DEAR DR. BLONZ: I was told by my optometrist that the irritation in my eyes is due to a condition known as blepharitis, and that I should be taking flax oil to provide the omega-3 fats that can help this condition. I recall in one of your columns that flax oil might not be the best way to get omega-3s, so I wanted some confirmation. Could you please give me an update of the best sources of omega-3s? -- K.L.F., Dobbs Ferry, N.Y.
DEAR K.L.F.: I am not a medical doctor (or an optometrist), so what I provide here should not be taken as medical advice. That being said, let's go through what's known.
Blepharitis is a condition in which there is swelling or inflammation of the eyelids (more details at tinyurl.com/mla285c). There are a number of possible treatments for this condition, and that's something you need to discuss with your health professional. If a decision is made to increase the body's omega-3 fatty acids, it usually refers to eating in a way to increase the long-chain omega-3s that include EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), which are 20 and 22 carbons long, respectively. This might be selected because increasing the level of EPA and DHA in the body can have anti-inflammatory effects. EPA and DHA are found in certain fish such as salmon, but not in plants such as flax, walnuts, canola, and soy. Plants can contain an omega-3 fat, but it is typically an 18-carbon-long omega-3 known as ALA (alpha-linolenic acid).
The body can convert ALA into EPA and DHA, but it's not an efficient process. One paper in the June 2006 supplement of the American Journal of Clinical Nutrition reported that, at most, women can only convert 21 percent of ALA into EPA, and only up to 9 percent of ALA into DHA. For men, the rates are only up to 8 percent conversion for EPA and 4 percent for DHA. Most of the ALA we eat gets burned for energy.
So why the recommendation for flax oil? In looking through the scientific literature I found an important study in the December 2008 issue of the Transactions of the American Ophthalmological Society that reported a beneficial effect from flax seed oil on blepharitis. This might be the source of the recommendation. The authors, however, pointed out that they used flax seed oil not because it was the best source, but rather because fish oil products can have an odor and the study was placebo-controlled. They did not want their subjects to be able to detect whether they were receiving an omega-3 supplement or the placebo (olive oil, in this case). There was also a concern regarding the potential for heavy metal contaminants in fish oil products. The authors correctly pointed out that flax seed oil must first be converted to EPA/DHA before it can act as an anti-inflammatory.
Our bottom line here is that if there is a desire to increase the level of EPA and DHA in the body, you should discuss with your health professional if it might be more effective to eat more fish, or take a fish oil supplement containing EPA and DHA. There are now odorless products and ones that are distilled to eliminate potential contaminants.
Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to email@example.com. Due to the volume of mail, personal replies cannot be provided.