Harvard study finds farmed salmon and other fatty species fall far short in “D” department
by Craig Weatherby
Good food sources of vitamin D are few and far between.
This is unfortunate, given the importance of the "sunshine and seafood" nutrient to prevention of cancer and osteoporosis... and the extreme, unscientific sun-avoidance campaign mounted by the dermatology community.
Sun exposure is the most reliable source, but among foods, fish are the best sources by far.
There are big differences in the vitamin D content of different fish species, and fairly substantial seasonal and geographic variations within fish of the same species.
The USDA nutrient database doesn’t provide vitamin D figures for most fish, and we’ve known even less about the effect of cooking on the vitamin D content of fish.
To redress this data gap, a group of researchers at Boston University (BU) Medical Center evaluated the vitamin D content in several species of fish, and the effect of baking and frying on their vitamin D content (Lu Z et al 2007).
Wild salmon beat other fatty fish, and farmed salmon
The Boston University team found that Wild Salmon (unspecified species) had 988 IU of vitamin D per 3.5 oz serving, which is almost two-thirds (65 percent) more than the US RDA (600 IU) set in 2010.
And Farmed Salmon had only 25 percent of the vitamin D content of Wild Salmon (245 IU).
More surprisingly, they found that other fatty fish—species thought to be high in vitamin D—fell far short of expectations and Wild Salmon.
These were the results, ranked vertically from most to least vitamin D:
Table 1: Boston University vitamin D analysis
International Units (IU) per 3.5 oz serving
Wild Salmon (species unspecified) - 988
Ahi Tuna - 404
Farmed Trout - 388
Bluefish - 280
Farmed Atlantic Salmon - 245*
Cod - 104
Gray Sole - 56
Mackerel - 24
Source: Lu Z et al. J Steroid Biochem Mol Biol. 2007
*Note: When the researchers baked a 3.5 oz serving of Farmed Salmon, it lost only 5 IU of vitamin D, but when it was fried in vegetable oil, it lost half of its vitamin D content (122 IU out of 245 IU). They did not test wild salmon in the same way.
These were some of the BU authors’ cogent conclusions:
“It has been suggested… that everyone can obtain enough of their vitamin D requirement from their diet and that any unprotected sun exposure should be avoided. However, most experts agree that 1,000 IU vitamin D3 [the form most useful to humans and found in fish and other animal foods] is required if there is no exposure to sunlight.
“…our analysis of the vitamin D content in a variety of fish species that were thought to contain an adequate amount of vitamin D did not have an amount of vitamin D that is listed in food charts. There needs to be a reevaluation of the vitamin D content in foods that have been traditionally recommended as good sources of naturally occurring vitamin D” (Lu Z et al 2007).
Table 2: Vitamin D in Vital Choice fish and other food sources
By way of contrast to the Boston University results, this table shows the vitamin D figures obtained from tests of Vital Choice fish, and from US NIH data for “leading” food sources. Of these, only canned tuna is a substantial source, and only cod liver oil—which is a supplement, not a whole food—exceeds the abundance of vitamin D in Wild Salmon.
Vitamin D in Vital Choice fish*
International Units (IU) per 3.5 oz serving
Sockeye Salmon - 687
Albacore Tuna - 544
Silver Salmon - 430
King Salmon - 236
Sardines - 222
Sablefish - 169
Halibut - 162
Other sources of vitamin D**
International Units (IU)
Cod Liver Oil, 1 Tbsp - 1,360
Light (skipjack) tuna canned in oil, 3 oz - 200
Milk (fortified), 1 cup - 98
1 Whole Egg*** - 20
Beef liver cooked, 3.5 oz - 15
Swiss Cheese, 1 oz - 12
*Vital Choice fish analysis conducted by Covance Laboratories, Inc..
**Office of Dietary Supplements, National Institutes of Health, accessed at http://ods.od.nih.gov/factsheets/vitamind.asp#h2
***All of the vitamin D in eggs is found in the yolk.
- Lu Z, Chen TC, Zhang A, Persons KS, Kohn N, Berkowitz R, Martinello S, Holick MF. An evaluation of the vitamin D(3) content in fish: Is the vitamin D content adequate to satisfy the dietary requirement for vitamin D? J Steroid Biochem Mol Biol. 2007 Jan 29; [Epub ahead of print] doi:10.1016/j.jsbmb.2006.12.010
- Whiting SJ, Green TJ, Calvo MS. Vitamin D intakes in North America and Asia-Pacific countries are not sufficient to prevent vitamin D insufficiency. J Steroid Biochem Mol Biol. 2007 Jan 9; [Epub ahead of print]
- Holick MF. High prevalence of vitamin D inadequacy and implications for health. Mayo Clin Proc. 2006 Mar;81(3):353-73. Review.
- Hollis BW. Circulating 25-hydroxyvitamin D levels indicative of vitamin D sufficiency: implications for establishing a new effective dietary intake recommendation for vitamin D. J Nutr. 2005 Feb;135(2):317-22. Review.
- Vieth R, Cole DE, Hawker GA, Trang HM, Rubin LA. Wintertime vitamin D insufficiency is common in young Canadian women, and their vitamin D intake does not prevent it. Eur J Clin Nutr. 2001 Dec;55(12):1091-7.