population.

6. One factor that can increase Type 2 diabetes risk the study did not take into account?  Sleep!  Studies have shown that insufficient sleep can affect blood glucose levels and insulin sensitivity quite dramatically, often times trumping dietary conditions.

So, should you now fear long-chain omega 3s?  Looking at the big picture, I certainly don’t think so.

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3 Comments

  1. Brandon said on January 25th, 2011

    I too question the biological significance. I’m really curious about the proposed mechanism of how Omega 3s affect blood sugar concentrations.

    Also, a #7 is that this is just one study, and it usually takes many studies/more than one study to declare something as “fact”.

    Also, I’m a little sad at your #4, which is a big no-no and you know you aren’t supposed to do. Omega 3 consumption isn’t the only lifestyle difference between the Japanese and Americans…

  2. cameo said on January 25th, 2011

    I am sorry, but no-one is getting diabetes from eating too much fish.

  3. Andy Bellatti said on April 13th, 2011

    Brandon,

    I didn’t say omega-3 consumption is the only lifestyle difference between the US and Japan. However, it is certainly one of the most significant. If you compare, say, carbohydrate intake or vitamin C intake, the difference isn’t as striking. In light of the relationship between omega 3s and heart disease, that difference is certainly worth pointing out.

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