Recently two Swiss researchers published a review of all the studies on the vitamin D content of various protein food groups.
Here is what they found:
Vitamin D in red meat and poultry
A search of the national food composition databases of Denmark, France, Germany, Switzerland, Canada, and the United States for vitamin D content in various raw meats yielded a wide variety of values. It was: 0–36 IU/100 gm for beef, 4- 92 IU/100 gm for pork, 40 – 240 IU/100 gm for lamb, 0– 200 IU/100 gm for veal, and 0–56 IU/100 gm for poultry.
The higher values of some meats may be due to high supplemental vitamin D content of animal feed in some studies. Also, the authors found that cooking does not much influence the vitamin D content of animal foods. However, exposure to light can significantly reduce vitamin D content.
As to the 25(OH)D content of some red meat, the vast majority of studies found very little 25(OH)D activity in muscle meats. However, one of the 20 meat studies reviewed found the 25(OH)D content of the longissmus muscle in pork (a muscle in the back) had a D3 equivalence of 1,300 IU/100 gm. However, this finding was such an outlier, that it’s hard to make much of it.
Vitamin D in eggs
The vitamin D content of egg yolks ranged between 27 to 46 IU per yolk. The 25(OH)D3 content ranged from 20 to 50 IU of D3 activity per yolk, meaning in eggs, the vitamin D and 25(OH)D activity is similar.
Also recall a recent study that found if you applied UV light to the legs of chickens, the vitamin D content of their eggs increased significantly. However, this method has not come into practice.
Vitamin D in dairy products
The vitamin D content [including 25(OH)D] of unfortified dairy products, including cheese and cream, is negligible except for butter, which ranged from 8 to 40 IU/100 gm.
Also, the authors found that the vitamin D bioavailability of vitamin D in fortified milk is not influenced by the fat content. Meaning there is the same amount of vitamin D in skim milk as there is from whole milk. They also found that thermal stress like pasteurization, ultra heat treatment or sterilization does not provoke a significant loss of added vitamin D in milk.
Vitamin D in fish
In fish, contrary to general belief, no significant correlation between the fat content of fish and vitamin D content was detected. The single biggest factor in how much vitamin D activity is in wild fish is the vitamin D content of the zooplankton in its food chain. The fish with the most vitamin D was not salmon; it was tilapia at 1,800 IU/100 gm. When 25(OH)D3 was analyzed in fish and fish products, the results were consistently very low and often there was no detectable 25(OH)D content.
The authors concluded:
“Because recommendations for vitamin D intake have recently been increased considerably, the possibility to cover the requirements with foodstuff is even more difficult.”
The time has come to fortify more foods with vitamin D. Many people need to get vitamin D in their diet or they will not get it. Eggs, cereals, breads, canned vegetables, fast foods, yogurt and cheese could all be fortified. Yogurt and cheese are made from unfortified milk and thus have little or no vitamin D.