Monday, February 14, 2011

Questions And Answers: Omega 3 Fatty Acids

I get a lot of questions about omega 3 fatty acids.  Many people don’t know much about what they do, but have heard they are healthy.   There is also a lot of confusion concerning the dangers of mercury consumption when eating fish.  I thought this topic would make a great post for my next Q and A, so here goes:

1) What are omega 3 fattys acids?
Omega 3 fattys acids are an essential polyunsaturated source of fat.  They are essential because our body can’t make them, we need to get them from our diet.  There are 3 subtypes of omega 3’s: 1) EPA 2) DHA 3) Alpha-linolenic acid.

2) Where are they found?
EPA and DHA are found in fish.  The fattier the fish, the higher the level of omega 3’s.  Alpha linolenic acid is found in vegetable oils like canola oil, nuts like walnuts, flaxseed, dark leafy vegetables and some animal fat, particularly if the animal was grass fed.

3) How do omega 3’s impact health?
Omega 3’s are believed to have an impact on the following: 1) The make up of cell membranes  2) Hormones that regulate clotting 3) Hormones that regulate contraction and relaxation of artery walls and 4) Inflammation.

Dietary intake of omega 3’s has been shown to decrease fatal heart arrhythmia, lower heart rate and blood pressure and improve the function of blood vessels.  At larger doses they have been shown to lower triglycerides and decrease inflammation. (See Reference 1)  These benefits appear to be strongest for EPA and DHA which are the marine sources of omega 3’s.

4) Do I need to supplement them?
Not at all.  If you work with me or have read my book, you’ll know I’m not a fan of supplementing in general.  There are several factors in whole foods that work synergistically to help nutrients work.  When you isolate a compound and put it in pill form, you lose this important aspect of nutrition.  If you get 2-3 servings of a variety of seafood such as fatty fish (tuna, salmon, sardines, mackerel) or shellfish each week you are doing great.  Vegetable sources of omega 3’s (oils, nuts, flaxseed) have generally not shown as much benefit, so try to focus on the marine sources.

Furthermore, there have been some reports of high levels of mercury in some of omega 3 supplements.  Since supplements are not regulated, you can never really be sure of the source.  This is another reason to get your omega 3’s from your food.

5) What about mercury in our fish- should I be concerned?
Yes and no.  Mercury is a compound that when ingested in large doses can damage nerves in adults and cause severe problems with the developing nervous systems of young children and fetuses. 

In general, the benefits of omega 3 consumption outweigh the risks.  I tell my client to strictly limit consumption of the 4 biggest sources of mercury in our fish: swordfish, shark, tilefish and king mackerel.   Outside of that, for adults, it appears that eating a variety of seafood will pose little problem, with the potential for serious benefit.

However, if you are pregnant or trying to become pregnant, you need to talk to your doctor about how to deal with the issue of mercury.  On the one hand, EPA and DHA from fish sources are extremely important to the neurological development of the fetus.  On the other hand, high amounts of mercury have the potential to have the opposite effect.  Your doctor will help you strike the proper balance of minimizing the risk and maximizing the benefit of fish.  Generally, the recommendation for pregnant women is to consume no more than 2 servings of seafood a week and only one of these servings should be albacore tuna.   Pregnant women are also told to avoid the 4 big sources of mercury: swordfish, shark, tilefish and king mackerel.

6) So what do you recommend?
I tell my clients to eat 2-3 servings of seafood each week and to vary the sources.  Good low mercury sources of omega 3’s are shrimp, canned light tuna, salmon, pollack and catfish.  I also have them limit the 4 big sources of mercury: swordfish, shark, tilefish and king mackerel.

I don’t have them supplement with fish oil and if they are pregnant or trying to get pregnant, I defer to the advice of their Ob/Gyn doctor.

Leaf A.  Prevention of sudden cardiac death by n-3 polyunsaturated fatty acids. Journal of Cardiovascular Medicine. 2007; 8 Suppl 1:S27-29.


Mike Alves said...

Hi Dr. Halton,

Thank you for this post. How large is a serving of seafood?

Dr. Thomas Halton said...

Hey Mike,
Good question! A serving is 3 ounces.

Anonymous said...

Great article, Tom! This is one of the main reasons that although the majority of my diet is vegan, I do have some seafood.

madhurithatta said...

I am a vegan how can i get omega-3 fatty acids
as you said vegetables are not great sources of
fatty acids

Dr. Thomas Halton said...

Although vegetable sources of omega 3 fatty acids have not shown to be as beneficial as marine sources, there is certainly still some benefit there. I would focus on the vegetable sources of omega 3 if you are a vegan. They are found in canola oil, walnuts, flaxseed and dark leafy vegetables.