The best and most natural way to get vitamin D is by sunbathing, or, when that is not possible, by taking supplements. However, most people will do neither and are thus severely vitamin D deficient. For that reason, enhanced dietary forms of vitamin D are desperately needed for the masses.
Wild-caught fatty fish, such as salmon and sardines are rich in vitamin D, although at about 700 IU per serving, one would have to eat about seven servings of fish per day to get enough vitamin D. Reindeer meat, sea gull eggs, and lichen are also rich sources of vitamin D, but they are not on many menus.
That brings us to food fortification. Many public health officials have contended that we need to have more foods enriched with vitamin D, especially when you consider how deficient some groups of people are in vitamin D.
One barrier to improving vitamin D status this method is that it is simply not possible to put large amounts of vitamin D in any one food, as safety issues arise for those consuming large quantities of that particular food. Thus increasing enrichment of a large variety of foods is important. For instance, several years ago, the idea of adding more vitamin D to cereal-grain products was recommended.
Another strategy is to try and increase the amount of vitamin D in foods that already have some vitamin D in them, naturally. Eggs are often listed as a rich source of vitamin D. Is that true?
According to the USDA, one large egg, which weighs about 50 g, contains approximately 50 IU vitamin D3, which is concentrated in the yolk. Dr Linxing Yao and colleagues of Iowa State University decided to see if they could increase the amount of vitamin D in eggs by feeding the chickens more vitamin D and see that fortification affected egg quality or palatability.
They conducted a 40-wk experiment using laying hens to investigate the impact of feeding various vitamin D3 enriched diets. Feeds were enriched with four different amounts of vitamin D3, about 9,700, 17,000, 25,000, and 100,000 IU/kg of chicken feed. The control diet, the amount given chickens today, was 2,200 IU D3/kg feed. The chickens tolerated the higher D3 doses without any side effects.
Eggs from each of the four vitamin D enriched diets were collected and analyzed over the 40 weeks of the experiment. The peak D3 concentrations in egg yolk occurred at week 3 and were between 200 IU/egg to about 8,000 IU/egg, depending on the amount of D3 given the hen.
The high D3 diets used demonstrate that up to 160 times higher D3 concentration than that of typical eggs can be obtained through safely feeding chickens a more vitamin D3-enriched diet. The scientists also checked many different indicators of egg quality, such as taste tests and palatability. The high D3 did not adversely affect any measure of egg quality.
Look for vitamin D3 enriched eggs to be in the supermarket soon. I hope we also see more vitamin D enriched cereal-grain products. It may be that only increasing fortification of a wide variety of foods can we improve 25(OH)D levels of the most deficient Americans.