DEAR DR. BLONZ: I have concerns about contaminants in fish oil supplements. Is an omega-3 supplement sourced from flax a better alternative? -- F.L., Phoenix
DEAR F.L.: I recommend eating fish over taking fish-oil supplements. Population studies have shown that those with a regular consumption of fish have a lower risk of several chronic diseases, including heart disease, hypertension and certain inflammatory conditions, such as arthritis.
Your question, however, relates to supplements, so let's consider the issue.
The key components are specific omega-3 fatty acids. Fish containing high levels of these include salmon, mackerel, tuna, herring, anchovies, sardines and trout. There are also omega-3 fatty acids in flaxseed and, to a lesser extent, canola and walnut oils, but these are not the same as those found in fish.
To be called an omega-3 means that the first unsaturated bond is on the third carbon of the chain. In fish, we have omega-3s often referred to by their initials: EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). They are 20 and 24 carbons long, respectively. The omega-3 in flaxseed and other plant sources is linolenic acid, which is 18 carbons long.
Most people need more omega-3 fats in their diet, whether they come from fish or flax, but there are unique benefits in EPA and DHA.
If you do consume the 18-carbon linolenic acid, your body has the ability to elongate some of it into EPA and DHA, but only a small amount makes it through this process. It is, however, better to have omega-3s from flaxseed than to not have any at all.
Plant sources of omega-3 fats are relied upon by vegans. In addition to fish, EPA and DHA can be found in krill (a crustacean) and in some forms of algae; it is up to the individual to decide the boundaries of their vegan eating plan. I would be remiss if I didn't mention that flaxseed has other health attributes: It is an excellent source of dietary fiber and lignan, a phytochemical that may have anti-cancer effects.
As for pollution, this remains a disturbing topic, and some fish populations have been affected by various contaminants. When eating fish, steer clear of those caught or raised near industrial plants, and stick with those from offshore or deep-sea areas, or from lakes and streams known to be free from harmful chemicals. You might seek guidance from a reputable fish market.
Where supplements are concerned, it is best to check individual products to find one that is free of contaminants. There are processes that allow manufacturers to filter out environmental toxins without affecting the level of the omega-3 fatty acids. Look for an appropriate description on the label stating that the product is contaminant-free. If in doubt, give the manufacturer a call.
One final note: Fish oil supplements should be avoided by those with bleeding disorders and those on anticoagulant medications. Caution is also dictated for those with high blood pressure. Always consult your physician if you have any questions.
Send questions to: "On Nutrition," Ed Blonz, c/o Universal Uclick, 1130 Walnut St., Kansas City, MO, 64106. Send email inquiries to firstname.lastname@example.org. Due to the volume of mail, personal replies cannot be provided.