Values Of Tuna Analyzed On Heart-Healthy Omega-3 ff

Q: What is the omega-3 value of a wild-tuna steak bought frozen and broiled in the oven? How does tuna compare with other sources?

A: There are several different species of tuna, and the omega-3 value will vary according to the species. Looking at more common types, 6 ounces of yellow-fin tuna, also known as ahi tuna, contains 400 grams. Bluefin tuna, the type most prized for sashimi, contains 2,200 grams of the omega-3 fatty acids. Skipjack tuna contains 460 milligrams, and for comparison, 6 ounces of canned light tuna contains 340 milligrams of omega-3.

Discussing how tuna compares with other sources requires a little background on the omega-3s. The short answer is that tuna is comparable to other fish sources, and fish sources are much better than plant sources for the omega-3 fatty acids.

The reason for this is that the omega-3s the body needs include EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), which are 20 and 22 carbons long, respectively. They are found in fish but not in plants such as walnuts, canola, soy and flax. The plant source of omega-3 is typically an 18-carbon-long omega-3 known as ALA (alpha-linolenic acid). The body has pathways that can convert the ALA into EPA and DHA, but it’s very inefficient. A paper in the June 2006 supplement of the American Journal of Clinical Nutrition reported that women can convert from 8 percent to 21 percent of ALA into EPA, and up to 9 percent of the ALA makes it to DHA. The conversion rate for men is up to 8 percent for EPA and 4 percent for DHA. Studies that labeled the ALA found that most is burned for energy, and only a small fraction gets converted into the essential omega-3s.

If you want the omega-3s, fish is the way to go. Tuna is in the middle of the pack of good sources, which include salmon, Pacific oysters, rainbow trout, pollack, flounder, halibut, sardines, anchovies and herring. Food safety can be a concern when considering fish, and it is always advisable to eat a variety of different types.

Q: I ran across a column you wrote concerning xanthan gum as an additive and have a comment. Xanthan gum is the end product of a fermentation process involving Xanthomonas campestris, which, with other nutrients, is mainly “fed” corn syrup as sugar source. These are gum-producing bacteria, which, in this case, yields xanthan gum. I don’t really agree that it is made from corn syrup as such. Sort of like prime rib being made of grass and other “feed” items. In that sense, yes, and possibly that was the slant you were taking. 

A: You are correct that xanthan gum is a fermentation product. However, much in the same way that we might think of beer as being made from grains, it is not that misleading to think of the xanthan gum as coming from corn. The issue in the column was a corn allergy, and I adapted the answer to fit that paradigm. I should have been more precise in the sentence, in which I stated “because it is made from corn” and stated instead, “because it is made using corn.” Thanks for your input.