Saturday, March 10, 2012

What is fish oil good for?

What is fish oil good for? 

It seems that most of the patients I see in the office each day are taking a fish oil supplement. Despite that, most can't say why they are taking it!

Should you take a fish oil supplement? If so, why? What is fish oil good for?
Did you know that a recent study suggested a new reason to consider taking a fish oil supplement?

Over the years, fish oil has been studied for a multitude of conditions.
But very few of those studies demonstrated conclusive benefit.

The key active components of fish oil are the omega-3 fatty acids known as docosahexaenoic acid and eicosapentaenoic acid or DHA and EPA. 
Omega-3 fatty acids cannot be made very well by your body. 
So that means they are important to have in your diet.

Omega-3 fatty acids are important for brain and retina development in infants. 
And omega-3 fatty acids may be important for many functions in the body and in modulating inflammation. 

So what if you don't eat fish. Should you take a fish oil supplement?

 What can you expect from taking a fish oil supplement?
The results of randomized trials can provide the most reliable scientific evidence to answer this question.

And this is what those trials have shown, thus far:

That trial used 1 gram of omega-3 fatty acids daily and was completed over 10 years ago. It was  large trial but was not placebo-controlled. Most of the benefit appeared to be due to a 43 percent reduction in the risk of sudden cardiac death.

A more recent trial in adults with a recent heart attack was placebo controlled, randomized and double blind. That study showed no benefit of 1 gram of omega-3 fatty acids.
It had one third the number of patients and newer therapies for myocardial infarction were available not used in the older trial.

Another randomized controlled trial in those with stable cardiovascular disease showed no benefit but a very low dose of 600 milligrams of omega-3 fatty acids was used.

Fish oil reduces death by 9% in those who have congestive heart failure. That trial used 1 gram of omega-3 fatty acids and was placebo-controlled and double blind.

Fish oil supplements providing 1.8 grams of EPA daily reduced cardiovascular events by 19% in adults with coronary artery disease. Those events were mostly nonfatal heart attacks . That trial was very large but was not placebo-controlled. These were impressive results even though that study was done in Japan where most people eat lots of fish.

 Fish oil providing 2 grams of omega-3 fatty acids daily, in certain circumstances, probably reduces the likelihood of getting the common heart arrhythmia called atrial fibrillation. 

One study showed reduction in atrial fibrillation after coronary artery bypass surgery.
Another placebo controlled double blind study of atrial fibrillation not related to cardiac surgery showed no benefit of 4 grams of omega-3 fatty acids.

Fish oil  providing about 4 grams of omega-3 fatty acids daily  reduces elevated fats in the blood called triglyceridesA prescription fish oil is available to treat high triglycerides. 
Early data suggest that the DHA and EPA components appear to act slightly differently on the blood fats called lipids. A new prescription fish oil preparation may be available soon.

Other isolated smaller studies suggest benefit from fish oil supplements in reducing anxiety in adults, in reducing liver fat in children with fatty liver disease, and symptoms in children with attention deficit hyperactivity disorder.

Now a recent study showed muscle benefit from fish oil providing around 700 milligrams of combined DHA and EPA daily. That's less than one gram of marine omega-3 fatty acids a day. These women, average age of 64 years, all underwent leg strength training three times a week for 12 weeks. At the end of that period, those who took fish oil had significantly better muscle strength than those not taking the fish oil.

 You can see that most of the benefit of fish oil has been shown in those with a history of heart disease or with elevated triglycerides.

But there appears to be no harm in taking fish oil even if you don't have those conditions.

And despite common belief, in the usual doses, recent findings show that fish oil does not affect how well your blood clots.
 A previous analysis concluded the same.

More studies are coming but that’s all the evidence for now.

If you choose to take fish oil you ought to read a previous post to be sure you are getting close to the amount you expect.
Keep in mind that the  content of combined EPA and DHA in non-prescription fish oil supplements is very variable.

And now you the know the answer to the question, "what is fish oil good for?"

Your Diabetes Endocrine Nutrition Group


  1. How does Lovasa compare to Omega 3 Fish Oil purchased over the counter? Does it have other benefits of regular fish oil or just in relation to triglycerides?

  2. Good question! There are no direct published comparisons of Lovaza and dietary supplement (non prescription) fish oil. Many of the studies I describe above were done with Lovaza. That's a lot of benefit outside of triglyceride lowering which is the only FDA approved use for Lovaza. Read my previous post on fish oil and the labels.