DHA…..does it really do anything? Does it help cardiovascular disease? Does it help inflammation? Does it help with weight? Does it work? I occasionally get a question about fish oil in the pharmacy and outside of the pharmacy as well. Does DHA live up to the hype?
Docosahexaenoic acid (DHA) is an omega 3 (n-3) fatty acid that is important in proper function of the body. DHA is converted from alpha-linoleic acid (ALA) in the body. EPA is also a product of ALA metabolism and can be converted into DHA. The conversion of ALA and EPA in the body to DHA is low. 1, 2 Relying on ALA alone and thinking this will help increase EPA and DHA is not a sound strategy for adequate levels.
DHA is also now thought to be one of the main chemicals responsible for the evolution of the human brain. 3 It is one of the major components of the brain and retina as well as neurons. DHA is most significantly obtained through fish, hence all of the claims for fish oil.
One study looked at the amount of n-3 in salmon and trout, both farmed and wild. Salmon seemed to have a bit more DHA per 100gm of fish than the wild while the opposite was true for the trout. Both were good sources and comparable. 4 So you can get supplementation through capsules or good ol fish. But the questions remain. Lets focus on some of the claims and evidence behind them.
This is no doubt one of the main controversies behind fish oil supplementation. Does DHA really help cardiovascular disease?
In the GISSI-Prevenzione Trial, researchers looked at patients with recent myocardial infarction and divided them up into groups of n-3, vitamin e, both, or control. This was a large study with 11,324 patients. The amount of EPA and DHA was 850/882 mg respectively. After being followed for 3.5 years, the researchers found that the n-3 group did the best with a 2.3% absolute risk reduction of death, non-fatal MI, and non-fatal stroke. 5 There was also a 2.5% risk reduction from cardiovascular death, non-fatal MI and non-fatal stroke. DHA and EPA combined seemed to do the trick. An interesting note is that blood lipid levels were the roughly the same.
Another study showed that just 5 days of pre-op treatment with n-3 for atrial fibrillation (AF – which is a bad rhythm in the heart) was beneficial. Analysis revealed that there was an 18.1% reduction in absolute risk of getting AF after CABG surgery compared to control. 6
One review discusses the role of n-3 in the rhythms of the heart as the mode of protection. Sudden cardiac death can result from arrhythmias and n-3 seems to be protective of that. Notice that it is a combo on EPA and DHA and not DHA alone.
In the women’s health study it was found that women who ate more fish seemed to be more protected from coronary heart disease (CHD). 7
One review looked at the studies of n-3 and ALA and found that while n-3 seemed to be beneficial to CHD, ALA appeared to have no effect. Again this could be attributed to the fact that we don’t convert it very well in our bodies. 8
A meta-analysis shows that n-3, either from diet or supplements is beneficial on CHD and death. 9
Yet another review recommends around 1gm of n-3 daily and maybe a higher dose with supervision of a physician. 10
There is a pharmaceutical preparation called Lovaza which some of you might be familiar with. I wouldn’t bother as it has hydrogenated oils in it. This makes zero sense to me. I mean seriously, c’mon! Hydrogenated oils in a purified n-3 prep? There is no curse or swear sufficient to explain that stupidity in any language that I’m aware of. There is another called Vascepa which is an ethyl ester of EPA. They both are to treat high triglycerides. Vascepa is under scrutiny right now because they are failing to show reduced risk of cardiovascular disease. Stick with the fish!
So yeah, n-3 rocks!….unless you are a purified and bastardized form of it. Just want to point out a few other things here.
1. Fish oil, krill oil, or whatever oil you may supplement with can have deceptive labeling. The label may say 1000mg of fish oil, but only have 200mg of EPA and DHA. Be sure to check the label if you decide to supplement so you know how much you’re actually getting.
2. N-3 are polyunsaturated oils, which means that they have some double bonds at the third carbon and then some. What the heck do you care? Because those bonds are far easier to break and interact with simple things like the air and light that they go rancid very easily. Don’t get fish oil that looks like it’s been sitting on the shelf for a year. And store it in your fridge to help prevent oxidation.
3. Some people have this idea that if some fish oil is good then tons is probably awesome. Not so fast. While n-3 are absolutely important for us to be healthy and are useful as supplements if we don’t have access to good fish, lots doesn’t necessarily help more. Remember that we don’t need a lot of n-3 to be healthy and we don’t need much n-6 to be healthy either. I’ve read that people who consume lots of n-6 prefer to down loads of fish oil to keep the balance right. How bout you just lower your n-6 and spare yourself blood thinning and possible bleeding.
4. If you’re taking anticoagulants such as warfarin (Coumadin), talk with your doc about supplementation because n-3 can increase the potential for bleeds.
5. Fish oil can cause fish burps. Fish can cause fish burps. Take your caps right before eating so there is less chance it will be floating on top of your food belching its way to the nose of your significant other.
6. Fish is the better source because its a whole food. But oil is a good option if you can’t afford or don’t have access to the fish.
In the next article we’ll talk about some of the neurological functions of DHA.
Disclaimer: All info on this website is for education purposes only. Any dietary or lifestyle changes that readers want to make should be done with the guidance of a competent medical practitioner. The author assumes no responsibility nor liability for the use or dissemination of this information. Anyone who chooses to apply this information for their own personal use does so at their own risk.
1. Brenna, J. Thomas, et al. “α-Linolenic acid supplementation and conversion to n-3 long-chain polyunsaturated fatty acids in humans.” Prostaglandins, leukotrienes and essential fatty acids 80.2 (2009): 85-91.