Enter food for NutritionData.com analysis or GlycemicIndex.com data
Food Name

Monday, January 12, 2009

New USDA salmon figures based on too-few samples?

Farm-raised salmon is cheap compared to fresh. You might find farm-raised for $9.00 a pound in the fresh case and $5.99 a pound in 2-pound package of individually-wrapped frozen fillets.

But farm-raised salmon has lately been known to have a lot of omega-6 fatty acids, making it very inflammatory -- just the sort of thing you DON'T want if you are looking for heart-healthy diet choices.

So I was surprised to read that they have suddenly gotten better. The newly-updated USDA database says that the ratio of omega-6 to omega-3 fatty acids in farmed Atlantic Salmon is now a favorable 1:2.6 instead of the former, very unfavorable 7:1 (is that right? 7:1? Who's got a copy of the old database?). So a serving farm-raised salmon has gone from being highly inflammatory to being highly anti-inflammatory. The ratio is not quite as good as for wild Atlantic Salmon (1:12), but since the farm-raised salmon is nearly twice as fatty, you get a bigger anti-inflammatory dose per ounce.

Monica Reinagel proposed that big changes in aquaculture practices have accounted for this change. But I am not sure this change is universal. I quickly searched for "salmon USDA" and came up with a USDA poster presentation from Experimental Biology 2007 giving lipid figures for salmon. Turns out, only 2 samples of farm-raised Atlantic Salmon were tested, from shopping trips to 12 different US grocery stores.

Two samples? Is that representative of all the farmed Atlantic salmon available in the US? How can I know if the salmon I see in my grocery store more closely resembles the new farmed salmon or the old?

Is it normal for the USDA to "improve" its database with data from such a narrow sampling? What other USDA figures should I start distrusting?


Sara DownToEarth said...

Your questions about being able to trust the new figures point to the problem with many nutritional comparisons between types of meat and produce.

The nutritional content of any living organism, especially higher on the food chain, is seriously impacted by its diet and other life factors.

That's part of why figures on nutrition of "organic" are so hard to believe: Organic milk from dry-lot dairies is a lot different than totally pastured. Even that difference will vary seasonally.

Family Nutritionist said...

Perhaps the USDA should publish the information about the samples taken. That would help a bit.

USDA has different NDB entries for ground beef and grass-fed ground beef, so maybe they'll add "grass-fed milk" in the future.